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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>
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<item>
            <title>[SERVER-61808] The cloning of sessions of the moveChunk gets slower after some migrations</title>
                <link>https://jira.mongodb.org/browse/SERVER-61808</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;As part of PM-2423 we have been measuring the performance of the migration protocol. We saw some weird numbers related to the cloning of the sessions that would be interesting to understand.&lt;/p&gt;

&lt;p&gt;&lt;ins&gt;Environment&lt;/ins&gt;&lt;br/&gt;
 3-shard Sharded cluster running 5.1 binaries.&lt;/p&gt;

&lt;p&gt;&lt;ins&gt;Experiment&lt;/ins&gt;&lt;br/&gt;
 We create a sharded collection with an initial pre-split of 1K chunks. The shard key is a hashed random number. After that we insert as bulk of 1K documents using retryable writes.&lt;/p&gt;

&lt;p&gt;After that we execute a few thousand random migrations. There are not CRUD operations during the execution of this phase.&lt;/p&gt;

&lt;p&gt;You can check the Genny worload we executed &lt;a href=&quot;https://spruce.mongodb.com/version/617ac4bd32f4174db4f39f21/tasks?sorts=STATUS%3AASC%3BBASE_STATUS%3ADESC&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;ins&gt;Results&lt;/ins&gt;&lt;br/&gt;
 You can find our results &lt;a href=&quot;https://docs.google.com/spreadsheets/d/1gjauHPkti-4gfuOu08XBJWicXyq0pJ9s-Vk4Tza6Ldo/edit#gid=419145228&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;We are plotting two different variables:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;the total execution time spent holding the critical section during the migration (catch-up phase of the migration).&lt;/li&gt;
	&lt;li&gt;the total execution time spent holding the critical section blocking reads and writes (commit phase of the migration).&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;The interesting time is the first one, the second one is more or less constant. We can see an slow down of 30x between the first move chunks and the lasts ones on my machine, after 4K moveChunks. We also got some numbers on EVG, you see them on the different tabs.&lt;/p&gt;</description>
                <environment></environment>
        <key id="1939369">SERVER-61808</key>
            <summary>The cloning of sessions of the moveChunk gets slower after some migrations</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="9">Done</resolution>
                                        <assignee username="luis.osta@mongodb.com">Luis Osta</assignee>
                                    <reporter username="sergi.mateo-bellido@mongodb.com">Sergi Mateo Bellido</reporter>
                        <labels>
                            <label>sharding-nyc-subteam1</label>
                    </labels>
                <created>Tue, 30 Nov 2021 16:41:51 +0000</created>
                <updated>Wed, 22 Dec 2021 20:14:55 +0000</updated>
                            <resolved>Wed, 22 Dec 2021 20:14:54 +0000</resolved>
                                    <version>5.1.0</version>
                                                    <component>Sharding</component>
                                        <votes>0</votes>
                                    <watches>7</watches>
                                                                                                                <comments>
                            <comment id="4264719" author="JIRAUSER1253452" created="Wed, 22 Dec 2021 20:14:41 +0000"  >&lt;p&gt;I&apos;ve filed &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-62233&quot; title=&quot;Make SessionCatalogMigrationSource handleWriteHistory filter out oplogs outside of the chunkRange with OpType &amp;#39;n&amp;#39;&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-62233&quot;&gt;&lt;del&gt;SERVER-62233&lt;/del&gt;&lt;/a&gt; to address the issue.&lt;/p&gt;</comment>
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            <issuekey id="1955696">SERVER-62233</issuekey>
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