destCh was being written to by one goroutine and closed by another
goroutine. This panic occurred in Travis:
```
=== FAIL: drivers/docker TestDockerCoordinator_ConcurrentPulls (117.66s)
=== PAUSE TestDockerCoordinator_ConcurrentPulls
=== CONT TestDockerCoordinator_ConcurrentPulls
panic: send on closed channel
goroutine 5358 [running]:
github.com/hashicorp/nomad/drivers/docker.dockerStatsCollector(0xc0003a4a20, 0xc0003a49c0, 0x3b9aca00)
/home/travis/gopath/src/github.com/hashicorp/nomad/drivers/docker/stats.go:108 +0x167
created by
github.com/hashicorp/nomad/drivers/docker.TestDriver_DockerStatsCollector
/home/travis/gopath/src/github.com/hashicorp/nomad/drivers/docker/stats_test.go:33 +0x1ab
```
The 2 ways to fix this kind of error are to either (1) add extra
coordination around multiple goroutines writing to a chan or (2) make it
so only one goroutines writes to a chan.
I implemented (2) first as it's simpler, but @notnoop pointed out since
the same destCh in reused in the stats loop there's now a double close
panic possible!
So this implements (1) by adding a *usageSender struct for handling
concurrent senders and closing.
This PR switches to using plain fifo files instead of golang structs
managed by containerd/fifo library.
The library main benefit is management of opening fifo files. In Linux,
a reader `open()` request would block until a writer opens the file (and
vice-versa). The library uses goroutines so that it's the first IO
operation that blocks.
This benefit isn't really useful for us: Given that logmon simply
streams output in a separate process, blocking of opening or first read
is effectively the same.
The library additionally makes further complications for managing state
and tracking read/write permission that seems overhead for our use,
compared to using a file directly.
Looking here, I made the following incidental changes:
* document that we do handle if fifo files are already created, as we
rely on that behavior for logmon restarts
* use type system to lock read vs write: currently, fifo library returns
`io.ReadWriteCloser` even if fifo is opened for writing only!
This capability will gate access to features that allow interacting with
a running allocation, for example, signalling, stopping, and rescheduling
specific allocations.
Fix a case where TotalTicks doesn't get serialized across executor grpc
calls.
Here, I opted to implicit add field, rather than explicitly mark it as a
measured field, because it's a derived field and to preserve 0.8
behavior where total ticks aren't explicitly marked as a measured field.
* Divest api/ package of deps elsewhere in the nomad repo.
This will allow making api/ a module without then pulling in the
external repo, leading to a package name conflict.
This required some migration of tests to an apitests/ folder (can be
moved anywhere as it has no deps on it). It also required some
duplication of code, notably some test helpers from api/ -> apitests/
and part (but not all) of testutil/ -> api/testutil/.
Once there's more separation and an e.g. sdk/ folder those can be
removed in favor of a dep on the sdk/ folder, provided the sdk/ folder
doesn't depend on api/ or /.
* Also remove consul dep from api/ package
* Fix stupid linters
* Some restructuring
This fixes a bug with JSON agent configuration parsing where the AST
for the plugin stanza had unnecessary flattening originating from hcl parsing
library. The workaround fixes the AST by popping off the flattened element and wrapping
it in a list. The workaround comes from similar code in terraform.
There were no existing test cases for json parsing so I added a few.
