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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-7964] Server at 100% CPU, slow queries (15s) in spite of indexes</title>
                <link>https://jira.mongodb.org/browse/SERVER-7964</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Every 2 days, our primary instance hits 100% CPU usage and has to be restarted. By setting the profiling level to 1, I discovered that there are about a dozen EXTREMELY slow count() queries being completed per second:&lt;/p&gt;

&lt;p&gt;&amp;gt; db.system.profile.find()&lt;br/&gt;
{ &quot;ts&quot; : ISODate(&quot;2012-12-16T20:31:39.078Z&quot;), &quot;op&quot; : &quot;command&quot;, &quot;ns&quot; : &quot;stylesaint.$cmd&quot;, &quot;command&quot; : { &quot;count&quot; : &quot;tears&quot;, &quot;query&quot; : { &quot;_id&quot; : &lt;/p&gt;
{ &quot;$gt&quot; : ObjectId(&quot;50cdeadeaf58d3de96000294&quot;) }
&lt;p&gt;, &quot;active&quot; : true, &quot;is_image_processed&quot; : true, &quot;hidden_from_feed&quot; : false, &quot;hidden_from_public_feeds&quot; : false }, &quot;fields&quot; : null }, &quot;ntoreturn&quot; : 1, &quot;responseLength&quot; : 48, &quot;millis&quot; : 13930, &quot;client&quot; : &quot;wouldntyouliketoknow&quot; }&lt;br/&gt;
... other similar results, only the ObjectId is different&lt;/p&gt;

&lt;p&gt;I&apos;ve run explain() on a number of these queries. Mongo seems to intelligently choose the index that gives it the fewest number of scanned documents, which is cool. But it means that one explain() does not explain them all. Here&apos;s an example:&lt;/p&gt;

&lt;p&gt;&amp;gt; db.tears.find({ &quot;_id&quot; : &lt;/p&gt;
{ &quot;$gt&quot; : ObjectId(&quot;50cdeadeaf58d3de96000294&quot;) }
&lt;p&gt;, &quot;active&quot; : true, &quot;is_image_processed&quot; : true, &quot;hidden_from_feed&quot; : false, &quot;hidden_from_public_feeds&quot; : false }).explain()&lt;br/&gt;
{&lt;br/&gt;
	&quot;cursor&quot; : &quot;BtreeCursor &lt;em&gt;id&lt;/em&gt;&quot;,&lt;br/&gt;
	&quot;isMultiKey&quot; : false,&lt;br/&gt;
	&quot;n&quot; : 4,&lt;br/&gt;
	&quot;nscannedObjects&quot; : 5,&lt;br/&gt;
	&quot;nscanned&quot; : 5,&lt;br/&gt;
	&quot;nscannedObjectsAllPlans&quot; : 23,&lt;br/&gt;
	&quot;nscannedAllPlans&quot; : 25,&lt;br/&gt;
	&quot;scanAndOrder&quot; : false,&lt;br/&gt;
	&quot;indexOnly&quot; : false,&lt;br/&gt;
	&quot;nYields&quot; : 0,&lt;br/&gt;
	&quot;nChunkSkips&quot; : 0,&lt;br/&gt;
	&quot;millis&quot; : 0,&lt;br/&gt;
	&quot;indexBounds&quot; : &lt;/p&gt;
{
		&quot;_id&quot; : [
			[
				ObjectId(&quot;50cdeadeaf58d3de96000294&quot;),
				ObjectId(&quot;ffffffffffffffffffffffff&quot;)
			]
		]
	}
&lt;p&gt;,&lt;br/&gt;
	&quot;server&quot; : &quot;ip-10-169-65-66:27017&quot;&lt;br/&gt;
}&lt;/p&gt;

&lt;p&gt;I have not found any queries yet where nscanned is more than a few hundred documents.&lt;/p&gt;

&lt;p&gt;This particular collection has less than half a million documents. Whether or not these slow queries are related to the server failure, I&apos;d like to speed them up. But my main issue is the server failure.&lt;/p&gt;

&lt;p&gt;I created a topic with the Google group. We can take the discussion there if you prefer: &lt;a href=&quot;https://groups.google.com/forum/#!topic/mongodb-user/NbiWPSeYg28&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://groups.google.com/forum/#!topic/mongodb-user/NbiWPSeYg28&lt;/a&gt;&lt;/p&gt;</description>
                <environment>Ubuntu 10.10 Server, Dual Core 2.7Ghz Xeon, 8GB RAM</environment>
        <key id="59678">SERVER-7964</key>
            <summary>Server at 100% CPU, slow queries (15s) in spite of indexes</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="-1">Unassigned</assignee>
                                    <reporter username="sebastian">Sebastian Goodman</reporter>
                        <labels>
                    </labels>
                <created>Mon, 17 Dec 2012 18:16:29 +0000</created>
                <updated>Mon, 17 Dec 2012 18:37:59 +0000</updated>
                            <resolved>Mon, 17 Dec 2012 18:37:59 +0000</resolved>
                                    <version>2.0.1</version>
                    <version>2.2.2</version>
                                                                        <votes>0</votes>
                                    <watches>3</watches>
                                                                                                                <comments>
                            <comment id="217490" author="ian@10gen.com" created="Mon, 17 Dec 2012 18:37:59 +0000"  >&lt;p&gt;Hi Sebastian, the Google Groups forums are definitely the best place to begin this conversation - I&apos;m going to close this for now and allow someone from our team to follow up at the link you provided.  If it turns out you&apos;ve identified a bug then please do reopen this ticket.&lt;/p&gt;</comment>
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