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https://issues.apache.org/jira/browse/HADOOP-13263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15344210#comment-15344210
 ] 

Hadoop QA commented on HADOOP-13263:
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| (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 
30s{color} | {color:blue} Docker mode activated. {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 1 new or modified test 
files. {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  6m 
55s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  7m  
5s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
32s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  0m 
56s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green}  0m 
13s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  1m 
27s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
45s{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  0m 
39s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  7m 
10s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  7m 
10s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
25s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  0m 
54s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green}  0m 
12s{color} | {color:green} the patch passed {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} findbugs {color} | {color:green}  1m 
32s{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
46s{color} | {color:green} the patch passed {color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red}  7m 47s{color} 
| {color:red} hadoop-common in the patch failed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 
20s{color} | {color:green} The patch does not generate ASF License warnings. 
{color} |
| {color:black}{color} | {color:black} {color} | {color:black} 38m 55s{color} | 
{color:black} {color} |
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|| Reason || Tests ||
| Failed junit tests | hadoop.metrics2.impl.TestGangliaMetrics |
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|| Subsystem || Report/Notes ||
| Docker |  Image:yetus/hadoop:e2f6409 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12812457/HADOOP-13263.006.patch
 |
| JIRA Issue | HADOOP-13263 |
| Optional Tests |  asflicense  compile  javac  javadoc  mvninstall  mvnsite  
unit  findbugs  checkstyle  |
| uname | Linux 7ab561abc2a1 3.13.0-36-lowlatency #63-Ubuntu SMP PREEMPT Wed 
Sep 3 21:56:12 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | /testptch/hadoop/patchprocess/precommit/personality/provided.sh 
|
| git revision | trunk / d433b16 |
| Default Java | 1.8.0_91 |
| findbugs | v3.0.0 |
| unit | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/9851/artifact/patchprocess/patch-unit-hadoop-common-project_hadoop-common.txt
 |
|  Test Results | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/9851/testReport/ |
| modules | C: hadoop-common-project/hadoop-common U: 
hadoop-common-project/hadoop-common |
| Console output | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/9851/console |
| Powered by | Apache Yetus 0.4.0-SNAPSHOT   http://yetus.apache.org |


This message was automatically generated.



> Reload cached groups in background after expiry
> -----------------------------------------------
>
>                 Key: HADOOP-13263
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13263
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Stephen O'Donnell
>            Assignee: Stephen O'Donnell
>         Attachments: HADOOP-13263.001.patch, HADOOP-13263.002.patch, 
> HADOOP-13263.003.patch, HADOOP-13263.004.patch, HADOOP-13263.005.patch, 
> HADOOP-13263.006.patch
>
>
> In HADOOP-11238 the Guava cache was introduced to allow refreshes on the 
> Namenode group cache to run in the background, avoiding many slow group 
> lookups. Even with this change, I have seen quite a few clusters with issues 
> due to slow group lookups. The problem is most prevalent in HA clusters, 
> where a slow group lookup on the hdfs user can fail to return for over 45 
> seconds causing the Failover Controller to kill it.
> The way the current Guava cache implementation works is approximately:
> 1) On initial load, the first thread to request groups for a given user 
> blocks until it returns. Any subsequent threads requesting that user block 
> until that first thread populates the cache.
> 2) When the key expires, the first thread to hit the cache after expiry 
> blocks. While it is blocked, other threads will return the old value.
> I feel it is this blocking thread that still gives the Namenode issues on 
> slow group lookups. If the call from the FC is the one that blocks and 
> lookups are slow, if can cause the NN to be killed.
> Guava has the ability to refresh expired keys completely in the background, 
> where the first thread that hits an expired key schedules a background cache 
> reload, but still returns the old value. Then the cache is eventually 
> updated. This patch introduces this background reload feature. There are two 
> new parameters:
> 1) hadoop.security.groups.cache.background.reload - default false to keep the 
> current behaviour. Set to true to enable a small thread pool and background 
> refresh for expired keys
> 2) hadoop.security.groups.cache.background.reload.threads - only relevant if 
> the above is set to true. Controls how many threads are in the background 
> refresh pool. Default is 1, which is likely to be enough.



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