This PR improves how killing a task is handled. Before the kill function
directly orchestrated the killing and was only valid while the task was
running. The new behavior is to mark the desired state and wait for the
task runner to converge to that state.
We were just emitting Killed/Terminated events before. In v0.8 we
emitted Killing/Killed, but lacked Terminated when explicitly stopping
a task. This change makes it so Terminated is always included, whether
explicitly stopping a task or it exiting on its own.
New output:
2019-01-04T14:58:51-08:00 Killed Task successfully killed
2019-01-04T14:58:51-08:00 Terminated Exit Code: 130, Signal: 2
2019-01-04T14:58:51-08:00 Killing Sent interrupt
2019-01-04T14:58:51-08:00 Leader Task Dead Leader Task in Group dead
2019-01-04T14:58:49-08:00 Started Task started by client
2019-01-04T14:58:49-08:00 Task Setup Building Task Directory
2019-01-04T14:58:49-08:00 Received Task received by client
Old (v0.8.6) output:
2019-01-04T22:14:54Z Killed Task successfully killed
2019-01-04T22:14:54Z Killing Sent interrupt. Waiting 5s before force killing
2019-01-04T22:14:54Z Leader Task Dead Leader Task in Group dead
2019-01-04T22:14:53Z Started Task started by client
2019-01-04T22:14:53Z Task Setup Building Task Directory
2019-01-04T22:14:53Z Received Task received by client
**The Bug:**
You may have seen log lines like this when running 0.9.0-dev:
```
... client.alloc_runner.task_runner: some environment variables not available for rendering: ... keys="attr.driver.docker.volumes.enabled, attr.driver.docker.version, attr.driver.docker.bridge_ip, attr.driver.qemu.version"
```
Not only should we not be erroring on builtin driver attributes, but the
results were nondeterministic due to map iteration order!
The root cause is that we have an old root attribute for all drivers
like:
```
attr.driver.docker = "1"
```
When attributes were opaque variable names it was fine to also have
"nested" attributes like:
```
attr.driver.docker.version = "1.2.3"
```
However in the HCLv2 world the variable names are no longer opaque: they
form an object tree. The `docker` object can no longer both hold a value
(`"1"`) *and* nested attributes (`version = "1.2.3"`).
**The Fix:**
Since the old `attr.driver.<name> = "1"` attribues are useless for task
config interpolation, create a new precedence rule for creating the task
config evaluation context:
*Maps take precedence over primitives.*
This means `attr.driver.docker.version` will always take precedence over
`attr.driver.docker`. The results are determinstic and give users access
to the more useful metadata.
I made this a general precedence rule instead of special-casing driver
attrs because it seemed like better default behavior than spamming
WARNings to logs that were likely unactionable by users.
Unfortunately I don't know how to test these errors. As far as I can
tell they should only happen if there was a programming error in the
upgrade code or the underlying boltdb was corrupted somehow.
* Prefix task bucket with task- to prevent name conflicts
* Shorten device manager bucket name
* Remove commented out outdated var
* Update layout comment
