NATS Queues

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Two types of queue workers

1. Standard queue with DLQ
2. Long running work queue

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Standard queue with DLQ

• Similar to SQS style work queues
• Very simple to implement DLQ as it is just built into NATS
• Length of work must be known and short. In this example 5 seconds, 10 seconds, and 15 seconds
  • Although since each consumer configures it's own timeouts you can probably have some interesting patterns

Example

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Long running work queue

• Instead of receiving work from a queue workers lobby for work
• That work is expected to run for a very long time but might be terminated at any time
  • if work is terminated it should be available to be reclaimed at a later date by another worker

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Long running work queue implementation

• Instead of using a queue, use a key value store

  • Redis has something available for this called a redlock/redsync
  • But we can simply implement it in NATS as well

• In NATS we use a separate KV bucket with a TTL

• When a worker wants to claim some work it attempts to write a lock to the KV bucket

• The worker updates the lock every X seconds to keep the lock owned

• If the worker fails to update the lock it will be deleted by the TTL and available to reclaim

Example