I re-ran the test with the source & sink batchSizes set to 100, the memory channel transactionCapacity set to 100 and its capacity on 300. With those values, the proof of concept works exactly as expected, so it indeed that bug that caused my problem. Thank you!
To specify the statement "the proof of concept works exactly as expected": if Flume isn't able to write events to the sink, it will read files from the spoolDir until the memory capacity is maxed out (i.e. 300 events). Any files that are added to the spoolDir are _not_ processed, until Flume is able to write to the sink. As soon as Flume is able to write to the sink again, all the stalled events are processed (the events in memory and the unread files in the spoolDir). -- Kind regards, Balthasar Schopman LeaseWeb CDN Innovation Engineer Kind regards, Balthasar Schopman Software Developer LeaseWeb Technologies B.V. T: +31 20 316 0232 E: [email protected] W: www.leaseweb.com<http://www.leaseweb.com> Luttenbergweg 8, 1101 EC Amsterdam, Netherlands ________________________________ From: Gonzalo Herreros [[email protected]] Sent: Tuesday, October 13, 2015 10:04 To: [email protected] Subject: Re: recovery after memory transaction capacity is exceeded I believe you are suffering from this bug: https://issues.apache.org/jira/browse/FLUME-2778 So when it's running is able to keep up but when the channel has more than 4 events queued, the Sink tried to extract 100 (default batch size) and you get that error. Regards, Gonzalo On 13 October 2015 at 08:12, Balthasar Schopman <[email protected]<mailto:[email protected]>> wrote: Hi, I'm creating a proof-of-concept of a Flume agent that'll buffer events and stops consuming events from the source when the sink is unavailable. Only when the sink is available again, the buffered events should be processed and then the source restarts consumption. For this I've created a simple agent, which reads from a SpoolDir and writes to a file. To simulate that the sink service is down, I change file permissions so Flume can't write to it. Then I start Flume some events are buffered in the memory channel and it stops consuming events when the channel capacity is full, as expected. As soon as the file becomes writeable, the sink is able to process the events and Flume recovers. However, that only works when the transaction capacity is not exceeded. As soon as the transaction capacity is exceeded, Flume never recovers and keeps writing the following error: 2015-10-02 14:52:51,940 (SinkRunner-PollingRunner-DefaultSinkProcessor) [ERROR - org.apache.flume.SinkRunner$PollingRunner.run(SinkRunner.java:160)] Unable to deliver event. Exception follows. org.apache.flume.EventDeliveryException: Failed to process transaction at org.apache.flume.sink.RollingFileSink.process(RollingFileSink.java:218) at org.apache.flume.sink.DefaultSinkProcessor.process(DefaultSinkProcessor.java:68) at org.apache.flume.SinkRunner$PollingRunner.run(SinkRunner.java:147) at java.lang.Thread.run(Thread.java:745) Caused by: org.apache.flume.ChannelException: Take list for MemoryTransaction, capacity 4 full, consider committing more frequently, increasing capacity, or increasing thread count at org.apache.flume.channel.MemoryChannel$MemoryTransaction.doTake(MemoryChannel.java:96) at org.apache.flume.channel.BasicTransactionSemantics.take(BasicTransactionSemantics.java:113) at org.apache.flume.channel.BasicChannelSemantics.take(BasicChannelSemantics.java:95) at org.apache.flume.sink.RollingFileSink.process(RollingFileSink.java:191) ... 3 more As soon as the number of events buffered in memory exceed the transaction capacity (4) this error occurs. I don't understand why, because the batchSize of the fileout is 1, so it should take out the events one by one. This is the config I'm using: agent.sources = spool-src agent.channels = mem-channel agent.sinks = fileout agent.sources.spool-src.channels = mem-channel agent.sources.spool-src.type = spooldir agent.sources.spool-src.spoolDir = /tmp/flume-spool agent.sources.spool-src.batchSize = 1 agent.channels.mem-channel.type = memory agent.channels.mem-channel.capacity = 10 agent.channels.mem-channel.transactionCapacity = 4 agent.sinks.fileout.channel = mem-channel agent.sinks.fileout.type = file_roll agent.sinks.fileout.sink.directory = /tmp/flume-output agent.sinks.fileout.sink.rollInterval = 0 agent.sinks.fileout.batchSize = 1 I've tested this config with different values for the channel capacity & transaction capacity (e.g., 3 and 3), but haven't found a config where Flume is able to recover after the channel capacity is full. Any ideas on how to achieve this? -- Kind regards, Balthasar Schopman LeaseWeb CDN Innovation Engineer Kind regards, Balthasar Schopman Software Developer LeaseWeb Technologies B.V. T: +31 20 316 0232 M: E: [email protected]<mailto:[email protected]> W: http://www.leaseweb.com Luttenbergweg 8, 1101 EC Amsterdam, Netherlands
