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From Kien Truong <duckientru...@gmail.com>
Subject Re: Memory Leak - Flink / RocksDB ?
Date Wed, 26 Jul 2017 06:40:59 GMT

What're your task manager memory configuration ? Can you post the 
TaskManager's log ?



On 7/25/2017 8:41 PM, Shashwat Rastogi wrote:
> Hi,
> We have several Flink jobs, all of which reads data from Kafka do some aggregations (over
sliding windows of (1d, 1h)) and writes data to Cassandra. Something like :
> ```
> DataStream<String> lines = env.addSource(new FlinkKafkaConsumer010( … ));
> DataStream<Event> events = lines.map(line -> parse(line));
> DataStream<Statistics> stats = stream
> 	.keyBy(“id”)
> 	.timeWindow(1d, 1h)
> 	.sum(new MyAggregateFunction());
> writeToCassandra(stats);
> ```
> We recently made a switch to RocksDbStateBackend, for it’s suitability for large states/long
windows. However, after making the switch a memory issues has come up, the memory utilisation
on TaskManager gradually increases from 50 GB to ~63GB until the container is killed. We are
unable to figure out what is causing this behaviour, is there some memory leak on the RocksDB
> How much memory should we allocate to the Flink TaskManager? Since, RocksDB is a native
application and it does not use the JVM how much of the memory should we allocate/leave for
RocksDB (out of 64GB of total memory).
> Is there a way to set the maximum amount of memory that will be used by RocksDB so that
it doesn’t overwhelms the system? Are there some recommended optimal settings for RocksDB
for larger states (for 1 day window average state size is 3GB).
> Any help would be greatly appreciated. I am using Flink v1.2.1.
> Thanks in advance.
> Best,
> Shashwat

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