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https://issues.apache.org/jira/browse/RATIS-619?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16924473#comment-16924473
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Tsz Wo Nicholas Sze commented on RATIS-619:
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> Yes, how about we divide this into 2 tasks, in the first one, we just avoid
> loading the segment data ...
I guess you mean reading the segment files but not caching them. For this
approach, I doubt if it is a real improvement since caching is cheap but
reading the file is expensive. If we already have paid the expensive cost to
read the files, why not keeping them in cache as well? Otherwise, when the
leader needs to send the log to a follower, we need to pay the expensive cost
to read the files again. The log entries seems to be not cached again, then we
pay the expensive cost each time when there is a follower needing the entries.
> Avoid loading cache with pre-snapshot entries for the group
> -----------------------------------------------------------
>
> Key: RATIS-619
> URL: https://issues.apache.org/jira/browse/RATIS-619
> Project: Ratis
> Issue Type: Bug
> Components: server
> Affects Versions: 0.3.0
> Reporter: Mukul Kumar Singh
> Assignee: Siddharth Wagle
> Priority: Major
> Labels: ozone
> Attachments: RATIS-619.01.patch, RATIS-619.02.patch
>
>
> Even after taking a snapshot, the raft log loads all the segment in the log
> {code}
> 2019-07-01 23:22:47,481 [pool-18-thread-1] INFO - Setting the last
> applied index to (t:2, i:15237039)
> {code}
> {code}
> 2019-07-01 23:22:47,516 INFO org.apache.ratis.server.RaftServerConfigKeys:
> raft.server.log.statemachine.data.caching.enabled = true (custom)
> 2019-07-01 23:22:47,531 INFO org.apache.ratis.server.impl.RaftServerImpl:
> 62941ca3-f244-4298-8497-f4c0bd57430a:group-4D230AB58084 set configuration 0:
> [1f3d7936-cb4e-4b68-86ed-578070472dea:1
> 0.17.213.36:9858, 62941ca3-f244-4298-8497-f4c0bd57430a:10.17.213.35:9858,
> f07c1f87-b377-40d9-8c56-4f1440c4fa77:10.17.213.37:9858], old=null at 0
> 2019-07-01 23:22:47,578 INFO org.apache.hadoop.http.HttpServer2: Jetty bound
> to port 9882
> 2019-07-01 23:22:47,579 INFO org.eclipse.jetty.server.Server:
> jetty-9.3.24.v20180605, build timestamp: 2018-06-05T10:11:56-07:00, git hash:
> 84205aa28f11a4f31f2a3b86d1bba2cc8ab69827
> 2019-07-01 23:22:47,601 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7461
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_0-7460
> 2019-07-01 23:22:47,608 INFO org.eclipse.jetty.server.handler.ContextHandler:
> Started
> o.e.j.s.ServletContextHandler@6ce90bc5{/logs,file:///var/log/ozone/,AVAILABLE}
> 2019-07-01 23:22:47,608 INFO org.eclipse.jetty.server.handler.ContextHandler:
> Started
> o.e.j.s.ServletContextHandler@4b1c0397{/static,jar:file:/var/lib/hadoop-ozone/ozone-0.5.0-SNAPSHOT/share
> /ozone/lib/hadoop-hdds-container-service-0.5.0-SNAPSHOT.jar!/webapps/static,AVAILABLE}
> 2019-07-01 23:22:47,635 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7386
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_7461-14846
> 2019-07-01 23:22:47,663 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7440
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_14847-22286
> 2019-07-01 23:22:47,664 INFO org.eclipse.jetty.server.handler.ContextHandler:
> Started
> o.e.j.w.WebAppContext@8a62297{/,file:///tmp/jetty-0.0.0.0-9882-hddsDatanode-_-any-7539213566265642568.di
> r/webapp/,AVAILABLE}{/hddsDatanode}
> 2019-07-01 23:22:47,681 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7353
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_22287-29639
> 2019-07-01 23:22:47,695 INFO org.eclipse.jetty.server.AbstractConnector:
> Started ServerConnector@5116ac09{HTTP/1.1,[http/1.1]}{0.0.0.0:9882}
> 2019-07-01 23:22:47,695 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7291
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_29640-36930
> 2019-07-01 23:22:47,695 INFO org.eclipse.jetty.server.Server: Started @56648ms
> 2019-07-01 23:22:47,695 INFO org.apache.hadoop.hdds.server.BaseHttpServer:
> HTTP server of HDDSDATANODE is listening at http://0.0.0.0:9882
> 2019-07-01 23:22:47,709 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7049
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_36931-43979
> 2019-07-01 23:22:47,732 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7141
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230
> ab58084/current/log_43980-51120
> 2019-07-01 23:22:47,747 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7321
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230ab58084/current/log_51121-58441
> 2019-07-01 23:22:47,768 INFO
> org.apache.ratis.server.raftlog.segmented.LogSegment: Successfully read 7081
> entries from segment file
> /data/1/ozone-0701/ratis/log/f7ddda32-45e0-4bec-a3e7-4d230ab58084/current/log_58442-65522
> {code}
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