concurrency - Chat bots: ensuring serial processing of messages on a per-conversation basis in clustered environment -

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in context of writing messenger chat bot in cloud environment, i'm facing concurrency issues.

specifically, i ensure incoming messages same conversation processed 1 after other.

as constraint, i'm processing messages workers in cloud environment (i.e worker pool of variable size , worker instances potentially short-lived , may crash). also, low latency important.

so abstracting little, requirements are:

  • i have stream of incoming messages
  • each of these messages has 'topic key' (the conversation id)
  • the set of topics not known ahead-of-time , virtually infinite
  • i want ensure messages of same topic processed serially
  • on cluster of potentially ephemeral workers
  • if possible, reliability guarantees e.g making sure each message processed once.

my questions are:

  1. is there name concurrency scenario?.
  2. are there technologies (message brokers, coordination services, etc.) implement out of box?
  3. if not, algorithms can use implement on top of lower-level concurrency tools? (distributed locks, actors, queues, etc.)

i don't know of widely-accepted name scenario, common strategy solve type of problem route messages messages same topic key end @ same destination. couple of technologies you:

some message broker vendors refer requirement message grouping, sticky sessions, or sticky message load balancing.

another common strategy on messaging systems weaker delivery/ordering guarantees (like amazon sqs) include sequence number in message , leave destination resequence , request redelivery of missing messages needed.


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