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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-8967] Memory leaks from DatabaseHolder::getOrCreate() and related</title>
                <link>https://jira.mongodb.org/browse/SERVER-8967</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;There appear to be several related leaks present:&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;DatabaseHolder::getOrCreate() allocates a new Database object and stores this pointer in _paths&lt;span class=&quot;error&quot;&gt;&amp;#91;path&amp;#93;&lt;/span&gt;&lt;span class=&quot;error&quot;&gt;&amp;#91;dbname&amp;#93;&lt;/span&gt;.  Although Database::closeDatabase() removes these entries, there doesn&apos;t seem to be any logic to remove entries for a database that is created but not written to.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;When we getOrCreate() a db that&apos;s never used, the global mmfiles set is updated with a MongoFile* that has no file name.  There is a comment in MongoFile::destroyed() which indicates this function should be called when a derived class is destroyed.  However, ~MongoMMF() doesn&apos;t appear to be called for a database which is not written to.  Note that ~MongoMMF() calls MongoMMF::close(), which calls MemoryMappedFile::close(), which finally calls MongoFile::destroy().  ~MongoMMF() is called from a few places; notably ~MongoDataFile(), ~NamespaceIndex(), and the journal recovery code.&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;There are additional leaks that have not yet been identified, but can be reproduced with the repro script.  The script not only causes a leak when the unused databases are &apos;accessed&apos;, but also a continuously increasing leak while mongod remains alive.  The leak rate is about 2mb per minute when the attached script is reduced to only execute 100 iterations.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;*Also, possibly worth noting, DataFileSync must iterate over all unique unwritten database names.&lt;/p&gt;</description>
                <environment></environment>
        <key id="68236">SERVER-8967</key>
            <summary>Memory leaks from DatabaseHolder::getOrCreate() and related</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="9">Done</resolution>
                                        <assignee username="backlog-server-execution">Backlog - Storage Execution Team</assignee>
                                    <reporter username="benjamin.becker">Ben Becker</reporter>
                        <labels>
                    </labels>
                <created>Wed, 13 Mar 2013 07:38:47 +0000</created>
                <updated>Tue, 6 Dec 2022 05:23:15 +0000</updated>
                            <resolved>Fri, 14 Sep 2018 20:10:27 +0000</resolved>
                                    <version>2.2.3</version>
                    <version>2.4.0-rc2</version>
                                                    <component>MMAPv1</component>
                    <component>Storage</component>
                                        <votes>0</votes>
                                    <watches>6</watches>
                                                                                                                <comments>
                            <comment id="326993" author="benjamin.becker" created="Thu, 2 May 2013 21:00:57 +0000"  >&lt;p&gt;Note that one manifestation of this bug is the following log entry, which accounts for more files than actually exist:&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;[DataFileSync] flushing mmaps took 12379ms  for 15642 files&lt;/span&gt;&lt;/pre&gt;
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&lt;p/&gt;

&lt;p&gt;Since &lt;tt&gt;MongoFile::_flushAll()&lt;/tt&gt; holds &lt;tt&gt;LockMongoFilesShared&lt;/tt&gt; while iterating over the set, additional lock contention may be observed for write operations, yielding, journaling, etc.  Also, commands like listDatabases and serverStatus will generally be slower.&lt;/p&gt;</comment>
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                                                                <inwardlinks description="is related to">
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            <issuekey id="14604">SERVER-2498</issuekey>
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&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;
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