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        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-45596] Maximum number of clients supported by change stream</title>
                <link>https://jira.mongodb.org/browse/SERVER-45596</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Hi Devs,&lt;/p&gt;

&lt;p&gt;I&apos;m running some tests to figure out the maximum number of clients that can be supported by change stream. I basically took the script from &lt;del&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-32946&quot; title=&quot;Multiple change streams cause severe performance drop&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-32946&quot;&gt;&lt;del&gt;SERVER-32946&lt;/del&gt;&lt;/a&gt;&lt;/del&gt;&#160;and changed the number of clients. I tested it on my own machine with three local replicas. When the client number is too high, like 100000, the primary replica constantly complains about &quot;Too Many Open Files&quot;. I tried to tune up the ulimit to 65536, but it didn&apos;t help.&lt;/p&gt;

&lt;p&gt;I wonder probably the change stream is not designed for such use cases? What would be the maximum number of supportable clients in this case? Thank you!&lt;/p&gt;</description>
                <environment></environment>
        <key id="1098337">SERVER-45596</key>
            <summary>Maximum number of clients supported by change stream</summary>
                <type id="6" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14720&amp;avatarType=issuetype">Question</type>
                                            <priority id="4" iconUrl="https://jira.mongodb.org/images/icons/priorities/minor.svg">Minor - P4</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="9">Done</resolution>
                                        <assignee username="carl.champain@mongodb.com">Carl Champain</assignee>
                                    <reporter username="xkkwww@gmail.com">Xikui Wang</reporter>
                        <labels>
                    </labels>
                <created>Thu, 16 Jan 2020 01:38:22 +0000</created>
                <updated>Fri, 17 Jan 2020 15:08:28 +0000</updated>
                            <resolved>Fri, 17 Jan 2020 15:07:26 +0000</resolved>
                                                                                        <votes>0</votes>
                                    <watches>5</watches>
                                                                                                                <comments>
                            <comment id="2735373" author="carl.champain" created="Thu, 16 Jan 2020 18:09:20 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=xkkwww%40gmail.com&quot; class=&quot;user-hover&quot; rel=&quot;xkkwww@gmail.com&quot;&gt;xkkwww@gmail.com&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;The&#160;recommended maximum number of change stream cursors that a node can handle is 1000 (because of memory limitations and CPU workload), but we don&apos;t think even close to that is a reasonable target given how expensive some underlying mechanisms are. Importantly, your testing&#160;approach doesn&#8217;t work well, a general suggestion for how to do it better would be to use one stream per collection. For more details, I encourage you to ask our community by posting on the &lt;a href=&quot;https://groups.google.com/group/mongodb-user&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;mongodb-user group&lt;/a&gt; or on &lt;a href=&quot;https://stackoverflow.com/questions/tagged/mongodb&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Stack Overflow with the &lt;tt&gt;mongodb&lt;/tt&gt; tag&lt;/a&gt;.&lt;br/&gt;
 As this ticket does not appear to be a bug, I will now close it.&lt;/p&gt;

&lt;p&gt;Kind regards,&lt;br/&gt;
 Carl&lt;/p&gt;</comment>
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