<!-- 
RSS generated by JIRA (9.7.1#970001-sha1:2222b88b221c4928ef0de3161136cc90c8356a66) at Thu Feb 08 04:43:16 UTC 2024

It is possible to restrict the fields that are returned in this document by specifying the 'field' parameter in your request.
For example, to request only the issue key and summary append 'field=key&field=summary' to the URL of your request.
-->
<rss version="0.92" >
<channel>
    <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>[SERVER-36495] Cache pressure issues during recovery oplog application</title>
                <link>https://jira.mongodb.org/browse/SERVER-36495</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;During recovery oplog application we don&apos;t advance the oldest timestamp. This can pin a lot of data in the cache. Resulting symptoms include&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;slow recovery due to resulting cache churn&lt;/li&gt;
	&lt;li&gt;growth of lookaside (cache overflow) table and corresponding file WiredTigerLAS.wt&lt;/li&gt;
	&lt;li&gt;in extreme cases cache-full hangs were observed. This was believed fixed with &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-33191&quot; title=&quot;Cache-full hangs on 3.6&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-33191&quot;&gt;&lt;del&gt;SERVER-33191&lt;/del&gt;&lt;/a&gt;, but we should be alert for new occurrences of this issue.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;&#160;&lt;/p&gt;</description>
                <environment></environment>
        <key id="585014">SERVER-36495</key>
            <summary>Cache pressure issues during recovery oplog application</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="backlog-server-repl">Backlog - Replication Team</assignee>
                                    <reporter username="bruce.lucas@mongodb.com">Bruce Lucas</reporter>
                        <labels>
                    </labels>
                <created>Tue, 7 Aug 2018 16:49:12 +0000</created>
                <updated>Sun, 29 Oct 2023 22:29:12 +0000</updated>
                            <resolved>Fri, 29 Apr 2022 23:10:39 +0000</resolved>
                                                    <fixVersion>4.4.0</fixVersion>
                                                        <votes>6</votes>
                                    <watches>45</watches>
                                                                                                                <comments>
                            <comment id="4517772" author="thomas.schubert" created="Fri, 29 Apr 2022 23:10:39 +0000"  >&lt;p&gt;This ticket filed describes a number of symptoms associated with cache pressure during oplog recovery. It does not describe a particular fix, which is why it has been open for a while as worked on a number of changes that would improve performance.&lt;/p&gt;

&lt;p&gt;There are two elements at play here, one is whether we can advance the oldest timestamp during recovery, this is very challenging to do safely and would be a significant change to the system architecture. Instead, we choose to focus on the second element which is how we perform when the timestamp lags. This change has significant benefits including during steady-state operation. We have invested around 30 engineering years between 4.2 and 4.4 to tackle this problem, resulting in significant improvement to throughput. However, given the scale of the change, it&#8217;s not safe or feasible to backport MongoDB 4.2.&lt;/p&gt;

&lt;p&gt;In MongoDB 4.2, we need to maintain the history of updates since the oldest timestamp in memory. If this history exceeds our cache, we use a cache overflow mechanism that functions similar to swap. As a consequence, performance may degrade - this is the expected behavior.&lt;/p&gt;

&lt;p&gt;In MongoDB 4.4, we introduced durable history, which allows us to more efficiently write out historical information associated with pages in cache, allowing us to reduce cache pressure and provides a significant performance boost. In some tests, we see a 10x improvement to write throughput during cache pressure.&lt;/p&gt;

&lt;p&gt;As the symptoms of described by this ticket have been significantly improved by architectural changes in MongoDB 4.4 and later, I&apos;m going to resolve this ticket.&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10420">
                    <name>Backports</name>
                                                                <inwardlinks description="backports">
                                                        </inwardlinks>
                                    </issuelinktype>
                            <issuelinktype id="10010">
                    <name>Duplicate</name>
                                                                <inwardlinks description="is duplicated by">
                                        <issuelink>
            <issuekey id="657861">SERVER-38698</issuekey>
        </issuelink>
                            </inwardlinks>
                                    </issuelinktype>
                            <issuelinktype id="10012">
                    <name>Related</name>
                                            <outwardlinks description="related to">
                                        <issuelink>
            <issuekey id="494491">SERVER-33191</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="542268">SERVER-34938</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="542299">SERVER-34941</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="548286">SERVER-35191</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="552745">SERVER-35339</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="574993">SERVER-36238</issuekey>
        </issuelink>
                            </outwardlinks>
                                                                <inwardlinks description="is related to">
                                        <issuelink>
            <issuekey id="632481">SERVER-38089</issuekey>
        </issuelink>
                            </inwardlinks>
                                    </issuelinktype>
                    </issuelinks>
                <attachments>
                    </attachments>
                <subtasks>
                    </subtasks>
                <customfields>
                                                <customfield id="customfield_10050" key="com.atlassian.jira.toolkit:comments">
                        <customfieldname># Replies</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1.0</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                <customfield id="customfield_12751" key="com.atlassian.jira.plugin.system.customfieldtypes:multiselect">
                        <customfieldname>Assigned Teams</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="25128"><![CDATA[Replication]]></customfieldvalue>
    
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                            <customfield id="customfield_10011" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Backwards Compatibility</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="10038"><![CDATA[Fully Compatible]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                    <customfield id="customfield_13552" key="com.go2group.jira.plugin.crm:crm_generic_field">
                        <customfieldname>Case</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue><![CDATA[[5002K00000d1590QAA, 5002K00000iMiatQAC, 5002K00000kEvlIQAS, 5002K00000lmqDhQAI, 5002K00000mquJOQAY, 5002K00000nmKabQAE, 5002K00000nmpEsQAI, 5002K00000nn6gIQAQ, 5002K00000npvQTQAY, 5002K00000ocY9iQAE, 5002K00000pEaMQQA0, 5002K00000qcb4PQAQ, 5002K00000fM8dQQAS, 5002K000011fFv1QAE, 5006R00001l8Q4TQAU, 5006R00001pldYRQAY]]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                            <customfield id="customfield_10055" key="com.atlassian.jira.ext.charting:firstresponsedate">
                        <customfieldname>Date of 1st Reply</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>Tue, 7 Aug 2018 16:50:02 +0000</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_10052" key="com.atlassian.jira.toolkit:dayslastcommented">
                        <customfieldname>Days since reply</customfieldname>
                        <customfieldvalues>
                                        1 year, 40 weeks, 5 days ago
    
                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_18254" key="com.onresolve.jira.groovy.groovyrunner:scripted-field">
                        <customfieldname>Dependencies</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue><![CDATA[]]></customfieldvalue>


                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_15850" key="com.atlassian.jira.plugins.jira-development-integration-plugin:devsummary">
                        <customfieldname>Development</customfieldname>
                        <customfieldvalues>
                            
                        </customfieldvalues>
                    </customfield>
                                                                                                                        <customfield id="customfield_17050" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Downstream Team Attention</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="16941"><![CDATA[Not Needed]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                    <customfield id="customfield_10857" key="com.pyxis.greenhopper.jira:gh-epic-link">
                        <customfieldname>Epic Link</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>PM-1310</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                <customfield id="customfield_10057" key="com.atlassian.jira.toolkit:lastusercommented">
                        <customfieldname>Last comment by Customer</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>true</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                            <customfield id="customfield_10056" key="com.atlassian.jira.toolkit:lastupdaterorcommenter">
                        <customfieldname>Last commenter</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>luke.bonanomi@mongodb.com</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_11151" key="com.atlassian.jira.toolkit:LastCommentDate">
                        <customfieldname>Last public comment date</customfieldname>
                        <customfieldvalues>
                            1 year, 40 weeks, 5 days ago
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                    <customfield id="customfield_10032" key="com.atlassian.jira.plugin.system.customfieldtypes:select">
                        <customfieldname>Operating System</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="10026"><![CDATA[ALL]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                <customfield id="customfield_10051" key="com.atlassian.jira.toolkit:participants">
                        <customfieldname>Participants</customfieldname>
                        <customfieldvalues>
                                        <customfieldvalue>backlog-server-repl</customfieldvalue>
            <customfieldvalue>bruce.lucas@mongodb.com</customfieldvalue>
            <customfieldvalue>kelsey.schubert@mongodb.com</customfieldvalue>
    
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                        <customfield id="customfield_14254" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Product Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1|hu4xm7:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                <customfield id="customfield_12550" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>2|htvjgf:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_10558" key="com.pyxis.greenhopper.jira:gh-global-rank">
                        <customfieldname>Rank (Obsolete)</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>9223372036854775807</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                    <customfield id="customfield_22250" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Special Downgrade Instructions Required</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="23343"><![CDATA[Not Needed]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                    <customfield id="customfield_10053" key="com.atlassian.jira.ext.charting:timeinstatus">
                        <customfieldname>Time In Status</customfieldname>
                        <customfieldvalues>
                            
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                                                                                                        <customfield id="customfield_22870" key="com.onresolve.jira.groovy.groovyrunner:scripted-field">
                        <customfieldname>Triagers</customfieldname>
                        <customfieldvalues>
                                

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                    <customfield id="customfield_14350" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>serverRank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1|hu4jvj:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                    </customfields>
    </item>
</channel>
</rss>