Writing to a mutable var is a particularly potent source of leaks since
it mostly defeats GHC's analysis. Here we add assertions to all mutable
writes, and fix a couple spots where we wrote some thunks to a mutable
var (compiled with -O2).
Some of these thunks were probably benign, but others looked liked they
might be retaining big args. Didn't do much analysis, just fixed.
Actually pretty happy with how easy this was to use and as a diagnostic,
once I sorted out some issues. We should consider using it elsewhere,
and maybe extending so that we can use it with tests, enable when
`-fenable-assertsions` etc.
Relates #3388
Also simplified codepaths that use `AcceptWith`, which has unnecessary
`Maybe` fields.
This is the result of a general audit of how we fork threads, with a
detour into how we're using mutable state especially in websocket
codepaths, making more robust to async exceptions and exceptions
resulting from bugs.
Some highlights:
- use a wrapper around 'immortal' so threads that die due to bugs are
restarted, and log the error
- use 'withAsync' some places
- use bracket a few places where we might break invariants
- log some codepaths that represent bugs
- export UnstructuredLog for ad hoc logging (the alternative is we
continue not logging useful stuff)
I had to timebox this. There are a few TODOs I didn't want to address.
And we'll wait until this is merged to attempt #3705 for
Control.Concurrent.Extended
We upload a set of accumulating timers and counters to track service
time for different types of operations, across several dimensions (e.g.
did we hit the plan cache, was a remote involved, etc.)
Also...
Standardize on DiffTime as a standard duration type, and try to use it
consistently.
See discussion here:
https://github.com/hasura/graphql-engine/pull/3584#pullrequestreview-340679369
It should be possible to overwrite that module so the new threadDelay
sticks per the pattern in #3705 blocked on #3558
Rename the Control.Concurrent.Extended.threadDelay to `sleep` since a
naive use with a literal argument would be very bad!
We catch a bug in 'computeTimeDiff'.
Add convenient 'Read' instances to the time unit utility types. Make
'Second' a newtype to support this.
