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https://issues.apache.org/jira/browse/YARN-10562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17260697#comment-17260697
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Hadoop QA commented on YARN-10562:
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|| Vote || Subsystem || Runtime ||  Logfile || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  1m 
26s{color} | {color:blue}{color} | {color:blue} Docker mode activated. {color} |
|| || || || {color:brown} Prechecks {color} || ||
| {color:green}+1{color} | {color:green} dupname {color} | {color:green}  0m  
0s{color} | {color:green}{color} | {color:green} No case conflicting files 
found. {color} |
| {color:green}+1{color} | {color:green} @author {color} | {color:green}  0m  
0s{color} | {color:green}{color} | {color:green} The patch does not contain any 
@author tags. {color} |
| {color:green}+1{color} | {color:green} {color} | {color:green}  0m  0s{color} 
| {color:green}test4tests{color} | {color:green} The patch appears to include 1 
new or modified test files. {color} |
|| || || || {color:brown} trunk Compile Tests {color} || ||
| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green} 24m 
12s{color} | {color:green}{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m 
16s{color} | {color:green}{color} | {color:green} trunk passed with JDK 
Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m  
8s{color} | {color:green}{color} | {color:green} trunk passed with JDK Private 
Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} checkstyle {color} | {color:green}  0m 
27s{color} | {color:green}{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  0m 
40s{color} | {color:green}{color} | {color:green} trunk passed {color} |
| {color:green}+1{color} | {color:green} shadedclient {color} | {color:green} 
18m 12s{color} | {color:green}{color} | {color:green} branch has no errors when 
building and testing our client artifacts. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
32s{color} | {color:green}{color} | {color:green} trunk passed with JDK 
Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
28s{color} | {color:green}{color} | {color:green} trunk passed with JDK Private 
Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 {color} |
| {color:blue}0{color} | {color:blue} spotbugs {color} | {color:blue}  1m 
25s{color} | {color:blue}{color} | {color:blue} Used deprecated FindBugs 
config; considering switching to SpotBugs. {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  1m 
23s{color} | {color:green}{color} | {color:green} trunk passed {color} |
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| {color:green}+1{color} | {color:green} mvninstall {color} | {color:green}  0m 
40s{color} | {color:green}{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m 
11s{color} | {color:green}{color} | {color:green} the patch passed with JDK 
Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  1m 
11s{color} | {color:green}{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} compile {color} | {color:green}  1m  
4s{color} | {color:green}{color} | {color:green} the patch passed with JDK 
Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} javac {color} | {color:green}  1m  
4s{color} | {color:green}{color} | {color:green} the patch passed {color} |
| {color:orange}-0{color} | {color:orange} checkstyle {color} | {color:orange}  
0m 21s{color} | 
{color:orange}https://ci-hadoop.apache.org/job/PreCommit-YARN-Build/437/artifact/out/diff-checkstyle-hadoop-yarn-project_hadoop-yarn_hadoop-yarn-server_hadoop-yarn-server-nodemanager.txt{color}
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hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager:
 The patch generated 4 new + 31 unchanged - 0 fixed = 35 total (was 31) {color} 
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| {color:green}+1{color} | {color:green} mvnsite {color} | {color:green}  0m 
35s{color} | {color:green}{color} | {color:green} the patch passed {color} |
| {color:green}+1{color} | {color:green} whitespace {color} | {color:green}  0m 
 0s{color} | {color:green}{color} | {color:green} The patch has no whitespace 
issues. {color} |
| {color:green}+1{color} | {color:green} shadedclient {color} | {color:green} 
16m 36s{color} | {color:green}{color} | {color:green} patch has no errors when 
building and testing our client artifacts. {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
31s{color} | {color:green}{color} | {color:green} the patch passed with JDK 
Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 {color} |
| {color:green}+1{color} | {color:green} javadoc {color} | {color:green}  0m 
26s{color} | {color:green}{color} | {color:green} the patch passed with JDK 
Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 {color} |
| {color:green}+1{color} | {color:green} findbugs {color} | {color:green}  1m 
28s{color} | {color:green}{color} | {color:green} the patch passed {color} |
|| || || || {color:brown} Other Tests {color} || ||
| {color:green}+1{color} | {color:green} unit {color} | {color:green} 22m 
27s{color} | {color:green}{color} | {color:green} 
hadoop-yarn-server-nodemanager in the patch passed. {color} |
| {color:green}+1{color} | {color:green} asflicense {color} | {color:green}  0m 
30s{color} | {color:green}{color} | {color:green} The patch does not generate 
ASF License warnings. {color} |
| {color:black}{color} | {color:black} {color} | {color:black} 96m 19s{color} | 
{color:black}{color} | {color:black}{color} |
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|| Subsystem || Report/Notes ||
| Docker | ClientAPI=1.41 ServerAPI=1.41 base: 
https://ci-hadoop.apache.org/job/PreCommit-YARN-Build/437/artifact/out/Dockerfile
 |
| JIRA Issue | YARN-10562 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/13018322/YARN-10562.002.patch |
| Optional Tests | dupname asflicense compile javac javadoc mvninstall mvnsite 
unit shadedclient findbugs checkstyle |
| uname | Linux 0d356a702cac 4.15.0-126-generic #129-Ubuntu SMP Mon Nov 23 
18:53:38 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux |
| Build tool | maven |
| Personality | personality/hadoop.sh |
| git revision | trunk / b612c310c26 |
| Default Java | Private Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 |
| Multi-JDK versions | 
/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.9.1+1-Ubuntu-0ubuntu1.18.04 
/usr/lib/jvm/java-8-openjdk-amd64:Private 
Build-1.8.0_275-8u275-b01-0ubuntu1~18.04-b01 |
|  Test Results | 
https://ci-hadoop.apache.org/job/PreCommit-YARN-Build/437/testReport/ |
| Max. process+thread count | 568 (vs. ulimit of 5500) |
| modules | C: 
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager
 U: 
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager
 |
| Console output | 
https://ci-hadoop.apache.org/job/PreCommit-YARN-Build/437/console |
| versions | git=2.17.1 maven=3.6.0 findbugs=4.0.6 |
| Powered by | Apache Yetus 0.13.0-SNAPSHOT https://yetus.apache.org |


This message was automatically generated.



> Alternate fix for DirectoryCollection.checkDirs() race
> ------------------------------------------------------
>
>                 Key: YARN-10562
>                 URL: https://issues.apache.org/jira/browse/YARN-10562
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: yarn
>    Affects Versions: 3.4.0
>            Reporter: Jim Brennan
>            Assignee: Jim Brennan
>            Priority: Major
>         Attachments: YARN-10562.001.patch, YARN-10562.002.patch
>
>
> In YARN-9833, a race condition in DirectoryCollection. {{getGoodDirs()}} and 
> related methods were returning an unmodifiable view of the lists. These 
> accesses were protected by read/write locks, but because the lists are 
> CopyOnWriteArrayLists, subsequent changes to the list, even when done under 
> the writelock, were exposed when a caller started iterating the list view. 
> CopyOnWriteArrayLists cache the current underlying list in the iterator, so 
> it is safe to iterate them even while they are being changed - at least the 
> view will be consistent.
> The problem was that checkDirs() was clearing the lists and rebuilding them 
> from scratch every time, so if a caller called getGoodDirs() just before 
> checkDirs cleared it, and then started iterating right after the clear, they 
> could get an empty list.
> The fix in YARN-9833 was to change {{getGoodDirs()}} and related methods to 
> return a copy of the list, which definitely fixes the race condition. The 
> disadvantage is that now we create a new copy of these lists every time we 
> launch a container. The advantage using CopyOnWriteArrayList was that the 
> lists should rarely ever change, and we can avoid all the copying. 
> Unfortunately, the way checkDirs() was written, it guaranteed that it would 
> modify those lists multiple times every time.
> So this Jira proposes an alternate solution for YARN-9833, which mainly just 
> rewrites checkDirs() to minimize the changes to the underlying lists. There 
> are still some small windows where a disk will have been added to one list, 
> but not yet removed from another if you hit it just right, but I think these 
> should be pretty rare and relatively harmless, and in the vast majority of 
> cases I suspect only one disk will be moving from one list to another at any 
> time.   The question is whether this type of inconsistency (which was always 
> there before -YARN-9833- is worth reducing all the copying.



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