<!-- 
RSS generated by JIRA (9.7.1#970001-sha1:2222b88b221c4928ef0de3161136cc90c8356a66) at Thu Feb 08 04:17:37 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-28263] 2 times WT rollback_transaction than WT commit_transaction in logs on a single thread YCSB workload</title>
                <link>https://jira.mongodb.org/browse/SERVER-28263</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;We are currently trying to evaluate MongoDB (with wiredTiger) for a project. We using YCSB (yahoo&apos;s cloud benchmark tool) as one of the tools for evaluating the performance and scalability. In one of our experiments (with global logging level of 0, and 5 for query, write and storage) we see in the logs that there are approximately 2 times transaction rollbacks than transaction commits. I have attached the log file from one such test session. Our test in ycsb inserts 1 record and then we use workload a (50% reads, 50% writes) that reads and updates the same record 100K times. We have tested this with two versions of MongoDB (3.4.2 and 3.2.11) on baremetal machine with 120GB of RAM and underlying SSDs (in raid 10)  and are able to reproduce it. &lt;br/&gt;
We use the following parameters in YCSB&lt;br/&gt;
Loading&lt;br/&gt;
----------&lt;br/&gt;
bin/ycsb load mongodb -s -threads 1 -P workloads/workloada -P workloadproperty.dat -p &quot;mongodb.url=mongodb://&amp;lt;mongoserver&amp;gt;:27017/ycsb?w=1&quot;&lt;/p&gt;

&lt;p&gt;Running&lt;br/&gt;
-----------&lt;br/&gt;
bin/ycsb run mongodb -s -threads 1 -P workloads/workloada -P workloadproperty.dat -p &quot;mongodb.url=mongodb://&amp;lt;mongoserver&amp;gt;:27017/ycsb?w=1&quot;&lt;br/&gt;
where workloadproperty.dat contains these two lines &lt;br/&gt;
recordcount=1&lt;br/&gt;
operationcount=100000&lt;/p&gt;</description>
                <environment>Centos 7, MongoDB binaries downloaded from website</environment>
        <key id="362976">SERVER-28263</key>
            <summary>2 times WT rollback_transaction than WT commit_transaction in logs on a single thread YCSB workload</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="milkie@mongodb.com">Eric Milkie</assignee>
                                    <reporter username="vyasa">Avinash Vyas</reporter>
                        <labels>
                            <label>Rollback</label>
                            <label>WiredTiger</label>
                    </labels>
                <created>Thu, 9 Mar 2017 18:34:03 +0000</created>
                <updated>Tue, 18 Apr 2017 20:00:57 +0000</updated>
                            <resolved>Thu, 9 Mar 2017 19:44:30 +0000</resolved>
                                    <version>3.2.11</version>
                    <version>3.4.2</version>
                                                                        <votes>0</votes>
                                    <watches>5</watches>
                                                                                                                <comments>
                            <comment id="1520455" author="vyasa" created="Thu, 9 Mar 2017 21:27:25 +0000"  >&lt;p&gt;I can definitely post it on user forums, but just an FYI to your comment, there were no writeConflict as per serverStatus() which is what makes it more interesting. Thanks a lot for your help.&lt;/p&gt;</comment>
                            <comment id="1520301" author="milkie" created="Thu, 9 Mar 2017 19:43:53 +0000"  >&lt;p&gt;I would expect that some of the rollbacks are due to reads and some are due to write conflicts.  To determine which are which, you could look at the &quot;metrics&quot; section of serverStatus output, which has a &quot;writeConflicts&quot; counter.  The write conflicts should already be logged at log level 1 in the WRITE component, so you should already be seeing those.&lt;/p&gt;

&lt;p&gt;Please note that SERVER project is for reporting bugs or feature suggestions for the MongoDB server. For MongoDB-related support discussion please post on the &lt;a href=&quot;http://groups.google.com/group/mongodb-user&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;mongodb-user group&lt;/a&gt; or &lt;a href=&quot;http://stackoverflow.com/questions/tagged/mongodb&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Stack Overflow with the &lt;tt&gt;mongodb&lt;/tt&gt; tag&lt;/a&gt;. A question like this involving more discussion would be best posted on the mongodb-users group.&lt;/p&gt;</comment>
                            <comment id="1520283" author="vyasa" created="Thu, 9 Mar 2017 19:32:33 +0000"  >&lt;p&gt;Thanks for the reply. For us, I think a reasonable expectation is to see a rollback when there is a conflict, something that is explained here &lt;a href=&quot;http://source.wiredtiger.com/2.4.1/transactions.html&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;http://source.wiredtiger.com/2.4.1/transactions.html&lt;/a&gt;. This is an interesting revelation that MongoDB aborts all read transactions. Even under the light of this revelation, for 100K request workload we would assume 50k rollbacks and 50k commits but what we see here is &lt;br/&gt;
$ grep &quot;begin_transaction&quot; test1.log | wc -l&lt;br/&gt;
150198&lt;br/&gt;
$ grep &quot;rollback_transaction&quot; test1.log | wc -l&lt;br/&gt;
100080&lt;br/&gt;
$ grep &quot;commit_transaction&quot; test1.log | wc -l&lt;br/&gt;
50118&lt;br/&gt;
So should we assume that all these rollbacks are due to reads ? How can we identify a rollback caused due to a concurrent conflicting updates ? &lt;br/&gt;
Will there be a difference in the log message when a transaction is rolled back for a read vs when it rolled back due to a conflict ?&lt;br/&gt;
Thanks in advance.&lt;/p&gt;</comment>
                            <comment id="1520233" author="milkie" created="Thu, 9 Mar 2017 19:06:07 +0000"  >&lt;p&gt;Can you describe what your expected behavior would be?  Keep in mind that MongoDB aborts all read transactions in WiredTiger, rather than commit an empty transaction.&lt;/p&gt;</comment>
                    </comments>
                    <attachments>
                            <attachment id="151173" name="problemlog.tar.gz" size="2581464" author="vyasa" created="Thu, 9 Mar 2017 18:33:19 +0000"/>
                    </attachments>
                <subtasks>
                    </subtasks>
                <customfields>
                                                <customfield id="customfield_10050" key="com.atlassian.jira.toolkit:comments">
                        <customfieldname># Replies</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>4.0</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                <customfield id="customfield_10055" key="com.atlassian.jira.ext.charting:firstresponsedate">
                        <customfieldname>Date of 1st Reply</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>Thu, 9 Mar 2017 19:06:07 +0000</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_10052" key="com.atlassian.jira.toolkit:dayslastcommented">
                        <customfieldname>Days since reply</customfieldname>
                        <customfieldvalues>
                                        6 years, 48 weeks, 6 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_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>ian@mongodb.com</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_11151" key="com.atlassian.jira.toolkit:LastCommentDate">
                        <customfieldname>Last public comment date</customfieldname>
                        <customfieldvalues>
                            6 years, 48 weeks, 6 days ago
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                <customfield id="customfield_10051" key="com.atlassian.jira.toolkit:participants">
                        <customfieldname>Participants</customfieldname>
                        <customfieldvalues>
                                        <customfieldvalue>vyasa</customfieldvalue>
            <customfieldvalue>milkie@mongodb.com</customfieldvalue>
    
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                        <customfield id="customfield_14254" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Product Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1|ht3xqv:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                <customfield id="customfield_12550" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>2|hswg53:</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_23361" key="com.onresolve.jira.groovy.groovyrunner:scripted-field">
                        <customfieldname>Requested By</customfieldname>
                        <customfieldvalues>
                                

                        </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|hrj1e7:</customfieldvalue>

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