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<title>3. Service Discovery with Consul</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud-consul.html" title="Spring Cloud Consul"><link rel="up" href="multi_spring-cloud-consul.html" title="Spring Cloud Consul"><link rel="prev" href="multi_spring-cloud-consul-agent.html" title="2. Consul Agent"><link rel="next" href="multi_spring-cloud-consul-config.html" title="4. Distributed Configuration with Consul"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">3. Service Discovery with Consul</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi_spring-cloud-consul-agent.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="multi_spring-cloud-consul-config.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-discovery" href="#spring-cloud-consul-discovery"></a>3. Service Discovery with Consul</h1></div></div></div><p>Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. Consul provides Service Discovery services via an <a class="link" href="https://www.consul.io/docs/agent/http.html" target="_top">HTTP API</a> and <a class="link" href="https://www.consul.io/docs/agent/dns.html" target="_top">DNS</a>. Spring Cloud Consul leverages the HTTP API for service registration and discovery. This does not prevent non-Spring Cloud applications from leveraging the DNS interface. Consul Agents servers are run in a <a class="link" href="https://www.consul.io/docs/internals/architecture.html" target="_top">cluster</a> that communicates via a <a class="link" href="https://www.consul.io/docs/internals/gossip.html" target="_top">gossip protocol</a> and uses the <a class="link" href="https://www.consul.io/docs/internals/consensus.html" target="_top">Raft consensus protocol</a>.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_how_to_activate" href="#_how_to_activate"></a>3.1 How to activate</h2></div></div></div><p>To activate Consul Service Discovery use the starter with group <code class="literal">org.springframework.cloud</code> and artifact id <code class="literal">spring-cloud-starter-consul-discovery</code>. See the <a class="link" href="http://projects.spring.io/spring-cloud/" target="_top">Spring Cloud Project page</a> for details on setting up your build system with the current Spring Cloud Release Train.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_registering_with_consul" href="#_registering_with_consul"></a>3.2 Registering with Consul</h2></div></div></div><p>When a client registers with Consul, it provides meta-data about itself such as host and port, id, name and tags. An HTTP <a class="link" href="https://www.consul.io/docs/agent/checks.html" target="_top">Check</a> is created by default that Consul hits the <code class="literal">/health</code> endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.</p><p>Example Consul client:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@SpringBootApplication</span></em>
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<em><span class="hl-annotation" style="color: gray">@EnableDiscoveryClient</span></em>
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<em><span class="hl-annotation" style="color: gray">@RestController</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> Application {
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consul:
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host: localhost
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port: 8500</pre><p>
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</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left">Caution</th></tr><tr><td align="left" valign="top"><p>If you use <a class="link" href="multi_spring-cloud-consul-config.html" title="4. Distributed Configuration with Consul">Spring Cloud Consul Config</a>, the above values will need to be placed in <code class="literal">bootstrap.yml</code> instead of <code class="literal">application.yml</code>.</p></td></tr></table></div><p>The default service name, instance id and port, taken from the <code class="literal">Environment</code>, are <code class="literal">${spring.application.name}</code>, the Spring Context ID and <code class="literal">${server.port}</code> respectively.</p><p><code class="literal">@EnableDiscoveryClient</code> make the app into both a Consul "service" (i.e. it registers itself) and a "client" (i.e. it can query Consul to locate other services).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_http_health_check" href="#_http_health_check"></a>3.3 HTTP Health Check</h2></div></div></div><p>The health check for a Consul instance defaults to "/health", which is the default locations of a useful endpoint in a Spring Boot Actuator application. You need to change these, even for an Actuator application if you use a non-default context path or servlet path (e.g. <code class="literal">server.servletPath=/foo</code>) or management endpoint path (e.g. <code class="literal">management.context-path=/admin</code>). The interval that Consul uses to check the health endpoint may also be configured. "10s" and "1m" represent 10 seconds and 1 minute respectively. Example:</p><p><b>application.yml. </b>
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</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left">Caution</th></tr><tr><td align="left" valign="top"><p>If you use <a class="link" href="multi_spring-cloud-consul-config.html" title="4. Distributed Configuration with Consul">Spring Cloud Consul Config</a>, the above values will need to be placed in <code class="literal">bootstrap.yml</code> instead of <code class="literal">application.yml</code>.</p></td></tr></table></div><p>The default service name, instance id and port, taken from the <code class="literal">Environment</code>, are <code class="literal">${spring.application.name}</code>, the Spring Context ID and <code class="literal">${server.port}</code> respectively.</p><p>To disable the Consul Discovery Client you can set <code class="literal">spring.cloud.consul.discovery.enabled</code> to <code class="literal">false</code>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_http_health_check" href="#_http_health_check"></a>3.3 HTTP Health Check</h2></div></div></div><p>The health check for a Consul instance defaults to "/health", which is the default locations of a useful endpoint in a Spring Boot Actuator application. You need to change these, even for an Actuator application if you use a non-default context path or servlet path (e.g. <code class="literal">server.servletPath=/foo</code>) or management endpoint path (e.g. <code class="literal">management.context-path=/admin</code>). The interval that Consul uses to check the health endpoint may also be configured. "10s" and "1m" represent 10 seconds and 1 minute respectively. Example:</p><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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@@ -18,7 +18,6 @@ turbine:
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appConfig: ${applications}</pre><p>
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</p><p>The <code class="literal">clusterConfig</code> and <code class="literal">appConfig</code> sections must match, so it’s useful to put the comma-separated list of service ID’s into a separate configuration property.</p><p><b>Turbine.java. </b>
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</p><pre class="screen">@EnableTurbine
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@EnableDiscoveryClient
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@SpringBootApplication
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public class Turbine {
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public static void main(String[] args) {
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@@ -7,7 +7,6 @@ application and build large distributed systems with Consul based components. Th
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patterns provided include Service Discovery, Control Bus and Configuration.
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Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Breaker
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(Hystrix) are provided by integration with Spring Cloud Netflix.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-install" href="#spring-cloud-consul-install"></a>1. Install Consul</h1></div></div></div><p>Please see the <a class="link" href="https://www.consul.io/intro/getting-started/install.html" target="_top">installation documentation</a> for instructions on how to install Consul.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-agent" href="#spring-cloud-consul-agent"></a>2. Consul Agent</h1></div></div></div><p>A Consul Agent client must be available to all Spring Cloud Consul applications. By default, the Agent client is expected to be at <code class="literal">localhost:8500</code>. See the <a class="link" href="https://consul.io/docs/agent/basics.html" target="_top">Agent documentation</a> for specifics on how to start an Agent client and how to connect to a cluster of Consul Agent Servers. For development, after you have installed consul, you may start a Consul Agent using the following command:</p><pre class="screen">./src/main/bash/local_run_consul.sh</pre><p>This will start an agent in server mode on port 8500, with the ui available at <a class="link" href="http://localhost:8500" target="_top">http://localhost:8500</a></p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-discovery" href="#spring-cloud-consul-discovery"></a>3. Service Discovery with Consul</h1></div></div></div><p>Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. Consul provides Service Discovery services via an <a class="link" href="https://www.consul.io/docs/agent/http.html" target="_top">HTTP API</a> and <a class="link" href="https://www.consul.io/docs/agent/dns.html" target="_top">DNS</a>. Spring Cloud Consul leverages the HTTP API for service registration and discovery. This does not prevent non-Spring Cloud applications from leveraging the DNS interface. Consul Agents servers are run in a <a class="link" href="https://www.consul.io/docs/internals/architecture.html" target="_top">cluster</a> that communicates via a <a class="link" href="https://www.consul.io/docs/internals/gossip.html" target="_top">gossip protocol</a> and uses the <a class="link" href="https://www.consul.io/docs/internals/consensus.html" target="_top">Raft consensus protocol</a>.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_how_to_activate" href="#_how_to_activate"></a>3.1 How to activate</h2></div></div></div><p>To activate Consul Service Discovery use the starter with group <code class="literal">org.springframework.cloud</code> and artifact id <code class="literal">spring-cloud-starter-consul-discovery</code>. See the <a class="link" href="http://projects.spring.io/spring-cloud/" target="_top">Spring Cloud Project page</a> for details on setting up your build system with the current Spring Cloud Release Train.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_registering_with_consul" href="#_registering_with_consul"></a>3.2 Registering with Consul</h2></div></div></div><p>When a client registers with Consul, it provides meta-data about itself such as host and port, id, name and tags. An HTTP <a class="link" href="https://www.consul.io/docs/agent/checks.html" target="_top">Check</a> is created by default that Consul hits the <code class="literal">/health</code> endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.</p><p>Example Consul client:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@SpringBootApplication</span></em>
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<em><span class="hl-annotation" style="color: gray">@EnableDiscoveryClient</span></em>
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<em><span class="hl-annotation" style="color: gray">@RestController</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> Application {
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@@ -26,7 +25,7 @@ Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Brea
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consul:
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host: localhost
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port: 8500</pre><p>
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</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left">Caution</th></tr><tr><td align="left" valign="top"><p>If you use <a class="link" href="#spring-cloud-consul-config" title="4. Distributed Configuration with Consul">Spring Cloud Consul Config</a>, the above values will need to be placed in <code class="literal">bootstrap.yml</code> instead of <code class="literal">application.yml</code>.</p></td></tr></table></div><p>The default service name, instance id and port, taken from the <code class="literal">Environment</code>, are <code class="literal">${spring.application.name}</code>, the Spring Context ID and <code class="literal">${server.port}</code> respectively.</p><p><code class="literal">@EnableDiscoveryClient</code> make the app into both a Consul "service" (i.e. it registers itself) and a "client" (i.e. it can query Consul to locate other services).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_http_health_check" href="#_http_health_check"></a>3.3 HTTP Health Check</h2></div></div></div><p>The health check for a Consul instance defaults to "/health", which is the default locations of a useful endpoint in a Spring Boot Actuator application. You need to change these, even for an Actuator application if you use a non-default context path or servlet path (e.g. <code class="literal">server.servletPath=/foo</code>) or management endpoint path (e.g. <code class="literal">management.context-path=/admin</code>). The interval that Consul uses to check the health endpoint may also be configured. "10s" and "1m" represent 10 seconds and 1 minute respectively. Example:</p><p><b>application.yml. </b>
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</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left">Caution</th></tr><tr><td align="left" valign="top"><p>If you use <a class="link" href="#spring-cloud-consul-config" title="4. Distributed Configuration with Consul">Spring Cloud Consul Config</a>, the above values will need to be placed in <code class="literal">bootstrap.yml</code> instead of <code class="literal">application.yml</code>.</p></td></tr></table></div><p>The default service name, instance id and port, taken from the <code class="literal">Environment</code>, are <code class="literal">${spring.application.name}</code>, the Spring Context ID and <code class="literal">${server.port}</code> respectively.</p><p>To disable the Consul Discovery Client you can set <code class="literal">spring.cloud.consul.discovery.enabled</code> to <code class="literal">false</code>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_http_health_check" href="#_http_health_check"></a>3.3 HTTP Health Check</h2></div></div></div><p>The health check for a Consul instance defaults to "/health", which is the default locations of a useful endpoint in a Spring Boot Actuator application. You need to change these, even for an Actuator application if you use a non-default context path or servlet path (e.g. <code class="literal">server.servletPath=/foo</code>) or management endpoint path (e.g. <code class="literal">management.context-path=/admin</code>). The interval that Consul uses to check the health endpoint may also be configured. "10s" and "1m" represent 10 seconds and 1 minute respectively. Example:</p><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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@@ -115,7 +114,6 @@ turbine:
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appConfig: ${applications}</pre><p>
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</p><p>The <code class="literal">clusterConfig</code> and <code class="literal">appConfig</code> sections must match, so it’s useful to put the comma-separated list of service ID’s into a separate configuration property.</p><p><b>Turbine.java. </b>
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</p><pre class="screen">@EnableTurbine
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@EnableDiscoveryClient
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@SpringBootApplication
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public class Turbine {
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public static void main(String[] args) {
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@@ -4,7 +4,7 @@
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<book xmlns="http://docbook.org/ns/docbook" xmlns:xl="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en">
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<info>
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<title>Spring Cloud Consul</title>
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<date>2017-09-07</date>
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<date>2017-09-27</date>
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</info>
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<preface>
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<title></title>
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@@ -39,7 +39,6 @@ Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Brea
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<simpara>When a client registers with Consul, it provides meta-data about itself such as host and port, id, name and tags. An HTTP <link xl:href="https://www.consul.io/docs/agent/checks.html">Check</link> is created by default that Consul hits the <literal>/health</literal> endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.</simpara>
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<simpara>Example Consul client:</simpara>
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<programlisting language="java" linenumbering="unnumbered">@SpringBootApplication
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@EnableDiscoveryClient
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@RestController
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public class Application {
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@@ -68,7 +67,7 @@ public class Application {
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<simpara>If you use <link linkend="spring-cloud-consul-config">Spring Cloud Consul Config</link>, the above values will need to be placed in <literal>bootstrap.yml</literal> instead of <literal>application.yml</literal>.</simpara>
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</caution>
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<simpara>The default service name, instance id and port, taken from the <literal>Environment</literal>, are <literal>${spring.application.name}</literal>, the Spring Context ID and <literal>${server.port}</literal> respectively.</simpara>
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<simpara><literal>@EnableDiscoveryClient</literal> make the app into both a Consul "service" (i.e. it registers itself) and a "client" (i.e. it can query Consul to locate other services).</simpara>
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<simpara>To disable the Consul Discovery Client you can set <literal>spring.cloud.consul.discovery.enabled</literal> to <literal>false</literal>.</simpara>
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</section>
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<section xml:id="_http_health_check">
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<title>HTTP Health Check</title>
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@@ -295,7 +294,6 @@ turbine:
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<title>Turbine.java</title>
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<para>
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<screen>@EnableTurbine
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@EnableDiscoveryClient
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@SpringBootApplication
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public class Turbine {
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public static void main(String[] args) {
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