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Posted to commits@servicecomb.apache.org by ni...@apache.org on 2017/12/12 09:18:17 UTC
[20/57] [partial] incubator-servicecomb-website git commit: Generated
the static pages for asf-site
http://git-wip-us.apache.org/repos/asf/incubator-servicecomb-website/blob/08e1b43f/content/docs/company-on-kubernetes/index.html
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+ <meta itemprop="datePublished" content="August 21, 2017">
+
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+
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+ <h1 class="page__title" itemprop="headline">One-click Deployment at Kubernetes
+</h1>
+
+ <p class="page__meta"><i class="fa fa-clock-o" aria-hidden="true"></i>
+
+
+
+
+ 3 minute read
+
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+
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+
+
+
+ <section class="page__content" itemprop="text">
+ <p>Blog <a href="/docs/linuxcon-workshop-demo/">Linux Con Workshop Demo</a> describes how to use the ServiceComb rapid development company example, the typical enterprise application company example for fast micro-serviced.</p>
+
+<p>Now, <a href="https://github.com/ServiceComb/ServiceComb-Company-WorkShop.git">github</a> already provides a one-click deployment on the kubernetes cluster. This article is going to focus on the corresponding yaml file and service communication, which will be useful for developers develop and deploy micro-serviced application to the cloud based on the Company model.</p>
+
+<h2 id="one-click-deployment">One-click Deployment</h2>
+
+<p><a href="https://github.com/ServiceComb/ServiceComb-Company-WorkShop/blob/master/kubernetes/README.md">Run Company on Kubernetes Cluster</a> Provides a detailed user guide, company can be deployed in the kubernetes cluster easily thourgh the following three instructions,</p>
+
+<div class="language-shell highlighter-rouge"><pre class="highlight"><code>git clone https://github.com/ServiceComb/ServiceComb-Company-WorkShop.git
+
+<span class="nb">cd </span>ServiceComb-Company-WorkShop/kubernetes/
+
+bash start.sh
+</code></pre>
+</div>
+
+<h2 id="yaml-file-interpretation">Yaml File Interpretation</h2>
+
+<p>Take the author’s actual environment as an example:</p>
+
+<div class="language-shell highlighter-rouge"><pre class="highlight"><code><span class="gp">root@zenlin:~/src/LinuxCon-Beijing-WorkShop/kubernetes# </span>kubectl get pod -owide
+NAME READY STATUS RESTARTS AGE IP NODE
+company-beekeeper-3737555734-48sxf 1/1 Running 0 17s 10.244.2.49 zenlinnode2
+company-bulletin-board-4113647782-th91w 1/1 Running 0 17s 10.244.1.53 zenlinnode1
+company-doorman-3391375245-g0p8c 1/1 Running 0 17s 10.244.1.55 zenlinnode1
+company-manager-454733969-0c1g8 1/1 Running 0 16s 10.244.2.50 zenlinnode2
+company-worker-1085546725-x7zl4 1/1 Running 0 17s 10.244.1.54 zenlinnode1
+zipkin-508217170-0khr3 1/1 Running 0 17s 10.244.2.48 zenlinnode2
+</code></pre>
+</div>
+<p>Total of six pods, company manager, company-doorman, company-bulletin-board, company-worker, company-beekeeper, and zipkin, K8S cluster assigns the corresponding cluster IP to them.</p>
+
+<div class="language-bash highlighter-rouge"><pre class="highlight"><code><span class="gp">root@zenlin:~/src/LinuxCon-Beijing-WorkShop/kubernetes# </span>kubectl get svc -owide
+NAME CLUSTER-IP EXTERNAL-IP PORT<span class="o">(</span>S<span class="o">)</span> AGE SELECTOR
+company-bulletin-board 10.99.70.46 <none> 30100/TCP 12m io.kompose.service<span class="o">=</span>company-bulletin-board
+company-manager 10.100.61.227 <nodes> 8083:30301/TCP 12m io.kompose.service<span class="o">=</span>company-manager
+zipkin 10.104.92.198 <none> 9411/TCP 12m io.kompose.service<span class="o">=</span>zipkin
+</code></pre>
+</div>
+
+<p>Only three services are started, zipkin, bulletin-board, and company-manager, that is because the address of call chain and the bulletin-board need to be passed in the cluster to be called by other services, and the manager is the api gateway nedd to be visited outside the cluster.</p>
+
+<p>Read company-bulletin-board-service.yaml,</p>
+
+<div class="language-yaml highlighter-rouge"><pre class="highlight"><code> <span class="s">apiVersion</span><span class="pi">:</span> <span class="s">v1</span>
+ <span class="s">kind</span><span class="pi">:</span> <span class="s">Service</span>
+ <span class="s">metadata</span><span class="pi">:</span>
+ <span class="s">creationTimestamp</span><span class="pi">:</span> <span class="s">null</span>
+ <span class="s">labels</span><span class="pi">:</span>
+<span class="err"> </span><span class="s">io.kompose.service</span><span class="pi">:</span> <span class="s">company-bulletin-board</span>
+ <span class="s">name</span><span class="pi">:</span> <span class="s">company-bulletin-board</span>
+ <span class="s">spec</span><span class="pi">:</span>
+ <span class="s">ports</span><span class="pi">:</span>
+<span class="err"> </span><span class="pi">-</span> <span class="s">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">30100"</span>
+ <span class="s">port</span><span class="pi">:</span> <span class="s">30100</span>
+ <span class="s">targetPort</span><span class="pi">:</span> <span class="s">30100</span>
+ <span class="s">selector</span><span class="pi">:</span>
+ <span class="s">io.kompose.service</span><span class="pi">:</span> <span class="s">company-bulletin-board</span>
+ <span class="s">status</span><span class="pi">:</span>
+ <span class="s">loadBalancer</span><span class="pi">:</span> <span class="pi">{}</span>
+</code></pre>
+</div>
+<p>The file defines the service of bulletin-board, and defines the name, port, and targetPort for the service, which is created by ‘kubectl expose’ to keep DNS capability in the cluster. Thus, other services can access the bulletin board and registry themselves.</p>
+
+<p>To the label and selector, it is useful to the situation of one-service to multiple-pods，When a pod dies, it is automatically removed from the endpoints, and new pods matching the Service’s selector will automatically get added to the endpoints.</p>
+
+<p>Read company-worker-deployment.yaml,</p>
+<div class="language-yaml highlighter-rouge"><pre class="highlight"><code><span class="s">apiVersion</span><span class="pi">:</span> <span class="s">extensions/v1beta1</span>
+<span class="s">kind</span><span class="pi">:</span> <span class="s">Deployment</span>
+<span class="s">metadata</span><span class="pi">:</span>
+ <span class="s">creationTimestamp</span><span class="pi">:</span> <span class="s">null</span>
+ <span class="s">labels</span><span class="pi">:</span>
+<span class="err"> </span><span class="s">io.kompose.service</span><span class="pi">:</span> <span class="s">company-worker</span>
+ <span class="s">name</span><span class="pi">:</span> <span class="s">company-worker</span>
+<span class="s">spec</span><span class="pi">:</span>
+ <span class="s">replicas</span><span class="pi">:</span> <span class="s">1</span>
+ <span class="s">strategy</span><span class="pi">:</span> <span class="pi">{}</span>
+ <span class="s">template</span><span class="pi">:</span>
+<span class="err"> </span><span class="s">metadata</span><span class="pi">:</span>
+<span class="err"> </span><span class="s">creationTimestamp</span><span class="pi">:</span> <span class="s">null</span>
+ <span class="err"> </span><span class="s">labels</span><span class="pi">:</span>
+<span class="err"> </span><span class="s">io.kompose.service</span><span class="pi">:</span> <span class="s">company-worker</span>
+<span class="s">spec</span><span class="pi">:</span>
+ <span class="s">containers</span><span class="pi">:</span>
+ <span class="pi">-</span> <span class="s">env</span><span class="pi">:</span>
+ <span class="pi">-</span> <span class="s">name</span><span class="pi">:</span> <span class="s">ARTIFACT_ID</span>
+ <span class="s">value</span><span class="pi">:</span> <span class="s">worker</span>
+ <span class="pi">-</span> <span class="s">name</span><span class="pi">:</span> <span class="s">JAVA_OPTS</span>
+ <span class="s">value</span><span class="pi">:</span> <span class="s">-Dcse.service.registry.address=http://company-bulletin-board:30100 -Dservicecomb.tracing.collector.adress=http://zipkin:9411</span>
+ <span class="s">image</span><span class="pi">:</span> <span class="s">servicecomb/worker:0.0.1-SNAPSHOT</span>
+ <span class="s">name</span><span class="pi">:</span> <span class="s">company-worker</span>
+ <span class="s">ports</span><span class="pi">:</span>
+ <span class="pi">-</span> <span class="s">containerPort</span><span class="pi">:</span> <span class="s">7070</span>
+ <span class="pi">-</span> <span class="s">containerPort</span><span class="pi">:</span> <span class="s">8080</span>
+ <span class="s">resources</span><span class="pi">:</span> <span class="pi">{}</span>
+ <span class="s">restartPolicy</span><span class="pi">:</span> <span class="s">Always</span>
+<span class="s">status</span><span class="pi">:</span> <span class="pi">{}</span>
+</code></pre>
+</div>
+<p>The yaml defines a pod with one replica (replicas: 1), which can be modified to control the number of replicas of the pod(Anyway, the flexibility of the K8S scalability to achieve on-demand dynamic horizontal expansion to reach the purpose, material of K8S scalability will be provided later in the website). We mentioned that the company-bulletin-board is a DNS name, it is used as the value of cse.service.registry.address and passed to the service within the pod, such as: -Dcse.service. Registry.address = http: // company-bulletin-board: 30100, <a href="https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/README.md">kube-dns</a> Automatically resolve the servicename.</p>
+
+<p>Read <a href="https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/">connect-applications-service</a> to understanding the communication of services in K8S cluster.</p>
+
+<p>Other deployment.yaml and service.yaml are similar to the above except manager service, nodePort is defined in the company-manager-service.yaml to provide External-IP and Service-Port, as follows,</p>
+<div class="language-yaml highlighter-rouge"><pre class="highlight"><code><span class="s">spec</span><span class="pi">:</span>
+ <span class="s">ports</span><span class="pi">:</span>
+ <span class="pi">-</span> <span class="s">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">8083"</span>
+<span class="err"> </span><span class="s">port</span><span class="pi">:</span> <span class="s">8083</span>
+ <span class="err"> </span><span class="s">targetPort</span><span class="pi">:</span> <span class="s">8080</span>
+ <span class="err"> </span><span class="s">nodePort</span><span class="pi">:</span> <span class="s">30301</span>
+ <span class="err"> </span><span class="s">protocol</span><span class="pi">:</span> <span class="s">TCP</span>
+ <span class="s">type</span><span class="pi">:</span> <span class="s">NodePort</span>
+</code></pre>
+</div>
+
+<p>Get the External-IP and Service-Port by commands,</p>
+
+<div class="language-shell highlighter-rouge"><pre class="highlight"><code>kubectl get svc company-manager -o yaml | grep ExternalIP -C 1
+kubectl get svc company-manager -o yaml | grep nodePort -C 1
+</code></pre>
+</div>
+
+<p>Now, you can use the External-IP and nodePort to visit company, Read <a href="https://github.com/ServiceComb/ServiceComb-Company-WorkShop/blob/master/kubernetes/README.md">github.com/ServiceComb/ServiceComb-Company-WorkShop/kubernetes</a> to get details about how to visit it inside or outside the cluster.</p>
+
+<h2 id="model-induction">Model induction</h2>
+
+<p>You can sort out the following model by reading all the deployment.yaml and service.yaml in detail,</p>
+
+<p><img src="/assets/images/kubernetes-company.png" alt="kubernetes-company" class="align-center" /></p>
+
+<p>In addition, the classic air ticketing system ‘Acmeair’ has also been supported <a href="https://github.com/WillemJiang/acmeair/tree/master/kubernetes">one-click-deployment-at-kubernetes</a> based on the version developed by the ServiceComb framework.</p>
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+ <meta itemprop="headline" content="Eventual Data Consistency Solution in ServiceComb - part 1">
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+
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+
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+ <header>
+ <h1 class="page__title" itemprop="headline">Eventual Data Consistency Solution in ServiceComb - part 1
+</h1>
+
+ <p class="page__meta"><i class="fa fa-clock-o" aria-hidden="true"></i>
+
+
+
+
+ 5 minute read
+
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+
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+
+
+
+ <section class="page__content" itemprop="text">
+ <p>Data consistency is a critical aspect of many systems, especially in cloud and microservice environment. We recently
+released <a href="https://github.com/ServiceComb/saga">Saga</a> project under ServiceComb to address data consistency issue.
+But why is data consistency so important and what is Saga?</p>
+
+<h2 id="data-consistency-of-monolithic-applications">Data Consistency of Monolithic Applications</h2>
+<p>Imagine we are a giant corporation who runs an airline, a car rental company, and a hotel chain. We provide one-stop trip
+planning experience for our customers, so that they only have to provide a destination and we will book a flight, rent a
+car, and reserve a hotel room for them. From the business point of view, we have to make sure <strong>bookings with all the three
+are successful to make a successful trip plan, or there will be no plan</strong>.</p>
+
+<p>This requirement is easily satisfied with our current monolithic application. We just had to wrap all the three bookings
+in a single database transaction and they would all be done successfully or none was done.</p>
+
+<p><img src="/assets/images/saga.monolithic.png" alt="Monolithic Application" class="align-center" /></p>
+
+<p>When this feature released, our business was happy, and our customer was happy.</p>
+
+<h2 id="data-consistency-in-the-microservice-scenario">Data Consistency in the Microservice Scenario</h2>
+<p>In a few years, our corporation is doing so well on this trip planning business and our customers grow over tenfold. As
+more services provided by our airline, car rental company, and hotel chain, our application and development teams also
+grow. Now our monolith is so big and complex that not a single person understands how everything works together. What's
+even worse is that it takes weeks for all the development teams to put together their changes for a new release. Our business
+is not happy, since our market share is dropping due to the delay of our new features.</p>
+
+<p>We decide to split our monolith into four microservices, flight booking, car rental, hotel reservation, and payment, after
+several rounds of discussions. Services use their own database and communicate through HTTP requests. They are released
+according to their own schedule to meet the market needs. But we face a new problem: how do we ensure the original business
+rule of bookings with all three services must be successful to make a trip plan? A service cannot just access another's
+database, because it violates the service boundary and services may not use the same database technology.</p>
+
+<p><img src="/assets/images/saga.service.boundary.png" alt="Service Boundary" class="align-center" /></p>
+
+<h2 id="sagas">Sagas</h2>
+<p>We found a <a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">great paper</a> by Hector & Kenneth on the Internet talking about data consistency issues and this paper mentioned
+a terminology named Saga.</p>
+
+<blockquote>
+ <p>A saga refers to a long live transaction that can be broken into a collection of sub-transactions that can be interleaved
+in any way with other transactions. Each sub transactions in this case is a real transaction in the sense that it preserves
+database consistency. [<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</p>
+</blockquote>
+
+<p>In case of our business, a trip transaction is a saga which consists of four sub-transactions: flight booking, car rental,
+hotel reservation, and payment.</p>
+
+<p><img src="/assets/images/saga.transactions.png" alt="Transactions" class="align-center" /></p>
+
+<p>Saga is also described in <a href="http://www.chrisrichardson.net/">Chris Richardson</a>'s article: <a href="http://microservices.io/patterns/data/saga.html">Pattern: Saga</a>.</p>
+<blockquote>
+ <p>Chris Richardson is an experienced software architect, author of POJOs in Action and the creator of the original CloudFoundry.com. [3]</p>
+</blockquote>
+
+<p>Caitie McCaffrey also showed how she applied saga pattern in <a href="https://en.wikipedia.org/wiki/Halo_4">Halo 4</a> by Microsoft in <a href="https://www.youtube.com/watch?v=xDuwrtwYHu8">her talk</a>.</p>
+
+<h3 id="how-saga-works">How Saga Works</h3>
+<blockquote>
+ <p>The transactions in a saga are related to each other and should be executed as a (non-atomic) unit. Any partial executions
+of the saga are undesirable, and if they occur, must be compensated for. To amend partial executions, each saga transaction
+T<sub>1</sub> should be provided with a compensating transaction C<sub>1</sub>.[<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</p>
+</blockquote>
+
+<p>We define the following transactions and their corresponding compensations for our services according to the rule above:</p>
+
+<table>
+ <thead>
+ <tr>
+ <th style="text-align: center">Service</th>
+ <th style="text-align: center">Transaction</th>
+ <th style="text-align: center">Compensation</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td style="text-align: center">flight booking</td>
+ <td style="text-align: center">book flight</td>
+ <td style="text-align: center">cancel booking</td>
+ </tr>
+ <tr>
+ <td style="text-align: center">car rental</td>
+ <td style="text-align: center">rent car</td>
+ <td style="text-align: center">cancel booking</td>
+ </tr>
+ <tr>
+ <td style="text-align: center">hotel reservation</td>
+ <td style="text-align: center">reserve room</td>
+ <td style="text-align: center">cancel reservation</td>
+ </tr>
+ <tr>
+ <td style="text-align: center">payment</td>
+ <td style="text-align: center">pay</td>
+ <td style="text-align: center">refund</td>
+ </tr>
+ </tbody>
+</table>
+
+<blockquote>
+ <p>Once compensating transactions C<sub>1</sub>, C<sub>2</sub>, …, C<sub>n-1</sub> are defined for saga T<sub>1</sub>, T<sub>2</sub>, …, T<sub>n</sub>,
+then the system can make the following guarantee [<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</p>
+ <ul>
+ <li>either the sequence T<sub>1</sub>, T<sub>2</sub>, …, T<sub>n</sub> (which is the preferable one)</li>
+ <li>or the sequence T<sub>1</sub>, T<sub>2</sub>, …, T<sub>j</sub>, C<sub>j</sub>, …, C<sub>2</sub>, C<sub>1</sub>, for some 0 < j < n, will be executed</li>
+ </ul>
+</blockquote>
+
+<p>In another word, with the above defined transaction/compensation pairs, saga guarantees the following business rules are met:</p>
+<ul>
+ <li>all the bookings are either executed successfully, or cancelled if any of them fails</li>
+ <li>if the payment fails in the last step, all bookings are cancelled too</li>
+</ul>
+
+<h3 id="saga-recovery">Saga Recovery</h3>
+<p>Two types of saga recovery were described in the <a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">original paper</a>:</p>
+<ul>
+ <li><strong>backward recovery</strong> <em>compensates</em> all completed transactions if one failed</li>
+ <li><strong>forward recovery</strong> <em>retries</em> failed transactions, assuming every sub-transaction will eventually succeed</li>
+</ul>
+
+<p>Apparently there is no need for compensating transactions in forward recovery, which is useful if sub-transactions will
+always succeed (eventually) or compensations are very hard or impossible for your business.</p>
+
+<p>Theoretically compensating transactions shall never fail. However, in the distributed world, servers may go down, network
+can fail, and even data centers may go dark. What can we do in such situations? The last resort is to have fallbacks which
+may involve manual intervention.</p>
+
+<h3 id="the-restrictions-of-saga">The Restrictions of Saga</h3>
+<p>That looks promising. Are all long live transactions can be done this way? There are a few restrictions:</p>
+<ul>
+ <li>A saga only permits two levels of nesting, the top level saga and simple transactions [<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</li>
+ <li>At the outer level, full atomicity is not provided. That is, sagas may view the partial results of other sagas [<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</li>
+ <li>Each sub-transaction should be an independent atomic action [2]</li>
+</ul>
+
+<p>In our case, flight booking, car rental, hotel reservation, and payment are naturally independent actions and transaction
+of each can be performed atomically with their corresponding databases.</p>
+
+<p>We don't need atomicity at the trip transaction level either. One user may book the last seat on a flight which gets
+cancelled later due to insufficient balance in credit card. Another user may see the flight fully booked and one seat freed
+up for booking due to the cancellation. He/she can grab the last flight seat and complete the trip plan. It does not really
+matter to our business.</p>
+
+<p>There are also things to consider on compensations.</p>
+<blockquote>
+ <p>The compensating transaction undoes, from a semantic point of view, any of the actions performed by T<sub>i</sub>, but
+does not necessarily return the database to the state that existed when the execution of T<sub>i</sub> began. (For instance,
+if a transaction fires a missile, it may not be possible to undo this action) [<a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">1</a>]</p>
+</blockquote>
+
+<p>However, this is not a problem at all for our business. And it is still possible to compensate for actions hard to undo. For
+example, a transaction sending an email can be compensated by sending another email explaining the problem.</p>
+
+<h2 id="summary">Summary</h2>
+<p>Now we have a solution to tackle our data consistency issue with saga. It allows us to either successfully perform all
+transactions or compensate succeeded ones in case any fails. Although saga does not provide <a href="https://en.wikipedia.org/wiki/ACID">ACID</a> guarantee, it still suits
+many scenarios where eventual data consistency is enough. How do we design a saga system? Let's address the question in our
+next blog post.</p>
+
+<h2 id="references">References</h2>
+<ol>
+ <li><a href="https://www.cs.cornell.edu/andru/cs711/2002fa/reading/sagas.pdf">Original Paper on Sagas</a> by By Hector Garcia-Molina & Kenneth Salem</li>
+ <li>Gifford, David K and James E Donahue, “Coordinating Independent Atomic Actions”, Proceedings of IEEE COMPCON, San Francisco, CA, February, 1985</li>
+ <li>Chris Richardson: http://www.chrisrichardson.net/</li>
+ <li>ServiceComb Saga Project: https://github.com/ServiceComb/saga</li>
+</ol>
+
+
+
+ </section>
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