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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
    </build-info>


<item>
            <title>[DOCS-15433] [SERVER] Secondary slowdown or hang due to pinned content</title>
                <link>https://jira.mongodb.org/browse/DOCS-15433</link>
                <project id="10380" key="DOCS">Documentation</project>
                    <description>    &lt;div class=&quot;panel&quot; style=&quot;background-color: #c2d2c2;border-width: 1px;&quot;&gt;&lt;div class=&quot;panelHeader&quot; style=&quot;border-bottom-width: 1px;background-color: #239eb0;&quot;&gt;&lt;b&gt;Original Downstream Change Summary&lt;/b&gt;&lt;/div&gt;&lt;/div&gt;
&lt;p&gt;    Document that maxNumberOfThreads is now capped with number of available cores.&lt;/p&gt;
&lt;h2&gt;&lt;a name=&quot;DescriptionofLinkedTicket&quot;&gt;&lt;/a&gt;Description of Linked Ticket&lt;/h2&gt;
&lt;p&gt;    We only advance the oldest timestamp at oplog batch boundaries. This means that all dirty content generated by the application of the operations in a single batch will be pinned in cache. If the batch is large enough and the operations are heavy enough this dirty content can exceed eviction_dirty_trigger (default 20% of cache) and the rate of applying operations will become dramatically slower because it has to wait for the dirty data to be reduced below the threshold.&lt;/p&gt;

&lt;p&gt;This can be triggered by a momentary slowdown on a secondary causing it to lag momentarily, so the next batch it processes will be unusually large, causing it to exceed 20% dirty cache. This will cause it to lag even further, so the next batch will be even larger, and so on. In extreme cases the node can become completely stuck due to full cache preventing a batch from completing and unpinning the data that is keeping the cache full.&lt;/p&gt;

&lt;p&gt;This can also occur if a secondary is offline for maintenance; when it comes back online and begins to catch up, it will be processing large batches that risk exceeding the dirty trigger threshold, so it may apply operations at a much slower rate than a secondary that is keeping up and processing operations in small batches.&lt;/p&gt;
</description>
                <environment></environment>
        <key id="2073774">DOCS-15433</key>
            <summary>[SERVER] Secondary slowdown or hang due to pinned content</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</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="13201">Fixed</resolution>
                                        <assignee username="dave.cuthbert@mongodb.com">Dave Cuthbert</assignee>
                                    <reporter username="backlog-server-pm">Backlog - Core Eng Program Management Team</reporter>
                        <labels>
                    </labels>
                <created>Tue, 21 Jun 2022 21:13:13 +0000</created>
                <updated>Mon, 13 Nov 2023 17:40:10 +0000</updated>
                            <resolved>Thu, 18 Aug 2022 15:17:33 +0000</resolved>
                                                    <fixVersion>5.0.0-rc0</fixVersion>
                    <fixVersion>4.2.16</fixVersion>
                    <fixVersion>4.0.27</fixVersion>
                    <fixVersion>4.4.9</fixVersion>
                    <fixVersion>Server_Docs_20231030</fixVersion>
                    <fixVersion>Server_Docs_20231106</fixVersion>
                    <fixVersion>Server_Docs_20231105</fixVersion>
                    <fixVersion>Server_Docs_20231113</fixVersion>
                                    <component>manual</component>
                    <component>Server</component>
                        <due></due>
                            <votes>0</votes>
                                    <watches>3</watches>
                                                                                                                <comments>
                            <comment id="4760600" author="xgen-internal-githook" created="Thu, 18 Aug 2022 15:07:02 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Dave Cuthbert&apos;, &apos;email&apos;: &apos;69165704+davemungo@users.noreply.github.com&apos;, &apos;username&apos;: &apos;davemungo&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15433&quot; title=&quot;[SERVER] Secondary slowdown or hang due to pinned content&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15433&quot;&gt;&lt;del&gt;DOCS-15433&lt;/del&gt;&lt;/a&gt; BACKPORT (#1665)&lt;br/&gt;
Branch: v4.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/fe29393d63de67778a155f8dfb1ce07249fe5695&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/fe29393d63de67778a155f8dfb1ce07249fe5695&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="4760599" author="xgen-internal-githook" created="Thu, 18 Aug 2022 15:06:55 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Dave Cuthbert&apos;, &apos;email&apos;: &apos;69165704+davemungo@users.noreply.github.com&apos;, &apos;username&apos;: &apos;davemungo&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15433&quot; title=&quot;[SERVER] Secondary slowdown or hang due to pinned content&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15433&quot;&gt;&lt;del&gt;DOCS-15433&lt;/del&gt;&lt;/a&gt; BACKPORT (#1664)&lt;br/&gt;
Branch: v5.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/8b7bbbdbbcf26df89da63a7347a77bb78689f731&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/8b7bbbdbbcf26df89da63a7347a77bb78689f731&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="4758291" author="xgen-internal-githook" created="Wed, 17 Aug 2022 18:02:42 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Dave Cuthbert&apos;, &apos;email&apos;: &apos;69165704+davemungo@users.noreply.github.com&apos;, &apos;username&apos;: &apos;davemungo&apos;}
&lt;p&gt;Message: Docs 15433 secondary slowdown v6.0 (#1569)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15433&quot; title=&quot;[SERVER] Secondary slowdown or hang due to pinned content&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15433&quot;&gt;&lt;del&gt;DOCS-15433&lt;/del&gt;&lt;/a&gt; secondary slowdown&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15433&quot; title=&quot;[SERVER] Secondary slowdown or hang due to pinned content&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15433&quot;&gt;&lt;del&gt;DOCS-15433&lt;/del&gt;&lt;/a&gt; secondary slowdown&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Review feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;Review feedback&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/c8a02f2c5bdf665c0342504b4daa2ba9b5eff39f&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/c8a02f2c5bdf665c0342504b4daa2ba9b5eff39f&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4630685" author="JIRAUSER1257896" created="Tue, 21 Jun 2022 21:16:10 +0000"  >&lt;p&gt; the relevant code is &lt;a href=&quot;https://github.com/10gen/mongo/blob/r4.4.14/src/mongo/db/repl/oplog_applier.cpp#L150&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;here&lt;/a&gt;:&lt;/p&gt;
&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;    auto numberOfThreads =&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;        std::min(replWriterThreadCount, 2 * &lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;static_cast&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;int&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&amp;gt;(ProcessInfo::getNumAvailableCores()));&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;And then we &lt;a href=&quot;https://github.com/10gen/mongo/blob/r4.4.14/src/mongo/db/repl/oplog_applier.cpp#L159-L161&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;fix the minNumberOfThreads accordingly&lt;/a&gt;:&lt;/p&gt;
&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; options.minThreads = replWriterMinThreadCount &amp;lt; threadCount ? replWriterMinThreadCount : threadCount;&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; options.maxThreads = &lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;static_cast&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&amp;lt;&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;size_t&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&amp;gt;(threadCount);&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;So this &quot;capped&quot; part should be documented here &lt;a href=&quot;https://www.mongodb.com/docs/manual/reference/parameters/#mongodb-parameter-param.replWriterThreadCount?&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://www.mongodb.com/docs/manual/reference/parameters/#mongodb-parameter-param.replWriterThreadCount?&lt;/a&gt;&lt;/p&gt;</comment>
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            <issuekey id="542268">SERVER-34938</issuekey>
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