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https://issues.apache.org/jira/browse/TEZ-3369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15412516#comment-15412516
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Ming Ma commented on TEZ-3369:
------------------------------
bq. For task level progress, we could do the same - just need to ensure that we
do not overload the AM
Here is a related MR jira we had MAPREDUCE-5954. If Tez counters are included,
it could cause AM to run out of memory. So to support task attempts at RPC
level, we either allow counters to be skipped, or support pagination.
[~pnarang] [~cwensel] [~fs111] how important is it to have cascading support
fetching running task attempts from Tez AM? IIUC Tez AM currently doesn't
provide such functionality. Thus from MR -> Tez cascading migration point of
view, only the completed tasks are compatible. I try to understand how
important it is and maybe we can fix the immediate issue e.g. to get cascading
running on Tez 0.9, and add the support to Tez AM RPC.
ATS v2 YARN-2928 has added support for query for running apps. Maybe in the
long term cascading can query ATS v2 for both running and completed apps.
> Fixing Tez's DAGClients to work with Cascading
> ----------------------------------------------
>
> Key: TEZ-3369
> URL: https://issues.apache.org/jira/browse/TEZ-3369
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Piyush Narang
>
> Hi,
> We seem to be running into issues when we try to use the newest version of
> Tez (0.9.0-SNAPSHOT) with Cascading. The issue seems to be:
> {code}
> java.lang.ClassCastException: cascading.stats.tez.util.TezTimelineClient
> cannot be cast to org.apache.tez.dag.api.client.DAGClient
> at
> cascading.stats.tez.util.TezStatsUtil.createTimelineClient(TezStatsUtil.java:142)
> {code}
> (Full stack trace at the end)
> Relevant Cascading code is:
> 1) [Cascading tries to create a TezTimelineClient and cast it to a DAGClient
> |
> https://github.com/Cascading/cascading/blob/3.1/cascading-hadoop2-tez-stats/src/main/java/cascading/stats/tez/util/TezStatsUtil.java#L142]
> 2) [TezTimelineClient extends from DAGClientTimelineImpl |
> https://github.com/Cascading/cascading/blob/3.1/cascading-hadoop2-tez-stats/src/main/java/cascading/stats/tez/util/TezTimelineClient.java#L53]
> 3) [DAGClientTimelineImpl extends from DAGClientInternal |
> https://github.com/apache/tez/blob/dacd0191b684208d71ea457ca849f2d01212bb7e/tez-api/src/main/java/org/apache/tez/dag/api/client/DAGClientTimelineImpl.java#L68]
> 4) [DAGClientInternal extends Closeable which is why things break |
> https://github.com/apache/tez/blob/dacd0191b684208d71ea457ca849f2d01212bb7e/tez-api/src/main/java/org/apache/tez/dag/api/client/DAGClientInternal.java#L38].
> This behavior was 'broken' in this [commit |
> https://github.com/apache/tez/commit/2af886b509015200e1c04527275474cbc771c667]
> (release 0.8.3)
> The TezTimelineClient in Cascading seems to do two things:
> 1) DAGClient functionalities - ends up delegating to the inner DAGClient
> object.
> 2) Retrieve stuff like vertexID, vertexChildren and vertexChild (from this
> [interface|https://github.com/Cascading/cascading/blob/3.1/cascading-hadoop2-tez-stats/src/main/java/cascading/stats/tez/util/TimelineClient.java#L31]).
>
> As there's no good way to get the vertexID / vertexChildren / vertexChild
> (correct me if I'm wrong), they end up extending from the
> DAGClientTimelineImpl which has the http client and json parsing code to
> allow [things like this |
> https://github.com/Cascading/cascading/blob/3.1/cascading-hadoop2-tez-stats/src/main/java/cascading/stats/tez/util/TezTimelineClient.java#L93]:
> {code}
> @Override
> public String getVertexID( String vertexName ) throws IOException,
> TezException
> {
> // the filter 'vertexName' is in the 'otherinfo' field, so it must be
> requested, otherwise timeline server throws
> // an NPE. to be safe, we include both fields in the result
> String format =
> "%s/%s?primaryFilter=%s:%s&secondaryFilter=vertexName:%s&fields=%s";
> String url = String.format( format, baseUri, TEZ_VERTEX_ID, TEZ_DAG_ID,
> dagId, vertexName, FILTER_BY_FIELDS );
> JSONObject jsonRoot = getJsonRootEntity( url );
> JSONArray entitiesNode = jsonRoot.optJSONArray( ENTITIES );
> ...
> {code}
> Some options I can think of:
> 1) Ideally these methods getVertexID / getVertexChildren / getVertexChild
> would be part of DAGClient? Or even part of the DAGClientTimelineImpl? That
> way the cascading code wouldn't need updating if the uri changed / json
> format changed, it would end up being updated in these clients as well. I
> suspect adding this to DAGClient would require more work as it'll also need
> to be supported by the RPCClient and I don't think there are the relevant
> protos and such available.
> 2) A simpler fix would be to have DAGClientInternal extend DAGClient
> (currently it just implements Closeable). This will not require any changes
> on the Cascading side as DAGClientTimelineImpl will continue to be a
> DAGClient.
> Full stack trace:
> {code}
> Exception in thread "flow
> com.twitter.data_platform.e2e_testing.jobs.parquet.E2ETestConvertThriftToParquet"
> java.lang.ClassCastException: cascading.stats.tez.util.TezTimelineClient
> cannot be cast to org.apache.tez.dag.api.client.DAGClient
> at
> cascading.stats.tez.util.TezStatsUtil.createTimelineClient(TezStatsUtil.java:142)
> at
> cascading.flow.tez.planner.Hadoop2TezFlowStepJob$1.getJobStatusClient(Hadoop2TezFlowStepJob.java:117)
> at
> cascading.flow.tez.planner.Hadoop2TezFlowStepJob$1.getJobStatusClient(Hadoop2TezFlowStepJob.java:105)
> at
> cascading.stats.tez.TezStepStats$1.getJobStatusClient(TezStepStats.java:60)
> at
> cascading.stats.tez.TezStepStats$1.getJobStatusClient(TezStepStats.java:56)
> at cascading.stats.CounterCache.cachedCounters(CounterCache.java:229)
> at cascading.stats.CounterCache.cachedCounters(CounterCache.java:187)
> at cascading.stats.CounterCache.getCounterValue(CounterCache.java:167)
> at
> cascading.stats.BaseCachedStepStats.getCounterValue(BaseCachedStepStats.java:105)
> at cascading.stats.FlowStats.getCounterValue(FlowStats.java:170)
> at
> cascading.flow.tez.Hadoop2TezFlow.getTotalSliceCPUMilliSeconds(Hadoop2TezFlow.java:303)
> at cascading.flow.BaseFlow.run(BaseFlow.java:1287)
> at cascading.flow.BaseFlow.access$100(BaseFlow.java:82)
> at cascading.flow.BaseFlow$1.run(BaseFlow.java:928)
> at java.lang.Thread.run(Thread.java:745)
> Exception in thread "main" java.lang.Throwable: If you know what exactly
> caused this error, please consider contributing to GitHub via following link.
> https://github.com/twitter/scalding/wiki/Common-Exceptions-and-possible-reasons#javalangclasscastexception
> at com.twitter.scalding.Tool$.main(Tool.scala:152)
> at com.twitter.scalding.Tool.main(Tool.scala)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:498)
> at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
> at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
> Caused by: java.lang.ClassCastException:
> cascading.stats.tez.util.TezTimelineClient cannot be cast to
> org.apache.tez.dag.api.client.DAGClient
> at
> cascading.stats.tez.util.TezStatsUtil.createTimelineClient(TezStatsUtil.java:142)
> at
> cascading.flow.tez.planner.Hadoop2TezFlowStepJob$1.getJobStatusClient(Hadoop2TezFlowStepJob.java:117)
> at
> cascading.flow.tez.planner.Hadoop2TezFlowStepJob$1.getJobStatusClient(Hadoop2TezFlowStepJob.java:105)
> at
> cascading.stats.tez.TezStepStats$1.getJobStatusClient(TezStepStats.java:60)
> at
> cascading.stats.tez.TezStepStats$1.getJobStatusClient(TezStepStats.java:56)
> at cascading.stats.CounterCache.cachedCounters(CounterCache.java:229)
> at cascading.stats.CounterCache.cachedCounters(CounterCache.java:187)
> at cascading.stats.CounterCache.getCountersFor(CounterCache.java:155)
> at
> cascading.stats.BaseCachedStepStats.getCountersFor(BaseCachedStepStats.java:93)
> at cascading.stats.FlowStats.getCountersFor(FlowStats.java:159)
> at com.twitter.scalding.Stats$.getAllCustomCounters(Stats.scala:93)
> at com.twitter.scalding.Job.handleStats(Job.scala:269)
> at com.twitter.scalding.Job.run(Job.scala:298)
> at com.twitter.scalding.Tool.start$1(Tool.scala:124)
> at com.twitter.scalding.Tool.run(Tool.scala:140)
> at com.twitter.scalding.Tool.run(Tool.scala:68)
> at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
> at com.twitter.scalding.Tool$.main(Tool.scala:148)
> ... 7 more
> {code}
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