Previously, Nomad was using a hand-made lookup table for looking
up EC2 CPU performance characteristics (core count + speed = ticks).
This data was incomplete and incorrect depending on region. The AWS
API has the correct data but requires API keys to use (i.e. should not
be queried directly from Nomad).
This change introduces a lookup table generated by a small command line
tool in Nomad's tools module which uses the Amazon AWS API.
Running the tool requires AWS_* environment variables set.
$ # in nomad/tools/cpuinfo
$ go run .
Going forward, Nomad can incorporate regeneration of the lookup table
somewhere in the CI pipeline so that we remain up-to-date on the latest
offerings from EC2.
Fixes#7830
Fixes#7681
The current behavior of the CPU fingerprinter in AWS is that it
reads the **current** speed from `/proc/cpuinfo` (`CPU MHz` field).
This is because the max CPU frequency is not available by reading
anything on the EC2 instance itself. Normally on Linux one would
look at e.g. `sys/devices/system/cpu/cpuN/cpufreq/cpuinfo_max_freq`
or perhaps parse the values from the `CPU max MHz` field in
`/proc/cpuinfo`, but those values are not available.
Furthermore, no metadata about the CPU is made available in the
EC2 metadata service.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-categories.html
Since `go-psutil` cannot determine the max CPU speed it defaults to
the current CPU speed, which could be basically any number between
0 and the true max. This is particularly bad on large, powerful
reserved instances which often idle at ~800 MHz while Nomad does
its fingerprinting (typically IO bound), which Nomad then uses as
the max, which results in severe loss of available resources.
Since the CPU specification is unavailable programmatically (at least
not without sudo) use a best-effort lookup table. This table was
generated by going through every instance type in AWS documentation
and copy-pasting the numbers.
https://aws.amazon.com/ec2/instance-types/
This approach obviously is not ideal as future instance types will
need to be added as they are introduced to AWS. However, using the
table should only be an improvement over the status quo since right
now Nomad miscalculates available CPU resources on all instance types.
Some code cleanup:
* Use a field for setting EC2 metadata instead of env-vars in testing;
but keep environment variables for backward compatibility reasons
* Update tests to use testify
This removes a cyclical dependency when importing client/structs from
dependencies of the plugin_loader, specifically, drivers. Due to
client/config also depending on the plugin_loader.
It also better reflects the ownership of fingerprint structs, as they
are fairly internal to the fingerprint manager.
This PR:
* Makes AWS network speeds more granular
* Makes `network_speed` an override and not a default
* Adds a default of 1000 MBits if no network link speed is detected.
Fixes#1985
