rxpy inject items into observable

Question

This question is regarding rxpy.

I am trying to build a reactive system that handles messages from a source observable. In addition to that, I am trying to integrate it with a leader election system based on zookeeper.

This combination will allow only one leader in a farm of processes to handle the message stream. Below is the gist of the code I am trying to construct.

# event_source is an observable of messages
# manager.leaders is an observable of leader election events
# manager.followers is an observable of leader relinquish events
event_source\
    .skip_until(manager.leaders)\
    .take_until(manager.followers)\
    .subscribe(observer)

It works fine and all, but I need to inject between skip_until and take_until a piece to handle backfill. This is designed to handle potential gap between a leader process failure and another process assuming leadership. Every processed message will leave a record so that a new leader can catch up on missing messages, if any, before proceeding with the stream.

I tried start_with operator without success. Am I not approaching it in a manner it is not meant to be used for?

Ultimately, the solution I am looking for is to inject a specific number of items in the stream triggered by an event from another stream.

score 0 · Answer 1 · answered Apr 28 '17 at 08:26

What about this:

manager.leaders \
    .flat_map(lambda e: event_source
                  .start_with(...)
                  .take_until(manager.followers))

Every time manager.leaders emits a message event_source will be subscribed to, starting with injected items, until manager.followers emits.

rxpy inject items into observable

1 Answers1