Hi Chris,
excellent question (and worth discussing).
In the java pool there currently is NO automatic reconnection (lazy connection).
I have no backup strategy there (but makes sense to have one although this may
depend on specific situations).
I currently fail one connection at a time after their specific timeout.
If e.g. you set the timeout for the connection request to 1 second then you
could easily have one connection failing but the next attempt working.
So I personally would go for sequential failing when their limit is due but I
think the other alternative is fine as well.
Julian
Von: Christofer Dutz <christofer.d...@c-ware.de>
Datum: Mittwoch, 19. Januar 2022 um 10:21
An: dev@plc4x.apache.org <dev@plc4x.apache.org>
Betreff: [DISCUSS] Behaviour of a ConnectionPool?
Hi all,
I'm currently working on the go connection-pool. Now while in general I would
assume the functionality of a connection pool to be quite clearly defined,
there still are some special cases where I want to make sure we consistently
implement them.
Right now, I'm implementing it so there is only one connection for one given
connection string ... we can later adjust this. Reasoning here is that in
general connections to plcs can be considered highly limited so we won't be
going much over 2 or 3 anyway.
The thing that I'm currently working on are the edge-cases. So, what happens if:
* The connection itself fails.
* Should the pool try automatically reconnecting?
* If yes, should it do it as fast as possible?
* Should there be an increasing back-off delay between attempts?
* Should there be a maximum number of retries?
* What happens to other waiting clients in case of a connection failure?
* Do all instantly get a "connection-error"?
* Does the connection get retried for each client in the queue
independently?
Right now, I would opt for a delay between attempts of 1s at first, the number
doubling between each attempt and giving up after 3 times and then failing all
waiting clients simultaneously. But I would make the limits configurable in the
pool (reconnectInitialDelay, reconnectMaxAttempts, reconnectBackoffStrategy,
reconnectFailureStrategy).
I think if I run into any other situations where I'm unsure, I'll continue this
thread.
Chris
