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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-69898] Wait for the critical section catch-up phase before refreshing the DB version</title>
                <link>https://jira.mongodb.org/browse/SERVER-69898</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Our framework for the critical sections allows to enter in&#160;&lt;em&gt;catch-up&lt;/em&gt; phase (only write ops are blocked) and in a &lt;em&gt;commit&lt;/em&gt; phase (both read and writes ops are blocked).&lt;/p&gt;

&lt;p&gt;The&#160;&lt;a href=&quot;https://github.com/10gen/mongo/blob/8bd3a016765aa131b9235f5f5e6a2b65690721f9/src/mongo/db/s/database_sharding_state.h#L103-L105&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;&lt;tt&gt;getCriticalSectionSignal&lt;/tt&gt;&lt;/a&gt;&#160;function accepts an argument,&#160;&lt;tt&gt;kWrite&lt;/tt&gt;&#160;or k&lt;tt&gt;Read&lt;/tt&gt;, to get the signal when a thread is entered in the&#160;&lt;em&gt;catch-up&lt;/em&gt;&#160;or&#160;&lt;em&gt;commit&lt;/em&gt;&#160;phases (&lt;tt&gt;kWrite&lt;/tt&gt;) or only in the&#160;&lt;em&gt;commit&lt;/em&gt;&#160;phase (&lt;tt&gt;kRead&lt;/tt&gt;).&lt;/p&gt;

&lt;p&gt;When the database version is needed to be refreshed, &lt;a href=&quot;https://github.com/10gen/mongo/blob/8bd3a016765aa131b9235f5f5e6a2b65690721f9/src/mongo/db/s/shard_filtering_metadata_refresh.cpp#L74-L75&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;the current logic gets the critical section signal only when another thread is entered in the &lt;em&gt;commit&lt;/em&gt;&#160;phase&lt;/a&gt; (which makes sense), BUT there is a problem. Suppose the following sequence of events:&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;Thread A enters in the&#160;&lt;em&gt;catch-up&lt;/em&gt;&#160;phase of the&#160;&lt;tt&gt;movePrimary&lt;/tt&gt;&lt;/li&gt;
	&lt;li&gt;Thread B refreshes the version of the same database, get the signal with&#160;&lt;tt&gt;kRead&lt;/tt&gt;&#160;and the result is&#160;&lt;tt&gt;boost::none&lt;/tt&gt;, so it continues&lt;/li&gt;
	&lt;li&gt;Thread B enters in the&#160;&lt;em&gt;commit&lt;/em&gt;&#160;phase and the ongoing refresh is not cancelled! In this case we have a race:&#160;&lt;tt&gt;movePrimary&lt;/tt&gt;&#160;and version refresh run in parallel.&lt;/li&gt;
&lt;/ol&gt;


&lt;p&gt;There are two solutions for this problem:&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;Get the signal with&#160;&lt;tt&gt;kRead&lt;/tt&gt;&#160;but we need to cancel ongoing refreshed when the&#160;&lt;em&gt;commit&lt;/em&gt;&#160;phase is entered.&lt;/li&gt;
	&lt;li&gt;Get the signal with&#160;&lt;tt&gt;kWrite&lt;/tt&gt;&#160;and cancel ongoing refreshed when the&#160;&lt;em&gt;catch-up&lt;/em&gt;&#160;phase is entered.&lt;/li&gt;
&lt;/ol&gt;


&lt;p&gt;What about secondaries? Currently, secondary nodes are notified &lt;a href=&quot;https://github.com/10gen/mongo/blob/8bd3a016765aa131b9235f5f5e6a2b65690721f9/src/mongo/db/s/move_primary_source_manager.cpp#L191-L202&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;only when the primary enters in the&#160;&lt;em&gt;catch-up&lt;/em&gt;&#160;phase&lt;/a&gt;. Consequently, we can only follow the solution 2 above, which is the target of this ticket.&lt;/p&gt;</description>
                <environment></environment>
        <key id="2143310">SERVER-69898</key>
            <summary>Wait for the critical section catch-up phase before refreshing the DB version</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="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="antonio.fuschetto@mongodb.com">Antonio Fuschetto</assignee>
                                    <reporter username="antonio.fuschetto@mongodb.com">Antonio Fuschetto</reporter>
                        <labels>
                    </labels>
                <created>Thu, 22 Sep 2022 15:04:14 +0000</created>
                <updated>Sun, 29 Oct 2023 21:32:56 +0000</updated>
                            <resolved>Fri, 30 Sep 2022 08:18:26 +0000</resolved>
                                                    <fixVersion>6.1.1</fixVersion>
                    <fixVersion>5.0.14</fixVersion>
                    <fixVersion>6.0.3</fixVersion>
                    <fixVersion>6.2.0-rc0</fixVersion>
                                                        <votes>0</votes>
                                    <watches>4</watches>
                                                                                                                <comments>
                            <comment id="4885769" author="xgen-internal-githook" created="Fri, 7 Oct 2022 13:36:09 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Antonio Fuschetto&apos;, &apos;email&apos;: &apos;antonio.fuschetto@mongodb.com&apos;, &apos;username&apos;: &apos;afuschetto&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-69898&quot; title=&quot;Wait for the critical section catch-up phase before refreshing the DB version&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-69898&quot;&gt;&lt;del&gt;SERVER-69898&lt;/del&gt;&lt;/a&gt; Wait for the critical section catch-up phase before refreshing the DB version&lt;br/&gt;
Branch: v6.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/29c8d88c97f9878f0d841adc61fcbf6758fca55f&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/29c8d88c97f9878f0d841adc61fcbf6758fca55f&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="4885764" author="xgen-internal-githook" created="Fri, 7 Oct 2022 13:33:02 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Antonio Fuschetto&apos;, &apos;email&apos;: &apos;antonio.fuschetto@mongodb.com&apos;, &apos;username&apos;: &apos;afuschetto&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-69898&quot; title=&quot;Wait for the critical section catch-up phase before refreshing the DB version&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-69898&quot;&gt;&lt;del&gt;SERVER-69898&lt;/del&gt;&lt;/a&gt; Wait for the critical section catch-up phase before refreshing the DB version&lt;br/&gt;
Branch: v6.1&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/8c8f7d1271c74da58b90f340436efdd8d4b603f3&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/8c8f7d1271c74da58b90f340436efdd8d4b603f3&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="4885744" author="xgen-internal-githook" created="Fri, 7 Oct 2022 13:27:59 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Antonio Fuschetto&apos;, &apos;email&apos;: &apos;antonio.fuschetto@mongodb.com&apos;, &apos;username&apos;: &apos;afuschetto&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-69898&quot; title=&quot;Wait for the critical section catch-up phase before refreshing the DB version&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-69898&quot;&gt;&lt;del&gt;SERVER-69898&lt;/del&gt;&lt;/a&gt; Wait for the critical section catch-up phase before refreshing the DB version&lt;br/&gt;
Branch: v5.0&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/83de4afb15a616fb8f40bf329ae17b65ae2c130a&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/83de4afb15a616fb8f40bf329ae17b65ae2c130a&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="4867772" author="xgen-internal-githook" created="Fri, 30 Sep 2022 08:00:37 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Antonio Fuschetto&apos;, &apos;email&apos;: &apos;antonio.fuschetto@mongodb.com&apos;, &apos;username&apos;: &apos;afuschetto&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-69898&quot; title=&quot;Wait for the critical section catch-up phase before refreshing the DB version&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-69898&quot;&gt;&lt;del&gt;SERVER-69898&lt;/del&gt;&lt;/a&gt; Wait for the critical section catch-up phase before refreshing the DB version&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/1723215716b31cdbcd9783673933426e1220afd1&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/1723215716b31cdbcd9783673933426e1220afd1&lt;/a&gt;&lt;/p&gt;</comment>
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