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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-42711] PyMongo&apos;s retryable reads spec tests causes server 4.0 to segfault with MMAPv1</title>
                <link>https://jira.mongodb.org/browse/SERVER-42711</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;The issue can be observed when running PyMongo&apos;s test-suite on server version 4.0.11 with 2 replicas and 1 arbiter using the MMAPv1 storage engine. I have been able to reproduce this on OSX.&lt;/p&gt;</description>
                <environment></environment>
        <key id="887836">SERVER-42711</key>
            <summary>PyMongo&apos;s retryable reads spec tests causes server 4.0 to segfault with MMAPv1</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="4">Incomplete</resolution>
                                        <assignee username="daniel.gottlieb@mongodb.com">Daniel Gottlieb</assignee>
                                    <reporter username="prashant.mital">Prashant Mital</reporter>
                        <labels>
                    </labels>
                <created>Thu, 8 Aug 2019 18:03:00 +0000</created>
                <updated>Tue, 20 Aug 2019 17:53:23 +0000</updated>
                            <resolved>Tue, 20 Aug 2019 17:47:59 +0000</resolved>
                                    <version>4.0.11</version>
                                                                        <votes>0</votes>
                                    <watches>6</watches>
                                                                                                                <comments>
                            <comment id="2379370" author="daniel.gottlieb@10gen.com" created="Tue, 20 Aug 2019 17:47:59 +0000"  >&lt;p&gt;I&apos;m closing this in favor of &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-42922&quot; title=&quot;failCommand + closeConnection can dereference a null session pointer&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-42922&quot;&gt;&lt;del&gt;SERVER-42922&lt;/del&gt;&lt;/a&gt; (though I arguably could have rewritten the contents of this ticket). For your convenience, I&apos;ve linked &lt;a href=&quot;https://jira.mongodb.org/browse/PYTHON-1948&quot; title=&quot;Test retryable reads on MMAPv1&quot; class=&quot;issue-link&quot; data-issue-key=&quot;PYTHON-1948&quot;&gt;PYTHON-1948&lt;/a&gt; as depending on this new ticket, though there might be workarounds available.&lt;/p&gt;

&lt;p&gt;What&apos;s being observed is a general server bug regarding the use of &lt;tt&gt;failCommand&lt;/tt&gt; with &lt;tt&gt;closeConnection&lt;/tt&gt;. It attempts to close the client connection, but the server can also run command code internally (DBDirectClient) which doesn&apos;t have an actual network interface to close. What you&apos;re seeing is a null dereference &lt;a href=&quot;https://github.com/mongodb/mongo/blob/abb1b353648260175c3dfe02ac8ae54c083956f7/src/mongo/db/service_entry_point_common.cpp#L569&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;here&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;I suspect why this is only showing for you on mmapv1 tests is that 4.0 mmapv1 has bugs which fail the retryable reads tests. My guess is the python suite is leaving the mongod in a state where the failpoint is still engaged. When a background thread that uses DBDirectClient runs an iteration, it encounters the failpoint (that was not intended for it), crashing the mongod. My hypothesis is that the crash is only observed after a python test has already failed.&lt;/p&gt;

&lt;p&gt;One thing worth trying is having the tests disable any outstanding failpoints on teardown. Technically there&apos;s still a race where the background thread can observe this failpoint state, even in a passing test. But it seems the window to hit the race is sufficiently small given you haven&apos;t observed this with WT (which I assume always passes the suite).&lt;/p&gt;</comment>
                            <comment id="2363411" author="prashant.mital" created="Thu, 8 Aug 2019 18:52:30 +0000"  >&lt;p&gt;I also encountered the same behavior on an evergreen spawn host &lt;span class=&quot;error&quot;&gt;&amp;#91;rhel62-small, Python 2.7 (/opt/python/2.7/bin/python), MMAPv1&amp;#93;&lt;/span&gt; running a 3-member replica set with MMAPv1 (no arbiter).&lt;/p&gt;</comment>
                            <comment id="2363313" author="daniel.hatcher" created="Thu, 8 Aug 2019 18:09:46 +0000"  >&lt;p&gt;As MMAPv1 is deprecated as a storage engine in 4.0, is this something we want to fix?&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10011">
                    <name>Depends</name>
                                                                <inwardlinks description="is depended on by">
                                        <issuelink>
            <issuekey id="887938">PYTHON-1948</issuekey>
        </issuelink>
                            </inwardlinks>
                                    </issuelinktype>
                            <issuelinktype id="10010">
                    <name>Duplicate</name>
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                                        <issuelink>
            <issuekey id="901351">SERVER-42922</issuekey>
        </issuelink>
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                                                        </issuelinktype>
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                            <attachment id="226629" name="mongod.log" size="605367" author="prashant.mital" created="Thu, 8 Aug 2019 18:02:50 +0000"/>
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                        <customfieldname>Steps To Reproduce</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>&lt;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;Spin up a replica set with 2 replicas and 1 arbiter running MongoDB 4.0.11 on the MMAPv1 storage engine with test commands enabled. &lt;tt&gt;mlaunch&lt;/tt&gt; command used was:&lt;/li&gt;
&lt;/ul&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;$ mlaunch init --replicaset --name repl0 --nodes 2 --arbiter --binarypath $MONGODB_4011_BIN --port 27017 --&lt;/span&gt;&lt;span style=&quot;color: #ff1493; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;hostname&lt;/span&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; localhost --setParameter enableTestCommands=1 --storageEngine mmapv1&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;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;Clone the following PyMongo branch:&lt;/li&gt;
&lt;/ul&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;$ git clone --branch PYTHON-1934&lt;/span&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;/retryWrites-with-MMAPv1-raises-actionable-error&lt;/span&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; https:&lt;/span&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;//github&lt;/span&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;.com&lt;/span&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;/prashantmital/mongo-python-driver&lt;/span&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;.git&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;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;Run the retryable reads tests:&lt;/li&gt;
&lt;/ul&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;$ python setup.py &lt;/span&gt;&lt;span style=&quot;color: #ff1493; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;test&lt;/span&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; -s &lt;/span&gt;&lt;span style=&quot;color: #ff1493; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;test&lt;/span&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;.test_retryable_reads&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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&lt;/table&gt;
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