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https://issues.apache.org/jira/browse/HADOOP-12482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14983102#comment-14983102
 ] 

Hadoop QA commented on HADOOP-12482:
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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 7s 
{color} | {color:blue} docker + precommit patch detected. {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} 3m 
35s {color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 4m 24s 
{color} | {color:green} trunk passed with JDK v1.8.0_60 {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 4m 8s 
{color} | {color:green} trunk passed with JDK v1.7.0_79 {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green} 0m 
14s {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 
37s {color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m 55s 
{color} | {color:green} trunk passed with JDK v1.8.0_60 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 1m 2s 
{color} | {color:green} trunk passed with JDK v1.7.0_79 {color} |
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 1m 
23s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 4m 18s 
{color} | {color:green} the patch passed with JDK v1.8.0_60 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 4m 18s 
{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green} 4m 7s 
{color} | {color:green} the patch passed with JDK v1.7.0_79 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green} 4m 7s 
{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green} 0m 
14s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} mvneclipse {color} | {color:green} 0m 
14s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green} 0m 
0s {color} | {color:green} Patch has no whitespace issues. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green} 1m 
45s {color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 0m 52s 
{color} | {color:green} the patch passed with JDK v1.8.0_60 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green} 1m 0s 
{color} | {color:green} the patch passed with JDK v1.7.0_79 {color} |
| {color:green}+1{color} | {color:green} unit {color} | {color:green} 6m 37s 
{color} | {color:green} hadoop-common in the patch passed with JDK v1.8.0_60. 
{color} |
| {color:red}-1{color} | {color:red} unit {color} | {color:red} 6m 31s {color} 
| {color:red} hadoop-common in the patch failed with JDK v1.7.0_79. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green} 0m 
24s {color} | {color:green} Patch does not generate ASF License warnings. 
{color} |
| {color:black}{color} | {color:black} {color} | {color:black} 44m 39s {color} 
| {color:black} {color} |
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|| Reason || Tests ||
| JDK v1.7.0_79 Failed junit tests | hadoop.security.TestShellBasedIdMapping |
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|| Subsystem || Report/Notes ||
| Docker | Client=1.7.1 Server=1.7.1 
Image:test-patch-base-hadoop-date2015-10-30 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12769820/HADOOP-12482.003.patch
 |
| JIRA Issue | HADOOP-12482 |
| Optional Tests |  asflicense  javac  javadoc  mvninstall  unit  findbugs  
checkstyle  compile  |
| uname | Linux 8d99547a218b 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 | 
/home/jenkins/jenkins-slave/workspace/PreCommit-HADOOP-Build/patchprocess/apache-yetus-e77b1ce/precommit/personality/hadoop.sh
 |
| git revision | trunk / 45d3967 |
| Default Java | 1.7.0_79 |
| Multi-JDK versions |  /usr/lib/jvm/java-8-oracle:1.8.0_60 
/usr/lib/jvm/java-7-openjdk-amd64:1.7.0_79 |
| findbugs | v3.0.0 |
| unit | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/7980/artifact/patchprocess/patch-unit-hadoop-common-project_hadoop-common-jdk1.7.0_79.txt
 |
| unit test logs |  
https://builds.apache.org/job/PreCommit-HADOOP-Build/7980/artifact/patchprocess/patch-unit-hadoop-common-project_hadoop-common-jdk1.7.0_79.txt
 |
| JDK v1.7.0_79  Test Results | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/7980/testReport/ |
| modules | C: hadoop-common-project/hadoop-common U: 
hadoop-common-project/hadoop-common |
| Max memory used | 227MB |
| Powered by | Apache Yetus   http://yetus.apache.org |
| Console output | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/7980/console |


This message was automatically generated.



> Race condition in JMX cache update
> ----------------------------------
>
>                 Key: HADOOP-12482
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12482
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 2.7.1
>            Reporter: Tony Wu
>            Assignee: Tony Wu
>         Attachments: HADOOP-12482.001.patch, HADOOP-12482.002.patch, 
> HADOOP-12482.003.patch
>
>
> updateJmxCache() was updated in HADOOP-11301. However the patch introduced a 
> race condition. In updateJmxCache() function in MetricsSourceAdapter.java:
> {code:java}
>   private void updateJmxCache() {
>     boolean getAllMetrics = false;
>     synchronized (this) {
>       if (Time.now() - jmxCacheTS >= jmxCacheTTL) {
>         // temporarilly advance the expiry while updating the cache
>         jmxCacheTS = Time.now() + jmxCacheTTL;
>         if (lastRecs == null) {
>           getAllMetrics = true;
>         }
>       } else {
>         return;
>       }
>       if (getAllMetrics) {
>         MetricsCollectorImpl builder = new MetricsCollectorImpl();
>         getMetrics(builder, true);
>       }
>       updateAttrCache();
>       if (getAllMetrics) {
>         updateInfoCache();
>       }
>       jmxCacheTS = Time.now();
>       lastRecs = null; // in case regular interval update is not running
>     }
>   }
> {code}
> Notice that getAllMetrics is set to true when:
> # jmxCacheTTL has passed
> # lastRecs == null
> lastRecs is set to null in the same function, but gets reassigned by 
> getMetrics().
> However getMetrics() can be called from a different thread:
> # MetricsSystemImpl.onTimerEvent()
> # MetricsSystemImpl.publishMetricsNow()
> Consider the following sequence:
> # updateJmxCache() is called by getMBeanInfo() from a thread getting cached 
> info. 
> ** lastRecs is set to null.
> # metrics sources is updated with new value/field.
> # getMetrics() is called by publishMetricsNow() or onTimerEvent() from a 
> different thread getting the latest metrics. 
> ** lastRecs is updated (!= null).
> # jmxCacheTTL passed.
> # updateJmxCache() is called again via getMBeanInfo().
> ** However because lastRecs is already updated (!= null), getAllMetrics will 
> not be set to true. So updateInfoCache() is not called and getMBeanInfo() 
> returns the old cached info.
> We ran into this issue on a cluster where a new metric did not get published 
> until much later.
> The case can be made worse by a periodic call to getMetrics() (driven by an 
> external program or script). In such case getMBeanInfo() may never be able to 
> retrieve the new record.
> The desired behavior should be that updateJmxCache() will guarantee to call 
> updateInfoCache() once after jmxCacheTTL, if lastRecs has been set to null by 
> updateJmxCache() itself.



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