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<h1>
<a id="user-content-pubsub-among-nginx-worker-processes" class="anchor" href="#pubsub-among-nginx-worker-processes" aria-hidden="true"><span class="octicon octicon-link"></span></a>Pub/Sub Among Nginx Worker Processes</h1>
<p>When <code>worker_processes > 1</code> in nginx.conf, there're more than one JVM instances viz. Nginx worker processes
and requests from the same session perhaps will be handled by different JVM instances. If we want to publish
message to all worker processes there're two way:</p>
<ol>
<li>PubSubTopic(Clojure)/NginxPubSubTopic(Java) -- A high level, shared map based, topic oriented API (since 0.4.3)</li>
<li>broadcast -- A low level, message limited API. (since 0.2.5)</li>
</ol>
<h2>
<a id="user-content-use-pubsubtopicclojurenginxpubsubtopicjava" class="anchor" href="#use-pubsubtopicclojurenginxpubsubtopicjava" aria-hidden="true"><span class="octicon octicon-link"></span></a>Use PubSubTopic(Clojure)/NginxPubSubTopic(Java)</h2>
<h3>
<a id="user-content-prepare" class="anchor" href="#prepare" aria-hidden="true"><span class="octicon octicon-link"></span></a>Prepare</h3>
<p>In nginx.conf we need declare a shared map named <code>PubSubTopic</code> first.
Messages will be temperately stored in it when the message is sent to all subscribers it will be removed.</p>
<pre lang="nginx.conf"><code>shared_map PubSubTopic tinymap?space=1M&entries=1024;
</code></pre>
<h3>
<a id="user-content-build-a-topic" class="anchor" href="#build-a-topic" aria-hidden="true"><span class="octicon octicon-link"></span></a>Build A Topic</h3>
<ul>
<li><strong>Clojure</strong></li>
</ul>
<div class="highlight highlight-source-clojure"><pre> (<span class="pl-k">require</span> '[nginx.clojure.core <span class="pl-c1">:as</span> ncc])
<span class="pl-c">;;build a topic</span>
(<span class="pl-k">def</span> <span class="pl-e">my-topic</span> (<span class="pl-en">ncc/build-topic!</span> <span class="pl-s"><span class="pl-pds">"</span>my-topic<span class="pl-pds">"</span></span>))
(<span class="pl-k">def</span> <span class="pl-e">msg-counter</span> (<span class="pl-en">atomic</span> <span class="pl-c1">0</span>))</pre></div>
<ul>
<li><strong>Java</strong></li>
</ul>
<div class="highlight highlight-source-java"><pre><span class="pl-smi">NginxPubSubTopic</span> myTopic <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-smi">NginxPubSubTopic</span>(<span class="pl-s"><span class="pl-pds">"</span>my-topic<span class="pl-pds">"</span></span>);
<span class="pl-smi">AtomicInteger</span> msgCounter <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-smi">AtomicInteger</span>(<span class="pl-c1">0</span>);</pre></div>
<h3>
<a id="user-content-subscribe-to-the-topic" class="anchor" href="#subscribe-to-the-topic" aria-hidden="true"><span class="octicon octicon-link"></span></a>Subscribe to the Topic</h3>
<ul>
<li><strong>Clojure</strong></li>
</ul>
<div class="highlight highlight-source-clojure"><pre>
(<span class="pl-k">defn</span> <span class="pl-e">sub-handler</span>[msg msg-counter]
(<span class="pl-en">println</span> <span class="pl-s"><span class="pl-pds">"</span>received :<span class="pl-pds">"</span></span> msg <span class="pl-s"><span class="pl-pds">"</span>, times=<span class="pl-pds">"</span></span> (<span class="pl-en">swap</span> counter inc)))
<span class="pl-c">;;subscribe the topic so that we can get all messages of the topic from all jvm instances</span>
<span class="pl-c">;;it returns an unsubscribing function for removal.</span>
(<span class="pl-k">def</span> <span class="pl-e">usub-fun</span> (<span class="pl-en">ncc/sub!</span> my-topic msg-counter sub-handler))</pre></div>
<ul>
<li><strong>Java</strong></li>
</ul>
<div class="highlight highlight-source-java"><pre><span class="pl-smi">PubSubListenerData</span> pd <span class="pl-k">=</span> myTopic<span class="pl-k">.</span>subscribe(, <span class="pl-k">new</span> <span class="pl-k">NginxPubSubListener<<span class="pl-smi">AtomicInteger</span>></span>() {
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">onMessage</span>(<span class="pl-smi">String</span> <span class="pl-v">msg</span>, <span class="pl-smi">AtomicInteger</span> <span class="pl-v">messageCounter</span>) <span class="pl-k">throws</span> <span class="pl-smi">IOException</span> {
<span class="pl-smi">System</span><span class="pl-k">.</span>out<span class="pl-k">.</span>println(<span class="pl-s"><span class="pl-pds">"</span>received: <span class="pl-pds">"</span></span> <span class="pl-k">+</span> msg <span class="pl-k">+</span> <span class="pl-s"><span class="pl-pds">"</span>, times=<span class="pl-pds">"</span></span> <span class="pl-k">+</span> messageCounter<span class="pl-k">.</span>increaseAndGet());
}
});
</pre></div>
<h3>
<a id="user-content-publish-message-to-the-topic" class="anchor" href="#publish-message-to-the-topic" aria-hidden="true"><span class="octicon octicon-link"></span></a>Publish Message to The Topic</h3>
<ul>
<li><strong>Clojure</strong></li>
</ul>
<div class="highlight highlight-source-clojure"><pre>(<span class="pl-en">ncc/pub!</span> my-topic <span class="pl-s"><span class="pl-pds">"</span>Hello!<span class="pl-pds">"</span></span>)</pre></div>
<ul>
<li><strong>Java/Groovy</strong></li>
</ul>
<div class="highlight highlight-source-java"><pre>myTopic<span class="pl-k">.</span>pubish(<span class="pl-s"><span class="pl-pds">"</span>Hello!<span class="pl-pds">"</span></span>);</pre></div>
<h3>
<a id="user-content-unsubscribe" class="anchor" href="#unsubscribe" aria-hidden="true"><span class="octicon octicon-link"></span></a>Unsubscribe</h3>
<ul>
<li><strong>Clojure</strong></li>
</ul>
<div class="highlight highlight-source-clojure"><pre><span class="pl-c">;; usub-fun is a return value from sub!</span>
(<span class="pl-en">usub-fun</span>)</pre></div>
<ul>
<li><strong>Java</strong></li>
</ul>
<div class="highlight highlight-source-java"><pre><span class="pl-c">//pd is a return value from subscribe</span>
myTopic<span class="pl-k">.</span>unsubscribe(pd);</pre></div>
<h2>
<a id="user-content-use-broadcast-api" class="anchor" href="#use-broadcast-api" aria-hidden="true"><span class="octicon octicon-link"></span></a>Use Broadcast API</h2>
<p>Broadcast API is a low level API which supports two kinds of events to broadcast, simple events and complex events.</p>
<ol>
<li>A simple event only has a event id which is a long integer and must be less than 0x0100000000000000L, it hasn't any body or its body is stored in some external stores, e.g. SharedHashMap, Memcached, Redis etc.</li>
<li>A complex event has a message with a length limitation <code>PIPE_BUF - 8</code>, generally on Linux/Windows is 4088, on MacosX is 504.</li>
</ol>
<p>Here's a simple Sub/Pub Service based on API of broadcast & Server Sent Events. More details can be found from issue #38 and its comments [nginx-clojure broadcast API][]</p>
<ul>
<li><strong>Clojure</strong></li>
</ul>
<div class="highlight highlight-source-clojure"><pre>
(<span class="pl-k">def</span> <span class="pl-e">sse-subscribers</span> (<span class="pl-en">atom</span> {}))
(<span class="pl-k">def</span> <span class="pl-e">sse-event-tag</span> (<span class="pl-en">int</span> (<span class="pl-en">+</span> <span class="pl-c1">0x80</span> <span class="pl-c1">10</span>)))
(<span class="pl-k">def</span> <span class="pl-e">init-broadcast-event-listener</span>
(<span class="pl-en">delay</span>
(<span class="pl-en">on-broadcast-event-decode!</span>
<span class="pl-c">;;tester</span>
(<span class="pl-k">fn</span> [{tag <span class="pl-c1">:tag</span>}]
(<span class="pl-en">=</span> tag sse-event-tag))
<span class="pl-c">;;decoder</span>
(<span class="pl-k">fn</span> [{<span class="pl-c1">:keys</span> [tag data offset length] <span class="pl-c1">:as</span> e}]
(<span class="pl-en">assoc</span> e <span class="pl-c1">:data</span> (<span class="pl-en">String.</span> data offset length <span class="pl-s"><span class="pl-pds">"</span>utf-8<span class="pl-pds">"</span></span>))))
(<span class="pl-en">on-broadcast!</span>
(<span class="pl-k">fn</span> [{<span class="pl-c1">:keys</span> [tag data]}]
(<span class="pl-en">log</span> <span class="pl-s"><span class="pl-pds">"</span>#%s ring_handlers_for_test: onbroadcast {%d %s} %s<span class="pl-pds">"</span></span> process-id tag data @sse-subscribers)
(<span class="pl-en">condp</span> = tag
sse-event-tag
(<span class="pl-en">doseq</span> [ch (<span class="pl-en">keys</span> @sse-subscribers)]
(<span class="pl-en">send!</span> ch (<span class="pl-en">str</span> <span class="pl-s"><span class="pl-pds">"</span>data: <span class="pl-pds">"</span></span> data <span class="pl-s"><span class="pl-pds">"</span><span class="pl-cce">\r\n\r\n</span><span class="pl-pds">"</span></span>) <span class="pl-c1">true</span> (<span class="pl-en">=</span> <span class="pl-s"><span class="pl-pds">"</span>finish!<span class="pl-pds">"</span></span> data) ))
<span class="pl-c1">nil</span>)))))
<span class="pl-c">;;server sent events publisher</span>
(<span class="pl-k">defn</span> <span class="pl-e">sse-publisher</span> [req]
(<span class="pl-en">broadcast!</span> {<span class="pl-c1">:tag</span> sse-event-tag, <span class="pl-c1">:data</span> (<span class="pl-c1">:query-string</span> req)})
{<span class="pl-c1">:body</span> <span class="pl-s"><span class="pl-pds">"</span>OK<span class="pl-pds">"</span></span>})
<span class="pl-c">;;server sent events subscriber</span>
(<span class="pl-k">defn</span> <span class="pl-e">sse-sub</span> [^NginxRequest req]
@<span class="pl-e">init-broadcast-event-listener</span>
(<span class="pl-k">let</span> [ch (<span class="pl-en">hijack!</span> req <span class="pl-c1">true</span>)]
(<span class="pl-en">on-close!</span> ch ch
(<span class="pl-k">fn</span> [ch] (<span class="pl-en">log</span> <span class="pl-s"><span class="pl-pds">"</span>channel closed. id=%d<span class="pl-pds">"</span></span> (<span class="pl-en">.nativeRequest</span> req))
(<span class="pl-en">log</span> <span class="pl-s"><span class="pl-pds">"</span>#%s sse-sub: onclose arg:%s, sse-subscribers=%s<span class="pl-pds">"</span></span> process-id ch (<span class="pl-en">pr-str</span> @sse-subscribers))
(<span class="pl-en">swap!</span> sse-subscribers dissoc ch)))
(<span class="pl-en">swap!</span> sse-subscribers assoc ch req)
(<span class="pl-en">send-header!</span> ch <span class="pl-c1">200</span> {<span class="pl-s"><span class="pl-pds">"</span>Content-Type<span class="pl-pds">"</span></span>, <span class="pl-s"><span class="pl-pds">"</span>text/event-stream<span class="pl-pds">"</span></span>} <span class="pl-c1">false</span> <span class="pl-c1">false</span>)
(<span class="pl-en">send!</span> ch <span class="pl-s"><span class="pl-pds">"</span>retry: 4500<span class="pl-cce">\r\n</span><span class="pl-pds">"</span></span> <span class="pl-c1">true</span> <span class="pl-c1">false</span>)))</pre></div>
<ul>
<li><strong>Java</strong></li>
</ul>
<div class="highlight highlight-source-java"><pre>
<span class="pl-k">public</span> <span class="pl-k">static</span> <span class="pl-k">class</span> <span class="pl-en">Init</span> <span class="pl-k">implements</span> <span class="pl-e">NginxJavaRingHandler</span>, <span class="pl-e">Listener</span> {
<span class="pl-k">public</span> <span class="pl-k">static</span> <span class="pl-k">final</span> <span class="pl-k">int</span> <span class="pl-c1">SEVER_SENT_EVENTS</span> <span class="pl-k">=</span> <span class="pl-c1">POST_EVENT_TYPE_COMPLEX_EVENT_IDX_START</span> <span class="pl-k">+</span> <span class="pl-c1">1</span>;
<span class="pl-k">public</span> <span class="pl-k">static</span> <span class="pl-k">Set<<span class="pl-smi">NginxHttpServerChannel</span>></span> serverSentEventSubscribers;
<span class="pl-k">public</span> <span class="pl-en">Init</span>() {
}
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">doInit</span>() {
serverSentEventSubscribers <span class="pl-k">=</span> <span class="pl-smi">Collections</span><span class="pl-k">.</span>newSetFromMap(<span class="pl-k">new</span> <span class="pl-k">ConcurrentHashMap<<span class="pl-smi">NginxHttpServerChannel</span>, <span class="pl-smi">Boolean</span>></span>());
<span class="pl-smi">NginxClojureRT</span><span class="pl-k">.</span>getAppEventListenerManager()<span class="pl-k">.</span>addListener(<span class="pl-v">this</span>);
}
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">onEvent</span>(<span class="pl-smi">PostedEvent</span> <span class="pl-v">event</span>) {
<span class="pl-k">if</span> (event<span class="pl-k">.</span>tag <span class="pl-k">!=</span> <span class="pl-c1">LONGPOLL_EVENT</span> <span class="pl-k">&&</span> event<span class="pl-k">.</span>tag <span class="pl-k">!=</span> <span class="pl-c1">SEVER_SENT_EVENTS</span>) {
<span class="pl-k">return</span>;
}
<span class="pl-smi">String</span> message <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-smi">String</span>((<span class="pl-k">byte</span>[])event<span class="pl-k">.</span>data, event<span class="pl-k">.</span>offset, event<span class="pl-k">.</span>length, <span class="pl-c1">DEFAULT_ENCODING</span>);
<span class="pl-k">if</span> (event<span class="pl-k">.</span>tag <span class="pl-k">==</span> <span class="pl-c1">SEVER_SENT_EVENTS</span>) {
<span class="pl-k">for</span> (<span class="pl-smi">NginxHttpServerChannel</span> channel <span class="pl-k">:</span> serverSentEventSubscribers) {
<span class="pl-k">if</span> (<span class="pl-s"><span class="pl-pds">"</span>shutdown!<span class="pl-pds">"</span></span><span class="pl-k">.</span>equals(message)) {
channel<span class="pl-k">.</span>send(<span class="pl-s"><span class="pl-pds">"</span>data: <span class="pl-pds">"</span></span><span class="pl-k">+</span>message<span class="pl-k">+</span><span class="pl-s"><span class="pl-pds">"</span><span class="pl-cce">\r\n\r\n</span><span class="pl-pds">"</span></span>, <span class="pl-c1">true</span>, <span class="pl-c1">true</span>);
}<span class="pl-k">else</span> <span class="pl-k">if</span> (<span class="pl-s"><span class="pl-pds">"</span>shutdownQuite!<span class="pl-pds">"</span></span><span class="pl-k">.</span>equals(message)) {
channel<span class="pl-k">.</span>close();
}<span class="pl-k">else</span> {
channel<span class="pl-k">.</span>send(<span class="pl-s"><span class="pl-pds">"</span>data: <span class="pl-pds">"</span></span><span class="pl-k">+</span>message<span class="pl-k">+</span><span class="pl-s"><span class="pl-pds">"</span><span class="pl-cce">\r\n\r\n</span><span class="pl-pds">"</span></span>, <span class="pl-c1">true</span>, <span class="pl-c1">false</span>);
}
}
}
}
}
<span class="pl-k">public</span> <span class="pl-k">static</span> <span class="pl-k">class</span> <span class="pl-en">SSESub</span> <span class="pl-k">implements</span> <span class="pl-e">NginxJavaRingHandler</span> {
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">SSESub</span>() {
<span class="pl-k">new</span> <span class="pl-smi">Init</span>()<span class="pl-k">.</span>doInit();
}
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">Object</span>[] <span class="pl-en">invoke</span>(<span class="pl-k">Map<<span class="pl-smi">String</span>, <span class="pl-smi">Object</span>></span> <span class="pl-v">request</span>) {
<span class="pl-smi">NginxJavaRequest</span> r <span class="pl-k">=</span> (<span class="pl-smi">NginxJavaRequest</span>) request;
<span class="pl-smi">NginxHttpServerChannel</span> channel <span class="pl-k">=</span> r<span class="pl-k">.</span>hijack(<span class="pl-c1">true</span>);
channel<span class="pl-k">.</span>addListener(channel, <span class="pl-k">new</span> <span class="pl-k">ChannelListener<<span class="pl-smi">NginxHttpServerChannel</span>></span>() {
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">onClose</span>(<span class="pl-smi">NginxHttpServerChannel</span> <span class="pl-v">data</span>) {
<span class="pl-smi">Init</span><span class="pl-k">.</span>serverSentEventSubscribers<span class="pl-k">.</span>remove(data);
<span class="pl-smi">NginxClojureRT</span><span class="pl-k">.</span>getLog()<span class="pl-k">.</span>info(<span class="pl-s"><span class="pl-pds">"</span>closing....<span class="pl-pds">"</span></span> <span class="pl-k">+</span> data<span class="pl-k">.</span>request()<span class="pl-k">.</span>nativeRequest());
}
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">void</span> <span class="pl-en">onConnect</span>(<span class="pl-k">long</span> <span class="pl-v">status</span>, <span class="pl-smi">NginxHttpServerChannel</span> <span class="pl-v">data</span>) {
}
});
<span class="pl-smi">Init</span><span class="pl-k">.</span>serverSentEventSubscribers<span class="pl-k">.</span>add(channel);
channel<span class="pl-k">.</span>sendHeader(<span class="pl-c1">200</span>, <span class="pl-smi">ArrayMap</span><span class="pl-k">.</span>create(<span class="pl-s"><span class="pl-pds">"</span>Content-Type<span class="pl-pds">"</span></span>, <span class="pl-s"><span class="pl-pds">"</span>text/event-stream<span class="pl-pds">"</span></span>)<span class="pl-k">.</span>entrySet(), <span class="pl-c1">true</span>, <span class="pl-c1">false</span>);
channel<span class="pl-k">.</span>send(<span class="pl-s"><span class="pl-pds">"</span>retry: 4500<span class="pl-cce">\r\n</span><span class="pl-pds">"</span></span>, <span class="pl-c1">true</span>, <span class="pl-c1">false</span>);
<span class="pl-k">return</span> <span class="pl-c1">null</span>;
}
}
<span class="pl-k">public</span> <span class="pl-k">static</span> <span class="pl-k">class</span> <span class="pl-en">SSEPub</span> <span class="pl-k">implements</span> <span class="pl-e">NginxJavaRingHandler</span> {
<span class="pl-k">@Override</span>
<span class="pl-k">public</span> <span class="pl-k">Object</span>[] <span class="pl-en">invoke</span>(<span class="pl-k">Map<<span class="pl-smi">String</span>, <span class="pl-smi">Object</span>></span> <span class="pl-v">request</span>) {
<span class="pl-c">/*</span>
<span class="pl-c"> * Or use NginxClojureRT.broadcastEvent(Init.SEVER_SENT_EVENTS, request.get(QUERY_STRING).toString());</span>
<span class="pl-c"> */</span>
<span class="pl-smi">PostedEvent</span> event <span class="pl-k">=</span> <span class="pl-k">new</span> <span class="pl-smi">PostedEvent</span>(<span class="pl-smi">Init</span><span class="pl-c1"><span class="pl-k">.</span>SEVER_SENT_EVENTS</span>, request<span class="pl-k">.</span>get(<span class="pl-c1">QUERY_STRING</span>)<span class="pl-k">.</span>toString());
<span class="pl-smi">NginxClojureRT</span><span class="pl-k">.</span>getAppEventListenerManager()<span class="pl-k">.</span>broadcast(event);
<span class="pl-k">return</span> <span class="pl-k">new</span> <span class="pl-smi">Object</span>[] { <span class="pl-c1">NGX_HTTP_OK</span>, <span class="pl-c1">null</span>, <span class="pl-s"><span class="pl-pds">"</span>OK<span class="pl-pds">"</span></span> };
}
}
</pre></div>