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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-52815] Investigate calling &apos;rollback_to_stable&apos; prior to shutting down WiredTiger</title>
                <link>https://jira.mongodb.org/browse/SERVER-52815</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;This specifically became of interest because one of the costs of WT shutdown in 4.2 and earlier was typically bounded by how much data had come into the system since the last checkpoint (or how far the stable timestamp moved since the last checkpoint). But with durable history, the cost is now bounded by how much data exists ahead of the stable timestamp (which is much easier to grow). This is because WT now calls&#160;&lt;tt&gt;rollback_to_stable&lt;/tt&gt;&#160;inside of&#160;&lt;tt&gt;WT_CONNECTION::close&lt;/tt&gt;.&lt;/p&gt;

&lt;p&gt;Assuming that&apos;s the correct motivation/area of interest to target, one compromising solution is that MDB can explicitly call&#160;&lt;tt&gt;rollback_to_stable&lt;/tt&gt;&#160;on shutdown while FTDC is still running. This would succeed if the following assumptions are true:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;&lt;tt&gt;WT_CONNECTION::close&lt;/tt&gt;&#160;would not need to duplicate much if any of the work accomplished by MDB calling&#160;&lt;tt&gt;rollback_to_stable&lt;/tt&gt;.&lt;/li&gt;
	&lt;li&gt;WT produces meaningful metrics while&#160;&lt;tt&gt;rollback_to_stable&lt;/tt&gt;&#160;is running.&lt;/li&gt;
&lt;/ul&gt;
</description>
                <environment></environment>
        <key id="1540275">SERVER-52815</key>
            <summary>Investigate calling &apos;rollback_to_stable&apos; prior to shutting down WiredTiger</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="10038" iconUrl="https://jira.mongodb.org/images/icons/subtask.gif" description="">Backlog</status>
                    <statusCategory id="2" key="new" colorName="default"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="backlog-server-execution">Backlog - Storage Execution Team</assignee>
                                    <reporter username="gregory.wlodarek@mongodb.com">Gregory Wlodarek</reporter>
                        <labels>
                    </labels>
                <created>Thu, 12 Nov 2020 14:48:12 +0000</created>
                <updated>Fri, 24 Feb 2023 16:41:31 +0000</updated>
                                                                            <component>Diagnostics</component>
                    <component>Storage</component>
                                        <votes>0</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="3530934" author="gregory.wlodarek" created="Tue, 15 Dec 2020 18:55:25 +0000"  >&lt;p&gt;I&apos;m re-assigning this back to the backlog for now as it&apos;s a fragile change and to explore alternatives.&lt;/p&gt;
&lt;ol&gt;
	&lt;li&gt;On shutdown, there&apos;s a global kill flag that puts newly created operation contexts into an interrupted state right away. FTDC creates a new operation context each time it runs.&lt;/li&gt;
	&lt;li&gt;&lt;b&gt;rollback_to_stable&lt;/b&gt; requires no transactions to be open. That&apos;s not guaranteed by the proposed change in the code review. It&apos;s more of a best-effort attempt by shutting down the majority of things. In the current code, this is protected by a global exclusive lock, which wouldn&apos;t be possible anymore.&lt;/li&gt;
	&lt;li&gt;Shutting down the &lt;b&gt;SessionCache&lt;/b&gt; prior to running &lt;b&gt;rollback_to_stable&lt;/b&gt; to support the &quot;no transactions running&quot; check prevents FTDC from being able to access WT statistics and would need a way to circumvent the &lt;b&gt;SessionCache&lt;/b&gt;.&lt;/li&gt;
&lt;/ol&gt;


&lt;p&gt;One alternative could be for WT to explore permitting the gathering of statistics during &lt;b&gt;WT_CONNECTION::close()&lt;/b&gt;.&lt;/p&gt;

&lt;p&gt;&#160;&lt;/p&gt;</comment>
                    </comments>
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                                            <outwardlinks description="related to">
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            <issuekey id="1351584">SERVER-48221</issuekey>
        </issuelink>
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            <issuekey id="2273802">SERVER-74331</issuekey>
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