Fixes https://github.com/hashicorp/nomad/issues/5593
Executor seems to die unexpectedly after nomad agent dies or is
restarted. The crash seems to occur at the first log message after
the nomad agent dies.
To ease debugging we forward executor log messages to executor.log as
well as to Stderr. `go-plugin` sets up plugins with Stderr pointing to
a pipe being read by plugin client, the nomad agent in our case[1].
When the nomad agent dies, the pipe is closed, and any subsequent
executor logs fail with ErrClosedPipe and SIGPIPE signal. SIGPIPE
results into executor process dying.
I considered adding a handler to ignore SIGPIPE, but hc-log library
currently panics when logging write operation fails[2]
This we opt to revert to v0.8 behavior of exclusively writing logs to
executor.log, while we investigate alternative options.
[1] https://github.com/hashicorp/nomad/blob/v0.9.0/vendor/github.com/hashicorp/go-plugin/client.go#L528-L535
[2] https://github.com/hashicorp/nomad/blob/v0.9.0/vendor/github.com/hashicorp/go-hclog/int.go#L320-L323
This PR fixes various instances of plugins being launched without using
the parent loggers. This meant that logs would not all go to the same
output, break formatting etc.
* client/executor: refactor client to remove interpolation
* executor: POC libcontainer based executor
* vendor: use hashicorp libcontainer fork
* vendor: add libcontainer/nsenter dep
* executor: updated executor interface to simplify operations
* executor: implement logging pipe
* logmon: new logmon plugin to manage task logs
* driver/executor: use logmon for log management
* executor: fix tests and windows build
* executor: fix logging key names
* executor: fix test failures
* executor: add config field to toggle between using libcontainer and standard executors
* logmon: use discover utility to discover nomad executable
* executor: only call libcontainer-shim on main in linux
* logmon: use seperate path configs for stdout/stderr fifos
* executor: windows fixes
* executor: created reusable pid stats collection utility that can be used in an executor
* executor: update fifo.Open calls
* executor: fix build
* remove executor from docker driver
* executor: Shutdown func to kill and cleanup executor and its children
* executor: move linux specific universal executor funcs to seperate file
* move logmon initialization to a task runner hook
* client: doc fixes and renaming from code review
* taskrunner: use shared config struct for logmon fifo fields
* taskrunner: logmon only needs to be started once per task
