<!-- 
RSS generated by JIRA (9.7.1#970001-sha1:2222b88b221c4928ef0de3161136cc90c8356a66) at Thu Feb 08 03:09:43 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-5729] Special-case concurrency model for oplog, make reads not block as much</title>
                <link>https://jira.mongodb.org/browse/SERVER-5729</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;It would be useful to special-case the concurrency model for the oplog so that reads don&apos;t block. Under sustained periods of high write load, secondaries can fall further and further behind the primary because of high lock% when trying to read from the oplog. But the oplog is a special beast that is an append-only (sorta, most of the time) capped collection. It might be possible to use this fact to make special locking rules that allowed reads to happen all the time, or at least dramatically reduce the period of lock contention.&lt;/p&gt;

&lt;p&gt;The situation will get markedly better with DB-level locking, but further special-casing could help as well. Currently we have to bump the horsepower on the nodes in the replica set, even if the boxes are otherwise healthy.&lt;/p&gt;

&lt;p&gt;There are sometimes reasons to actually write to the oplog manually. Would need to figure out a way to deal with those cases.&lt;/p&gt;</description>
                <environment>Ubuntu 10.10 64-bit</environment>
        <key id="37494">SERVER-5729</key>
            <summary>Special-case concurrency model for oplog, make reads not block as much</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</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="jared">Jared D. Cottrell</reporter>
                        <labels>
                            <label>sync</label>
                    </labels>
                <created>Mon, 30 Apr 2012 21:22:25 +0000</created>
                <updated>Tue, 6 Dec 2022 05:33:38 +0000</updated>
                            <resolved>Fri, 14 Sep 2018 20:14:51 +0000</resolved>
                                    <version>2.0.4</version>
                                                    <component>MMAPv1</component>
                    <component>Replication</component>
                    <component>Storage</component>
                                        <votes>4</votes>
                                    <watches>9</watches>
                                                                                                                <comments>
                            <comment id="1758246" author="asya" created="Thu, 21 Dec 2017 21:32:22 +0000"  >&lt;p&gt;Probably can be closed as duplicate of &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-20328&quot; title=&quot;Allow secondary reads while applying oplog entries&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-20328&quot;&gt;&lt;del&gt;SERVER-20328&lt;/del&gt;&lt;/a&gt; since implementing that ticket will resolve this one.&lt;/p&gt;</comment>
                            <comment id="115019" author="schwerin" created="Mon, 30 Apr 2012 21:45:08 +0000"  >&lt;p&gt;I&apos;m labeling this &quot;features we&apos;re not sure of&quot;, because we don&apos;t know, yet, if a special-case approach to oplog access will be appropriate.  That will depend a lot on how other concurrency improvements improve or stymy oplog data distribution.&lt;/p&gt;</comment>
                            <comment id="115018" author="schwerin" created="Mon, 30 Apr 2012 21:43:22 +0000"  >&lt;p&gt;It&apos;s an interesting thought.  Since the oplog is in a distinct database (&quot;local&quot;), which is only write-locked for a brief period at the end of document write operations, we&apos;re expecting distinctly improved secondary performance under high write load.  Further down the road, finer grained locking (i.e., sub collection level), or other concurrency techniques should improve read access to all databases under heavy write load, and raise the performance of replication along with it.&lt;/p&gt;

&lt;p&gt;Once db-level locking is in place, I think a bigger problem will be keeping secondaries caught up applying the oplog, rather than getting the oplog data off the primaries.  The v2.0 approach to oplog application is inherently single-threaded, and that&apos;s not going to suffice in the world of db-level locking.&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10012">
                    <name>Related</name>
                                            <outwardlinks description="related to">
                                        <issuelink>
            <issuekey id="228962">SERVER-20328</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="243461">SERVER-21862</issuekey>
        </issuelink>
                            </outwardlinks>
                                                        </issuelinktype>
                    </issuelinks>
                <attachments>
                    </attachments>
                <subtasks>
                    </subtasks>
                <customfields>
                                                <customfield id="customfield_10050" key="com.atlassian.jira.toolkit:comments">
                        <customfieldname># Replies</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>3.0</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                <customfield id="customfield_12751" key="com.atlassian.jira.plugin.system.customfieldtypes:multiselect">
                        <customfieldname>Assigned Teams</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="25136"><![CDATA[Storage Execution]]></customfieldvalue>
    
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    <customfield id="customfield_10055" key="com.atlassian.jira.ext.charting:firstresponsedate">
                        <customfieldname>Date of 1st Reply</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>Mon, 30 Apr 2012 21:43:22 +0000</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_10052" key="com.atlassian.jira.toolkit:dayslastcommented">
                        <customfieldname>Days since reply</customfieldname>
                        <customfieldvalues>
                                        6 years, 7 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>alexander.golin@mongodb.com</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_11151" key="com.atlassian.jira.toolkit:LastCommentDate">
                        <customfieldname>Last public comment date</customfieldname>
                        <customfieldvalues>
                            6 years, 7 weeks, 6 days ago
                        </customfieldvalues>
                    </customfield>
                                                                                                                        <customfield id="customfield_10000" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Old_Backport</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="10000"><![CDATA[No]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                <customfield id="customfield_10051" key="com.atlassian.jira.toolkit:participants">
                        <customfieldname>Participants</customfieldname>
                        <customfieldvalues>
                                        <customfieldvalue>schwerin@mongodb.com</customfieldvalue>
            <customfieldvalue>asya.kamsky@mongodb.com</customfieldvalue>
            <customfieldvalue>backlog-server-execution</customfieldvalue>
            <customfieldvalue>jared</customfieldvalue>
    
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                        <customfield id="customfield_14254" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Product Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1|hro4en:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                <customfield id="customfield_12550" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>2|hr8hl3:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                <customfield id="customfield_10558" key="com.pyxis.greenhopper.jira:gh-global-rank">
                        <customfieldname>Rank (Obsolete)</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>4503</customfieldvalue>
                        </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|hrixvb:</customfieldvalue>

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