Hi Ajay, when repartitioning the stream the events need to transferred between Taskmanagers (processes/nodes). Just passing a reference there won't work.
If it is serialization you are worried about and you don't need access to the List of messages inside the job, you might as well store this list of String as a byte[]. This will make serialization cheaper. Generally, events of a few MBs should not be a problem by itself. Cheers, Konstantin On Mon, Feb 11, 2019 at 6:39 PM Aggarwal, Ajay <[email protected]> wrote: > I looked a little into broadcast state and while its interesting I don’t > think it will help me. Since broadcast state is kept all in-memory, I am > worried about memory requirement if I make all these LargeMessages part of > broadcast state. Furthermore these LargeMessages need to be processed in a > Keyed context, so sharing all of these across all downstream tasks does not > seem efficient. > > > > > > *From: *Chesnay Schepler <[email protected]> > *Date: *Sunday, February 10, 2019 at 4:57 AM > *To: *"Aggarwal, Ajay" <[email protected]>, "[email protected]" > <[email protected]> > *Subject: *Re: stream of large objects > > > > *NetApp Security WARNING*: This is an external email. Do not click links > or open attachments unless you recognize the sender and know the content is > safe. > > > > The Broadcast State > <https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/state/broadcast_state.html#the-broadcast-state-pattern> > may be interesting to you. > > On 08.02.2019 15:57, Aggarwal, Ajay wrote: > > Yes, another KeyBy will be used. The “small size” messages will be strings > of length 500 to 1000. > > > > Is there a concept of “global” state in flink? Is it possible to keep > these lists in global state and only pass the list reference (by name?) in > the LargeMessage? > > > > > > *From: *Chesnay Schepler <[email protected]> <[email protected]> > *Date: *Friday, February 8, 2019 at 8:45 AM > *To: *"Aggarwal, Ajay" <[email protected]> > <[email protected]>, "[email protected]" > <[email protected]> <[email protected]> <[email protected]> > *Subject: *Re: stream of large objects > > > > Whether a LargeMessage is serialized depends on how the job is structured. > For example, if you were to only apply map/filter functions after the > aggregation it is likely they wouldn't be serialized. > If you were to apply another keyBy they will be serialized again. > > When you say "small size" messages, what are we talking about here? > > On 07.02.2019 20:37, Aggarwal, Ajay wrote: > > In my use case my source stream contain small size messages, but as part > of flink processing I will be aggregating them into large messages and > further processing will happen on these large messages. The structure of > this large message will be something like this: > > > > Class LargeMessage { > > String key > > List <String> messages; // this is where the aggregation of smaller > messages happen > > } > > > > In some cases this list field of LargeMessage can get very large (1000’s > of messages). Is it ok to create an intermediate stream of these > LargeMessages? What should I be concerned about while designing the flink > job? Specifically with parallelism in mind. As these LargeMessages flow > from one flink subtask to another, do they get serialized/deserialized ? > > > > Thanks. > > > > > > > -- Konstantin Knauf | Solutions Architect +49 160 91394525 <https://www.ververica.com/> Follow us @VervericaData -- Join Flink Forward <https://flink-forward.org/> - The Apache Flink Conference Stream Processing | Event Driven | Real Time -- Data Artisans GmbH | Invalidenstrasse 115, 10115 Berlin, Germany -- Data Artisans GmbH Registered at Amtsgericht Charlottenburg: HRB 158244 B Managing Directors: Dr. Kostas Tzoumas, Dr. Stephan Ewen
