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<channel>
    <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-39683] shard request to split a same chunk at the same time.</title>
                <link>https://jira.mongodb.org/browse/SERVER-39683</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Hello, in the environment of my production server, there is occasional increase in machine load, the normal time is 0-1, the abnormal time is 5-10, the shard node cpu is very high when viewing, the machine always prints some information when viewing the log. When the log is not printed, the machine load drops and resumes. The &quot;Finding the split vector for ctu.mobileToken&quot; will always operate, how to avoid it, during this time, the request volume has not increased significantly, io utils 40%. I am looking forward to your reply, thank you!&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;
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						&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;   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;2019-02-20T04:58:26.144+0000 I SHARDING [conn68389] received splitChunk request: { splitChunk: &quot;ctu.mobileToken&quot;, configdb: &quot;crs/10.60.96.104:21001,10.60.96.81:21001,10.60.96.92:21001&quot;, from: &quot;rs3&quot;, keyPattern: { token: 1.0 }, shardVersion: [ Timestamp 4419000|633, ObjectId(&apos;5bc858a5c9ebaf2f1aafd8db&apos;) ], min: { token: &quot;5c6bc051xbpFF1evtQv1JhORbtFRiBkFeIl8Ws83&quot; }, max: { token: MaxKey }, splitKeys: [ { token: &quot;5c6bc2301lWzOdbLzOYXcibfkgMDHi7XKN4xkRW3&quot; }, { token: &quot;5c6bc40dU74I7yewg2ifmA2XCUEtrwvwlmzRP0m3&quot; }, { token: &quot;5c6bc5f0tTGE1yJKpZIkoISq99cmTTqeu74XKTe3&quot; }, { token: &quot;5c6bc7d8pm0SayzAzdIC8gYssmU6PjGhozzv0iF3&quot; }, { token: &quot;5c6bc9c3gRS7D56NkHv7UalFsAxz9dXkAWtI7tI3&quot; }, { token: &quot;5c6bcba5kTeFzefCUUKcVXI16C4LXYeuA8GtcAW3&quot; }, { token: &quot;5c6bcd8elMIjPAmVT2yJRO8cB80LItVVURDgErj3&quot; }, { token: &quot;5c6bcf853Zlt9Hhfl6zZualYooyCCpkdFQ6vere3&quot; }, { token: &quot;5c6bd180q3wyUljtRQ3dlyqSCJJO0R6itPWGyPg2&quot; }, { token: &quot;5c6bd382FCnxqHujlhcyfGWciqMXQCbhBGPND6u3&quot; }, { token: &quot;5c6bd53eaQdVIbd5NquKxr5Wx66DvRU6qaPYoIR3&quot; }, { token: &quot;5c6bd6e58Z5iBK9SnMhlPF5q1pQB5PaeZ2xjpoe3&quot; }, { token: &quot;5c6bd884CGMAajikF1JRksBiLsJWIfG2A9RLCD43&quot; }, { token: &quot;5c6bda2dYS0ccVBJuZ5d5LmFSljvXPsxENL8xL43&quot; }, { token: &quot;5c6bdbedFUq4zx2kuHxUfhFqk6Rjrzohsu6Jx3I3&quot; }, { token: &quot;5c6bddabUMYMsVXQQ6w9HibJI4fZDk7rttx9NQy2&quot; }, { token: &quot;5c6bdf69ve7X83v2E9rFZNZ9WL2LaTCnccEATcL3&quot; }, { token: &quot;5c6be11eB5ZywhbVM2fTOUjrz6OdTNpnc9ZQ0Jq3&quot; }, { token: &quot;5c6be2a5WPt9bMt9doFB2v7vA3uWKv1vapGwzYU3&quot; }, { token: &quot;5c6be42aHdlCe4Mg5Vylmj5Grv7iZIhq01Wn4wl3&quot; 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}, { token: &quot;5c6cda15XJ4xiAsY2PAs7wx5nDiei9LfkImgdMj2&quot; }, { token: &quot;5c6cdbc4Plwak4CedPxxPRwndEe5kvFenGSzr7F3&quot; }, { token: &quot;5c6cde72cvQMouAe4SNgu0pYwu4tH3VaXK3L61D3&quot; } ] }&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;</description>
                <environment></environment>
        <key id="701094">SERVER-39683</key>
            <summary>shard request to split a same chunk at the same time.</summary>
                <type id="6" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14720&amp;avatarType=issuetype">Question</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="eric.sedor@mongodb.com">Eric Sedor</assignee>
                                    <reporter username="JackWang@180721">JackWang [X]</reporter>
                        <labels>
                    </labels>
                <created>Wed, 20 Feb 2019 06:55:36 +0000</created>
                <updated>Wed, 27 Feb 2019 08:40:05 +0000</updated>
                            <resolved>Mon, 25 Feb 2019 21:09:51 +0000</resolved>
                                    <version>3.4.3</version>
                                                    <component>Sharding</component>
                                        <votes>0</votes>
                                    <watches>4</watches>
                                                                                                                <comments>
                            <comment id="2164438" author="jackwang@180721" created="Wed, 27 Feb 2019 08:40:05 +0000"  >&lt;p&gt;Hello, I am here for help. This is related to my work. My production line has accumulated 500 million data. Now the machine resources are alarmed. When I perform the remove operation, there is very little data (such as 10,000), and the machine loads the alarm. A lot of slow queries; I want to know how to quickly delete some of the data in the shard collection, looking forward to your reply&lt;/p&gt;


&lt;p&gt;------------------ Original ------------------&lt;br/&gt;
From:  &quot;Eric Sedor (Jira)&quot;&amp;lt;jira@mongodb.org&amp;gt;;&lt;br/&gt;
Date:  Wed, Feb 27, 2019 04:57 AM&lt;br/&gt;
To:  &quot;hao.wang&quot;&amp;lt;hao.wang@dingxiang-inc.com&amp;gt;; &lt;/p&gt;

&lt;p&gt;Subject:  &lt;span class=&quot;error&quot;&gt;&amp;#91;MongoDB-JIRA&amp;#93;&lt;/span&gt; (&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683&quot; title=&quot;shard request to split a same chunk at the same time.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-39683&quot;&gt;&lt;del&gt;SERVER-39683&lt;/del&gt;&lt;/a&gt;) shard request to split a same chunk at the same time.&lt;/p&gt;



&lt;p&gt;    [ &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&amp;amp;focusedCommentId=2163534#comment-2163534&quot; class=&quot;external-link&quot; rel=&quot;nofollow&quot;&gt;https://jira.mongodb.org/browse/SERVER-39683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&amp;amp;focusedCommentId=2163534#comment-2163534&lt;/a&gt; ] &lt;/p&gt;

&lt;p&gt;Eric Sedor &#20110; 19-2-26 &#19979;&#21320;8:56 &#32534;&#36753;&#20102;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683&quot; title=&quot;shard request to split a same chunk at the same time.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-39683&quot;&gt;&lt;del&gt;SERVER-39683&lt;/del&gt;&lt;/a&gt; &#30340;&#35780;&#35770;:&lt;br/&gt;
-------------------------------------------------&lt;/p&gt;

&lt;p&gt;To clarify, we are suggesting adding 2 mongos to bring the total to 5, and this is considered a mitigation but not a solution. &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-34448&quot; title=&quot;Disable chunk splitting functionality in mongos&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-34448&quot;&gt;&lt;del&gt;SERVER-34448&lt;/del&gt;&lt;/a&gt; in MongoDB 4.2 is considered the solution.&lt;/p&gt;

&lt;p&gt;You would need to direct write traffic at all 5 via a connection string that included all of them. The goal of this change is to ensure that the majority of mongos-driven split attempts coincide with a chunk reaching its maximum size. Currently this is most accurately attained with 5 mongos receiving evenly distributed writes.&lt;/p&gt;

&lt;p&gt;For further discussion about how the system works, please post 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 &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;. A question like this involving more discussion would be best posted on the mongodb-user group.&lt;/p&gt;




&lt;p&gt;&#21407;&#20540; (&#20316;&#32773;: eric.sedor):&lt;br/&gt;
To clarify, we are suggesting adding 2 mongos to bring the total to 5, and this is considered a mitigation but not a solution. &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-34448&quot; title=&quot;Disable chunk splitting functionality in mongos&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-34448&quot;&gt;&lt;del&gt;SERVER-34448&lt;/del&gt;&lt;/a&gt; in MongoDB 4.2 is considered the solution.&lt;/p&gt;

&lt;p&gt;You would need to direct write traffic at all 5 via a connection string that included all of them. The goal of this change is to ensure that the majority of mongos-driven split attempts to coincide with a chunk reaching its maximum size. Currently this is most accurately attained with 5 mongos receiving evenly distributed writes.&lt;/p&gt;

&lt;p&gt;For further discussion about how the system works, please post 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 &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;. A question like this involving more discussion would be best posted on the mongodb-user group.&lt;/p&gt;




&lt;p&gt;----------------------&lt;br/&gt;
This message was sent from MongoDB&apos;s issue tracking system. To respond to this ticket, please login to &lt;a href=&quot;https://jira.mongodb.org&quot; class=&quot;external-link&quot; rel=&quot;nofollow&quot;&gt;https://jira.mongodb.org&lt;/a&gt; using your JIRA or MMS credentials.&lt;/p&gt;</comment>
                            <comment id="2163873" author="jackwang@180721" created="Wed, 27 Feb 2019 02:24:57 +0000"  >&lt;p&gt;&#24863;&#35874;&#20320;&#30340;&#32784;&#24515;&#35762;&#35299;&#65292;&#20294;&#26159;&#25105;&#30340;&#29983;&#20135;&#29615;&#22659;&#20381;&#28982;&#26159;&#20598;&#23572;&#26426;&#22120;&#36127;&#36733;&#39640;&#65292;&#24182;&#19988;&#37027;&#20010;&#26102;&#21051;&#65292;shard&#33410;&#28857;&#19968;&#30452;&#25171;&#21360;&#8220;find the split vector &#8221;&#65292;&#25105;&#24182;&#27809;&#26377;&#20855;&#20307;&#30340;&#35299;&#20915;&#25514;&#26045;&#65292;&#25105;&#30340;&#29615;&#22659;&#26377;5&#20159;&#25968;&#25454;&#65292;&#25105;&#24819;&#24555;&#36895;&#21024;&#38500;&#19968;&#37096;&#20998;&#65292;&#20294;&#26159;&#27809;&#26377;&#22909;&#30340;&#26041;&#26696;&#12290;&#25105;&#29616;&#22312;&#24456;&#26159;&#33510;&#24700;&#65292;&#24076;&#26395;&#24471;&#21040;&#20320;&#30340;&#24110;&#21161;&lt;/p&gt;


&lt;p&gt;------------------ Original ------------------&lt;br/&gt;
From:  &quot;Eric Sedor (Jira)&quot;&amp;lt;jira@mongodb.org&amp;gt;;&lt;br/&gt;
Date:  Wed, Feb 27, 2019 04:57 AM&lt;br/&gt;
To:  &quot;hao.wang&quot;&amp;lt;hao.wang@dingxiang-inc.com&amp;gt;; &lt;/p&gt;

&lt;p&gt;Subject:  &lt;span class=&quot;error&quot;&gt;&amp;#91;MongoDB-JIRA&amp;#93;&lt;/span&gt; (&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683&quot; title=&quot;shard request to split a same chunk at the same time.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-39683&quot;&gt;&lt;del&gt;SERVER-39683&lt;/del&gt;&lt;/a&gt;) shard request to split a same chunk at the same time.&lt;/p&gt;



&lt;p&gt;    [ &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&amp;amp;focusedCommentId=2163534#comment-2163534&quot; class=&quot;external-link&quot; rel=&quot;nofollow&quot;&gt;https://jira.mongodb.org/browse/SERVER-39683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&amp;amp;focusedCommentId=2163534#comment-2163534&lt;/a&gt; ] &lt;/p&gt;

&lt;p&gt;Eric Sedor &#22312; &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-39683&quot; title=&quot;shard request to split a same chunk at the same time.&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-39683&quot;&gt;&lt;del&gt;SERVER-39683&lt;/del&gt;&lt;/a&gt;&#20013;&#30041;&#35328;:&lt;br/&gt;
-------------------------------------&lt;/p&gt;

&lt;p&gt;To clarify, we are suggesting adding 2 mongos to bring the total to 5, and this is considered a mitigation but not a solution. &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-34448&quot; title=&quot;Disable chunk splitting functionality in mongos&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-34448&quot;&gt;&lt;del&gt;SERVER-34448&lt;/del&gt;&lt;/a&gt; in MongoDB 4.2 is considered the solution.&lt;/p&gt;

&lt;p&gt;You would need to direct write traffic at all 5 via a connection string that included all of them. The goal of this change is to ensure that the majority of mongos-driven split attempts to coincide with a chunk reaching its maximum size. Currently this is most accurately attained with 5 mongos receiving evenly distributed writes.&lt;/p&gt;

&lt;p&gt;For further discussion about how the system works, please post 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 &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;. A question like this involving more discussion would be best posted on the mongodb-user group.&lt;/p&gt;




&lt;p&gt;----------------------&lt;br/&gt;
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                            <comment id="2163534" author="eric.sedor" created="Tue, 26 Feb 2019 20:56:07 +0000"  >&lt;p&gt;To clarify, we are suggesting adding 2 mongos to bring the total to 5, and this is considered a mitigation but not a solution.&#160;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-34448&quot; title=&quot;Disable chunk splitting functionality in mongos&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-34448&quot;&gt;&lt;del&gt;SERVER-34448&lt;/del&gt;&lt;/a&gt;&#160;in MongoDB 4.2 is considered the solution.&lt;/p&gt;

&lt;p&gt;You would need to direct write traffic at all 5 via a connection string that included all of them. The goal of this change is to ensure that the majority of mongos-driven split attempts coincide with a chunk reaching its maximum size. Currently this is most accurately attained with 5 mongos receiving evenly distributed writes.&lt;/p&gt;

&lt;p&gt;For further discussion about how the system works, please post 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 &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;. A question like this involving more discussion would be best posted on the mongodb-user group.&lt;/p&gt;

&lt;p&gt;&#160;&lt;/p&gt;</comment>
                            <comment id="2162734" author="jackwang@180721" created="Tue, 26 Feb 2019 10:48:47 +0000"  >&lt;p&gt;Thank you for your reply, but I still can&apos;t understand why adding 5 mongos can solve this problem. If I increase it from 5 mongos to 5, but there are no application connection operations, can I do this? Still 5 mongos must have a connection.&lt;/p&gt;</comment>
                            <comment id="2162126" author="eric.sedor" created="Mon, 25 Feb 2019 20:22:55 +0000"  >&lt;p&gt;Hi &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=JackWang%40180721&quot; class=&quot;user-hover&quot; rel=&quot;JackWang@180721&quot;&gt;JackWang@180721&lt;/a&gt;, thank you for your patience.&lt;/p&gt;

&lt;p&gt;We believe this is expected behavior resulting from how mongos nodes estimate when a chunk split needs to occur. Our current efforts around &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-34448&quot; title=&quot;Disable chunk splitting functionality in mongos&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-34448&quot;&gt;&lt;del&gt;SERVER-34448&lt;/del&gt;&lt;/a&gt; are expected to remove this issue by shifting split responsibility to mongod.&lt;/p&gt;

&lt;p&gt;In the meantime, you may be able to work around the impact of this issue by increasing the number of your mongos routers to 5 to match assumptions made by the mongos autoSplit algorithm (which is influenced by a&#160;&lt;a href=&quot;https://github.com/mongodb/mongo/blob/308c006003937ef496f24c7e12676c007a185cd2/src/mongo/s/chunk.cpp#L44&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;&lt;tt&gt;splitTestFactor&lt;/tt&gt;&lt;/a&gt;&#160;of 5).&lt;/p&gt;</comment>
                            <comment id="2157940" author="jackwang@180721" created="Thu, 21 Feb 2019 01:48:11 +0000"  >&lt;p&gt;3 mongos 3 config and 3 shard &#65307;&lt;br/&gt;
Looking forward to your reply&lt;/p&gt;</comment>
                            <comment id="2157930" author="eric.sedor" created="Thu, 21 Feb 2019 01:15:00 +0000"  >&lt;p&gt;Thanks for writing in. We are investigating and will get back to you with any questions we have. For now we did have one:&lt;/p&gt;

&lt;p&gt;Can you let us know how many mongos routers are in this deployment?&lt;/p&gt;</comment>
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