[EventHubs] Buffered Producer Implementation

[yunhaoling]

Overall architecture:

EHProducerClient 1 -> 1 EHBufferedProducerDispatcher 1 -> n EHBufferedProducer (for single partition)

Duty of EHBufferedProducerDispatcher:

1. life cycle management of all single partition buffered producer
2. dispatch events (partition determination) to single partition buffered producer
3. flush all partitions
4. statics information from all single partition buffered producer

Duty of EHBufferedProducer

1. flush(send) events
2. max_wait_time flush timing control
3. backpressure handling
4. buffering
5. batching

Answers for behavior questions raised in the arch board:

what happens if calling close/flush in on_error callback (e.g. think about infinite error case)

deadlock in current implementation, we should be explicit that users should not perform flush in on_error/on_success.

definition for various timeout behavior and how users could handle

• send_event/send_batch times out: retry
• flush/close times out: flush timing out would raise error, close time out would log warning

investigation of the buffer max behavior (limitation vs timing control? back pressure?)

in current implementation, if the remaining buffer isn't enough for the incoming events, call flush to clear the buffer first

Tasks

• sync implementation
• async implementation
• test
• doc
• mypy/pylint
• sample

Related issue:

#23062
#23063

[azure-sdk]

API change check for azure-eventhub

API changes have been detected in azure-eventhub. You can review API changes here

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