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From Stephan Ewen <se...@apache.org>
Subject Re: Storage options for RocksDBStateBackend
Date Thu, 11 May 2017 19:35:16 GMT
Small addition to Till's comment:

In the case where file:// points to a mounted distributed file system (NFS,
MapRFs, ...), then it actually works. The important thing is that the
filesystem where the checkpoints go is replicated (fault tolerant) and
accessible from all nodes.

On Thu, May 11, 2017 at 2:16 PM, Till Rohrmann <trohrmann@apache.org> wrote:

> Hi Ayush,
>
> you’re right that RocksDB is the recommend state backend because of the
> above-mentioned reasons. In order to make the recovery properly work, you
> have to configure a shared directory for the checkpoint data via
> state.backend.fs.checkpointdir. You can basically configure any file
> system which is supported by Hadoop (no HDFS required). The reason is that
> we use Hadoop to bridge between different file systems. The only thing you
> have to make sure is that you have the respective file system
> implementation in your class path.
>
> I think you can access Windows Azure Blob Storage via Hadoop [1] similarly
> to access S3, for example.
>
> If you use S3 to store your checkpoint data, then you will benefit from
> all the advantages of S3 but also suffer from its drawbacks (e.g. that list
> operations are more costly). But these are not specific to Flink.
>
> A URL like file:// usually indicates a local file. Thus, if your Flink
> cluster is not running on a single machine, then this won’t work.
>
> [1] https://hadoop.apache.org/docs/stable/hadoop-azure/index.html
>
> Cheers,
> Till
> ​
>
> On Thu, May 11, 2017 at 10:41 AM, Ayush Goyal <ayush@helpshift.com> wrote:
>
>> Hello,
>>
>> I had a few questions regarding checkpoint storage options using
>> RocksDBStateBackend. In the flink 1.2 documentation, it is the
>> recommended state
>> backend due to it's ability to store large states and asynchronous
>> snapshotting.
>> For high availabilty it seems HDFS is the recommended store for state
>> backend
>> data. In AWS deployment section, it is also mentioned that s3 can be used
>> for
>> storing state backend data.
>>
>> We don't want to depend on a hadoop cluster for flink deployment, so I had
>>
>> following questions:
>>
>> 1. Can we use any storage backend supported by flink for storing RocksDB
>> StateBackend data with file urls: there are quite a few supported as
>> mentioned here:
>> https://ci.apache.org/projects/flink/flink-docs-release-1.3/
>> internals/filesystems.html
>> and here:
>> https://github.com/apache/flink/blob/master/docs/dev/batch/connectors.md
>>
>> 2. Is there some work already done to support Windows Azure Blob Storage
>> for
>> storing State backend data? There are some docs here:
>> https://github.com/apache/flink/blob/master/docs/dev/batch/connectors.md
>> can we utilize this for that?
>>
>> 3. If utilizing S3 for state backend, is there any performance impact?
>>
>> 4. For high availability can we use a NFS volume for state backend, with
>> "file://" urls? Will there be any performance impact?
>>
>> PS: I posted this email earlier via nabble, but it's not showing up in
>> apache archive. So sending again. Apologies if it results in multiple
>> threads.
>>
>> -- Ayush
>>
>
>

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