Remove the NOMAD_TEST_RKT flag as a guard for rkt tests. Still require
Linux, root, and rkt to be installed. Only check for rkt installation
once in hopes of speeding up rkt tests a bit.
Adding this fields to the DriverContext object, will allow us to pass
them to the drivers.
An use case for this, will be to emit tagged metrics in the drivers,
which contain all relevant information:
- Job
- TaskGroup
- Task
- ...
Ref: https://github.com/hashicorp/nomad/pull/4185
Having the Nomad executor create parent cgroups that rkt is launched
within allows the stats collection code used for the exec driver to Just
Work. The only downside is that now the Nomad executor's resource
utilization counts against the cgroups resource limits just as it does
for the exec driver.
This PR does:
1. Health message based on detection has format "Driver XXX detected"
and "Driver XXX not detected"
2. Set initial health description based on detection status and don't
wait for the first health check.
3. Combine updating attributes on the node, fingerprint and health
checking update for drivers into a single call back.
4. Condensed driver info in `node status` only shows detected drivers
and make the output less wide by removing spaces.
The interface+mock just to test this one little error handling may seem
like overkill but there was just no other way to write an automated test
around this logic as there's no way to simluate this error with stock
Docker.
A comment in the nomad source code states that swapping for
executor_linux allocations is disabled but it wasn't.
Nomad wrote -1 to the memsw.limit_in_bytes cgroup file to disable
swapping.
This has the following problems:
1.) Writing -1 to the file does not disable swapping. It sets
the limit for memory and swap to unlimited.
2.) On common Linux distributions like Ubuntu 16.04 LTS the
memsw.limit_in_bytes cgroup file does not exist by default.
The memsw.limit_in_bytes file only exist if the Linux kernel is
build with CONFIG_MEMCG_SWAP=yes and either
CONFIG_MEMCG_SWAP_ENABLED=yes or when the kernel parameter
swapaccount=1 is passed during boot.
Most Linux distributions disable swap accounting by default because
of higher memory usage.
Nomad silently ignores if writing to the memsw.limit_in_bytes file
fails. The allocation succeeds, no message is logged to notify the
user.
To ensure that disabling swap works on common Linux kernels, disable
swapping by writing 0 to the memory.swappiness file.
Using the memory.swappiness file only requires that the kernel is
compiled with CONFIG_MEMCG=yes. This is the default in common Linux
kernels.
Michael Schurter