Sorry about being cryptic there. What I meant is that it will be much better if we don't make assumptions about frequency of failure rates in topologies. I know it is more of a commonsense but out of curiosity, can you point me to any Storm documentation which makes a comment on preferable failure rates. I was suggesting if we can offer the user an optimization through clean API, the user will be free to decide on the rationale of using it.
On Tue, Jul 11, 2017 at 12:06 AM, Bobby Evans <ev...@yahoo-inc.com.invalid> wrote: > I'm not sure what assumptions you want to make that this is preventing, or > why they would be helpful. > > - Bobby > > > On Monday, July 10, 2017, 12:14:53 PM CDT, chandan singh < > cks07...@gmail.com> wrote: > > Hi Stig & Bobby > > Thanks for confirming my understanding. > > 1) Ensuring that calls to nexTuple(), ack() and fail() are non-blocking > has been a guideline on http://storm.apache.org/ > releases/1.1.0/Concepts.html > for long. Copying verbatim here : "The main method on spouts is nextTuple. > nextTuple either emits a new tuple into the topology or simply returns if > there are no new tuples to emit. It is imperative that nextTuple does not > block for any spout implementation, because Storm calls all the spout > methods on the same thread." I admit that there is some chance my > interpretation is partially incorrect but I have been following it in a > custom spout till now. Even though the objective is different, there is a > similar hint on Kafka official documentation. Please see under heading "2. > Decouple Consumption and Processing" on > https://kafka.apache.org/0110/javadoc/index.html?org/apache/ > kafka/clients/consumer/KafkaConsumer.html. > Essentially, a thread polls Kafka and spout thread gets the messages > through a shared queue. If pre-fetching is present in Kafka (I will read > about it further), I assume we do not have to fetch in another thread but I > am not sure how does the pre-fetching behave with re-seeking before every > poll. > > 2) @Bobby, you are correct in pointing what needs to be optimized but the > facts, sometimes, prevent us from making assumptions. We do optimize our > retry loop such that we don't poll the messages again. I especially see > problems when combined with exponential back off. I am not sure how > difficult or clean will it be to expose some sort of configuration to allow > such optimization? Do you think it will be worth trying out something? > > Thanks > Chandan >
