Using the API as provided from the `mounts` package imposes validation
on the `src:dest` which shouldn't be performed at this time. To workaround
that lift the internal code from that library required to only perform
the split.
Currently, nomad "plugin" processes (e.g. executor, logmon, docker_logger) are started as CLI
commands to be handled by command CLI framework. Plugin launchers use
`discover.NomadBinary()` to identify the binary and start it.
This has few downsides: The trivial one is that when running tests, one
must re-compile the nomad binary as the tests need to invoke the nomad
executable to start plugin. This is frequently overlooked, resulting in
puzzlement.
The more significant issue with `executor` in particular is in relation
to external driver:
* Plugin must identify the path of invoking nomad binary, which is not
trivial; `discvoer.NomadBinary()` now returns the path to the plugin
rather than to nomad, preventing external drivers from launching
executors.
* The external driver may get a different version of executor than it
expects (specially if we make a binary incompatible change in future).
This commit addresses both downside by having the plugin invocation
handling through an `init()` call, similar to how libcontainer init
handler is done in [1] and recommened by libcontainer [2]. `init()`
will be invoked and handled properly in tests and external drivers.
For external drivers, this change will cause external drivers to launch
the executor that's compiled against.
There a are a couple of downsides to this approach:
* These specific packages (i.e executor, logmon, and dockerlog) need to
be careful in use of `init()`, package initializers. Must avoid having
command execution rely on any other init in the package. I prefixed
files with `z_` (golang processes files in lexical order), but ensured
we don't depend on order.
* The command handling is spread in multiple packages making it a bit
less obvious how plugin starts are handled.
[1] drivers/shared/executor/libcontainer_nsenter_linux.go
[2] eb4aeed24f/libcontainer (using-libcontainer)
- updated region in job metadata that gets persisted to nomad datastore
- fixed many unrelated unit tests that used an invalid region value
(they previously passed because hcl wasn't getting picked up and
the job would default to global region)
When an alloc is due to be rescheduleLater, it goes through the
reconciler twice: once to be ignored with a follow up evals, and once
again when processing the follow up eval where they appear as
rescheduleNow.
Here, we ignore them in the first run and mark them as stopped in second
iteration; rather than stop them twice.
It is possible to provide multiple identically named services with
different port assignments in a Nomad configuration.
We introduced a regression when migrating to stable service identifiers where
multiple services with the same name would conflict, and the last definition
would take precedence.
This commit includes the port label in the stable service identifier to
allow the previous behaviour where this was supported, for example
providing:
```hcl
service {
name = "redis-cache"
tags = ["global", "cache"]
port = "db"
check {
name = "alive"
type = "tcp"
interval = "10s"
timeout = "2s"
}
}
service {
name = "redis-cache"
tags = ["global", "foo"]
port = "foo"
check {
name = "alive"
type = "tcp"
port = "db"
interval = "10s"
timeout = "2s"
}
}
service {
name = "redis-cache"
tags = ["global", "bar"]
port = "bar"
check {
name = "alive"
type = "tcp"
port = "db"
interval = "10s"
timeout = "2s"
}
}
```
in a nomad task definition is now completely valid. Each service
definition with the same name must still have a unique port label however.
Mahmood Ali