You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@flink.apache.org by uc...@apache.org on 2015/06/30 12:16:02 UTC
[32/51] [partial] flink-web git commit: [hotfix] Manual build of docs
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/internals/types_serialization.html
----------------------------------------------------------------------
diff --git a/content/docs/0.9/internals/types_serialization.html b/content/docs/0.9/internals/types_serialization.html
new file mode 100644
index 0000000..8637ada
--- /dev/null
+++ b/content/docs/0.9/internals/types_serialization.html
@@ -0,0 +1,438 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+<!DOCTYPE html>
+
+<html lang="en">
+ <head>
+ <meta charset="utf-8">
+ <meta http-equiv="X-UA-Compatible" content="IE=edge">
+ <meta name="viewport" content="width=device-width, initial-scale=1">
+ <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->
+
+ <title>Apache Flink 0.9.0 Documentation: Type Extraction and Serialization</title>
+
+ <link rel="shortcut icon" href="http://flink.apache.org/docs/0.9/page/favicon.ico" type="image/x-icon">
+ <link rel="icon" href="http://flink.apache.org/docs/0.9/page/favicon.ico" type="image/x-icon">
+
+ <!-- Bootstrap -->
+ <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
+ <link rel="stylesheet" href="http://flink.apache.org/docs/0.9/page/css/flink.css">
+ <link rel="stylesheet" href="http://flink.apache.org/docs/0.9/page/css/syntax.css">
+ <link rel="stylesheet" href="http://flink.apache.org/docs/0.9/page/css/codetabs.css">
+
+ <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
+ <!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
+ <!--[if lt IE 9]>
+ <script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
+ <script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
+ <![endif]-->
+ </head>
+ <body>
+
+
+
+
+
+
+ <!-- Top navbar. -->
+ <nav class="navbar navbar-default navbar-fixed-top">
+ <div class="container">
+ <!-- The logo. -->
+ <div class="navbar-header">
+ <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
+ <span class="icon-bar"></span>
+ <span class="icon-bar"></span>
+ <span class="icon-bar"></span>
+ </button>
+ <div class="navbar-logo">
+ <a href="http://flink.apache.org"><img alt="Apache Flink" src="http://flink.apache.org/docs/0.9/page/img/navbar-brand-logo.jpg"></a>
+ </div>
+ </div><!-- /.navbar-header -->
+
+ <!-- The navigation links. -->
+ <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
+ <ul class="nav navbar-nav">
+ <li><a href="http://flink.apache.org/docs/0.9/index.html">Overview<span class="hidden-sm hidden-xs"> 0.9.0</span></a></li>
+
+ <!-- Setup -->
+ <li class="dropdown">
+ <a href="http://flink.apache.org/docs/0.9/setup" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Setup <span class="caret"></span></a>
+ <ul class="dropdown-menu" role="menu">
+ <li><a href="http://flink.apache.org/docs/0.9/setup/building.html">Get Flink 0.9-SNAPSHOT</a></li>
+
+ <li class="divider"></li>
+ <li role="presentation" class="dropdown-header"><strong>Deployment</strong></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/local_setup.html" class="active">Local</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/cluster_setup.html">Cluster (Standalone)</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/yarn_setup.html">YARN</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/gce_setup.html">GCloud</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/flink_on_tez.html">Flink on Tez <span class="badge">Beta</span></a></li>
+
+ <li class="divider"></li>
+ <li><a href="http://flink.apache.org/docs/0.9/setup/config.html">Configuration</a></li>
+ </ul>
+ </li>
+
+ <!-- Programming Guides -->
+ <li class="dropdown">
+ <a href="http://flink.apache.org/docs/0.9/apis" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Programming Guides <span class="caret"></span></a>
+ <ul class="dropdown-menu" role="menu">
+ <li><a href="http://flink.apache.org/docs/0.9/apis/programming_guide.html"><strong>Batch: DataSet API</strong></a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/streaming_guide.html"><strong>Streaming: DataStream API</strong> <span class="badge">Beta</span></a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/python.html">Python API <span class="badge">Beta</span></a></li>
+
+ <li class="divider"></li>
+ <li><a href="scala_shell.html">Interactive Scala Shell</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/dataset_transformations.html">Dataset Transformations</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/best_practices.html">Best Practices</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/example_connectors.html">Connectors</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/examples.html">Examples</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/local_execution.html">Local Execution</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/cluster_execution.html">Cluster Execution</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/cli.html">Command Line Interface</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/web_client.html">Web Client</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/iterations.html">Iterations</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/java8.html">Java 8</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/apis/hadoop_compatibility.html">Hadoop Compatability <span class="badge">Beta</span></a></li>
+ </ul>
+ </li>
+
+ <!-- Libraries -->
+ <li class="dropdown">
+ <a href="http://flink.apache.org/docs/0.9/libs" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Libraries <span class="caret"></span></a>
+ <ul class="dropdown-menu" role="menu">
+ <li><a href="http://flink.apache.org/docs/0.9/libs/spargel_guide.html">Graphs: Spargel</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/libs/gelly_guide.html">Graphs: Gelly <span class="badge">Beta</span></a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/libs/ml/">Machine Learning <span class="badge">Beta</span></a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/libs/table.html">Relational: Table <span class="badge">Beta</span></a></li>
+ </ul>
+ </li>
+
+ <!-- Internals -->
+ <li class="dropdown">
+ <a href="http://flink.apache.org/docs/0.9/internals" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Internals <span class="caret"></span></a>
+ <ul class="dropdown-menu" role="menu">
+ <li role="presentation" class="dropdown-header"><strong>Contribute</strong></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/how_to_contribute.html">How to Contribute</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/coding_guidelines.html">Coding Guidelines</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/ide_setup.html">IDE Setup</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/logging.html">Logging</a></li>
+ <li class="divider"></li>
+ <li role="presentation" class="dropdown-header"><strong>Internals</strong></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/general_arch.html">Architecture & Process Model</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/types_serialization.html">Type Extraction & Serialization</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/job_scheduling.html">Jobs & Scheduling</a></li>
+ <li><a href="http://flink.apache.org/docs/0.9/internals/add_operator.html">How-To: Add an Operator</a></li>
+ </ul>
+ </li>
+ </ul>
+ <form class="navbar-form navbar-right hidden-sm hidden-md" role="search" action="http://flink.apache.org/docs/0.9/search-results.html">
+ <div class="form-group">
+ <input type="text" class="form-control" name="q" placeholder="Search all pages">
+ </div>
+ <button type="submit" class="btn btn-default">Search</button>
+ </form>
+ </div><!-- /.navbar-collapse -->
+ </div><!-- /.container -->
+ </nav>
+
+
+
+
+ <!-- Main content. -->
+ <div class="container">
+
+
+<div class="row">
+ <div class="col-sm-10 col-sm-offset-1">
+ <h1>Type Extraction and Serialization</h1>
+
+
+
+<p>Flink handles types in a unique way, containing its own type descriptors,
+generic type extraction, and type serialization framework.
+This document describes the concepts and the rationale behind them.</p>
+
+<p>There are fundamental differences in the way that the Scala API and
+the Java API handle type information, so most of the issues described
+here relate only to one of the to APIs.</p>
+
+<ul id="markdown-toc">
+ <li><a href="#type-handling-in-flink" id="markdown-toc-type-handling-in-flink">Type handling in Flink</a></li>
+ <li><a href="#flinks-typeinformation-class" id="markdown-toc-flinks-typeinformation-class">Flink’s TypeInformation class</a></li>
+ <li><a href="#type-information-in-the-scala-api" id="markdown-toc-type-information-in-the-scala-api">Type Information in the Scala API</a></li>
+ <li><a href="#type-information-in-the-java-api" id="markdown-toc-type-information-in-the-java-api">Type Information in the Java API</a></li>
+</ul>
+
+<h2 id="type-handling-in-flink">Type handling in Flink</h2>
+
+<p>Flink tries to know as much information about what types enter and leave user functions as possible.
+This stands in contrast to the approach to just assuming nothing and letting the
+programming language and serialization framework handle all types dynamically.</p>
+
+<ul>
+ <li>
+ <p>To allow using POJOs and grouping/joining them by referring to field names, Flink needs the type
+information to make checks (for typos and type compatibility) before the job is executed.</p>
+ </li>
+ <li>
+ <p>The more we know, the better serialization and data layout schemes the compiler/optimizer can develop.
+That is quite important for the memory usage paradigm in Flink (work on serialized data
+inside/outside the heap and make serialization very cheap).</p>
+ </li>
+ <li>
+ <p>For the upcoming logical programs (see roadmap draft) we need this to know the “schema” of functions.</p>
+ </li>
+ <li>
+ <p>Finally, it also spares users having to worry about serialization frameworks and having to register
+types at those frameworks.</p>
+ </li>
+</ul>
+
+<h2 id="flinks-typeinformation-class">Flink’s TypeInformation class</h2>
+
+<p>The class <a href="https://github.com/apache/flink/blob/master//flink-core/src/main/java/org/apache/flink/api/common/typeinfo/TypeInformation.java">TypeInformation</a>
+is the base class for all type descriptors. It reveals some basic properties of the type and can generate serializers
+and, in specializations, comparators for the types.
+(<em>Note that comparators in Flink do much more than defining an order - they are basically the utility to handle keys</em>)</p>
+
+<p>Internally, Flink makes the following distinctions between types:</p>
+
+<ul>
+ <li>
+ <p>Basic types: All Java primitives and their boxed form, plus <code>void</code>, <code>String</code>, and <code>Date</code>.</p>
+ </li>
+ <li>
+ <p>Primitive arrays and Object arrays</p>
+ </li>
+ <li>
+ <p>Composite types</p>
+
+ <ul>
+ <li>
+ <p>Flink Java Tuples (part of the Flink Java API)</p>
+ </li>
+ <li>
+ <p>Scala <em>case classes</em> (including Scala tuples)</p>
+ </li>
+ <li>
+ <p>POJOs: classes that follow a certain bean-like pattern</p>
+ </li>
+ </ul>
+ </li>
+ <li>
+ <p>Scala auxiliary types (Option, Either, Lists, Maps, …)</p>
+ </li>
+ <li>
+ <p>Generic types: These will not be serialized by Flink itself, but by Kryo.</p>
+ </li>
+</ul>
+
+<p>POJOs are of particular interest, because they support the creation of complex types and the use of field
+names in the definition of keys: <code>dataSet.join(another).where("name").equalTo("personName")</code>.
+They are also transparent to the runtime and can be handled very efficiently by Flink.</p>
+
+<p><strong>Rules for POJO types</strong></p>
+
+<p>Flink recognizes a data type as a POJO type (and allows “by-name” field referencing) if the following
+conditions are fulfilled:</p>
+
+<ul>
+ <li>The class is public and standalone (no non-static inner class)</li>
+ <li>The class has a public no-argument constructor</li>
+ <li>All fields in the class (and all superclasses) are either public or
+or have a public getter and a setter method that follows the Java beans
+naming conventions for getters and setters.</li>
+</ul>
+
+<h2 id="type-information-in-the-scala-api">Type Information in the Scala API</h2>
+
+<p>Scala has very elaborate concepts for runtime type information though <em>type manifests</em> and <em>class tags</em>. In
+general, types and methods have access to the types of their generic parameters - thus, Scala programs do
+not suffer from type erasure as Java programs do.</p>
+
+<p>In addition, Scala allows to run custom code in the Scala Compiler through Scala Macros - that means that some Flink
+code gets executed whenever you compile a Scala program written against Flink’s Scala API.</p>
+
+<p>We use the Macros to look at the parameter types and return types of all user functions during compilation - that
+is the point in time when certainly all type information is perfectly available. Within the macro, we create
+a <em>TypeInformation</em> for the function’s return types (or parameter types) and make it part of the operation.</p>
+
+<h4 id="no-implicit-value-for-evidence-parameter-error">No Implicit Value for Evidence Parameter Error</h4>
+
+<p>In the case where TypeInformation could not be created, programs fail to compile with an error
+stating <em>“could not find implicit value for evidence parameter of type TypeInformation”</em>.</p>
+
+<p>A frequent reason if that the code that generates the TypeInformation has not been imported.
+Make sure to import the entire flink.api.scala package.</p>
+
+<div class="highlight"><pre><code class="language-scala" data-lang="scala"><span class="k">import</span> <span class="nn">org.apache.flink.api.scala._</span></code></pre></div>
+
+<p>Another common cause are generic methods, which can be fixed as described in the following section.</p>
+
+<h4 id="generic-methods">Generic Methods</h4>
+
+<p>Consider the following case below:</p>
+
+<div class="highlight"><pre><code class="language-scala" data-lang="scala"><span class="k">def</span><span class="o">[</span><span class="kt">T</span><span class="o">]</span> <span class="n">selectFirst</span><span class="o">(</span><span class="n">input</span><span class="k">:</span> <span class="kt">DataSet</span><span class="o">[(</span><span class="kt">T</span>, <span class="k">_</span><span class="o">)])</span> <span class="k">:</span> <span class="kt">DataSet</span><span class="o">[</span><span class="kt">T</span><span class="o">]</span> <span class="k">=</span> <span class="o">{</span>
+ <span class="n">input</span><span class="o">.</span><span class="n">map</span> <span class="o">{</span> <span class="n">v</span> <span class="k">=></span> <span class="n">v</span><span class="o">.</span><span class="n">_1</span> <span class="o">}</span>
+<span class="o">}</span>
+
+<span class="k">val</span> <span class="n">data</span> <span class="k">:</span> <span class="kt">DataSet</span><span class="o">[(</span><span class="kt">String</span>, <span class="kt">Long</span><span class="o">)</span> <span class="kt">=</span> <span class="kt">...</span>
+
+<span class="kt">val</span> <span class="kt">result</span> <span class="kt">=</span> <span class="kt">selectFirst</span><span class="o">(</span><span class="kt">data</span><span class="o">)</span></code></pre></div>
+
+<p>For such generic methods, the data types of the function parameters and return type may not be the same
+for every call and are not known at the site where the method is defined. The code above will result
+in an error that not enough implicit evidence is available.</p>
+
+<p>In such cases, the type information has to be generated at the invocation site and passed to the
+method. Scala offers <em>implicit parameters</em> for that.</p>
+
+<p>The following code tells Scala to bring a type information for <em>T</em> into the function. The type
+information will then be generated at the sites where the method is invoked, rather than where the
+method is defined.</p>
+
+<div class="highlight"><pre><code class="language-scala" data-lang="scala"><span class="k">def</span><span class="o">[</span><span class="kt">T</span> <span class="kt">:</span> <span class="kt">TypeInformation</span><span class="o">]</span> <span class="n">selectFirst</span><span class="o">(</span><span class="n">input</span><span class="k">:</span> <span class="kt">DataSet</span><span class="o">[(</span><span class="kt">T</span>, <span class="k">_</span><span class="o">)])</span> <span class="k">:</span> <span class="kt">DataSet</span><span class="o">[</span><span class="kt">T</span><span class="o">]</span> <span class="k">=</span> <span class="o">{</span>
+ <span class="n">input</span><span class="o">.</span><span class="n">map</span> <span class="o">{</span> <span class="n">v</span> <span class="k">=></span> <span class="n">v</span><span class="o">.</span><span class="n">_1</span> <span class="o">}</span>
+<span class="o">}</span></code></pre></div>
+
+<h2 id="type-information-in-the-java-api">Type Information in the Java API</h2>
+
+<p>Java in general erases generic type information. Only for subclasses of generic classes, the subclass
+stores the type to which the generic type variables bind.</p>
+
+<p>Flink uses reflection on the (anonymous) classes that implement the user functions to figure out the types of
+the generic parameters of the function. This logic also contains some simple type inference for cases where
+the return types of functions are dependent on input types, such as in the generic utility method below:</p>
+
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">AppendOne</span><span class="o"><</span><span class="n">T</span><span class="o">></span> <span class="kd">extends</span> <span class="n">MapFunction</span><span class="o"><</span><span class="n">T</span><span class="o">,</span> <span class="n">Tuple2</span><span class="o"><</span><span class="n">T</span><span class="o">,</span> <span class="n">Long</span><span class="o">>></span> <span class="o">{</span>
+
+ <span class="kd">public</span> <span class="n">Tuple2</span><span class="o"><</span><span class="n">T</span><span class="o">,</span> <span class="n">Long</span><span class="o">></span> <span class="nf">map</span><span class="o">(</span><span class="n">T</span> <span class="n">value</span><span class="o">)</span> <span class="o">{</span>
+ <span class="k">return</span> <span class="k">new</span> <span class="n">Tuple2</span><span class="o"><</span><span class="n">T</span><span class="o">,</span> <span class="n">Long</span><span class="o">>(</span><span class="n">value</span><span class="o">,</span> <span class="mi">1L</span><span class="o">);</span>
+ <span class="o">}</span>
+<span class="o">}</span></code></pre></div>
+
+<p>Not in all cases can Flink figure out the data types of functions reliably in Java.
+Some issues remain with generic lambdas (we are trying to solve this with the Java community,
+see below) and with generic type variables that we cannot infer.</p>
+
+<h4 id="type-hints-in-the-java-api">Type Hints in the Java API</h4>
+
+<p>To help cases where Flink cannot reconstruct the erased generic type information, the Java API
+offers so called <em>type hints</em> from version 0.9 on. The type hints tell the system the type of
+the data set produced by a function. The following gives an example:</p>
+
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">DataSet</span><span class="o"><</span><span class="n">SomeType</span><span class="o">></span> <span class="n">result</span> <span class="o">=</span> <span class="n">dataSet</span>
+ <span class="o">.</span><span class="na">map</span><span class="o">(</span><span class="k">new</span> <span class="n">MyGenericNonInferrableFunction</span><span class="o"><</span><span class="n">Long</span><span class="o">,</span> <span class="n">SomeType</span><span class="o">>())</span>
+ <span class="o">.</span><span class="na">returns</span><span class="o">(</span><span class="n">SomeType</span><span class="o">.</span><span class="na">class</span><span class="o">);</span></code></pre></div>
+
+<p>The <code>returns</code> statement specifies the produced type, in this case via a class. The hints support
+type definition through</p>
+
+<ul>
+ <li>Classes, for non-parameterized types (no generics)</li>
+ <li>Strings in the form of <code>returns("Tuple2<Integer, my.SomeType>")</code>, which are parsed and converted
+to a TypeInformation.</li>
+ <li>A TypeInformation directly</li>
+</ul>
+
+<h4 id="type-extraction-for-java-8-lambdas">Type extraction for Java 8 lambdas</h4>
+
+<p>Type extraction for Java 8 lambdas works differently than for non-lambdas, because lambdas are not associated
+with an implementing class that extends the function interface.</p>
+
+<p>Currently, Flink tries to figure out which method implements the lambda and uses Java’s generic signatures to
+determine the parameter types and the return type. However, these signatures are not generated for lambdas
+by all compilers (as of writing this document only reliably by the Eclipse JDT compiler 4.5 from Milestone 2
+onwards)</p>
+
+<p><strong>Improving Type information for Java Lambdas</strong></p>
+
+<p>One of the Flink committers (Timo Walther) has actually become active in the Eclipse JDT compiler community and
+in the OpenJDK community and submitted patches to the compiler to improve availability of type information
+available for Java 8 lambdas.</p>
+
+<p>The Eclipse JDT compiler has added support for this as of version 4.5 M4. Discussion about the feature in the
+OpenJDK compiler is pending.</p>
+
+<h4 id="serialization-of-pojo-types">Serialization of POJO types</h4>
+
+<p>The PojoTypeInformation is creating serializers for all the fields inside the POJO. Standard types such as
+int, long, String etc. are handled by serializers we ship with Flink.
+For all other types, we fall back to Kryo.</p>
+
+<p>If Kryo is not able to handle the type, you can ask the PojoTypeInfo to serialize the POJO using Avro.
+To do so, you have to call</p>
+
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">final</span> <span class="n">ExecutionEnvironment</span> <span class="n">env</span> <span class="o">=</span> <span class="n">ExecutionEnvironment</span><span class="o">.</span><span class="na">getExecutionEnvironment</span><span class="o">();</span>
+<span class="n">env</span><span class="o">.</span><span class="na">getConfig</span><span class="o">().</span><span class="na">enableForceAvro</span><span class="o">();</span></code></pre></div>
+
+<p>Note that Flink is automatically serializing POJOs generated by Avro with the Avro serializer.</p>
+
+<p>If you want your <strong>entire</strong> POJO Type to be treated by the Kryo serializer, set</p>
+
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">final</span> <span class="n">ExecutionEnvironment</span> <span class="n">env</span> <span class="o">=</span> <span class="n">ExecutionEnvironment</span><span class="o">.</span><span class="na">getExecutionEnvironment</span><span class="o">();</span>
+<span class="n">env</span><span class="o">.</span><span class="na">getConfig</span><span class="o">().</span><span class="na">enableForceKryo</span><span class="o">();</span></code></pre></div>
+
+<p>If Kryo is not able to serialize your POJO, you can add a custom serializer to Kryo, using</p>
+
+<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">env</span><span class="o">.</span><span class="na">getConfig</span><span class="o">().</span><span class="na">addDefaultKryoSerializer</span><span class="o">(</span><span class="n">Class</span><span class="o"><?></span> <span class="n">type</span><span class="o">,</span> <span class="n">Class</span><span class="o"><?</span> <span class="kd">extends</span> <span class="n">Serializer</span><span class="o"><?>></span> <span class="n">serializerClass</span><span class="o">)</span></code></pre></div>
+
+<p>There are different variants of these methods available.</p>
+
+
+ </div>
+
+ <div class="col-sm-10 col-sm-offset-1">
+ <!-- Disqus thread and some vertical offset -->
+ <div style="margin-top: 75px; margin-bottom: 50px" id="disqus_thread"></div>
+ </div>
+</div>
+
+ </div><!-- /.container -->
+
+ <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
+ <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
+ <!-- Include all compiled plugins (below), or include individual files as needed -->
+ <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
+ <script src="http://flink.apache.org/docs/0.9/page/js/codetabs.js"></script>
+
+ <!-- Google Analytics -->
+ <script>
+ (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
+ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
+ m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
+ })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
+
+ ga('create', 'UA-52545728-1', 'auto');
+ ga('send', 'pageview');
+ </script>
+
+ <!-- Disqus -->
+ <script type="text/javascript">
+ var disqus_shortname = 'stratosphere-eu';
+ (function() {
+ var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true;
+ dsq.src = '//' + disqus_shortname + '.disqus.com/embed.js';
+ (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq);
+ })();
+</script>
+ </body>
+</html>
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/LICENSE.txt
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/LICENSE.txt b/content/docs/0.9/libs/fig/LICENSE.txt
new file mode 100644
index 0000000..35b8673
--- /dev/null
+++ b/content/docs/0.9/libs/fig/LICENSE.txt
@@ -0,0 +1,17 @@
+All image files in the folder and its subfolders are
+licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
\ No newline at end of file
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-example-graph.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-example-graph.png b/content/docs/0.9/libs/fig/gelly-example-graph.png
new file mode 100644
index 0000000..abef960
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-example-graph.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-filter.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-filter.png b/content/docs/0.9/libs/fig/gelly-filter.png
new file mode 100644
index 0000000..cb09744
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-filter.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-gsa-sssp-result.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-gsa-sssp-result.png b/content/docs/0.9/libs/fig/gelly-gsa-sssp-result.png
new file mode 100644
index 0000000..6ae74dd
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-gsa-sssp-result.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-gsa-sssp1.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-gsa-sssp1.png b/content/docs/0.9/libs/fig/gelly-gsa-sssp1.png
new file mode 100644
index 0000000..1141e14
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-gsa-sssp1.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-gsa-sssp2.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-gsa-sssp2.png b/content/docs/0.9/libs/fig/gelly-gsa-sssp2.png
new file mode 100644
index 0000000..edf19b8
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-gsa-sssp2.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-reduceOnEdges.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-reduceOnEdges.png b/content/docs/0.9/libs/fig/gelly-reduceOnEdges.png
new file mode 100644
index 0000000..ffb674d
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-reduceOnEdges.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-reduceOnNeighbors.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-reduceOnNeighbors.png b/content/docs/0.9/libs/fig/gelly-reduceOnNeighbors.png
new file mode 100644
index 0000000..63137b8
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-reduceOnNeighbors.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-union.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-union.png b/content/docs/0.9/libs/fig/gelly-union.png
new file mode 100644
index 0000000..b00f831
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-union.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-vc-sssp1.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-vc-sssp1.png b/content/docs/0.9/libs/fig/gelly-vc-sssp1.png
new file mode 100644
index 0000000..5feab62
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-vc-sssp1.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/gelly-vc-sssp2.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/gelly-vc-sssp2.png b/content/docs/0.9/libs/fig/gelly-vc-sssp2.png
new file mode 100644
index 0000000..67976b3
Binary files /dev/null and b/content/docs/0.9/libs/fig/gelly-vc-sssp2.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/spargel_example.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/spargel_example.png b/content/docs/0.9/libs/fig/spargel_example.png
new file mode 100644
index 0000000..21d20f8
Binary files /dev/null and b/content/docs/0.9/libs/fig/spargel_example.png differ
http://git-wip-us.apache.org/repos/asf/flink-web/blob/396616d4/content/docs/0.9/libs/fig/spargel_example_input.png
----------------------------------------------------------------------
diff --git a/content/docs/0.9/libs/fig/spargel_example_input.png b/content/docs/0.9/libs/fig/spargel_example_input.png
new file mode 100644
index 0000000..01ead46
Binary files /dev/null and b/content/docs/0.9/libs/fig/spargel_example_input.png differ