carto
/
grpc


			
				
					
						
						
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130
							<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
<meta name="generator" content="Doxygen 1.8.17"/>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<title>GRPC Core: gRPC Completion Queue</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="dynsections.js"></script>
<link href="search/search.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="search/searchdata.js"></script>
<script type="text/javascript" src="search/search.js"></script>
<link href="doxygen.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="top"><!-- do not remove this div, it is closed by doxygen! -->
<div id="titlearea">
<table cellspacing="0" cellpadding="0">
 <tbody>
 <tr style="height: 56px;">
  <td id="projectalign" style="padding-left: 0.5em;">
   <div id="projectname">GRPC Core
   &#160;<span id="projectnumber">15.0.0</span>
   </div>
  </td>
 </tr>
 </tbody>
</table>
</div>
<!-- end header part -->
<!-- Generated by Doxygen 1.8.17 -->
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
var searchBox = new SearchBox("searchBox", "search",false,'Search');
/* @license-end */
</script>
<script type="text/javascript" src="menudata.js"></script>
<script type="text/javascript" src="menu.js"></script>
<script type="text/javascript">
/* @license magnet:?xt=urn:btih:cf05388f2679ee054f2beb29a391d25f4e673ac3&amp;dn=gpl-2.0.txt GPL-v2 */
$(function() {
  initMenu('',true,false,'search.php','Search');
  $(document).ready(function() { init_search(); });
});
/* @license-end */</script>
<div id="main-nav"></div>
<!-- window showing the filter options -->
<div id="MSearchSelectWindow"
     onmouseover="return searchBox.OnSearchSelectShow()"
     onmouseout="return searchBox.OnSearchSelectHide()"
     onkeydown="return searchBox.OnSearchSelectKey(event)">
</div>

<!-- iframe showing the search results (closed by default) -->
<div id="MSearchResultsWindow">
<iframe src="javascript:void(0)" frameborder="0" 
        name="MSearchResults" id="MSearchResults">
</iframe>
</div>

</div><!-- top -->
<div class="PageDoc"><div class="header">
  <div class="headertitle">
<div class="title">gRPC Completion Queue </div>  </div>
</div><!--header-->
<div class="contents">
<div class="textblock"><p><em>Author: Sree Kuchibhotla (@sreecha) - Sep 2018</em></p>
<p>Code: <a href="https://github.com/grpc/grpc/blob/v1.15.1/src/core/lib/surface/completion_queue.cc">completion_queue.cc</a></p>
<p>This document gives an overview of completion queue architecture and focuses mainly on the interaction between completion queue and the Polling engine layer.</p>
<h1><a class="anchor" id="autotoc_md99"></a>
Completion queue attributes</h1>
<p>Completion queue has two attributes</p>
<ul>
<li>Completion_type:<ul>
<li>GRPC_CQ_NEXT: <a class="el" href="grpc_8h.html#ab43d55077bcbeb324044d3dcd26a5c80" title="Blocks until an event is available, the completion queue is being shut down, or deadline is reached.">grpc_completion_queue_next()</a> can be called (but not <a class="el" href="grpc_8h.html#a0292bf7a0c794771cd66766dc4b8276c" title="Blocks until an event with tag &#39;tag&#39; is available, the completion queue is being shutdown or deadline...">grpc_completion_queue_pluck()</a>)</li>
<li>GRPC_CQ_PLUCK: <a class="el" href="grpc_8h.html#a0292bf7a0c794771cd66766dc4b8276c" title="Blocks until an event with tag &#39;tag&#39; is available, the completion queue is being shutdown or deadline...">grpc_completion_queue_pluck()</a> can be called (but not <a class="el" href="grpc_8h.html#ab43d55077bcbeb324044d3dcd26a5c80" title="Blocks until an event is available, the completion queue is being shut down, or deadline is reached.">grpc_completion_queue_next()</a>)</li>
<li>GRPC_CQ_CALLBACK: The tags in the queue are function pointers to callbacks. Also, neither next() nor pluck() can be called on this</li>
</ul>
</li>
<li>Polling_type:<ul>
<li>GRPC_CQ_NON_POLLING: Threads calling completion_queue_next/pluck do not do any polling</li>
<li>GRPC_CQ_DEFAULT_POLLING: Threads calling completion_queue_next/pluck do polling</li>
<li>GRPC_CQ_NON_LISTENING: Functionally similar to default polling except for a boolean attribute that states that the cq is non-listening. This is used by the grpc-server code to not associate any listening sockets with this completion-queue’s pollset</li>
</ul>
</li>
</ul>
<h1><a class="anchor" id="autotoc_md100"></a>
Details</h1>
<p><img src="../images/grpc-cq.png" alt="image" class="inline"/></p>
<h2><a class="anchor" id="autotoc_md101"></a>
&lt;strong&gt;grpc_completion_queue_next()&lt;/strong&gt; &amp; &lt;strong&gt;grpc_completion_queue_pluck()&lt;/strong&gt; APIS</h2>
<div class="fragment"><div class="line">grpc_completion_queue_next(cq, deadline)/pluck(cq, deadline, tag) {</div>
<div class="line">  while(true) {</div>
<div class="line">    \\ 1. If an event is queued in the completion queue, dequeue and return</div>
<div class="line">    \\    (in case of pluck() dequeue only if the tag is the one we are interested in)</div>
<div class="line"> </div>
<div class="line">    \\ 2. If completion queue shutdown return</div>
<div class="line"> </div>
<div class="line">    \\ 3. In case of pluck, add (tag, worker) pair to the tag&lt;-&gt;worker map on the cq</div>
<div class="line"> </div>
<div class="line">    \\ 4.  Call grpc_pollset_work(cq’s-pollset, deadline) to do polling</div>
<div class="line">    \\     Note that if this function found some fds to be readable/writable/error,</div>
<div class="line">    \\     it would have scheduled those closures (which may queue completion events</div>
<div class="line">    \\    on SOME completion queue - not necessarily this one)</div>
<div class="line">  }</div>
<div class="line">}</div>
</div><!-- fragment --><h2><a class="anchor" id="autotoc_md102"></a>
Queuing a completion event (i.e., "tag")</h2>
<div class="fragment"><div class="line">grpc_cq_end_op(cq, tag) {</div>
<div class="line">  \\ 1. Queue the tag in the event queue</div>
<div class="line"> </div>
<div class="line">  \\ 2. Find the pollset corresponding to the completion queue</div>
<div class="line">  \\     (i)  If the cq is of type GRPC_CQ_NEXT, then KICK ANY worker</div>
<div class="line">  \\          i.e., call grpc_pollset_kick(pollset, nullptr)</div>
<div class="line">  \\     (ii) If the cq is of type GRPC_CQ_PLUCK, then search the tag&lt;-&gt;worker</div>
<div class="line">  \\          map on the completion queue to find the worker. Then specifically</div>
<div class="line">  \\          kick that worker i.e  call grpc_pollset_kick(pollset, worker)</div>
<div class="line">}</div>
</div><!-- fragment --> </div></div><!-- contents -->
</div><!-- PageDoc -->
<!-- start footer part -->
<hr class="footer"/><address class="footer"><small>
Generated on Wed Mar 3 2021 19:17:11 for GRPC Core by &#160;<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/>
</a> 1.8.17
</small></address>
</body>
</html>