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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-15210] Add Warning for ReadConcern: Majority on PSA Replicasets</title>
                <link>https://jira.mongodb.org/browse/DOCS-15210</link>
                <project id="10380" key="DOCS">Documentation</project>
                    <description>&lt;p&gt;We ran into an issue where the documentation was a bit unclear about the downsides of using ReadConcern: Majority on PSA replicasets &lt;a href=&quot;https://www.mongodb.com/docs/manual/reference/read-concern-majority/#primary-secondary-arbiter-replica-sets&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;&#160;&lt;/p&gt;

&lt;p&gt;&lt;b&gt;Using ReadConcern: majority after doing writes with a WriteConcern value less than the majority can cause the user to receive stale data on all versions.&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;Additionally, using ReadConcern: Majority in PSA replicasets can cause immobilization of the entire deployment through increased cache pressure on failure of majority of the data-bearing nodes on older versions of MongoDB.&#160; Stennie made some notes on a &lt;a href=&quot;https://dba.stackexchange.com/questions/257831/why-mongodb-needs-to-disable-majority-read-concern-for-psa-architecture&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;stackexchange post here&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;&quot;The caveat on Read Concern Majority applies to a PSSAA deployment (or any where you can lose a majority of data-bearing voting nodes but still maintain a primary). With a PSSAA deployment degraded to PSxAA, the replica set can no longer acknowledge majority writes and there will be increased cache pressure which will degrade performance and eventually immobilise the deployment unless Read Concern Majority is disabled.&quot;&lt;/p&gt;</description>
                <environment></environment>
        <key id="2016098">DOCS-15210</key>
            <summary>Add Warning for ReadConcern: Majority on PSA Replicasets</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="4" iconUrl="https://jira.mongodb.org/images/icons/priorities/minor.svg">Minor - P4</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="ian.fogelman@mongodb.com">Ian Fogelman</assignee>
                                    <reporter username="chris.kelly@mongodb.com">Chris Kelly</reporter>
                        <labels>
                    </labels>
                <created>Mon, 4 Apr 2022 15:47:36 +0000</created>
                <updated>Mon, 13 Nov 2023 18:45:33 +0000</updated>
                            <resolved>Mon, 18 Apr 2022 17:50:08 +0000</resolved>
                                                    <fixVersion>5.0.0</fixVersion>
                    <fixVersion>5.3.0</fixVersion>
                    <fixVersion>6.0.0</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>4</watches>
                                                                                                                <comments>
                            <comment id="4488320" author="xgen-internal-githook" created="Mon, 18 Apr 2022 15:58:08 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;ianf-mongodb&apos;, &apos;email&apos;: &apos;85948430+ianf-mongodb@users.noreply.github.com&apos;, &apos;username&apos;: &apos;ianf-mongodb&apos;}
&lt;p&gt;Message: Docs-15210 v5.0 (#973)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;writeConcern -&amp;gt; write concern&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;CR 1 Feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update verbiage&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove duplicate your&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove ref&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update&lt;br/&gt;
Branch: v5.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/c59aff543c3a0b33d83a40f729479f8237d41742&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/c59aff543c3a0b33d83a40f729479f8237d41742&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4488319" author="xgen-internal-githook" created="Mon, 18 Apr 2022 15:58:04 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;ianf-mongodb&apos;, &apos;email&apos;: &apos;85948430+ianf-mongodb@users.noreply.github.com&apos;, &apos;username&apos;: &apos;ianf-mongodb&apos;}
&lt;p&gt;Message: Docs-15210 v5.0 (#973)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;writeConcern -&amp;gt; write concern&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;CR 1 Feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update verbiage&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove duplicate your&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove ref&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update&lt;br/&gt;
Branch: v5.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/c59aff543c3a0b33d83a40f729479f8237d41742&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/c59aff543c3a0b33d83a40f729479f8237d41742&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4488317" author="xgen-internal-githook" created="Mon, 18 Apr 2022 15:57:45 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;ianf-mongodb&apos;, &apos;email&apos;: &apos;85948430+ianf-mongodb@users.noreply.github.com&apos;, &apos;username&apos;: &apos;ianf-mongodb&apos;}
&lt;p&gt;Message: Docs-15210 v5.3 (#972)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;writeConcern -&amp;gt; write concern&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;CR 1 Feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update verbiage&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove duplicate your&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove ref&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update&lt;br/&gt;
Branch: v5.3&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/2fc400b888a286ede760ceb32799bf75b68c3dc0&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/2fc400b888a286ede760ceb32799bf75b68c3dc0&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4488315" author="xgen-internal-githook" created="Mon, 18 Apr 2022 15:57:41 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;ianf-mongodb&apos;, &apos;email&apos;: &apos;85948430+ianf-mongodb@users.noreply.github.com&apos;, &apos;username&apos;: &apos;ianf-mongodb&apos;}
&lt;p&gt;Message: Docs-15210 v5.3 (#972)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;writeConcern -&amp;gt; write concern&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;CR 1 Feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update verbiage&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove duplicate your&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove ref&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update&lt;br/&gt;
Branch: v5.3&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/2fc400b888a286ede760ceb32799bf75b68c3dc0&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/2fc400b888a286ede760ceb32799bf75b68c3dc0&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4488314" author="xgen-internal-githook" created="Mon, 18 Apr 2022 15:57:30 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;ianf-mongodb&apos;, &apos;email&apos;: &apos;85948430+ianf-mongodb@users.noreply.github.com&apos;, &apos;username&apos;: &apos;ianf-mongodb&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention (#923)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;&lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15210&quot; title=&quot;Add Warning for ReadConcern: Majority on PSA Replicasets&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15210&quot;&gt;&lt;del&gt;DOCS-15210&lt;/del&gt;&lt;/a&gt; add readConcern mention&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;writeConcern -&amp;gt; write concern&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;CR 1 Feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update verbiage&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove duplicate your&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;remove ref&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;update&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/3c7e2e9320900be5e442781e65d46e379eb65558&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/3c7e2e9320900be5e442781e65d46e379eb65558&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
                            <comment id="4459084" author="JIRAUSER1265262" created="Tue, 5 Apr 2022 19:49:43 +0000"  >&lt;p&gt;Hi Joseph,&lt;/p&gt;

&lt;p&gt;I think I miscommunicated the exact issue. Specifically, it is not the&#160;&lt;b&gt;enableMajorityReadConcern&lt;/b&gt;&#160;that is the issue, but rather actually using the read concern &quot;majority&quot; in a PSA replica set. In the case referenced in&#160;HELP-32506, it is not actually poor performance that is the issue - it is the fact the user attempts to query with&#160;readConcernlevel: &quot;majority&quot; on a write to the replicaset that uses&#160;&lt;tt&gt;w:1&lt;/tt&gt;, and receives stale results.&lt;/p&gt;

&lt;p&gt;In this case, we request a note to be made about using readConcern: majority, advising against using a global default readConcern of majority if writeConcern is less than the size of the majority (1 is implicit default), as there is a chance of not being able to read data back to the user that isn&apos;t fully replicated. Because of the implicit default writeConcern of 1, and enableMajorityReadConcern enabled by default in MongoDB 5.0 and above, this is a pitfall that can adversely affect those using PSA replica sets and may not be very obvious to troubleshoot, experienced in&#160;HELP-29194.&lt;/p&gt;</comment>
                            <comment id="4455416" author="JIRAUSER1257483" created="Mon, 4 Apr 2022 17:01:43 +0000"  >&lt;p&gt;I&apos;m not sure there&apos;s much point in going into too much detail here since&#160;&lt;b&gt;enableMajorityReadConcern&lt;/b&gt; has one setting (`true`) and cannot be set to false in v5.0 and later.&lt;/p&gt;

&lt;p&gt;Would it help to point users who want add&apos;l info to the&#160;&lt;a href=&quot;https://www.mongodb.com/docs/manual/tutorial/mitigate-psa-performance-issues/&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Mitigate Performance Issues with PSA Replica Set&lt;/a&gt; page?&lt;/p&gt;</comment>
                    </comments>
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