[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17716656#comment-17716656 ] Tao Li commented on HDFS-16422: --- Hi [~cndaimin] , have you tested the impact on performance? And have you used it in a production environment? Thanks. > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.10#820010) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17522275#comment-17522275 ] Steve Loughran commented on HDFS-16422: --- this patch is going in to 3.3.3, for people who need it > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.4 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17520357#comment-17520357 ] Takanobu Asanuma commented on HDFS-16422: - [~cndaimin] Thanks for your confirmation! > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17520328#comment-17520328 ] daimin commented on HDFS-16422: --- [~tasanuma] I think NativeRSRawDecoder is thread safe after HDFS-16422, and it is not before. > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17520310#comment-17520310 ] Takanobu Asanuma commented on HDFS-16422: - Hi [~cndaimin], bq. In conclusion: RSRawDecoder seems to be thread safe, NativeRSRawDecoder is not thread safe, the read/write lock seems unable to protect the native decodeImpl method. Do you mean HDFS-16422 also made NativeRSRawDecoder thread safe? Or NativeRSRawDecoder is still not thread safe after HDFS-16422? > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[
https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17511224#comment-17511224
]
daimin commented on HDFS-16422:
---
[~jingzhao] I tested this again, and my test steps are:
# Setup a cluster with 11 datanodes, and write 4 EC RS-8-2 files: 1g, 2g, 4g,
8g
# Stop one datanode
# Check md5sum of these files through HDFS FUSE, this is a simple way to
create concurrent preads(indirect IO on FUSE)
Here is test result:
* md5sum check before datanode down:
{quote}md5sum /mnt/fuse/*g
5e6c32c0b572e2ff24fb14f93c4cc45b /mnt/fuse/1g
782173623681c129558c09e89251f46d /mnt/fuse/2g
e107f9a83a383b98aa23fdd3171b589c /mnt/fuse/4g
adb81da2c34161f249439597c515db1d /mnt/fuse/8g
{quote} * md5sum after datanode down, with native(ISA-L) decoder:
{quote}md5sum /mnt/fuse/*g
206288b264b92af42563a14a242aa629 /mnt/fuse/1g
bc86f9f549912d78c8b3d02ada5621a2 /mnt/fuse/2g
c201356b7437e6aac1b574ade08b6ccb /mnt/fuse/4g
ef2e6f6b4b6ab96a24e5f734e93bacc3 /mnt/fuse/8g
{quote} * md5sum after datanode down, with pure Java decoder:
{quote}md5sum /mnt/fuse/*g
5e6c32c0b572e2ff24fb14f93c4cc45b /mnt/fuse/1g
782173623681c129558c09e89251f46d /mnt/fuse/2g
e107f9a83a383b98aa23fdd3171b589c /mnt/fuse/4g
adb81da2c34161f249439597c515db1d /mnt/fuse/8g
{quote}
In conclusion: RSRawDecoder seems to be thread safe, NativeRSRawDecoder is not
thread safe, the read/write lock seems unable to protect the native decodeImpl
method.
And I also tested on md5sum check on same file with native(ISA-L) decoder, the
result is different every time.
{quote}for i in \{1..5};do md5sum /mnt/fuse/1g;done
2e68ea6738dccb4f248df81b5c55d464 /mnt/fuse/1g
54944120797266fc4e26bd465ae5e67a /mnt/fuse/1g
ef4d099269fb117e357015cf424723a9 /mnt/fuse/1g
6a40dbca2636ae796b6380385ddfbc83 /mnt/fuse/1g
126fc40073dcebb67d413de95571c08b /mnt/fuse/1g
{quote}
IMO, HADOOP-15499 did improve the performance of decoder, however it breaked
the correctness of decode method when invoked concurrently. We should take
synchronized back, and I will submit a new PR later to do this work. Thanks
[~jingzhao] again.
> Fix thread safety of EC decoding during concurrent preads
> -
>
> Key: HDFS-16422
> URL: https://issues.apache.org/jira/browse/HDFS-16422
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: dfsclient, ec, erasure-coding
>Affects Versions: 3.3.0, 3.3.1
>Reporter: daimin
>Assignee: daimin
>Priority: Critical
> Labels: pull-request-available
> Fix For: 3.4.0, 3.2.3, 3.3.3
>
> Time Spent: 3h 40m
> Remaining Estimate: 0h
>
> Reading data on an erasure-coded file with missing replicas(internal block of
> block group) will cause online reconstruction: read dataUnits part of data
> and decode them into the target missing data. Each DFSStripedInputStream
> object has a RawErasureDecoder object, and when we doing pread concurrently,
> RawErasureDecoder.decode will be invoked concurrently too.
> RawErasureDecoder.decode is not thread safe, as a result of that we get wrong
> data from pread occasionally.
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[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17507969#comment-17507969 ] daimin commented on HDFS-16422: --- I tested both NativeRSRawDecoder and RSRawDecoder before, and they seems both not thread safe to decode, therefore I simply add a synchronized to the decode method. In consideration of HADOOP-15499, I will do some more tests to find out what's missing of the original lock protection. Thanks for your reminding. [~jingzhao] > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads
[ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17503858#comment-17503858 ] Jing Zhao commented on HDFS-16422: -- Looks like we already have r/w lock protection in AbstractNativeRawDecoder and its subclasses (NativeRSRawDecoder and NativeXORRawDecoder). So does that mean the extra protection is only necessary for other decoder implementations (such as RSRawDecoder)? HADOOP-15499 used r/w lock to replace the original object monitor (i.e. synchronized) so as to improve performance. Now looks like we're adding "synchronized" back to the APIs defined in the parent class. I guess instead of updating the decode APIs in RawErasureDecoder, we may want to only fix the subclasses without lock protection. What do you think, [~weichiu] [~cndaimin] ? > Fix thread safety of EC decoding during concurrent preads > - > > Key: HDFS-16422 > URL: https://issues.apache.org/jira/browse/HDFS-16422 > Project: Hadoop HDFS > Issue Type: Bug > Components: dfsclient, ec, erasure-coding >Affects Versions: 3.3.0, 3.3.1 >Reporter: daimin >Assignee: daimin >Priority: Critical > Labels: pull-request-available > Fix For: 3.4.0, 3.2.3, 3.3.3 > > Time Spent: 3h 40m > Remaining Estimate: 0h > > Reading data on an erasure-coded file with missing replicas(internal block of > block group) will cause online reconstruction: read dataUnits part of data > and decode them into the target missing data. Each DFSStripedInputStream > object has a RawErasureDecoder object, and when we doing pread concurrently, > RawErasureDecoder.decode will be invoked concurrently too. > RawErasureDecoder.decode is not thread safe, as a result of that we get wrong > data from pread occasionally. -- This message was sent by Atlassian Jira (v8.20.1#820001) - To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
