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https://issues.apache.org/jira/browse/HBASE-21418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16672052#comment-16672052
 ] 

Hadoop QA commented on HBASE-21418:
-----------------------------------

| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m 
36s{color} | {color:blue} Docker mode activated. {color} |
|| || || || {color:brown} Prechecks {color} ||
| {color:blue}0{color} | {color:blue} findbugs {color} | {color:blue}  0m  
5s{color} | {color:blue} Findbugs executables are not available. {color} |
| {color:green}+1{color} | {color:green} hbaseanti {color} | {color:green}  0m  
0s{color} | {color:green} Patch does not have any anti-patterns. {color} |
| {color:green}+1{color} | {color:green} @author {color} | {color:green}  0m  
0s{color} | {color:green} The patch does not contain any @author tags. {color} |
| {color:green}+1{color} | {color:green} test4tests {color} | {color:green}  0m 
 0s{color} | {color:green} The patch appears to include 2 new or modified test 
files. {color} |
|| || || || {color:brown} branch-1.2 Compile Tests {color} ||
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  2m 
38s{color} | {color:blue} Maven dependency ordering for branch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  8m 
28s{color} | {color:green} branch-1.2 passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m 
16s{color} | {color:green} branch-1.2 passed with JDK v1.8.0_181 {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 
52s{color} | {color:green} branch-1.2 passed with JDK v1.7.0_191 {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  1m 
44s{color} | {color:green} branch-1.2 passed {color} |
| {color:green}+1{color} | {color:green} shadedjars {color} | {color:green}  2m 
31s{color} | {color:green} branch has no errors when building our shaded 
downstream artifacts. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
50s{color} | {color:green} branch-1.2 passed with JDK v1.8.0_181 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
56s{color} | {color:green} branch-1.2 passed with JDK v1.7.0_191 {color} |
|| || || || {color:brown} Patch Compile Tests {color} ||
| {color:blue}0{color} | {color:blue} mvndep {color} | {color:blue}  0m 
11s{color} | {color:blue} Maven dependency ordering for patch {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  1m 
30s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 
45s{color} | {color:green} the patch passed with JDK v1.8.0_181 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  0m 
45s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  0m 
51s{color} | {color:green} the patch passed with JDK v1.7.0_191 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  0m 
51s{color} | {color:green} the patch passed {color} |
| {color:red}-1{color} | {color:red} checkstyle {color} | {color:red}  1m 
16s{color} | {color:red} hbase-server: The patch generated 13 new + 164 
unchanged - 1 fixed = 177 total (was 165) {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green}  0m 
 0s{color} | {color:green} The patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} shadedjars {color} | {color:green}  2m 
21s{color} | {color:green} patch has no errors when building our shaded 
downstream artifacts. {color} |
| {color:green}+1{color} | {color:green} hadoopcheck {color} | {color:green}  
8m 29s{color} | {color:green} Patch does not cause any errors with Hadoop 2.4.1 
2.5.2 2.6.5 2.7.4. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
39s{color} | {color:green} the patch passed with JDK v1.8.0_181 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
53s{color} | {color:green} the patch passed with JDK v1.7.0_191 {color} |
|| || || || {color:brown} Other Tests {color} ||
| {color:green}+1{color} | {color:green} unit {color} | {color:green}  2m  
2s{color} | {color:green} hbase-client in the patch passed. {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red}140m 51s{color} 
| {color:red} hbase-server in the patch failed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 
41s{color} | {color:green} The patch does not generate ASF License warnings. 
{color} |
| {color:black}{color} | {color:black} {color} | {color:black}181m 41s{color} | 
{color:black} {color} |
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|| Reason || Tests ||
| Failed junit tests | 
hadoop.hbase.replication.regionserver.TestRegionReplicaReplicationEndpoint |
|   | hadoop.hbase.mapreduce.TestLoadIncrementalHFilesUseSecurityEndPoint |
|   | hadoop.hbase.master.TestAssignmentManagerOnCluster |
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|| Subsystem || Report/Notes ||
| Docker | Client=17.05.0-ce Server=17.05.0-ce Image:yetus/hbase:34a9b27 |
| JIRA Issue | HBASE-21418 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12946565/HBASE-21418.branch-1.2.001.patch
 |
| Optional Tests |  dupname  asflicense  javac  javadoc  unit  findbugs  
shadedjars  hadoopcheck  hbaseanti  checkstyle  compile  |
| uname | Linux caf953f2bef6 4.4.0-138-generic #164-Ubuntu SMP Tue Oct 2 
17:16:02 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | 
/home/jenkins/jenkins-slave/workspace/PreCommit-HBASE-Build@2/component/dev-support/hbase-personality.sh
 |
| git revision | branch-1.2 / 1add8f1 |
| maven | version: Apache Maven 3.0.5 |
| Default Java | 1.7.0_191 |
| Multi-JDK versions |  /usr/lib/jvm/java-8-openjdk-amd64:1.8.0_181 
/usr/lib/jvm/java-7-openjdk-amd64:1.7.0_191 |
| checkstyle | 
https://builds.apache.org/job/PreCommit-HBASE-Build/14928/artifact/patchprocess/diff-checkstyle-hbase-server.txt
 |
| unit | 
https://builds.apache.org/job/PreCommit-HBASE-Build/14928/artifact/patchprocess/patch-unit-hbase-server.txt
 |
|  Test Results | 
https://builds.apache.org/job/PreCommit-HBASE-Build/14928/testReport/ |
| Max. process+thread count | 4413 (vs. ulimit of 10000) |
| modules | C: hbase-client hbase-server U: . |
| Console output | 
https://builds.apache.org/job/PreCommit-HBASE-Build/14928/console |
| Powered by | Apache Yetus 0.8.0   http://yetus.apache.org |


This message was automatically generated.



> Reduce a number of reseek operations in MemstoreScanner when seek point is 
> close to the current row.
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-21418
>                 URL: https://issues.apache.org/jira/browse/HBASE-21418
>             Project: HBase
>          Issue Type: Improvement
>          Components: scan, Scanners
>    Affects Versions: 1.2.5
>            Reporter: Jeongdae Kim
>            Assignee: Jeongdae Kim
>            Priority: Minor
>              Labels: performance
>         Attachments: HBASE-21418.branch-1.2.001.patch, 
> HBASE-21418.branch-1.2.001.patch
>
>
> We observed “responseTooSlow” logs for Get requests in our production 
> clusters. even some get requests were responded after 10 seconds.
> Affected get requests were done with the timerange, and target rows have many 
> columns that have some versions.
> We reproduced this issue, and found this behavior happens only when scanning 
> in the memstore. after flushing the HStore, this slow response issue for Get 
> disappeared and all same get requests are responded very quickly.
>  
> We investigated this case, and found this performance difference between 
> memstore scanner and hfile scanner is caused by the number of reseek 
> operations executed while scanning. When a store scanner needs to reseek the 
> next column, Hfile scanner wisely decide whether it have to reseek or not by 
> checking the seek point is in current block, whereas memstore scanner just do 
> reseek without decision unlike Hfile scanner. In our case, almost all columns 
> in the memstore have older timestamp than scan(get)’s timerange, and so many 
> reseek operations occur as much as about the number of columns. This results 
> in increasing the response time of Get requests sporadically.
>  
> To improve the reseek operation of the memstore scanner, i think it’s better 
> skipping than seeking when reseek requested, if seek point is quite close to 
> current cell that the scanner is pointing now.(Actually, i changed 
> MatchCode.SEEK_NEXT_COL to MatchCode.Skip in our case, and the response time 
> of Get was 6x faster than before) But we can’t decide whether seek point is 
> close to the current cell or not, because memstore scannner has no 
> information such as next block index.
>  Before HBASE-13109, Scan.HINT_LOOKAHEAD was introduced to handle like this 
> case, and it may be deprecated someday. But, i think that hint is still be 
> useful for the memstore scanner to try to skip first, before reseeking, and 
> with this option we can make reseek operations of memstore scanner smarter.
>  
> I tested this patch in our case, and got the same result as i changed 
> matchcode (mentioned above).



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