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--- websites/staging/ode/trunk/content/developerguide/jacob.html (added)
+++ websites/staging/ode/trunk/content/developerguide/jacob.html Tue Dec 11 12:48:20 2012
@@ -0,0 +1,589 @@
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+ <title>JaCOb – Virtual Processing Unit</title>
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+
+ <h1>JaCOb – Virtual Processing Unit</h1>
+
+ </div>
+ </header>
+
+
+ <!-- Content -->
+ <div class="container">
+
+ <div class="row">
+ <div class="span12">
+ <p><a name="Jacob-Introduction"></a></p>
+<h2 id="introduction">Introduction</h2>
+<p>ODE's BPEL implementation relies on the JaCOb (Java Concurrent Objects) framework to implement the BPEL constructs. The framework provides the mechanism necessary to deal with two key issues in implementing BPEL constructs:</p>
+<ol>
+<li>Persistence of execution state.</li>
+<li>Concurrency.</li>
+</ol>
+<p>By rolling up these concerns in the framework, the implementation of the BPEL constructs can be simpler by limiting itself to implementing the BPEL logic and not the infrastructure necessary to support it.</p>
+<p>The approach we'll take in this tutorial is looking at the <a href="#rationale">rationale</a> of JaCOb and its <a href="#concepts">concepts</a> first. Then we'll illustrate with one complete <a href="#example">example</a>. But if you're a reverse reader, you can also decide to start with the <a href="#example">example</a>.</p>
+<p><a name="rationale"></a></p>
+<h2 id="rationale-behind-the-model">Rationale behind the model</h2>
+<p>Let's start from the most classical example of all:</p>
+<div class="codehilite"><pre><span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="n">order</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">billingService</span><span class="o">.</span><span class="na">bill</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">billing</span><span class="o">);</span>
+ <span class="n">shippingService</span><span class="o">.</span><span class="na">ship</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">product</span><span class="o">,</span> <span class="n">order</span><span class="o">.</span><span class="na">shipping</span><span class="o">,</span> <span class="n">self</span><span class="o">);</span>
+ <span class="n">shipping</span> <span class="o">=</span> <span class="n">receive</span><span class="o">(</span><span class="s">"shipping"</span><span class="o">)</span>
+ <span class="n">order</span><span class="o">.</span><span class="na">customer</span><span class="o">.</span><span class="na">send</span><span class="o">(</span><span class="n">shipping</span><span class="o">.</span><span class="na">details</span><span class="o">);</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>It's Java like pseudo code that works extremely well, unless:</p>
+<ul>
+<li>You fail somewhere in the middle and the customer has to order a second time.</li>
+<li>Your have too many waiting threads and the VM crashes.</li>
+</ul>
+<p>So you change it to:</p>
+<div class="codehilite"><pre><span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="n">order</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">billingService</span><span class="o">.</span><span class="na">bill</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">billing</span><span class="o">);</span>
+ <span class="n">shippingService</span><span class="o">.</span><span class="na">ship</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">product</span><span class="o">,</span> <span class="n">order</span><span class="o">.</span><span class="na">shipping</span><span class="o">,</span> <span class="n">self</span><span class="o">);</span>
+ <span class="n">listenOn</span><span class="o">(</span><span class="s">"shipping"</span><span class="o">,</span> <span class="n">part2</span><span class="o">);</span>
+<span class="o">}</span>
+
+<span class="kt">void</span> <span class="nf">part2</span><span class="o">(</span><span class="n">shipping</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">order</span><span class="o">.</span><span class="na">customer</span><span class="o">.</span><span class="na">send</span><span class="o">(</span><span class="n">shipping</span><span class="o">.</span><span class="na">details</span><span class="o">);</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>That's almost better, but still has a lot of points of failure, where you're not sure if you actually billed the customer and shipped the product or not. So:</p>
+<div class="codehilite"><pre><span class="kt">void</span> <span class="nf">process</span><span class="o">(</span><span class="n">order</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">billingService</span><span class="o">.</span><span class="na">bill</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">billing</span><span class="o">);</span>
+ <span class="k">continue</span><span class="o">(</span><span class="s">"part2"</span><span class="o">);</span>
+<span class="o">}</span>
+
+<span class="kt">void</span> <span class="nf">part2</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">shippingService</span><span class="o">.</span><span class="na">ship</span><span class="o">(</span><span class="n">order</span><span class="o">.</span><span class="na">product</span><span class="o">,</span> <span class="n">order</span><span class="o">.</span><span class="na">shipping</span><span class="o">,</span> <span class="n">self</span><span class="o">);</span>
+ <span class="n">listenOn</span><span class="o">(</span><span class="s">"shipping"</span><span class="o">,</span> <span class="n">part2</span><span class="o">);</span>
+<span class="o">}</span>
+
+<span class="kt">void</span> <span class="nf">part2</span><span class="o">(</span><span class="n">shipping</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">order</span><span class="o">.</span><span class="na">customer</span><span class="o">.</span><span class="na">send</span><span class="o">(</span><span class="n">shipping</span><span class="o">.</span><span class="na">details</span><span class="o">);</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>You're just fracturing the code with two primitives: <em>continue</em> which lets you persist state and go to the next one, and <em>listenOn</em> which lets you persist state and wait for an external event.</p>
+<p>Fracturing the code also addresses concurrency of execution even if you only have one thread. For example you could have a large number of 'process' calls to bill and ship an order. As we've broken down the whole treatment into several small parts, we can control when these separate parts actually get called and executed. And we're free to order them.</p>
+<p>Let's say we have a small process doing in a sequence:</p>
+<ol>
+<li>Invoke</li>
+<li>Receive</li>
+<li>Wait</li>
+<li>Invoke</li>
+</ol>
+<p>If we have 2 parrallel executions of this process and implement it in a simple way we'd have:</p>
+<ol>
+<li>Invoke1</li>
+<li>Receive1</li>
+<li>Wait1</li>
+<li>Invoke1</li>
+<li>Invoke2</li>
+<li>Receive2</li>
+<li>Wait2</li>
+<li>Invoke2</li>
+</ol>
+<p>However if we break down the code as shown above by introducing a "middle man" (or stack) and do not allow activities to directly call each other (or do not have the activity directly calling the sequence that directly calls the next activity) we could well obtain the following:</p>
+<ol>
+<li>Invoke1</li>
+<li>Invoke2</li>
+<li>Receive1</li>
+<li>Wait1</li>
+<li>Receive2</li>
+<li>Wait2</li>
+<li>Invoke1</li>
+<li>Invoke2</li>
+</ol>
+<p>From a client standpoint, we've achieved concurrency of execution even with one thread.</p>
+<p>Next step is adding links, fault handling/termination, compensation and event handlers and seeing that continue/listenOn is all you need. The last step is just adding implementation details.</p>
+<p><a name="example"></a></p>
+<h2 id="jacob-example">JaCOb Example</h2>
+<p>Consider the issue of persistence. Imagine a simplified and naive implementation of the BPEL constructs <code><sequence></code>, <code><wait></code>, and <code><empty></code>:</p>
+<div class="codehilite"><pre><span class="kd">class</span> <span class="nc">Sequence</span> <span class="kd">extends</span> <span class="n">Activity</span> <span class="o">{</span>
+ <span class="cm">/** From BPEL Definition */</span>
+ <span class="n">OSequence</span> <span class="n">def</span><span class="o">;</span>
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="k">for</span> <span class="o">(</span><span class="n">OActivity</span> <span class="nl">child:</span><span class="n">def</span><span class="o">.</span><span class="na">children</span><span class="o">)</span>
+ <span class="n">createActivity</span><span class="o">(</span><span class="n">child</span><span class="o">).</span><span class="na">run</span><span class="o">();</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">class</span> <span class="nc">Wait</span> <span class="kd">extends</span> <span class="n">Activity</span> <span class="o">{</span>
+ <span class="cm">/** From BPEL Definition */</span>
+ <span class="n">OWait</span> <span class="n">def</span><span class="o">;</span>
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">Thread</span><span class="o">.</span><span class="na">wait</span><span class="o">(</span><span class="n">def</span><span class="o">.</span><span class="na">duration</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">class</span> <span class="nc">Empty</span> <span class="kd">extends</span> <span class="n">Activity</span> <span class="o">{</span>
+ <span class="cm">/** From BPEL Definition */</span>
+ <span class="n">OEmpty</span> <span class="n">def</span><span class="o">;</span>
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// <empty> activity: do nothing.</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>The above is the "natural" implementation of the constructs in the Java language. However, this implementation has some serious and obvious problems: the <code><wait></code> may specify a duration of days in which case a system failure during those days of waiting would mean that the process execution state would be lost. It would be nice to replace Thread.wait() in the Wait class with some sort of "suspend" operator that would save the execution state to disk.</p>
+<p>However there are practical issues to "suspending" to disk. At the point we wish to suspend, the call stack looks like:
+ :::java
+ Sequence.run()
+ Wait.run()</p>
+<p>In order to save the process to disk, we need to end the current thread of control which means popping both stack frames. To do this we have no choice but to require the implementation of Wait and Sequence to "cooperate" with this requirement thereby greatly complicating the implementation of those constructs. This also means that the "natural" implementation model cannot be used directly.</p>
+<p>JaCOb aims to solve this problem by providing an alternate "natural" model that allows execution state to be suspended ''without cooperation from the implementation classes''. The idea in JaCOb is to flatten the call stack and rely on explicit communication channels to handle control flow. We now consider a simplified JaCOb representation of our three BPEL activities:</p>
+<div class="codehilite"><pre><span class="kd">class</span> <span class="nc">Empty</span> <span class="o">{</span>
+ <span class="n">OEmpty</span> <span class="n">def</span><span class="o">;</span>
+
+ <span class="cm">/** channel we use to notify parent we are done. */</span>
+ <span class="n">CompletionChannel</span> <span class="n">myCompletionChannel</span><span class="o">;</span>
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// <empty> activity: do nothing...except to</span>
+ <span class="c1">// notify our parent that we are done.</span>
+ <span class="n">myCompletionChannel</span><span class="o">.</span><span class="na">completed</span><span class="o">();</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">class</span> <span class="nc">Sequence</span> <span class="o">{</span>
+ <span class="n">OSequence</span> <span class="n">def</span><span class="o">;</span>
+ <span class="n">CompletionChannel</span> <span class="n">myCompletionChannel</span><span class="o">;</span>
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// Start of by instantiating a sequential child runner for the first</span>
+ <span class="c1">// (0th) child...</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">SequenceChildRunner</span><span class="o">(</span><span class="mi">0</span><span class="o">))</span>
+ <span class="o">}</span>
+
+ <span class="kd">class</span> <span class="nc">SequenceChildRunner</span> <span class="o">{</span>
+ <span class="kt">int</span> <span class="n">currentchild</span><span class="o">;</span>
+ <span class="n">SequenceChildRunner</span><span class="o">(</span><span class="kt">int</span> <span class="n">childNumber</span><span class="o">)</span> <span class="o">{</span> <span class="n">currentchild</span> <span class="o">=</span> <span class="n">childNumber</span><span class="o">;</span> <span class="o">}</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="k">if</span><span class="o">(</span><span class="n">currentChild</span> <span class="o">==</span> <span class="n">def</span><span class="o">.</span><span class="na">children</span><span class="o">.</span><span class="na">size</span><span class="o">())</span> <span class="o">{</span>
+ <span class="c1">// We are past the last child, the sequence is done.</span>
+ <span class="n">myCompletionChannel</span><span class="o">.</span><span class="na">completed</span><span class="o">();</span>
+ <span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
+ <span class="c1">// We still have more children to run..</span>
+
+ <span class="c1">// Create a completion channel for our child.</span>
+ <span class="n">CompletionChannel</span> <span class="n">childCompletionChannel</span> <span class="o">=</span>
+ <span class="n">newChannel</span><span class="o">(</span><span class="n">CompletionChannel</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
+
+ <span class="c1">// create a child activity based on the activity type</span>
+ <span class="c1">// and parameterized with the model and the completion</span>
+ <span class="c1">// channel we just created</span>
+ <span class="n">Activity</span> <span class="n">childActivity</span> <span class="o">=</span>
+ <span class="n">createActivity</span><span class="o">(</span><span class="n">def</span><span class="o">.</span><span class="na">children</span><span class="o">.</span><span class="na">get</span><span class="o">(</span><span class="n">currentChild</span><span class="o">),</span>
+ <span class="n">childCompletionChannel</span><span class="o">);</span>
+
+ <span class="c1">// instantiate the child activity</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">childActivity</span><span class="o">);</span>
+
+ <span class="c1">// create an object to wait for the "completed()" notification</span>
+ <span class="c1">// from the child activity.</span>
+ <span class="n">object</span><span class="o">(</span><span class="k">new</span> <span class="n">CompletionChannelML</span><span class="o">(</span><span class="n">childCompletionChannel</span><span class="o">))</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">completed</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// Ok, finished with the child, create a runner</span>
+ <span class="c1">// to do the next child.</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">SequenceChildRunner</span><span class="o">(</span><span class="n">currentChild</span><span class="o">+</span><span class="mi">1</span><span class="o">));</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="kd">class</span> <span class="nc">Wait</span> <span class="kd">extends</span> <span class="n">Activity</span> <span class="o">{</span>
+ <span class="n">OWait</span> <span class="n">def</span><span class="o">;</span>
+ <span class="n">CompletionChannel</span> <span class="n">myCompletionChannel</span><span class="o">;</span>
+
+ <span class="o">...</span>
+ <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// Create a channel for an externally managed alarm.</span>
+ <span class="n">TimerChannel</span> <span class="n">timerChannel</span> <span class="o">=</span> <span class="n">newChannel</span><span class="o">(</span><span class="n">TimerChannel</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
+ <span class="c1">// register the alarm with the runtime.</span>
+ <span class="n">getRuntimeContext</span><span class="o">().</span><span class="na">registerTimer</span><span class="o">(</span><span class="n">timerChannel</span><span class="o">,</span> <span class="n">def</span><span class="o">.</span><span class="na">duration</span><span class="o">);</span>
+
+ <span class="c1">// create an object to wait for the alarm and then send an</span>
+ <span class="c1">// activity completed message to our parent.</span>
+ <span class="n">object</span><span class="o">(</span><span class="k">new</span> <span class="n">TimerChannelML</span><span class="o">(</span><span class="n">timerChannel</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">onTimer</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">myCompletionChannel</span><span class="o">.</span><span class="na">completed</span><span class="o">();</span>
+ <span class="o">}</span>
+ <span class="o">});</span>
+
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>So JaCOb constructs help us in breaking the execution stack.</p>
+<p><a name="concepts></a></p>
+<h2 id="main-jacob-concepts">Main JaCOb Concepts</h2>
+<p><a name="Jacob-Channels"></a></p>
+<h3 id="channels">Channels</h3>
+<p>As briefly demonstrated above, channels are interfaces used for communication between activities in ODE engine. There are several types of channels like TerminationChannel, ParentScopeChannel or CompensationChannel (their respective purpose should be obvious from their name). Some basic channels are provided to all activities when they're created to allow them to interact with their environment. When an activity wants to notifies its parent that it has terminated for example, it just calls its parent TerminationChannel (see the Empty example above).</p>
+<p>Don't look for channels implementations because there are none. Channels implementation is provided through a dynamic proxy (see <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/vpu/ChannelFactory.java">ChannelFactory</a>.createChannel() and <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/vpu/ChannelFactory.java">ChannelFactory</a>.ChannelInvocationHandler for more). That's one of the levels of decoupling between invocation and actual execution in JaCOb.</p>
+<p><a name="Jacob-JacobObject/JacobRunnable"></a></p>
+<h3 id="jacobobject-jacobrunnable">JacobObject / JacobRunnable</h3>
+<p>If you don't care much about the details, the bottom line is: a <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/JacobObject.java">JacobObject</a> and an <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/JacobRunnable.java">JacobRunnable</a> are just a method implementation. This method gets executed when the abstraction is executed.</p>
+<p>A JacobObject is meant to be a closure. From Wikipedia: "A closure combines the code of a function with a special lexical environment bound to that function (scope). Closure lexical variables differ from global variables in that they do not occupy the global variable namespace. They differ from object oriented object variables in that they are bound to functions, not objects.". Normally closures aren't supported in Java so <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/JacobObject.java">JacobObject</a> tries to feel that gap. But it's not a true closure anyway, which makes thing easier. Closures in JaCOb are statically coded, whereas in most languages supporting closures these are dynamic. So basically in JaCOb, a closure is expected to implement some methods and provides other utility methods to manipulate channels and replicate itself.</p>
+<p><a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/JacobRunnable.java">JacobRunnable</a> is just a JacobObject that requires the implementation of only one method: run(). As ''all activities inherit from <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/JacobRunnable.java">JacobRunnable</a> they're all supposed to implement their main processing in this run() method. Their initialization occur in their respective constructors.</p>
+<p><a name="Jacob-MethodLists(MLs)"></a></p>
+<h3 id="method-lists-mls">Method Lists (MLs)</h3>
+<p>ML classes can be seen as the other end of a channel. Only they're not invoked directly when one calls a channel method, but only once the JaCOb engine has popped the channel invocation from its internal stack (again you can see how the execution stack gets broken here).</p>
+<p>Usually MLs implementations in ODE are inlined because it's just easier to declare them in the activities run() method. For example if you look at the Sequence example shown above you'll see something like:</p>
+<div class="codehilite"><pre><span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+<span class="o">...</span>
+ <span class="c1">// create an object to wait for the "completed()" notification</span>
+ <span class="c1">// from the child activity.</span>
+ <span class="n">object</span><span class="o">(</span><span class="k">new</span> <span class="n">CompletionChannelML</span><span class="o">(</span><span class="n">childCompletionChannel</span><span class="o">))</span> <span class="o">{</span>
+ <span class="kt">void</span> <span class="nf">completed</span><span class="o">()</span> <span class="o">{</span>
+ <span class="c1">// Ok, finished with the child, create a runner</span>
+ <span class="c1">// to do the next child.</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">SequenceChildRunner</span><span class="o">(</span><span class="n">currentChild</span><span class="o">+</span><span class="mi">1</span><span class="o">));</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>The object method here is inherited from !JacobObject and is just a way to hand our ML to JaCOb. So that the JaCOb runtime can match it with an incoming channel message later on.</p>
+<h2 id="vpu-and-executionqueue">VPU and ExecutionQueue</h2>
+<p>The <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/vpu/JacobVPU.java">VPU</a> is where all the JaCOb processing is occuring. When a JacobObject is injected inside the VPU, it's actually registered as a <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/soup/Continuation.java">Continuation</a>, which is just wrapping the JacobObject with the method to call on the JacobObject to execute it (in our case always the run() method as we're only dealing with JacobRunnable instances).</p>
+<p>The <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/soup/ExecutionQueue.java">ExecutionQueue</a> (and its implementation <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/vpu/FastExecutionQueueImpl.java">FastExecutionQueueImpl</a>) is just a container for all the artifacts managed by the VPU (mostly channels and reactions) to organize them in queues where artifacts can be pushed and popped. It also records some execution statistics.</p>
+<p>So the VPU main processing is just dequeuing a reaction from the soup and executing it by calling its abstraction's run() method (remember that the reaction just wraps an abstraction). That's all (check <a href="http://svn.apache.org/repos/asf/ode/trunk/jacob/src/main/java/org/apache/ode/jacob/vpu/JacobVPU.java">JacobVPU</a>.execute(), you'll see that I'm not lying). However when the JacobRunnable (usually an activity) gets executed the following things can happen:</p>
+<ul>
+<li>if other abstractions (usually other activities) are created, they will be appended to the reaction queue,</li>
+<li>if new channels are created, they will be saved for later usage,</li>
+<li>if channels are invoked, the message will be saved to match against a new ML,</li>
+<li>if a new ML instance is created, it will be submitted to the VPU that will try to match it against a channel invocation.</li>
+</ul>
+<p>The VPU is also responsible for persisting its internal state. So when an execution stops (for example our process has reach a receive) the VPU state is serialized and saved for later reuse. This logic can be seen in <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/RuntimeContextImpl">RuntimeContextImpl</a>.execute().</p>
+<p>There's one more thing that should be mentioned here. Continuations (and hence JacobRunnables) don't "stay" in the VPU queues. They just get popped, executed and that's it. So if an abstraction must last more than one execution, it should simply fork itself. This explains why in our Sequence example already pasted above we see the line:</p>
+<div class="codehilite"><pre><span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">SequenceChildRunner</span><span class="o">(</span><span class="n">currentChild</span><span class="o">+</span><span class="mi">1</span><span class="o">));</span>
+</pre></div>
+
+
+<p>This simple adds a new !ChildRunner that will monitor the next child completion. If you browse ODE's activities code you will even find things like instance(this) which directly enqueues a new instance of the same JaCOb abstraction.</p>
+<p><a name="Jacob-Walkingthroughexamples"></a></p>
+<h2 id="walking-through-examples">Walking through examples</h2>
+<p><a name="Jacob-While"></a></p>
+<h3 id="while">While</h3>
+<div class="codehilite"><pre><span class="nt"><process</span> <span class="na">name=</span><span class="s">"while1"</span>
+ <span class="na">targetNamespace=</span><span class="s">"http://ode/bpel/unit-test"</span>
+ <span class="na">xmlns:bpws=</span><span class="s">"http://schemas.xmlsoap.org/ws/2003/03/business-process/"</span>
+ <span class="na">xmlns=</span><span class="s">"http://schemas.xmlsoap.org/ws/2003/03/business-process/"</span>
+ <span class="na">xmlns:tns=</span><span class="s">"http://ode/bpel/unit-test"</span>
+ <span class="na">xmlns:xsd=</span><span class="s">"http://www.w3.org/2001/XMLSchema"</span>
+ <span class="na">xmlns:test=</span><span class="s">"http://ode/bpel/unit-test.wsdl"</span>
+ <span class="na">suppressJoinFailure=</span><span class="s">"yes"</span><span class="nt">></span>
+ <span class="nt"><partnerLinks></span>
+ <span class="nt"><partnerLink</span> <span class="na">name=</span><span class="s">"testPartnerLink"</span>
+ <span class="na">partnerLinkType=</span><span class="s">"test:TestPartnerLinkType"</span>
+ <span class="na">myRole=</span><span class="s">"me"</span> <span class="nt">/></span>
+ <span class="nt"></partnerLinks></span>
+
+ <span class="nt"><variables></span>
+ <span class="nt"><variable</span> <span class="na">name=</span><span class="s">"var1"</span> <span class="na">messageType=</span><span class="s">"test:TestMessage2"</span><span class="nt">/></span>
+ <span class="nt"></variables></span>
+
+ <span class="nt"><sequence></span>
+ <span class="nt"><receive</span>
+ <span class="na">createInstance=</span><span class="s">"yes"</span>
+ <span class="na">name=</span><span class="s">"startReceive"</span>
+ <span class="na">partnerLink=</span><span class="s">"testPartnerLink"</span>
+ <span class="na">portType=</span><span class="s">"test:TestPortType"</span>
+ <span class="na">operation=</span><span class="s">"testOperation"</span>
+ <span class="na">variable=</span><span class="s">"var1"</span><span class="nt">/></span>
+ <span class="nt"><while</span> <span class="na">condition=</span><span class="s">"bpws:getVariableData('var1', 'TestPart') &lt; 10"</span><span class="nt">></span>
+ <span class="nt"><assign></span>
+ <span class="nt"><copy></span>
+ <span class="nt"><from</span> <span class="na">expression=</span><span class="s">"bpws:getVariableData('var1', 'TestPart') + 1"</span><span class="nt">/></span>
+ <span class="nt"><to</span> <span class="na">variable=</span><span class="s">"var1"</span> <span class="na">part=</span><span class="s">"TestPart"</span><span class="nt">/></span>
+ <span class="nt"></copy></span>
+ <span class="nt"></assign></span>
+ <span class="nt"></while></span>
+ <span class="nt"><reply</span> <span class="na">name=</span><span class="s">"endReply"</span>
+ <span class="na">operation=</span><span class="s">"testOperation"</span>
+ <span class="na">partnerLink=</span><span class="s">"testPartnerLink"</span>
+ <span class="na">portType=</span><span class="s">"test:TestPortType"</span>
+ <span class="na">variable=</span><span class="s">"var1"</span><span class="nt">/></span>
+ <span class="nt"></sequence></span>
+<span class="nt"></process></span>
+</pre></div>
+
+
+<p>Everything starts with a receive. So our entry point here in our JaCOb-focused discussion is going to be <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/BpelProcess.java">BpelProcess</a>.PartnerLinkMyRoleImpl.inputMsgRcvd(). The code that matters to us now is the following (executed when a message is targeted at a createInstance receive):</p>
+<div class="codehilite"><pre><span class="n">BpelRuntimeContextImpl</span> <span class="n">instance</span> <span class="o">=</span> <span class="n">createRuntimeContext</span><span class="o">(</span><span class="n">newInstance</span><span class="o">,</span> <span class="k">new</span> <span class="n">PROCESS</span><span class="o">(</span><span class="n">_oprocess</span><span class="o">),</span> <span class="n">messageExchange</span><span class="o">);</span>
+<span class="o">...</span>
+<span class="c1">// run the vpu</span>
+<span class="n">instance</span><span class="o">.</span><span class="na">execute</span><span class="o">();</span>
+</pre></div>
+
+
+<p>If you check the code executed by !BpelRuntimeContextImpl constructor you'll see among other things the following:</p>
+<div class="codehilite"><pre><span class="k">if</span> <span class="o">(</span><span class="n">PROCESS</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">vpu</span><span class="o">.</span><span class="na">inject</span><span class="o">(</span><span class="n">PROCESS</span><span class="o">);</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>The process itself get injected. When executed, <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/PROCESS.java">PROCESS</a> just instantiates a scope to control the execution of its child activity and starts listening on compensation and completion channel. From the process we go to a scope, then our main sequence and finally our receive.</p>
+<p>Receives are just mapped to a pick onMessage so its JaCOb implementation should be looked for in <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/PICK.java">PICK</a>. The <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/PICK.java">PICK</a> is just about isolating the right correlations and selecting a message for it, then waiting for the message. In our createInstance case we'll be more interested in the following code, located in <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/BpelRuntimeContextImpl.java">BpelRuntimeContextImpl</a>.select() (and called by PICK):</p>
+<div class="codehilite"><pre><span class="k">if</span> <span class="o">(</span><span class="n">_instantiatingMessageExchange</span> <span class="o">!=</span> <span class="kc">null</span> <span class="o">&&</span> <span class="n">_dao</span><span class="o">.</span><span class="na">getState</span><span class="o">()</span> <span class="o">==</span> <span class="n">ProcessState</span><span class="o">.</span><span class="na">STATE_READY</span><span class="o">)</span> <span class="o">{</span>
+ <span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span> <span class="o">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">correlators</span><span class="o">.</span><span class="na">size</span><span class="o">();</span> <span class="o">++</span><span class="n">i</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">CorrelatorDAO</span> <span class="n">ci</span> <span class="o">=</span> <span class="n">correlators</span><span class="o">.</span><span class="na">get</span><span class="o">(</span><span class="n">i</span><span class="o">);</span>
+ <span class="k">if</span> <span class="o">(</span><span class="n">ci</span><span class="o">.</span><span class="na">equals</span><span class="o">(</span><span class="n">_dao</span><span class="o">.</span><span class="na">getInstantiatingCorrelator</span><span class="o">()))</span> <span class="o">{</span>
+ <span class="n">inputMsgMatch</span><span class="o">(</span><span class="n">pickResponseChannelStr</span><span class="o">,</span> <span class="n">i</span><span class="o">,</span> <span class="n">_instantiatingMessageExchange</span><span class="o">);</span>
+ <span class="k">return</span><span class="o">;</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>Which just happens to call something like:</p>
+<div class="codehilite"><pre><span class="n">vpu</span><span class="o">.</span><span class="na">inject</span><span class="o">(</span><span class="k">new</span> <span class="n">JacobRunnable</span><span class="o">()</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">PickResponseChannel</span> <span class="n">responseChannel</span> <span class="o">=</span> <span class="n">importChannel</span><span class="o">(</span><span class="n">responsechannel</span><span class="o">,</span> <span class="n">PickResponseChannel</span><span class="o">.</span><span class="na">class</span><span class="o">);</span>
+ <span class="n">responseChannel</span><span class="o">.</span><span class="na">onRequestRcvd</span><span class="o">(</span><span class="n">idx</span><span class="o">,</span> <span class="n">mex</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">});</span>
+</pre></div>
+
+
+<p>That's where things really start. When injected, this abstraction just calls the response channel for our receive. The other side of this channel is implemented as a ML in the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/PICK.java">PICK</a>:</p>
+<div class="codehilite"><pre><span class="n">object</span><span class="o">(</span><span class="kc">false</span><span class="o">,</span> <span class="k">new</span> <span class="n">PickResponseML</span><span class="o">(</span><span class="n">_pickResponseChannel</span><span class="o">)</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">onRequestRcvd</span><span class="o">(</span><span class="kt">int</span> <span class="n">selectorIdx</span><span class="o">,</span> <span class="n">Object</span> <span class="n">msgex</span><span class="o">)</span> <span class="o">{</span>
+ <span class="o">...</span>
+ <span class="n">ActivityInfo</span> <span class="n">child</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ActivityInfo</span><span class="o">(</span><span class="n">genMonotonic</span><span class="o">(),</span> <span class="n">onMessage</span><span class="o">.</span><span class="na">activity</span><span class="o">,</span> <span class="n">_self</span><span class="o">.</span><span class="na">self</span><span class="o">,</span> <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">);</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">createChild</span><span class="o">(</span><span class="n">child</span><span class="o">,</span><span class="n">_scopeFrame</span><span class="o">,</span><span class="n">_linkFrame</span><span class="o">));</span>
+ <span class="o">}</span>
+<span class="o">});</span>
+</pre></div>
+
+
+<p>This method just does what a receive needs to do (like variable and correlation initialization) and creates a new child. When dealing with a real pick, this child would be the onMessage activity, however in the case of a receive, this is an empty activity. So when does our receive completes? Well, when the child completes. As you can see on the child constructor, we're passing the same ParentScopeML that we've been provided. So when the child completes, the receive's parent is notified which means to our receive doesn't need to do it itself. And an empty immediately completes: </p>
+<div class="codehilite"><pre><span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">completed</span><span class="o">(</span><span class="kc">null</span><span class="o">,</span> <span class="n">CompensationHandler</span><span class="o">.</span><span class="na">emptySet</span><span class="o">());</span>
+</pre></div>
+
+
+<p>The parent sequence gets notified almost immediately after the onRequestRcvd() methods finishes.</p>
+<p>Now how does our sequence gets the control back? Well, once again, let's look at the ML, the other side of the channel. As one of the most important job of the VPU is matching channels invocations and MLs, we'll get to the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/SEQUENCE.java">sequence</a> by its ParentScopeML implementation:</p>
+<div class="codehilite"><pre><span class="kd">class</span> <span class="nc">SEQUENCE</span> <span class="kd">extends</span> <span class="n">ACTIVITY</span> <span class="o">{</span>
+ <span class="o">...</span>
+ <span class="kd">private</span> <span class="kd">class</span> <span class="nc">ACTIVE</span> <span class="kd">extends</span> <span class="n">BpelJacobRunnable</span> <span class="o">{</span>
+ <span class="o">....</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="o">...</span>
+ <span class="n">object</span><span class="o">(</span><span class="k">new</span> <span class="n">ParentScopeML</span><span class="o">(</span><span class="n">_child</span><span class="o">.</span><span class="na">parent</span><span class="o">)</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">compensate</span><span class="o">(</span><span class="n">OScope</span> <span class="n">scope</span><span class="o">,</span> <span class="n">SynchChannel</span> <span class="n">ret</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">compensate</span><span class="o">(</span><span class="n">scope</span><span class="o">,</span><span class="n">ret</span><span class="o">);</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">ACTIVE</span><span class="o">.</span><span class="na">this</span><span class="o">);</span>
+ <span class="o">}</span>
+
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">completed</span><span class="o">(</span><span class="n">FaultData</span> <span class="n">faultData</span><span class="o">,</span> <span class="n">Set</span><span class="o"><</span><span class="n">CompensationHandler</span><span class="o">></span> <span class="n">compensations</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">HashSet</span><span class="o"><</span><span class="n">CompensationHandler</span><span class="o">></span> <span class="n">comps</span> <span class="o">=</span> <span class="k">new</span> <span class="n">HashSet</span><span class="o"><</span><span class="n">CompensationHandler</span><span class="o">>(</span><span class="n">_compensations</span><span class="o">);</span>
+ <span class="n">comps</span><span class="o">.</span><span class="na">addAll</span><span class="o">(</span><span class="n">compensations</span><span class="o">);</span>
+ <span class="k">if</span> <span class="o">(</span><span class="n">faultData</span> <span class="o">!=</span> <span class="kc">null</span> <span class="o">||</span> <span class="n">_terminateRequested</span> <span class="o">||</span> <span class="n">_remaining</span><span class="o">.</span><span class="na">size</span><span class="o">()</span> <span class="o"><=</span> <span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">completed</span><span class="o">(</span><span class="n">faultData</span><span class="o">,</span> <span class="n">comps</span><span class="o">);</span>
+ <span class="o">}</span> <span class="k">else</span> <span class="cm">/* !fault && ! terminateRequested && !remaining.isEmpty */</span> <span class="o">{</span>
+ <span class="n">ArrayList</span><span class="o"><</span><span class="n">OActivity</span><span class="o">></span> <span class="n">remaining</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayList</span><span class="o"><</span><span class="n">OActivity</span><span class="o">>(</span><span class="n">_remaining</span><span class="o">);</span>
+ <span class="n">remaining</span><span class="o">.</span><span class="na">remove</span><span class="o">(</span><span class="mi">0</span><span class="o">);</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">SEQUENCE</span><span class="o">(</span><span class="n">_self</span><span class="o">,</span> <span class="n">_scopeFrame</span><span class="o">,</span> <span class="n">_linkFrame</span><span class="o">,</span> <span class="n">remaining</span><span class="o">,</span> <span class="n">comps</span><span class="o">));</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">}));</span>
+ <span class="o">}</span>
+ <span class="o">}</span>
+ <span class="o">...</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>The method that will get executed is of course the completed() method. It simply completes if a fault has been thrown, a termination has been requested and if no child activities remain. Being of an optimistic nature, we'll check what happens when everything goes just fine. In this second case a remaining activity is removed and the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/SEQUENCE.java">SEQUENCE</a> abstraction itself is reinstantiated. Which leads us to what the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/SEQUENCE.java">SEQUENCE</a> does:</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="kd">final</span> <span class="n">ActivityInfo</span> <span class="n">child</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ActivityInfo</span><span class="o">(</span><span class="n">genMonotonic</span><span class="o">(),</span>
+ <span class="n">_remaining</span><span class="o">.</span><span class="na">get</span><span class="o">(</span><span class="mi">0</span><span class="o">),</span>
+ <span class="n">newChannel</span><span class="o">(</span><span class="n">TerminationChannel</span><span class="o">.</span><span class="na">class</span><span class="o">),</span> <span class="n">newChannel</span><span class="o">(</span><span class="n">ParentScopeChannel</span><span class="o">.</span><span class="na">class</span><span class="o">));</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">createChild</span><span class="o">(</span><span class="n">child</span><span class="o">,</span> <span class="n">_scopeFrame</span><span class="o">,</span> <span class="n">_linkFrame</span><span class="o">));</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">ACTIVE</span><span class="o">(</span><span class="n">child</span><span class="o">));</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>As you can see, it just instantiates the next child abstraction and also another abstraction named ACTIVE. So what's this ACTIVE that we've already seen a bit before? Well, it's just the abstraction that keeps on following child activities when they execute. It's more like a convention on all containment-based activity in ODE (while, sequence, pick, ...) that the main activity abstraction just kicks off the processing. Then an ACTIVE (also sometimes called WAITER) abstraction takes care of following the children.</p>
+<p>Continuing to the next step, we've just instantiated an abstraction for the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/WHILE.java">while</a> in our example process, as it's the next child of the sequence. So what happens there?</p>
+<div class="codehilite"><pre><span class="kd">public</span> <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="kt">boolean</span> <span class="n">condResult</span> <span class="o">=</span> <span class="kc">false</span><span class="o">;</span>
+ <span class="k">try</span> <span class="o">{</span>
+ <span class="n">condResult</span> <span class="o">=</span> <span class="n">checkCondition</span><span class="o">();</span>
+ <span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="n">FaultException</span> <span class="n">fe</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">completed</span><span class="o">(</span><span class="n">createFault</span><span class="o">(</span><span class="n">fe</span><span class="o">.</span><span class="na">getQName</span><span class="o">(),</span> <span class="n">_self</span><span class="o">.</span><span class="na">o</span><span class="o">),</span><span class="n">_compHandlers</span><span class="o">);</span>
+ <span class="k">return</span><span class="o">;</span>
+ <span class="o">}</span>
+ <span class="k">if</span> <span class="o">(</span><span class="n">condResult</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">ActivityInfo</span> <span class="n">child</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ActivityInfo</span><span class="o">(</span><span class="n">genMonotonic</span><span class="o">(),</span>
+ <span class="n">getOWhile</span><span class="o">().</span><span class="na">activity</span><span class="o">,</span>
+ <span class="n">newChannel</span><span class="o">(</span><span class="n">TerminationChannel</span><span class="o">.</span><span class="na">class</span><span class="o">),</span> <span class="n">newChannel</span><span class="o">(</span><span class="n">ParentScopeChannel</span><span class="o">.</span><span class="na">class</span><span class="o">));</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">createChild</span><span class="o">(</span><span class="n">child</span><span class="o">,</span> <span class="n">_scopeFrame</span><span class="o">,</span> <span class="n">_linkFrame</span><span class="o">));</span>
+ <span class="n">instance</span><span class="o">(</span><span class="k">new</span> <span class="n">WAITER</span><span class="o">(</span><span class="n">child</span><span class="o">));</span>
+ <span class="o">}</span> <span class="k">else</span> <span class="cm">/* stop. */</span> <span class="o">{</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">completed</span><span class="o">(</span><span class="kc">null</span><span class="o">,</span> <span class="n">_compHandlers</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>Now you should be getting more familiar with that sort of code. First step is evaluating the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/WHILE.java">while</a> condition. If it turns out it's true, then a child abstraction gets created as well as a WAITER to follow its execution. The WAITER implementation is again pretty straightforward:</p>
+<div class="codehilite"><pre><span class="kd">private</span> <span class="kd">class</span> <span class="nc">WAITER</span> <span class="kd">extends</span> <span class="n">BpelJacobRunnable</span> <span class="o">{</span>
+ <span class="kd">private</span> <span class="n">ActivityInfo</span> <span class="n">_child</span><span class="o">;</span>
+ <span class="kd">private</span> <span class="kt">boolean</span> <span class="n">_terminated</span><span class="o">;</span>
+
+ <span class="n">WAITER</span><span class="o">(</span><span class="n">ActivityInfo</span> <span class="n">child</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_child</span> <span class="o">=</span> <span class="n">child</span><span class="o">;</span>
+ <span class="o">}</span>
+
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">run</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">object</span><span class="o">(</span><span class="kc">false</span><span class="o">,</span> <span class="k">new</span> <span class="n">TerminationML</span><span class="o">(</span><span class="n">_self</span><span class="o">.</span><span class="na">self</span><span class="o">)</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">terminate</span><span class="o">()</span> <span class="o">{</span>
+ <span class="n">_terminated</span> <span class="o">=</span> <span class="kc">true</span><span class="o">;</span>
+ <span class="n">_child</span><span class="o">.</span><span class="na">self</span><span class="o">.</span><span class="na">terminate</span><span class="o">();</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">WAITER</span><span class="o">.</span><span class="na">this</span><span class="o">);</span>
+ <span class="o">}</span>
+ <span class="o">}.</span><span class="na">or</span><span class="o">(</span><span class="k">new</span> <span class="n">ParentScopeML</span><span class="o">(</span><span class="n">_child</span><span class="o">.</span><span class="na">parent</span><span class="o">)</span> <span class="o">{</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">compensate</span><span class="o">(</span><span class="n">OScope</span> <span class="n">scope</span><span class="o">,</span> <span class="n">SynchChannel</span> <span class="n">ret</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">compensate</span><span class="o">(</span><span class="n">scope</span><span class="o">,</span><span class="n">ret</span><span class="o">);</span>
+ <span class="n">instance</span><span class="o">(</span><span class="n">WAITER</span><span class="o">.</span><span class="na">this</span><span class="o">);</span>
+ <span class="o">}</span>
+ <span class="kd">public</span> <span class="kt">void</span> <span class="nf">completed</span><span class="o">(</span><span class="n">FaultData</span> <span class="n">faultData</span><span class="o">,</span> <span class="n">Set</span><span class="o"><</span><span class="n">CompensationHandler</span><span class="o">></span> <span class="n">compensations</span><span class="o">)</span> <span class="o">{</span>
+ <span class="n">_compHandlers</span><span class="o">.</span><span class="na">addAll</span><span class="o">(</span><span class="n">compensations</span><span class="o">);</span>
+ <span class="k">if</span> <span class="o">(</span><span class="n">_terminated</span> <span class="o">||</span> <span class="n">faultData</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span>
+ <span class="n">_self</span><span class="o">.</span><span class="na">parent</span><span class="o">.</span><span class="na">completed</span><span class="o">(</span><span class="n">faultData</span><span class="o">,</span> <span class="n">compensations</span><span class="o">);</span>
+ <span class="k">else</span>
+ <span class="nf">instance</span><span class="o">(</span><span class="n">WHILE</span><span class="o">.</span><span class="na">this</span><span class="o">);</span>
+ <span class="o">}</span>
+ <span class="o">}));</span>
+ <span class="o">}</span>
+<span class="o">}</span>
+</pre></div>
+
+
+<p>Termination and compensation aren't doing anything really interesting. Completion, just like for the sequence, re-instantiates the <a href="http://svn.apache.org/repos/asf/ode/trunk/bpel-runtime/src/main/java/org/apache/ode/bpel/runtime/WHILE.java">WHILE</a> abstraction. And that's how we get our loop, by re-instantiating the main WHILE abstraction (again evaluating the condition and creating a child if it's true).</p>
+<p>Finally, when the while condition becomes false, it notifies its parent channel. The sequence then goes to our last activity: reply. As expected, the reply replies, just sending the variable content and notifying its parent for completion. The sequence has no more children to execute so it also notifies its own parent, which is the process. We then just declare the process to be completed and that's it! We're done!</p>
+ </div>
+ </div>
+
+
+ <!-- Footer -->
+ <footer class="footer">
+ <div class='row'>
+ <div class='span3'>
+ <img src="/img/asf.png" alt="Apache Software Foundation"/>
+ </div>
+ <div class='span9'>
+ <p><strong>Apache ODE</strong><sup>™</sup> is a top-level project at the <a href="http://www.apache.org">Apache Software Foundation<sup>™</sup></a>,
+ having graduated from the ASF Incubator in July 2007. Through a collaborative and meritocratic development process, Apache
+ projects deliver enterprise-grade, freely available software products that
+ attract large communities of users.</p>
+ <p>Apache ODE, ODE, Apache, the Apache feather logo, and the Apache ODE project logo are trademarks of The Apache Software Foundation. All other marks mentioned may be trademarks or registered trademarks of their respective owners.</p>
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Added: websites/staging/ode/trunk/content/developerguide/release-guidelines.html
==============================================================================
--- websites/staging/ode/trunk/content/developerguide/release-guidelines.html (added)
+++ websites/staging/ode/trunk/content/developerguide/release-guidelines.html Tue Dec 11 12:48:20 2012
@@ -0,0 +1,155 @@
+<!DOCTYPE html>
+<html>
+ <head>
+ <title>Release Guidelines</title>
+ <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
+ <meta property="og:image" content="http://ode.apache.org/img/ode-logo.png" />
+
+ <link href="/css/application.min.css" rel="stylesheet" media="screen">
+
+
+
+
+ </head>
+ <body>
+
+ <!-- Navbar -->
+ <div class="navbar navbar-fixed-top">
+ <div class="navbar-inner">
+ <div class="container">
+ <button type="button" class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse">
+ <span class="icon-bar"></span>
+ <span class="icon-bar"></span>
+ <span class="icon-bar"></span>
+ </button>
+ <a class="brand" href="/index.html">Apache ODE</a>
+ <div class="nav-collapse collapse">
+ <ul class="nav">
+ <li class="">
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+ </li>
+ <li class="active dropdown">
+ <a href="/user-guide.html" class="dropdown-toggle" data-toggle="dropdown" data-target="#">Documentation<b class="caret"></b></a>
+ <ul class="dropdown-menu">
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+ <li><a href="/developer-guide.html">Developer Guide</a></li>
+ <li><a href="/ws-bpel-20-specification-compliance.html">WS-BPEL Compliance</a></li>
+ <li><a href="/bpel-extensions.html">WS-BPEL Extensions</a></li>
+ <li><a href="/resource-services.html">Resources & Services</a></li>
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+
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+
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+
+
+ <!-- Content -->
+ <div class="container">
+
+ <div class="row">
+ <div class="span12">
+ <p><a name="ReleaseGuidelines-CheckList"></a></p>
+<h2 id="check-list">Check List</h2>
+<p>These guidelines are extracted from the <a href="http://incubator.apache.org/guides/releasemanagement.html#rules">incubator release guidelines</a> and other projects (like <a href="http://wiki.apache.org/avalon/AvalonReleaseManagerHowto">Avalon</a>) guidelines and are meant to be used as a reference for coming releases. It's not really a todo list for the next release (that will be handled in JIRA) but a general list of things to have right and the places they're best described.</p>
+<ul>
+<li>Analyze the list of bugs left for this specific release. Assess whether they're critical for the release or can be postponed to a subsequent release.</li>
+<li>The released archives should have "apache" and "ode" in their naming.</li>
+<li>A release should include both a source and a binary package.</li>
+<li>The source distro should include a BUILDING document.</li>
+<li>make sure the RELEASE_NOTES are up to date (version number, list of issues, links to JIRA, etc)</li>
+<li>Both distros should include a RELEASE_NOTES, the LICENSE</li>
+<li>Different distribution types should unpack to directories with different names (say apache-ode-x.x and apache-ode-src-x.x).</li>
+<li>Our releases don't include general documentation (only Javadoc) but a link to our website main documentation pages in the README.</li>
+<li>All our jars must include in the META-INF the LICENSE, the NOTICE, a <a href="http://jakarta.apache.org/commons/releases/prepare.html#checkjarmanifest">valid</a> MANIFEST.</li>
+<li>The NOTICE file must include: the standard Apache attribution and copyright notice, inherited copyright and attributions notices, all attribution and copyright notices required by licenses for third party documents.</li>
+<li>Releases should be built from tagged versions named APACHE_ODE_X_X (roughly same as the release itself but in capital to mark it different from other tags).</li>
+<li>All our source files should include the legal Apache header.</li>
+<li>The Java version should be clearly indicated either in README or RELEASE_NOTES (in addition to the MANIFEST).</li>
+</ul>
+<p><a name="ReleaseGuidelines-Verifyingtherelease"></a></p>
+<h2 id="verifying-the-release">Verifying the release</h2>
+<p>A complete <a href="http://incubator.apache.org/guides/releasemanagement.html#check-list">check list</a>.</p>
+<p><a name="ReleaseGuidelines-ReleaseProcess"></a></p>
+<h2 id="release-process">Release Process</h2>
+<p>Before the release is finalized, successive releases can be made release candidates. It is traditional that release managers use their Apache home space to make available release candidates. Release <a href="http://www.apache.org/dev/release-signing.html">signatures</a> should be included.</p>
+<p>Once the release has been cut, a vote should be done by the PPMC to validate the release. Once approved by the PPMC another vote must be done by the Incubator PMC for release final approval. This should be done on the incubator general mailing list and include a link to the release artifacts, a link to the PPMC release vote thread and a link to the tag from which the release has been cut. 3 binding +1s are required by members of the Incubator PMC.</p>
+<p><a name="ReleaseGuidelines-AnnouncingTheRelease"></a></p>
+<h2 id="announcing-the-release">Announcing The Release</h2>
+<ol>
+<li>Perform a release in JIRA and create a new release version in JIRA</li>
+<li>Update the download page for the release on the Website</li>
+<li>Mail the dev & user lists, and announce@apache.org</li>
+<li>Post a news entry on the Website</li>
+<li>Have a beer!</li>
+</ol>
+<p>Announcements should be signed by the release manager with the key used to sign the release. Note that this may mean creating a plain text signature on the machine used to sign the release and then transferring this.</p>
+<p>Announcements should be posted from the release manager's apache.org address.</p>
+ </div>
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+ <p><strong>Apache ODE</strong><sup>™</sup> is a top-level project at the <a href="http://www.apache.org">Apache Software Foundation<sup>™</sup></a>,
+ having graduated from the ASF Incubator in July 2007. Through a collaborative and meritocratic development process, Apache
+ projects deliver enterprise-grade, freely available software products that
+ attract large communities of users.</p>
+ <p>Apache ODE, ODE, Apache, the Apache feather logo, and the Apache ODE project logo are trademarks of The Apache Software Foundation. All other marks mentioned may be trademarks or registered trademarks of their respective owners.</p>
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