the request body can be potentially very large
the reply context is sent to the async call handler and kept
in its memory until the async reply is received from bridge
target service.
this commit tries to minimize the size of the reply context
by replacing the request body with `[]`.
With this, we avoid performing work or replying to callers that are no
longer waiting on a result.
Also introduces two new counters:
- `dropped.expired` :: happens when a request expires before being
sent downstream
- `late_reply` :: when a response is receive from downstream, but the
caller is no longer for a reply because the request has expired, and
the caller might even have retried it.
Some requests should not be retried during the blocked state. For
example, if some async requests are just taking some time to process,
we should avoid retrying them periodically, lest risk overloading the
downstream further.
Related: https://emqx.atlassian.net/browse/EMQX-8692
This should also correctly account for `retried.*` metrics for sync
requests.
Also fixes cases where race conditions for retrying async requests
could potentially lead to inconsistent metrics.
Fixes more cases where a stale reference to `replayq` was being held
accidentally after a `pop`.
https://emqx.atlassian.net/browse/EMQX-8700
Fixes a few errors in the usage of `replayq` queues.
- Close `replayq` when `emqx_resource_worker` terminates.
- Do not keep old references to `replayq` after any `pop`s.
- Clear `replayq`'s data directories when removing a resource.
This makes the buffer/resource workers always use `replayq` for
queuing, along with collecting multiple requests in a single call.
This is done to avoid long message queues for the buffer workers and
rely on `replayq`'s capabilities of offloading to disk and detecting
overflow.
Also, this deprecates the `enable_batch` and `enable_queue` resource
creation options, as: i) queuing is now always enables; ii) batch_size
> 1 <=> batch_enabled. The corresponding metric
`dropped.queue_not_enabled` is dropped, along with `batching`. The
batching is too ephemeral, especially considering a default batch time
of 20 ms, and is not shown in the dashboard, so it was removed.
https://emqx.atlassian.net/browse/EMQX-8548
Currently, we face several issues trying to keep resource metrics
reasonable. For example, when a resource is re-created and has its
metrics reset, but then its durable queue resumes its previous work
and leads to strange (often negative) metrics.
Instead using `counters` that are shared by more than one worker to
manage gauges, we introduce an ETS table whose key is not only scoped
by the Resource ID as before, but also by the worker ID. This way,
when a worker starts/terminates, they should set their own gauges to
their values (often 0 or `replayq:count` when resuming off a queue).
With this scoping and initialization procedure, we'll hopefully avoid
hitting those strange metrics scenarios and have better control over
the gauges.
