Spring/spring-cloud
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Sync docs from master to gh-pages

Browse Source
This commit is contained in:
Dave Syer
2014-10-24 15:46:46 +00:00
parent ad1cebcbaa
commit 7749116ad5
1 changed files with 125 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

142
spring-cloud.html
View File

@@ -452,7 +452,13 @@ body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-b
<li><a href="#_why_is_it_so_slow_to_register_a_service">Why is it so Slow to Register a Service?</a></li>
</ul>
</li>
<li><a href="#_service_discovery_eureka_server">Service Discovery: Eureka Server</a></li>
<li><a href="#_service_discovery_eureka_server">Service Discovery: Eureka Server</a>
<ul class="sectlevel2">
<li><a href="#_high_availability_zones_and_regions">High Availability, Zones and Regions</a></li>
<li><a href="#_standalone_mode">Standalone Mode</a></li>
<li><a href="#_peer_awareness">Peer Awareness</a></li>
</ul>
</li>
<li><a href="#_circuit_breaker_hystrix_clients">Circuit Breaker: Hystrix Clients</a></li>
<li><a href="#_circuit_breaker_hystrix_dashboard">Circuit Breaker: Hystrix Dashboard</a>
<ul class="sectlevel2">
@@ -1205,7 +1211,7 @@ Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon).
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>@Configuration
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
@ComponentScan
@EnableAutoConfiguration
@EnableEurekaClient
@@ -1228,16 +1234,23 @@ public class Application {
<p>(i.e. utterly normal Spring Boot app). Configuration is required to locate the Eureka server. Example:</p>
</div>
<div class="listingblock">
<div class="title">application.yml</div>
<div class="content">
<pre class="highlight"><code>eureka:
<pre>eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/</code></pre>
defaultZone: http://localhost:8761/eureka/</pre>
</div>
</div>
<div class="paragraph">
<p>The default application name, virtual host and non-secure port are taken from the <code>Environment</code> is
<code>${spring.application.name}</code>, <code>${spring.application.name}.mydomain.net</code> and <code>${server.port}</code> respectively.</p>
<p>where "defaultZone" is a magic string fallback value that provides the
service URL for any client that doesn&#8217;t express a preference
(i.e. it&#8217;s a useful default).</p>
</div>
<div class="paragraph">
<p>The default application name (service ID), virtual host and non-secure
port, taken from the <code>Environment</code>, are <code>${spring.application.name}</code>,
<code>${spring.application.name}</code> and <code>${server.port}</code> respectively.</p>
</div>
<div class="paragraph">
<p><code>@EnableEurekaClient</code> makes the app into both a Eureka "instance"
@@ -1276,7 +1289,7 @@ assumptions about the lease renewal period.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>@Configuration
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
@EnableAutoConfiguration
@EnableEurekaServer
public class Application {
@@ -1346,6 +1359,103 @@ springBoot {
</tr>
</table>
</div>
<div class="sect2">
<h3 id="_high_availability_zones_and_regions">High Availability, Zones and Regions</h3>
<div class="paragraph">
<p>The Eureka server does not have a backend store, but the service
instances in the registry all have to send heartbeats to keep their
resistrations up to date (so this can be done in memory). Clients also
have an in-memory cache of eureka registrations (so they don&#8217;t have to
go to the registry for every single request to a service).</p>
</div>
<div class="paragraph">
<p>By default every Eureka server is also a Eureka client and requires
(at least one) service URL to locate a peer. If you don&#8217;t provide it
the service will run and work, but it will shower your logs with a lot
of noise about not being able to register with the peer.</p>
</div>
</div>
<div class="sect2">
<h3 id="_standalone_mode">Standalone Mode</h3>
<div class="paragraph">
<p>The combination of the two caches (client and server) and the
heartbeats make a standalone Eureka server fairly resilient to
failure, as long as there is some sort of monitor or elastic runtime
keeping it alive (e.g. Cloud Foundry). In standalone mode, you might
prefer to switch off the client side behaviour, so it doesn&#8217;t keep
trying and failing to reach its peers. Example:</p>
</div>
<div class="listingblock">
<div class="title">application.yml (Standalone Eureka Server)</div>
<div class="content">
<pre>server:
port: 8761
eureka:
instance:
hostname: localhost
client:
registerWithEureka: false
fetchRegistry: false
serviceUrl:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/</pre>
</div>
</div>
<div class="paragraph">
<p>Notice that the <code>serviceUrl</code> is pointing to the same host as the local
instance.</p>
</div>
</div>
<div class="sect2">
<h3 id="_peer_awareness">Peer Awareness</h3>
<div class="paragraph">
<p>Eureka can be made even more resilient and available by running
multiple instances and asking them to register with each other. In
fact, this is the default behaviour, so all you need to do to make it
work is add a valid <code>serviceUrl</code> to a peer, e.g.</p>
</div>
<div class="listingblock">
<div class="title">application.yml (Two Peer Aware Eureka Servers)</div>
<div class="content">
<pre>---
spring:
profiles: peer1
eureka:
instance:
hostname: peer1
client:
serviceUrl:
defaultZone: http://peer2/eureka/
---
spring:
profiles: peer2
eureka:
instance:
hostname: peer2
client:
serviceUrl:
defaultZone: http://peer1/eureka/</pre>
</div>
</div>
<div class="paragraph">
<p>In this example we have a YAML file that can be used to run the same
server on 2 hosts (peer1 and peer2), by running it in different
Spring profiles. You could use this configuration to test the peer
awareness on a single host (there&#8217;s not much value in doing that in
production) by manipulating <code>/etc/hosts</code> to resolve the host names. In
fact, the <code>eureka.instance.hostname</code> is not needed if you are running
on a machine that knows its own hostname (it is looked up using
<code>java.net.InetAddress</code> by default).</p>
</div>
<div class="paragraph">
<p>You can add multiple peers to a system, and as long as they are all
connected to each other by at least one edge, they will synchronize
the registrations amongst themselves. If the peers are physically
separated (inside a data centre or between multiple data centres) then
the system can in principle survive split-brain type failures.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
@@ -1377,7 +1487,7 @@ springBoot {
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>@Configuration
<pre>@Configuration
@EnableAutoConfiguration
@EnableHystrix
public class Application {
@@ -1399,7 +1509,7 @@ public class StoreIntegration {
public Object defaultStores(Map&lt;String, Object&gt; parameters) {
return /* something useful */;
}
}</code></pre>
}</pre>
</div>
</div>
<div class="paragraph">
@@ -1445,7 +1555,7 @@ circuit, and what to do in case of a failure.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>@Configuration
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
@ComponentScan
@EnableAutoConfiguration
@EnableEurekaClient
@@ -1463,12 +1573,10 @@ public class Application extends FeignConfigurer {
}</code></pre>
</div>
</div>
<div class="paragraph">
<p>StoreClient.java</p>
</div>
<div class="listingblock">
<div class="title">StoreClient.java</div>
<div class="content">
<pre class="highlight"><code>public interface StoreClient {
<pre class="highlight"><code class="language-java" data-lang="java">public interface StoreClient {
@RequestMapping(method = RequestMethod.GET, value = "/stores")
Stores getStores();
@@ -1487,7 +1595,7 @@ public class Application extends FeignConfigurer {
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>public class MyClass {
<pre class="highlight"><code class="language-java" data-lang="java">public class MyClass {
@Autowired
private LoadBalancerClient loadBalancer;
@@ -1504,7 +1612,7 @@ public class Application extends FeignConfigurer {
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code>public class MyClass {
<pre class="highlight"><code class="language-java" data-lang="java">public class MyClass {
@Autowired
private RestTemplate restTemplate;
@@ -1903,7 +2011,7 @@ and puts it in a request header for the downstream requests.</p>
</div>
<div id="footer">
<div id="footer-text">
Last updated 2014-10-23 19:59:43 UTC
Last updated 2014-10-24 15:46:04 UTC
</div>
</div>
</body>