You are right. Sorry for making you state the obvious J.
Last question : If my spout has incoming information that I want to have in the same last bolt (the one creating the XML) for deduplication logic, what is the best way to achieve this ? My instinct says to try to work with Fields grouping and the correct key (probably conversation since I am working with emails).
From: Stephen Powis [mailto:email@example.com]
Sent: Tuesday, December 01, 2015 10:27 AM
Subject: Re: Using Storm to parse emails and creates batches
If you are using Storm's guaranteed message processing there is no need to 'persist' the collection anywhere other than in memory. IE List<Tuple> myListOfTuples = new ArrayList<Tuple>(); If the third bolt crashes and loses its in memory collection, after Config.TOPOLOGY_MESSAGE_TIMEOUT_SECS the tuples will timeout and be replayed thru your entire storm topology and your collection will be repopulated
On Tue, Dec 1, 2015 at 5:15 PM, Kalogeropoulos, Andreas <Andreas.Kalogeropoulos@emc.com> wrote:
I think you got I correctly. Thanks a lot for the idea.
If you have seen limitations, please send the disclaimers J . For example, how did you handle persistence of this collection ? If the third bolt failed while populating the collection (size and time has not been reached) we just lost everything, so I need to have a status loopback of what was really output. Right ?
Of course, if you can send me the code of your third bolt (especially the collection handling), I’ll be grateful.
In all cases, thanks a lot for your help, even without the code, you really give me example advice, and now I can start building something.
From what I understand from your description, you want bolt 3 to collect results from multiple tuples and build a single xml for them. We've done this by essentially doing the following:
Bolt 3 has a collection of tuples. As a tuple comes in, we add it to the collection and check the size of the collection. Once the size of the collection exceeds some number, we then
process all of the tuples in one go, and then ACK all of them after the processing completes.
Building on that, we've implemented an additional constraint on time. If the collection size > N OR if we've waited more than X seconds, process the batch. This way your output won't stall out if your topology has a lull in data being ingested.
And then lastly, there's a corner case where say 10 tuples come in and get held by our collection but then no other tuples come in for a long period of time. If no tuples enter, that means the size and timeout checks are never executed and your bolt will hold onto those tuples for a long time (potentially causing timeouts). To handle this, we made use of tick tuples. Tick tuples essentially allow you to you to send a special tuple to your bolt every Y seconds. We use that to trigger checking the time constraint is checked on a regular basis (example being send a tick tuple every 1, 5, or 10 seconds)
On Tue, Dec 1, 2015 at 1:42 AM, Kalogeropoulos, Andreas <Andreas.Kalogeropoulos@emc.com> wrote:
I want to use Storm to do three things :
1. Parse emails data (from/ to / cc/ subject ) from incoming SMTP source
2. Add additional information (based on sender email)
3. Create an XML based on this data, to inject in another solution
Only issue, I want step 1 (and 2) to be as fast as possible so creating the maximum bolts/tasks possible,
But I want the XML to be as big as possible so gathering information for multiple output of bolts.
In this logic, I fi have 100 mails per second in original input, I would want to have step1 and step 2 to work on the smallest number of emails to do it faster.
But I still want to be able to have an XML that represent 10 000+ emails at the end.
I can’t think of topology to address this.
Can someone give me some pointers to the best way to handle this ?