Hi Sud, The batch read of the Iceberg table should just read the latest snapshot. I think this case is that your large tables have a large number of manifest files.
1.The simple way is reducing manifest file numbers: - For reducing manifest file number, you can try `Actions.rewriteManifests`(Thanks Anton) to compact manifest files. - If there are too many small data files, leading to too many manifest files even after compacting, you can try `Actions.rewriteDataFiles`(Thanks jerryshao) to compact data files. 2.Another way is parallelizing the opening of the manifest reader. Your stack looks like the thread is stuck in `DataFileReader.openReader`, at least, it will need to read magic bytes from the input stream in `open`, and this looks slow. (At least, the input stream needs to read an IO block) So can we make `DataFileReader.openReader` parallelize? We should make `ManifestGroup.entries` returns a parallel iterable. Best, Jingsong On Fri, Jul 17, 2020 at 7:23 AM Sud <sudssf2...@gmail.com> wrote: > HI Iceberg-devs > > We are trying to root cause issue where driver get stuck when trying to > read comparatively large tables ( > 2000 snapshots) > > When I tried to look at the thread dump of the driver's main thread I see > that thread is stuck in planning tasks. I also noticed that > iceberg-worker-pool > is idle and mostly 1 thread is active. > Has anyone faced a similar issue? what parameters can be used to optimize > reads for tables with large number of snapshots ( with smaller data files) > > > java.net.SocketInputStream.socketRead0(Native Method) > java.net.SocketInputStream.socketRead(SocketInputStream.java:116) > java.net.SocketInputStream.read(SocketInputStream.java:171) > java.net.SocketInputStream.read(SocketInputStream.java:141) > sun.security.ssl.InputRecord.readFully(InputRecord.java:465) > sun.security.ssl.InputRecord.read(InputRecord.java:503) > sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:990) => holding > Monitor(java.lang.Object@580832623}) > sun.security.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:948) > sun.security.ssl.AppInputStream.read(AppInputStream.java:105) => holding > Monitor(sun.security.ssl.AppInputStream@894541691}) > org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:137) > org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:153) > org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:280) > org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:138) > org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56) > org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259) > org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163) > org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:157) > org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273) > com.amazonaws.http.protocol.SdkHttpRequestExecutor.doReceiveResponse(SdkHttpRequestExecutor.java:82) > org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125) > org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272) > org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186) > org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185) > org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) > org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) > com.amazonaws.http.apache.client.impl.SdkHttpClient.execute(SdkHttpClient.java:72) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeOneRequest(AmazonHttpClient.java:1297) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeHelper(AmazonHttpClient.java:1113) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.doExecute(AmazonHttpClient.java:770) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeWithTimer(AmazonHttpClient.java:744) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.execute(AmazonHttpClient.java:726) > com.amazonaws.http.AmazonHttpClient$RequestExecutor.access$500(AmazonHttpClient.java:686) > com.amazonaws.http.AmazonHttpClient$RequestExecutionBuilderImpl.execute(AmazonHttpClient.java:668) > com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:532) > com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:512) > com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:4926) > com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:4872) > com.amazonaws.services.s3.AmazonS3Client.getObject(AmazonS3Client.java:1472) > org.apache.hadoop.fs.s3a.S3AInputStream.reopen(S3AInputStream.java:148) > org.apache.hadoop.fs.s3a.S3AInputStream.lazySeek(S3AInputStream.java:281) > org.apache.hadoop.fs.s3a.S3AInputStream.read(S3AInputStream.java:364) => > holding Monitor(org.apache.hadoop.fs.s3a.S3AInputStream@1577065760}) > java.io.DataInputStream.read(DataInputStream.java:149) > org.apache.iceberg.hadoop.HadoopStreams$HadoopSeekableInputStream.read(HadoopStreams.java:112) > org.apache.iceberg.avro.AvroIO$AvroInputStreamAdapter.read(AvroIO.java:106) > org.apache.iceberg.shaded.org.apache.avro.file.DataFileReader.openReader(DataFileReader.java:55) > org.apache.iceberg.avro.AvroIterable.newFileReader(AvroIterable.java:94) > org.apache.iceberg.avro.AvroIterable.getMetadata(AvroIterable.java:66) > org.apache.iceberg.ManifestReader.<init>(ManifestReader.java:141) > org.apache.iceberg.ManifestReader.read(ManifestReader.java:119) > org.apache.iceberg.ManifestGroup.lambda$entries$13(ManifestGroup.java:212) > org.apache.iceberg.ManifestGroup$$Lambda$89/1042679820.apply(Unknown Source) > org.apache.iceberg.shaded.com.google.common.collect.Iterators$6.transform(Iterators.java:783) > org.apache.iceberg.shaded.com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) > org.apache.iceberg.shaded.com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) > org.apache.iceberg.util.ParallelIterable$ParallelIterator.submitNextTask(ParallelIterable.java:113) > org.apache.iceberg.util.ParallelIterable$ParallelIterator.checkTasks(ParallelIterable.java:100) > org.apache.iceberg.util.ParallelIterable$ParallelIterator.hasNext(ParallelIterable.java:137) > => holding > Monitor(org.apache.iceberg.util.ParallelIterable$ParallelIterator@1724178871}) > org.apache.iceberg.shaded.com.google.common.collect.TransformedIterator.hasNext(TransformedIterator.java:42) > org.apache.iceberg.shaded.com.google.common.collect.TransformedIterator.hasNext(TransformedIterator.java:42) > org.apache.iceberg.shaded.com.google.common.collect.Iterators$ConcatenatedIterator.getTopMetaIterator(Iterators.java:1309) > org.apache.iceberg.shaded.com.google.common.collect.Iterators$ConcatenatedIterator.hasNext(Iterators.java:1325) > org.apache.iceberg.util.BinPacking$PackingIterator.next(BinPacking.java:111) > org.apache.iceberg.util.BinPacking$PackingIterator.next(BinPacking.java:87) > org.apache.iceberg.io.CloseableIterable$3$1.next(CloseableIterable.java:94) > org.apache.iceberg.shaded.com.google.common.collect.Iterators.addAll(Iterators.java:356) > org.apache.iceberg.shaded.com.google.common.collect.Lists.newArrayList(Lists.java:143) > org.apache.iceberg.shaded.com.google.common.collect.Lists.newArrayList(Lists.java:130) > org.apache.iceberg.spark.source.Reader.tasks(Reader.java:295) > org.apache.iceberg.spark.source.Reader.planInputPartitions(Reader.java:196) > org.apache.spark.sql.execution.datasources.v2.DataSourceV2ScanExec.partitions$lzycompute(DataSourceV2ScanExec.scala:76) > => holding > Monitor(org.apache.spark.sql.execution.datasources.v2.DataSourceV2ScanExec@853913013}) > org.apache.spark.sql.execution.datasources.v2.DataSourceV2ScanExec.partitions(DataSourceV2ScanExec.scala:75) > org.apache.spark.sql.execution.datasources.v2.DataSourceV2ScanExec.outputPartitioning(DataSourceV2ScanExec.scala:65) > > > > > -- > Thanks > -- Best, Jingsong Lee
