Thanks Arun, very helpful.
From: Arun Mahadevan [mailto:[email protected]]
Sent: 14 August 2017 16:52
To: Wijekoon, Manusha [ICG-IT]
Cc: [email protected]
Subject: Re: is stateful bolts production ready?
>2. Subclass StateProvider to return State objects for namespaces of interest.
>For example, in our case, we wish to use a custom state class in one of the
>bolts >and use defaults for spouts. In this case, is it safe to return custom
>states for the bolt in concern and use the default state provider
>(InMemoryKeyValueStateProvider) for other namespaces? Is the custom provider
>supposed to load last saved state for the namespace in concern from the
>>persistent store. Again if state persistence is handled by framework, how do
>we know where to get state from?
The state provider config ("topology.state.provider") is per topology, so you
need to choose one of the implementations. You can always have a mix of
stateless (regular) and stateful bolts in your topology. If you are providing
your own state implementation, basically you need to maintain a separate
key-value space for each" namespace". In the case of Redis the namespace maps
to a Redis hash.
See
https://github.com/apache/storm/blob/master/external/storm-redis/src/main/java/org/apache/storm/redis/state/RedisKeyValueStateProvider.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_external_storm-2Dredis_src_main_java_org_apache_storm_redis_state_RedisKeyValueStateProvider.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=9Vc-Ho_RSvqpUhKBQEhfIH8sGNDDjPzsvdfDE-v0VzI&s=3Sx3UWw3XtysN90e5zjMYXrtA0zytRWLxz5VrXjvYPo&e=>
and
https://github.com/apache/storm/blob/master/external/storm-redis/src/main/java/org/apache/storm/redis/state/RedisKeyValueState.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_external_storm-2Dredis_src_main_java_org_apache_storm_redis_state_RedisKeyValueState.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=9Vc-Ho_RSvqpUhKBQEhfIH8sGNDDjPzsvdfDE-v0VzI&s=XNFV6uCDey5iwhSKM4v8-DMAG81FMaG5MeqVrUaKZh4&e=>
> 3. Are checkpoint related methods called by the same bolt or spout thread?
Yes its invoked by the same thread that invokes execute.
Thanks,
Arun
On 14 August 2017 at 18:13, Wijekoon, Manusha
<[email protected]<mailto:[email protected]>> wrote:
Hi Arun,
Could you please help me with my questions 2 and 3 if possible?
Thanks
Manusha
From: Arun Iyer [mailto:[email protected]<mailto:[email protected]>] On
Behalf Of Arun Mahadevan
Sent: 11 August 2017 10:20
To: Wijekoon, Manusha [ICG-IT]
Cc: [email protected]<mailto:[email protected]>
Subject: Re: is stateful bolts production ready?
If you want to use the provided state implementations, you don’t need to do any
of what you mentioned. You bolt would be initialed with its last know state in
“initState” and the bolt can keep updating the state in “execute". The
framework will automatically save the state to the state backend periodically.
See StatefulTopology[1] for example.
Right now Storm supports Redis and Hbase as state backends. If you are want
your own state backend, you need to implement the get/put/delete and the logic
for prepare/commit/rollback etc. See Hbase[2] and Redis[3] state
implementations to get a better idea. Anyways I don’t think Kafka would be
ideal as a KV state backend since its not easy to do KV lookups without loading
all the data into memory or you put some KV store on top of it.
>In addition to the query, what is the intent of stateful bolt since we can
>just hold state in bolt instance?
It mostly automates what you would have to implement otherwise and also ensures
that the state is saved consistently across the whole topology (i.e. If you
have multiple bolts with state, all of their states are saved in an atomic
manner).
Thanks,
Arun
[1]
https://github.com/apache/storm/blob/master/examples/storm-starter/src/jvm/org/apache/storm/starter/StatefulTopology.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_examples_storm-2Dstarter_src_jvm_org_apache_storm_starter_StatefulTopology.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=1skdYniP4f4eOD8je0RHN-9CjoU790CMGiTMUHz5FV4&s=3mxs_eU-TOeBVqVbQgAj5M7ZYjvBDTrYiIWErFD8nnE&e=>
[2]
https://github.com/apache/storm/blob/master/external/storm-hbase/src/main/java/org/apache/storm/hbase/state/HBaseKeyValueState.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_external_storm-2Dhbase_src_main_java_org_apache_storm_hbase_state_HBaseKeyValueState.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=1skdYniP4f4eOD8je0RHN-9CjoU790CMGiTMUHz5FV4&s=HkPAFVdkNwWKHjGlWUZjpe_jz86FCtmCHPO0P7A5Bhg&e=>
[3]
https://github.com/apache/storm/blob/master/external/storm-redis/src/main/java/org/apache/storm/redis/state/RedisKeyValueState.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_external_storm-2Dredis_src_main_java_org_apache_storm_redis_state_RedisKeyValueState.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=1skdYniP4f4eOD8je0RHN-9CjoU790CMGiTMUHz5FV4&s=YmOOKJPS-WDUBjfBefJNr6D9lX3dIB9WXqQx6_jHgGY&e=>
From: 王 纯超 <[email protected]<mailto:[email protected]>>
Reply-To: "[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Date: Friday, August 11, 2017 at 11:21 AM
To: "Wijekoon, Manusha"
<[email protected]<mailto:[email protected]>>,
"[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Subject: Re: RE: is stateful bolts production ready?
In addition to the query, what is the intent of stateful bolt since we can just
hold state in bolt instance?
________________________________
[email protected]<mailto:[email protected]>
From: Wijekoon, Manusha<mailto:[email protected]>
Date: 2017-08-10 18:56
To: [email protected]<mailto:[email protected]>
Subject: RE: is stateful bolts production ready?
In our case we prefer to use our own state implementation. After going through
the code and reading documentation, following is how I understand it. Could you
please see if my understanding is correct?
1. Derive from State and provide an implementation. In the commit (txID) method
are we supposed to persists the state by our selves or does the framework take
care of that? If it is taken care of by the framework, how do we add our own
persisting mechanism - for example one that use Kafka to persist state?
2. Subclass StateProvider to return State objects for namespaces of interest.
For example, in our case, we wish to use a custom state class in one of the
bolts and use defaults for spouts. In this case, is it safe to return custom
states for the bolt in concern and use the default state provider
(InMemoryKeyValueStateProvider) for other namespaces? Is the custom provider
supposed to load last saved state for the namespace in concern from the
persistent store. Again if state persistence is handled by framework, how do we
know where to get state from?
3. Are checkpoint related methods called by the same bolt or spout thread?
Thanks
Manusha
________________________________
From: Arun Iyer [[email protected]<mailto:[email protected]>] on behalf
of Arun Mahadevan [[email protected]<mailto:[email protected]>]
Sent: Monday, July 24, 2017 2:29 PM
To: [email protected]<mailto:[email protected]>
Subject: Re: is stateful bolts production ready?
The bolt just needs to “put” the values into the Key-Value state that the bolt
gets initialized with during “initState”. The framework automatically takes
care of saving the state behind the scenes.
Theres an example in storm-starter that you might find useful -
https://github.com/apache/storm/blob/master/examples/storm-starter/src/jvm/org/apache/storm/starter/StatefulTopology.java<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_examples_storm-2Dstarter_src_jvm_org_apache_storm_starter_StatefulTopology.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=1skdYniP4f4eOD8je0RHN-9CjoU790CMGiTMUHz5FV4&s=3mxs_eU-TOeBVqVbQgAj5M7ZYjvBDTrYiIWErFD8nnE&e=><https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_examples_storm-2Dstarter_src_jvm_org_apache_storm_starter_StatefulTopology.java&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=afgts--lg7Jf3oTEhOyGvkwmkT8RVx1LedYRwfuTwLg&s=TLi3IYjWB8QoSVTxXNx7O2mJk5kuXb5w1SbFUj47OVQ&e=>
You can also find the more elaborate documentation here -
https://github.com/apache/storm/blob/master/docs/State-checkpointing.md<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_docs_State-2Dcheckpointing.md&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=1skdYniP4f4eOD8je0RHN-9CjoU790CMGiTMUHz5FV4&s=p2KJuxYVQ48X-BUf2IdYREdWdRA-tnk7Po0ZB51ZwIM&e=><https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_apache_storm_blob_master_docs_State-2Dcheckpointing.md&d=DwMFaQ&c=j-EkbjBYwkAB4f8ZbVn1Fw&r=3V6DSqhjAEmq5iy51r9vVgFw9iAHiTSNsZl3DKb4ONM&m=afgts--lg7Jf3oTEhOyGvkwmkT8RVx1LedYRwfuTwLg&s=dV6qlBomTiYIN23BV3fzJl7nhJBd9ewoFsDi3HkxD6I&e=>
Thanks,
Arun
From: "Wijekoon, Manusha"
<[email protected]<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]%3e>>
Reply-To:
"[email protected]<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]%3e>"
<[email protected]<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]%3e>>
Date: Monday, July 24, 2017 at 4:04 PM
To:
"[email protected]<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]%3e>"
<[email protected]<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]%3e>>
Subject: is stateful bolts production ready?
Hello
I am thinking of using stateful bolts to manage state of a bolt. From the
documentation it is not clear how to save the bolt state however. I understand
it has to be done when we process the checkpoint tuple, but how? Do I just need
to update the state object and storm pick it up during three phase commit? How
does Strom know which state object to pick for check pointing?
I wasn’t able to fine more complete examples either, specifically when we can’t
keep the state in a kev/value map.
Also, Is this functionality tested in production like environments before?
Thanks
M
