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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-42343] WiredTigerLAS.wt grows when lagged node is in maintenance mode</title>
                <link>https://jira.mongodb.org/browse/SERVER-42343</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;As part of rolling index builds and similar operations, we&apos;ll often take nodes offline for O(hours).  When the node comes back online, we&apos;ll put it into maintenance mode (using replSetMaintenance) until the node catches back up.  We&apos;ve observed that such nodes often end up with a huge WiredTigerLAS.wt file.  We&apos;ve done some investigation and it seems to be the case that this only happens when we put the node into maintenance mode; if we simply let a lagged node stay in secondary mode, we don&apos;t see WiredTigerLAS.wt grow.&lt;/p&gt;

&lt;p&gt;We suspect this is related to cache pressure of majority read concern since we only started seeing these issues when we enabled that.&lt;/p&gt;</description>
                <environment></environment>
        <key id="870930">SERVER-42343</key>
            <summary>WiredTigerLAS.wt grows when lagged node is in maintenance mode</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="benety.goh@mongodb.com">Benety Goh</assignee>
                                    <reporter username="bartle">David Bartley</reporter>
                        <labels>
                    </labels>
                <created>Tue, 23 Jul 2019 04:13:42 +0000</created>
                <updated>Sun, 29 Oct 2023 22:18:53 +0000</updated>
                            <resolved>Wed, 14 Aug 2019 19:10:03 +0000</resolved>
                                    <version>3.4.20</version>
                                    <fixVersion>3.4.23</fixVersion>
                                                        <votes>0</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="2382767" author="daniel.hatcher" created="Thu, 22 Aug 2019 15:00:38 +0000"  >&lt;p&gt;I&apos;ve confirmed that my repro does not grow the WiredTigerLAS.wt file while running with this commit.&lt;/p&gt;</comment>
                            <comment id="2371441" author="bartle" created="Wed, 14 Aug 2019 20:36:02 +0000"  >&lt;p&gt;Thanks for fixing this so quickly!&lt;/p&gt;</comment>
                            <comment id="2371250" author="xgen-internal-githook" created="Wed, 14 Aug 2019 19:07:23 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;Benety Goh&apos;, &apos;email&apos;: &apos;benety@mongodb.com&apos;, &apos;username&apos;: &apos;benety&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-42343&quot; title=&quot;WiredTigerLAS.wt grows when lagged node is in maintenance mode&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-42343&quot;&gt;&lt;del&gt;SERVER-42343&lt;/del&gt;&lt;/a&gt; drop all snapshots on transition from a readable state to a non-readable one&lt;/p&gt;

&lt;p&gt;This avoids accumulating unnecessary historical information in the storage engine while&lt;br/&gt;
we are in a non-readable state.&lt;br/&gt;
Branch: v3.4&lt;br/&gt;
&lt;a href=&quot;https://github.com/mongodb/mongo/commit/7fbb8c5c17f457b8c28ecfa03b4083ce9fe0e8d9&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/mongodb/mongo/commit/7fbb8c5c17f457b8c28ecfa03b4083ce9fe0e8d9&lt;/a&gt;&lt;/p&gt;</comment>
                            <comment id="2341494" author="milkie" created="Wed, 24 Jul 2019 14:26:20 +0000"  >&lt;p&gt;My guess is that the bug is due to this code in the snapshot thread:&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;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;            if (!replCoord-&amp;gt;getMemberState().readable()) {&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // If our MemberState isn&apos;t readable, we may not be in a consistent state so don&apos;t                                                                                                                                                                                 &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // take snapshots. When we transition into a readable state from a non-readable                                                                                                                                                                                    &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // state, a snapshot is forced to ensure we don&apos;t miss the latest write. This must                                                                                                                                                                                 &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // be checked each time we acquire the global IS lock since that prevents the node                                                                                                                                                                                 &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // from transitioning to a !readable() state from a readable() one in the cases                                                                                                                                                                                    &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                // where we shouldn&apos;t be creating a snapshot.                                                                                                                                                                                                                      &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;   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;                continue;&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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-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;            }&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;So it&apos;s probably fine logic to do this for times when the node is in RECOVERING state (the maintenance mode command sets this state), but we also need to delete all active snapshots when this occurs, to unpin the pages involved in those snapshots.&lt;/p&gt;</comment>
                            <comment id="2339874" author="bartle" created="Tue, 23 Jul 2019 20:44:53 +0000"  >&lt;p&gt;Yup, we&apos;ve been SIGKILLing the node (SIGTERM works too but sometimes takes many minutes).&lt;/p&gt;</comment>
                            <comment id="2339807" author="daniel.hatcher" created="Tue, 23 Jul 2019 20:22:28 +0000"  >&lt;p&gt;Hello &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=bartle&quot; class=&quot;user-hover&quot; rel=&quot;bartle&quot;&gt;bartle&lt;/a&gt;,&lt;/p&gt;

&lt;p&gt;I&apos;ve confirmed what you suspected in my own environment. On 3.4.20 with Read Concern &quot;Majority&quot; enabled a node placed into RECOVERING via &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;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&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;db.adminCommand({replSetMaintenance:true})&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;
&lt;p&gt;will see a rise in the WiredTigerLAS.wt file size (given writes are  happening on the Primary). I have also confirmed that this does not happen on 3.6.0. I imagine this was one of the many items fixed by the changes we made to Read Concern &quot;Majority&quot; in 3.6.&lt;/p&gt;

&lt;p&gt;If you restart the node, the file should reset. I understand that this isn&apos;t really optimal and I will see if it will be possible to do a backport.&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10012">
                    <name>Related</name>
                                                                <inwardlinks description="is related to">
                                        <issuelink>
            <issuekey id="416180">SERVER-30638</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="213867">SERVER-19209</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="195718">SERVER-18022</issuekey>
        </issuelink>
                            </inwardlinks>
                                    </issuelinktype>
                    </issuelinks>
                <attachments>
                            <attachment id="225099" name="Screen Shot 2019-07-24 at 10.05.39 AM.png" size="202484" author="daniel.hatcher@mongodb.com" created="Wed, 24 Jul 2019 14:06:16 +0000"/>
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