Distributed delay queues based on Dynomite

Netflix’s Content Platform Engineering runs a number of business processes which are driven by asynchronous orchestration of micro-services based tasks, and queues form an integral part of the orchestration layer amongst these services.
Few examples of these processes are:
  • IMF based content ingest from our partners
  • Process of setting up new titles within Netflix
  • Content Ingest, encode and deployment to CDN
Traditionally, we have been using a Cassandra based queue recipe along with Zookeeper for distributed locks, since Cassandra is the de facto storage engine at Netflix. Using Cassandra for queue like data structure is a known anti-pattern, also using a global lock on queue while polling, limits the amount of concurrency on the consumer side as the lock ensures only one consumer can poll from the queue at a time.  This can be addressed a bit by sharding the queue but the concurrency is still limited within the shard.  As we started to build out a new orchestration engine, we looked at Dynomite for handling the task queues.
We wanted the following in the queue recipe:
  1. Distributed
  2. No external locks (e.g. Zookeeper locks)
  3. Highly concurrent
  4. At-least-once delivery semantics
  5. No strict FIFO
  6. Delayed queue (message is not taken out of the queue until some time in the future)
  7. Priorities within the shard
The queue recipe described here is used to build a message broker server that exposes various operations (push, poll, ack etc.) via REST endpoints and can potentially be exposed by other transports (e.g. gRPC).  Today, we are open sourcing the queue recipe.
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