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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-78414] Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes</title>
                <link>https://jira.mongodb.org/browse/SERVER-78414</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;The recipient shard fetches changes to the documents in the range being migrated by continuously running the &amp;#95;transferMods command against the donor shard. The donor shard has the changes buffer in memory.&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://github.com/mongodb/mongo/blob/293535c6e1dc7a07035b91f7e46a6ca60a4b62d9/src/mongo/db/s/migration_destination_manager.cpp#L1585-L1594&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;The termination condition for when the recipient shard stops attempting to fetch changes from the donor shard&lt;/a&gt; is when both of the following conditions are satisfied:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;The recipient shard has run at least one &amp;#95;transferMods command after the &amp;#95;recvChunkCommit was received.&lt;/li&gt;
	&lt;li&gt;The &amp;#95;transferMods command returned an empty result set or &lt;a href=&quot;https://github.com/mongodb/mongo/blob/293535c6e1dc7a07035b91f7e46a6ca60a4b62d9/src/mongo/db/s/migration_destination_manager.cpp#L1780-L1786&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;none of the changes returned by the &amp;#95;transferMods command are in the range being migrated&lt;/a&gt;.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;However it is possible even when none of the changes returned by the &amp;#95;transferMods commands are in the range being migrated for there to still be a pending batch on the donor shard which &lt;em&gt;would&lt;/em&gt; have changes in the range being migrated. In particular, transactions are not filtering out changes which are unrelated to range being migrated and can lead to an entire &amp;#95;transferMods command having changes which are wholly unrelated to the range being migrated (&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78415&quot; title=&quot;Avoid sending unrelated operations from transactions to recipient shard during chunk migration&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78415&quot;&gt;SERVER-78415&lt;/a&gt;).&lt;/p&gt;</description>
                <environment></environment>
        <key id="2376240">SERVER-78414</key>
            <summary>Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes</summary>
                <type id="1" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14703&amp;avatarType=issuetype">Bug</type>
                                            <priority id="2" iconUrl="https://jira.mongodb.org/images/icons/priorities/critical.svg">Critical - P2</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="max.hirschhorn@mongodb.com">Max Hirschhorn</assignee>
                                    <reporter username="max.hirschhorn@mongodb.com">Max Hirschhorn</reporter>
                        <labels>
                    </labels>
                <created>Fri, 23 Jun 2023 23:20:14 +0000</created>
                <updated>Sun, 29 Oct 2023 21:19:34 +0000</updated>
                            <resolved>Mon, 26 Jun 2023 19:49:04 +0000</resolved>
                                    <version>4.2.0</version>
                    <version>4.4.0</version>
                    <version>5.0.0</version>
                    <version>6.0.0</version>
                    <version>7.0.0-rc5</version>
                                    <fixVersion>7.1.0-rc0</fixVersion>
                    <fixVersion>5.0.19</fixVersion>
                    <fixVersion>4.4.23</fixVersion>
                    <fixVersion>7.0.0-rc6</fixVersion>
                    <fixVersion>6.0.8</fixVersion>
                                    <component>Sharding</component>
                                        <votes>0</votes>
                                    <watches>14</watches>
                                                                                                                <comments>
                            <comment id="5526453" author="xgen-internal-githook" created="Tue, 27 Jun 2023 00:02:46 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Max Hirschhorn&apos;, &apos;email&apos;: &apos;max.hirschhorn@mongodb.com&apos;, &apos;username&apos;: &apos;visemet&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78414&quot; title=&quot;Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78414&quot;&gt;&lt;del&gt;SERVER-78414&lt;/del&gt;&lt;/a&gt; Apply _transferMods batches until size returned == 0.&lt;/p&gt;

&lt;p&gt;It is possible for the entire _transferMods command response to contain&lt;br/&gt;
changes which aren&apos;t relevant for the range being migrated. The&lt;br/&gt;
recipient shard should continue running the _transferMods command on the&lt;br/&gt;
donor shard primary in this case until it learns there are no further&lt;br/&gt;
changes.&lt;/p&gt;

&lt;p&gt;(cherry picked from commit a8fdfb121dfc5e35e20a036c8198f2e9240d5b61)&lt;br/&gt;
Branch: v4.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/dccf28cd32cf5caddfd538ea3b698619468f74ea&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/dccf28cd32cf5caddfd538ea3b698619468f74ea&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="5526444" author="xgen-internal-githook" created="Mon, 26 Jun 2023 23:56:34 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Max Hirschhorn&apos;, &apos;email&apos;: &apos;max.hirschhorn@mongodb.com&apos;, &apos;username&apos;: &apos;visemet&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78414&quot; title=&quot;Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78414&quot;&gt;&lt;del&gt;SERVER-78414&lt;/del&gt;&lt;/a&gt; Apply _transferMods batches until size returned == 0.&lt;/p&gt;

&lt;p&gt;It is possible for the entire _transferMods command response to contain&lt;br/&gt;
changes which aren&apos;t relevant for the range being migrated. The&lt;br/&gt;
recipient shard should continue running the _transferMods command on the&lt;br/&gt;
donor shard primary in this case until it learns there are no further&lt;br/&gt;
changes.&lt;/p&gt;

&lt;p&gt;(cherry picked from commit a8fdfb121dfc5e35e20a036c8198f2e9240d5b61)&lt;br/&gt;
Branch: v7.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/453091a36400607b1e0c57aff596cffe22a82eed&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/453091a36400607b1e0c57aff596cffe22a82eed&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="5526439" author="xgen-internal-githook" created="Mon, 26 Jun 2023 23:53:30 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Max Hirschhorn&apos;, &apos;email&apos;: &apos;max.hirschhorn@mongodb.com&apos;, &apos;username&apos;: &apos;visemet&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78414&quot; title=&quot;Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78414&quot;&gt;&lt;del&gt;SERVER-78414&lt;/del&gt;&lt;/a&gt; Apply _transferMods batches until size returned == 0.&lt;/p&gt;

&lt;p&gt;It is possible for the entire _transferMods command response to contain&lt;br/&gt;
changes which aren&apos;t relevant for the range being migrated. The&lt;br/&gt;
recipient shard should continue running the _transferMods command on the&lt;br/&gt;
donor shard primary in this case until it learns there are no further&lt;br/&gt;
changes.&lt;/p&gt;

&lt;p&gt;(cherry picked from commit a8fdfb121dfc5e35e20a036c8198f2e9240d5b61)&lt;br/&gt;
Branch: v6.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/a06a6bb1c890c8d84e94e48d0110cd67d0ef9da3&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/a06a6bb1c890c8d84e94e48d0110cd67d0ef9da3&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="5526425" author="xgen-internal-githook" created="Mon, 26 Jun 2023 23:44:25 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Max Hirschhorn&apos;, &apos;email&apos;: &apos;max.hirschhorn@mongodb.com&apos;, &apos;username&apos;: &apos;visemet&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78414&quot; title=&quot;Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78414&quot;&gt;&lt;del&gt;SERVER-78414&lt;/del&gt;&lt;/a&gt; Apply _transferMods batches until size returned == 0.&lt;/p&gt;

&lt;p&gt;It is possible for the entire _transferMods command response to contain&lt;br/&gt;
changes which aren&apos;t relevant for the range being migrated. The&lt;br/&gt;
recipient shard should continue running the _transferMods command on the&lt;br/&gt;
donor shard primary in this case until it learns there are no further&lt;br/&gt;
changes.&lt;/p&gt;

&lt;p&gt;(cherry picked from commit a8fdfb121dfc5e35e20a036c8198f2e9240d5b61)&lt;br/&gt;
Branch: v5.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/db4db96b4b66a4fb366694dfef103847921d5299&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/db4db96b4b66a4fb366694dfef103847921d5299&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="5525540" author="xgen-internal-githook" created="Mon, 26 Jun 2023 17:40:39 +0000"  >&lt;p&gt;Author: &lt;/p&gt;
{&apos;name&apos;: &apos;Max Hirschhorn&apos;, &apos;email&apos;: &apos;max.hirschhorn@mongodb.com&apos;, &apos;username&apos;: &apos;visemet&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-78414&quot; title=&quot;Recipient shard in chunk migration can skip fetching changes to the migrated range, leading to lost writes&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-78414&quot;&gt;&lt;del&gt;SERVER-78414&lt;/del&gt;&lt;/a&gt; Apply _transferMods batches until size returned == 0.&lt;/p&gt;

&lt;p&gt;It is possible for the entire _transferMods command response to contain&lt;br/&gt;
changes which aren&apos;t relevant for the range being migrated. The&lt;br/&gt;
recipient shard should continue running the _transferMods command on the&lt;br/&gt;
donor shard primary in this case until it learns there are no further&lt;br/&gt;
changes.&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/a8fdfb121dfc5e35e20a036c8198f2e9240d5b61&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/a8fdfb121dfc5e35e20a036c8198f2e9240d5b61&lt;/a&gt;&lt;/p&gt;</comment>
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