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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>
    </build-info>


<item>
            <title>[SERVER-20128] too many open duplicate files my mongod with WT</title>
                <link>https://jira.mongodb.org/browse/SERVER-20128</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Hi , I have many open fd by mongod process. &lt;br/&gt;
lsof | grep mongod | grep &quot;/disk2/mongodb_account/&quot; |wc -l  &lt;br/&gt;
66045&lt;br/&gt;
Over time, number fd is growing to 250k - 300k.  &lt;br/&gt;
lsof | grep mongo | grep &quot;disk2&quot; | grep &quot;/63--6528694272700620922.wt&quot; | wc -l &lt;br/&gt;
111 &lt;br/&gt;
mongod open file 63--6528694272700620922.wt 111 times . &lt;br/&gt;
what caused this behavior?&lt;/p&gt;

&lt;p&gt;I use WT engine and 3.0.6 version. &lt;/p&gt;


</description>
                <environment></environment>
        <key id="227124">SERVER-20128</key>
            <summary>too many open duplicate files my mongod with WT</summary>
                <type id="6" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14720&amp;avatarType=issuetype">Question</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="david.hows">David Hows</assignee>
                                    <reporter username="uchti">Denis</reporter>
                        <labels>
                    </labels>
                <created>Wed, 26 Aug 2015 10:58:13 +0000</created>
                <updated>Fri, 28 Aug 2015 19:55:21 +0000</updated>
                            <resolved>Fri, 28 Aug 2015 19:55:21 +0000</resolved>
                                                                    <component>WiredTiger</component>
                                        <votes>0</votes>
                                    <watches>8</watches>
                                                                                                                <comments>
                            <comment id="1016767" author="uchti" created="Fri, 28 Aug 2015 08:35:33 +0000"  >&lt;p&gt;It&apos;s my mistake. Thanks for explain&lt;/p&gt;</comment>
                            <comment id="1016669" author="david.hows" created="Fri, 28 Aug 2015 06:09:50 +0000"  >&lt;p&gt;Hi Denis,&lt;/p&gt;

&lt;p&gt;The issue here is a misinterpretation of what lsof is outputting.&lt;/p&gt;

&lt;p&gt;By default when you run lsof with no arguments it will report each instance of a held file handle by each thread in the system, this means you wind up with many duplicates of the same file handle being held by many threads within a process. You can see this by reviewing the &lt;tt&gt;FD&lt;/tt&gt; column in lsof; for example, in the attached &lt;tt&gt;lsof_with_grep.txt&lt;/tt&gt; file you will see that the second column is static (as this is the MongoDB PID), you will see that the third column is increasing, as this represents the thread ID within the given PID. Finally in the fifth column you will see that everything shares the same value of &lt;tt&gt;15u&lt;/tt&gt;. This &lt;tt&gt;15u&lt;/tt&gt; value states that this is the systems &quot;15&quot; file descriptor open in read/write mode (see the lsof man page for more details) and this single file handle is opened by each of the threads, this is expected behaviour in MongoDB all of the threads reported will want access to the underlying WiredTiger files.&lt;/p&gt;

&lt;p&gt;Can you please re-run the lsof command and specify the MongoDB PID with the -p option to detail only the open file handles for the process rather than each thread. Eg, please run:&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;lsof -p 5467&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;or&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;lsof -p `pidof mongod`&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;Thanks,&lt;br/&gt;
David&lt;/p&gt;</comment>
                    </comments>
                    <attachments>
                            <attachment id="87604" name="lsof_dumps.zip" size="785396" author="uchti" created="Wed, 26 Aug 2015 10:58:13 +0000"/>
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