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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>[SERVER-84421] Unexpected flow control engaged during benchmark</title>
                <link>https://jira.mongodb.org/browse/SERVER-84421</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;During a benchmark, we found there is many slow log waiting for flow control tickets, we decompress the diagnostic metric data, and find flow control engaged&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499708/499708_image-2023-12-27-17-00-25-921.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;But we don&apos;t find any majority committed lay in corresponding point&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499705/499705_image-2023-12-27-17-02-40-532.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499707/499707_image-2023-12-27-17-02-05-514.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499706/499706_image-2023-12-27-17-02-24-056.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;According to the configuration of flow control, only replication lay greater than 5s, can flow control engaged&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499704/499704_image-2023-12-27-17-04-46-702.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;&#160;&lt;/p&gt;</description>
                <environment></environment>
        <key id="2532888">SERVER-84421</key>
            <summary>Unexpected flow control engaged during benchmark</summary>
                <type id="1" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14703&amp;avatarType=issuetype">Bug</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="11262" iconUrl="https://jira.mongodb.org/images/icons/statuses/generic.png" description="">Investigating</status>
                    <statusCategory id="4" key="indeterminate" colorName="inprogress"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="edwin.zhou@mongodb.com">Edwin Zhou</assignee>
                                    <reporter username="zhangwenjumlovercl@gmail.com">jum zhang</reporter>
                        <labels>
                    </labels>
                <created>Wed, 27 Dec 2023 09:08:50 +0000</created>
                <updated>Mon, 29 Jan 2024 08:00:59 +0000</updated>
                                                                                                <votes>0</votes>
                                    <watches>6</watches>
                                                                                                                <comments>
                            <comment id="5993571" author="JIRAUSER1257066" created="Mon, 8 Jan 2024 12:36:52 +0000"  >&lt;p&gt;Thank you for uploading the diagnostic data for the primary node &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=zhangwenjumlovercl%40gmail.com&quot; class=&quot;user-hover&quot; rel=&quot;zhangwenjumlovercl@gmail.com&quot;&gt;zhangwenjumlovercl@gmail.com&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;I took a look at the data and also observed that replication lag reported on the primary did not exceed 5s, so it is unusual that flow control was engaged during your benchmark. &lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/501369/501369_Screenshot+2024-01-08+at+12.33.31%E2%80%AFPM.png&quot; width=&quot;100%&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt; &lt;/p&gt;

&lt;p&gt;However, we will need diagnostic data from the secondary nodes as well to see how they were behaving leading up to flow control engaging.&lt;/p&gt;

&lt;p&gt;Could you also upload diagnostic data from both secondary members 8 and 10 during this time?&lt;/p&gt;</comment>
                            <comment id="5973501" author="JIRAUSER1273878" created="Thu, 28 Dec 2023 11:47:34 +0000"  >&lt;p&gt;The metrics files and log file have been uploaded. As i mentioned before, we decomposed the diagnostic metrics file and found that flow control engaged in IOSDate(&quot;2023-12-26T16:21:32Z&quot;). There is no flow control related log entries in mongod.log,only slow log entries show that update operations are waitting to hold flow control tickets &lt;br/&gt;
&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/attachment/499871/499871_image-2023-12-28-19-46-51-844.png&quot; id=&quot;04f79526&quot; style=&quot;border: 0px solid black&quot; /&gt;&lt;/span&gt;&lt;/p&gt;</comment>
                            <comment id="5972345" author="JIRAUSER1257066" created="Wed, 27 Dec 2023 16:46:04 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=zhangwenjumlovercl%40gmail.com&quot; class=&quot;user-hover&quot; rel=&quot;zhangwenjumlovercl@gmail.com&quot;&gt;zhangwenjumlovercl@gmail.com&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;For us to further investigate this issue, would you please archive (tar or zip) the mongod.log files and the &lt;tt&gt;$dbpath/diagnostic.data&lt;/tt&gt; directory (the contents are described &lt;a href=&quot;https://docs.mongodb.com/manual/administration/analyzing-mongodb-performance/#full-time-diagnostic-data-capture&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;here&lt;/a&gt;) and upload them to this &lt;a href=&quot;https://amphora.corp.mongodb.com/public/upload/eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmb2xkZXJfaWQiOiIyNDE2ODgzMjk2NzAiLCJleHAiOjE3MDYyODc1NDV9.LQN78wOsE2-xEQmyFAFY3JpW00B5GL_DsA3Vecl-27Y&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;support uploader&lt;/a&gt; location?&lt;/p&gt;

&lt;p&gt;Files uploaded to this portal are visible only to MongoDB employees and are routinely deleted after some time.&lt;/p&gt;

&lt;p&gt;Kind regards,&lt;br/&gt;
Edwin&lt;/p&gt;</comment>
                    </comments>
                    <attachments>
                            <attachment id="501369" name="Screenshot 2024-01-08 at 12.33.31&#8239;PM.png" size="210495" author="edwin.zhou@mongodb.com" created="Mon, 8 Jan 2024 12:36:14 +0000"/>
                            <attachment id="499708" name="image-2023-12-27-17-00-25-921.png" size="812415" author="zhangwenjumlovercl@gmail.com" created="Wed, 27 Dec 2023 09:00:29 +0000"/>
                            <attachment id="499707" name="image-2023-12-27-17-02-05-514.png" size="187832" author="zhangwenjumlovercl@gmail.com" created="Wed, 27 Dec 2023 09:02:08 +0000"/>
                            <attachment id="499706" name="image-2023-12-27-17-02-24-056.png" size="198899" author="zhangwenjumlovercl@gmail.com" created="Wed, 27 Dec 2023 09:02:26 +0000"/>
                            <attachment id="499705" name="image-2023-12-27-17-02-40-532.png" size="198151" author="zhangwenjumlovercl@gmail.com" created="Wed, 27 Dec 2023 09:02:42 +0000"/>
                            <attachment id="499704" name="image-2023-12-27-17-04-46-702.png" size="219061" author="zhangwenjumlovercl@gmail.com" created="Wed, 27 Dec 2023 09:04:49 +0000"/>
                            <attachment id="499871" name="image-2023-12-28-19-46-51-844.png" size="175331" author="zhangwenjumlovercl@gmail.com" created="Thu, 28 Dec 2023 11:46:54 +0000"/>
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