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From Meghashyam Sandeep V <vr1meghash...@gmail.com>
Subject Re: Reg. custom sinks in Flink
Date Mon, 12 Dec 2016 18:12:39 GMT
Thank you Till. I wanted to contribute towards Flink. Looks like this could
be a good start. I couldn't find the place where the insert query is built
for Pojo sinks in CassandraSink.java, CassandraPojoSink.java, or
CassandraSinkBase.java. Could you throw some light about how that insert
query is built automatically by the sink?

Thanks,

On Mon, Dec 12, 2016 at 7:56 AM, Till Rohrmann <trohrmann@apache.org> wrote:

> (1) A subtask is a parallel instance of an operator and thus responsible
> for a partition (possibly infinite) of the whole DataStream/DataSet.
>
> (2) Maybe you can add this feature to Flink's Cassandra Sink.
>
> Cheers,
> Till
>
> On Mon, Dec 12, 2016 at 4:30 PM, Meghashyam Sandeep V <
> vr1meghashyam@gmail.com> wrote:
>
>> Data piles up in Cassandra without TTL. Is there a workaround for this
>> problem? Is there a way to specify my query and still use Pojo?
>>
>> Thanks,
>>
>> On Mon, Dec 12, 2016 at 7:26 AM, Chesnay Schepler <chesnay@apache.org>
>> wrote:
>>
>>> Regarding 2) I don't think so. That would require access to the datastax
>>> MappingManager.
>>> We could add something similar as the ClusterBuilder for that though.
>>>
>>> Regards,
>>> Chesnay
>>>
>>>
>>> On 12.12.2016 16:15, Meghashyam Sandeep V wrote:
>>>
>>> Hi Till,
>>>
>>> Thanks for the information.
>>>
>>> 1. What do you mean by 'subtask', is it every partition or every message
>>> in the stream?
>>>
>>> 2. I tried using CassandraSink with a Pojo. Is there a way to specify
>>> TTL as I can't use a query when I have a datastream with Pojo?
>>>
>>> CassandraSink.addSink(messageStream)
>>>          .setClusterBuilder(new ClusterBuilder() {
>>>              @Override             protected Cluster buildCluster(Cluster.Builder
builder) {
>>>                  return buildCassandraCluster();
>>>              }
>>>          })
>>>          .build();
>>>
>>> Thanks,
>>>
>>>
>>> On Mon, Dec 12, 2016 at 3:17 AM, Till Rohrmann <trohrmann@apache.org>
>>> wrote:
>>>
>>>> Hi Meghashyam,
>>>>
>>>>    1.
>>>>
>>>>    You can perform initializations in the open method of the
>>>>    RichSinkFunction interface. The open method will be called once for
>>>>    every sub task when initializing it. If you want to share the resource
>>>>    across multiple sub tasks running in the same JVM you can also store the
>>>>    dbSession in a class variable.
>>>>    2.
>>>>
>>>>    The Flink community is currently working on adding security support
>>>>    including ssl encryption to Flink. So maybe in the future you can use
>>>>    Flink’s Cassandra sink again.
>>>>
>>>> Cheers,
>>>> Till
>>>> ​
>>>>
>>>> On Fri, Dec 9, 2016 at 8:05 PM, Meghashyam Sandeep V <
>>>> <vr1meghashyam@gmail.com>vr1meghashyam@gmail.com> wrote:
>>>>
>>>>> Thanks a lot for the quick reply Shannon.
>>>>>
>>>>> 1. I will create a class that extends SinkFunction and write my
>>>>> connection logic there. My only question here is- will a dbSession be
>>>>> created for each message/partition which might affect the performance?
>>>>> Thats the reason why I added this line to create a connection once and
use
>>>>> it along the datastream. if(dbSession == null && store!=null)
{ dbSession
>>>>> = getSession();}
>>>>> 2. I couldn't use flink-connector-cassandra as I have SSL enabled for
>>>>> my C* cluster and I couldn't get it work with all my SSL
>>>>> config(truststore,keystore etc) added to cluster building. I didn't find
a
>>>>> proper example with SSL enabled flink-connector-cassandra
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Dec 9, 2016 at 10:54 AM, Shannon Carey <scarey@expedia.com>
>>>>> wrote:
>>>>>
>>>>>> You haven't really added a sink in Flink terminology, you're just
>>>>>> performing a side effect within a map operator. So while it may work,
if
>>>>>> you want to add a sink proper you need have an object that extends
>>>>>> SinkFunction or RichSinkFunction. The method call on the stream should
be
>>>>>> ".addSink(…)".
>>>>>>
>>>>>> Also, the dbSession isn't really Flink state as it will not vary
>>>>>> based on the position in or content in the stream. It's a necessary
helper
>>>>>> object, yes, but you don't need Flink to checkpoint it.
>>>>>>
>>>>>> You can still use the sinks provided with flink-connector-cassandra
>>>>>> and customize the cluster building by passing your own ClusterBuilder
into
>>>>>> the constructor.
>>>>>>
>>>>>> -Shannon
>>>>>>
>>>>>> From: Meghashyam Sandeep V < <vr1meghashyam@gmail.com>
>>>>>> vr1meghashyam@gmail.com>
>>>>>> Date: Friday, December 9, 2016 at 12:26 PM
>>>>>> To: < <user@flink.apache.org>user@flink.apache.org>,
<
>>>>>> dev@flink.apache.org>
>>>>>> Subject: Reg. custom sinks in Flink
>>>>>>
>>>>>> Hi there,
>>>>>>
>>>>>> I have a flink streaming app where my source is Kafka and a custom
>>>>>> sink to Cassandra(I can't use standard C* sink that comes with flink
as I
>>>>>> have customized auth to C*). I'm currently have the following:
>>>>>>
>>>>>> messageStream
>>>>>>         .rebalance()
>>>>>>
>>>>>>         .map( s-> {
>>>>>>
>>>>>>     return mapper.readValue(s, JsonNode.class);)
>>>>>>
>>>>>>         .filter(//filter some messages)
>>>>>>
>>>>>>         .map(
>>>>>>
>>>>>>          (MapFunction<JsonNode, String>) message -> {
>>>>>>
>>>>>>          getDbSession.execute("QUERY_TO_EXEC")
>>>>>>
>>>>>>          })
>>>>>>
>>>>>> private static Session getDbSession() {
>>>>>>     if(dbSession == null && store!=null) {
>>>>>>         dbSession = getSession();
>>>>>>     }
>>>>>>
>>>>>>     return dbSession;
>>>>>> }
>>>>>>
>>>>>> 1. Is this the right way to add a custom sink? As you can see, I
have dbSession as a class variable here and I'm storing its state.
>>>>>>
>>>>>> 2. This setup works fine in a standalone flink (java -jar MyJar.jar).
When I run using flink with YARN on EMR I get a NPE at the session which is kind of weird.
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>>
>>
>

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