Now that alloc.Canonicalize() is called in all alloc sources in the
client (i.e. on state restore and RPC fetching), we no longer need to
check alloc.TaskResources.
alloc.AllocatedResources is always non-nil through alloc runner.
Though, early on, we check for alloc validity, so NewTaskRunner and
TaskEnv must still check. `TestClient_AddAllocError` test validates
that behavior.
This commit ensures that Alloc.AllocatedResources is properly populated
when read from persistence stores (namely Raft and client state store).
The alloc struct may have been written previously by an arbitrary old
version that may only populate Alloc.TaskResources.
In 0.10.2 (specifically 387b016) we added interpolation to group
service blocks and centralized the logic for task environment
interpolation. This wasn't also added to script checks, which caused a
regression where the IDs for script checks for services w/
interpolated fields (ex. the service name) didn't match the service ID
that was registered with Consul.
This changeset calls the same taskenv interpolation logic during
`script_check` configuration, and adds tests to reduce the risk of
future regressions by comparing the IDs of service hook and the check hook.
copy struct values
ensure groupserviceHook implements RunnerPreKillhook
run deregister first
test that shutdown times are delayed
move magic number into variable
Previously, Nomad used hand rolled HTTP requests to interact with the
EC2 metadata API. Recently however, we switched to using the AWS SDK for
this fingerprinting.
The default behaviour of the AWS SDK is to perform retries with
exponential backoff when a request fails. This is problematic for Nomad,
because interacting with the EC2 API is in our client start path.
Here we revert to our pre-existing behaviour of not performing retries
in the fast path, as if the metadata service is unavailable, it's likely
that nomad is not running in AWS.
Copy the updated version of freeport (sdk/freeport), and tweak it for use
in Nomad tests. This means staying below port 10000 to avoid conflicts with
the lib/freeport that is still transitively used by the old version of
consul that we vendor. Also provide implementations to find ephemeral ports
of macOS and Windows environments.
Ports acquired through freeport are supposed to be returned to freeport,
which this change now also introduces. Many tests are modified to include
calls to a cleanup function for Server objects.
This should help quite a bit with some flakey tests, but not all of them.
Our port problems will not go away completely until we upgrade our vendor
version of consul. With Go modules, we'll probably do a 'replace' to swap
out other copies of freeport with the one now in 'nomad/helper/freeport'.
Operators commonly have docker logs aggregated using various tools and
don't need nomad to manage their docker logs. Worse, Nomad uses a
somewhat heavy docker api call to collect them and it seems to cause
problems when a client runs hundreds of log collections.
Here we add a knob to disable log aggregation completely for nomad.
When log collection is disabled, we avoid running logmon and
docker_logger for the docker tasks in this implementation.
The downside here is once disabled, `nomad logs ...` commands and API
no longer return logs and operators must corrolate alloc-ids with their
aggregated log info.
This is meant as a stop gap measure. Ideally, we'd follow up with at
least two changes:
First, we should optimize behavior when we can such that operators don't
need to disable docker log collection. Potentially by reverting to
using pre-0.9 syslog aggregation in linux environments, though with
different trade-offs.
Second, when/if logs are disabled, nomad logs endpoints should lookup
docker logs api on demand. This ensures that the cost of log collection
is paid sparingly.
Add an RPC timeout for logmon. In
https://github.com/hashicorp/nomad/issues/6461#issuecomment-559747758 ,
`logmonClient.Stop` locked up and indefinitely blocked the task runner
destroy operation.
This is an incremental improvement. We still need to follow up to
understand how we got to that state, and the full impact of locked-up
Stop and its link to pending allocations on restart.
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
TestClient_UpdateNodeFromFingerprintKeepsConfig checks a test node
network interface, which is hardcoded to `eth0` and is updated
asynchronously. This causes flakiness when eth0 isn't available.
Here, we hardcode the value to an arbitrary network interface.
When spinning a second client, ensure that it uses new driver
instances, rather than reuse the already shutdown unhealthy drivers from
first instance.
This speeds up tests significantly, but cutting ~50 seconds or so, the
timeout in NewClient until drivers fingerprints. They never do because
drivers were shutdown already.
TestClient_RestoreError is very slow, taking ~81 seconds.
It has few problematic patterns. It's unclear what it tests, it
simulates a failure condition where all state db lookup fails and
asserts that alloc fails. Though starting from
https://github.com/hashicorp/nomad/pull/6216 , we don't fail allocs in
that condition but rather restart them.
Also, the drivers used in second client `c2` are the same singleton
instances used in `c1` and already shutdown. We ought to start healthy
new driver instances.
* client: improve group service stanza interpolation and check_restart support
Interpolation can now be done on group service stanzas. Note that some task runtime specific information
that was previously available when the service was registered poststart of a task is no longer available.
The check_restart stanza for checks defined on group services will now properly restart the allocation upon
check failures if configured.
Adds new package that can be used by client and server RPC endpoints to
facilitate monitoring based off of a logger
clean up old code
small comment about write
rm old comment about minsize
rename to Monitor
Removes connection logic from monitor command
Keep connection logic in endpoints, use a channel to send results from
monitoring
use new multisink logger and interfaces
small test for dropped messages
update go-hclogger and update sink/intercept logger interfaces
makeAllocTaskServices did not do a nil check on AllocatedResources
which causes a panic when upgrading directly from 0.8 to 0.10. While
skipping 0.9 is not supported we intend to fix serious crashers caused
by such upgrades to prevent cluster outages.
I did a quick audit of the client package and everywhere else that
accesses AllocatedResources appears to be properly guarded by a nil
check.
Fix a bug where a millicious user can access or manipulate an alloc in a
namespace they don't have access to. The allocation endpoints perform
ACL checks against the request namespace, not the allocation namespace,
and performs the allocation lookup independently from namespaces.
Here, we check that the requested can access the alloc namespace
regardless of the declared request namespace.
Ideally, we'd enforce that the declared request namespace matches
the actual allocation namespace. Unfortunately, we haven't documented
alloc endpoints as namespaced functions; we suspect starting to enforce
this will be very disruptive and inappropriate for a nomad point
release. As such, we maintain current behavior that doesn't require
passing the proper namespace in request. A future major release may
start enforcing checking declared namespace.
fixes https://github.com/hashicorp/nomad/issues/6382
The prestart hook for templates blocks while it resolves vault secrets.
If the secret is not found it continues to retry. If a task is shutdown
during this time, the prestart hook currently does not receive
shutdownCtxCancel, causing it to hang.
This PR joins the two contexts so either killCtx or shutdownCtx cancel
and stop the task.
In a job registration request, ensure that the request namespace "header" and job
namespace field match. This should be the case already in prod, as http
handlers ensures that the values match [1].
This mitigates bugs that exploit bugs where we may check a value but act
on another, resulting into bypassing ACL system.
[1] https://github.com/hashicorp/nomad/blob/v0.9.5/command/agent/job_endpoint.go#L415-L418
Currently, there is an issue when running on Windows whereby under some
circumstances the Windows stats API's will begin to return errors (such
as internal timeouts) when a client is under high load, and potentially
other forms of resource contention / system states (and other unknown
cases).
When an error occurs during this collection, we then short circuit
further metrics emission from the client until the next interval.
This can be problematic if it happens for a sustained number of
intervals, as our metrics aggregator will begin to age out older
metrics, and we will eventually stop emitting various types of metrics
including `nomad.client.unallocated.*` metrics.
However, when metrics collection fails on Linux, gopsutil will in many cases
(e.g cpu.Times) silently return 0 values, rather than an error.
Here, we switch to returning empty metrics in these failures, and
logging the error at the source. This brings the behaviour into line
with Linux/Unix platforms, and although making aggregation a little
sadder on intermittent failures, will result in more desireable overall
behaviour of keeping metrics available for further investigation if
things look unusual.
Some drivers will automatically create directories when trying to mount
a path into a container, but some will not.
To unify this behaviour, this commit requires that host volumes already exist,
and can be stat'd by the Nomad Agent during client startup.
Currently, using a Volume in a job uses the following configuration:
```
volume "alias-name" {
type = "volume-type"
read_only = true
config {
source = "host_volume_name"
}
}
```
This commit migrates to the following:
```
volume "alias-name" {
type = "volume-type"
source = "host_volume_name"
read_only = true
}
```
The original design was based due to being uncertain about the future of storage
plugins, and to allow maxium flexibility.
However, this causes a few issues, namely:
- We frequently need to parse this configuration during submission,
scheduling, and mounting
- It complicates the configuration from and end users perspective
- It complicates the ability to do validation
As we understand the problem space of CSI a little more, it has become
clear that we won't need the `source` to be in config, as it will be
used in the majority of cases:
- Host Volumes: Always need a source
- Preallocated CSI Volumes: Always needs a source from a volume or claim name
- Dynamic Persistent CSI Volumes*: Always needs a source to attach the volumes
to for managing upgrades and to avoid dangling.
- Dynamic Ephemeral CSI Volumes*: Less thought out, but `source` will probably point
to the plugin name, and a `config` block will
allow you to pass meta to the plugin. Or will
point to a pre-configured ephemeral config.
*If implemented
The new design simplifies this by merging the source into the volume
stanza to solve the above issues with usability, performance, and error
handling.
On macOS, `os.TempDir` returns a symlinked path under `/var` which is
outside of the directories shared into the VM used for Docker, and
that fails tests using Docker that need that mount. If we expand the
symlink to get the real path in `/private`, we're in the shared
folders and can safely mount them.
This is an attempt to ease dependency management for external driver
plugins, by avoiding requiring them to compile ugorji/go generated
files. Plugin developers reported some pain with the brittleness of
ugorji/go dependency in particular, specially when using go mod, the
default go mod manager in golang 1.13.
Context
--------
Nomad uses msgpack to persist and serialize internal structs, using
ugorji/go library. As an optimization, we use ugorji/go code generation
to speedup process and aovid the relection-based slow path.
We commit these generated files in repository when we cut and tag the
release to ease reproducability and debugging old releases. Thus,
downstream projects that depend on release tag, indirectly depends on
ugorji/go generated code.
Sadly, the generated code is brittle and specific to the version of
ugorji/go being used. When go mod picks another version of ugorji/go
then nomad (go mod by default uses release according to semver),
downstream projects face compilation errors.
Interestingly, downstream projects don't commonly serialize nomad
internal structs. Drivers and device plugins use grpc instead of
msgpack for the most part. In the few cases where they use msgpag (e.g.
decoding task config), they do without codegen path as they run on
driver specific structs not the nomad internal structs. Also, the
ugorji/go serialization through reflection is generally backward
compatible (mod some ugorji/go regression bugs that get introduced every
now and then :( ).
Proposal
---------
The proposal here is to keep committing ugorji/go codec generated files
for releases but to use a go tag for them.
All nomad development through the makefile, including releasing, CI and
dev flow, has the tag enabled.
Downstream plugin projects, by default, will skip these files and life
proceed as normal for them.
The downside is that nomad developers who use generated code but avoid
using make must start passing additional go tag argument. Though this
is not a blessed configuration.
Splitting the immutable and mutable components of the scriptCheck led
to a bug where the environment interpolation wasn't being incorporated
into the check's ID, which caused the UpdateTTL to update for a check
ID that Consul didn't have (because our Consul client creates the ID
from the structs.ServiceCheck each time we update).
Task group services don't have access to a task environment at
creation, so their checks get registered before the check can be
interpolated. Use the original check ID so they can be updated.
* ar: refactor network bridge config to use go-cni lib
* ar: use eth as the iface prefix for bridged network namespaces
* vendor: update containerd/go-cni package
* ar: update network hook to use TODO contexts when calling configurator
* unnecessary conversion
In Nomad prior to Consul Connect, all Consul checks work the same
except for Script checks. Because the Task being checked is running in
its own container namespaces, the check is executed by Nomad in the
Task's context. If the Script check passes, Nomad uses the TTL check
feature of Consul to update the check status. This means in order to
run a Script check, we need to know what Task to execute it in.
To support Consul Connect, we need Group Services, and these need to
be registered in Consul along with their checks. We could push the
Service down into the Task, but this doesn't work if someone wants to
associate a service with a task's ports, but do script checks in
another task in the allocation.
Because Nomad is handling the Script check and not Consul anyways,
this moves the script check handling into the task runner so that the
task runner can own the script check's configuration and
lifecycle. This will allow us to pass the group service check
configuration down into a task without associating the service itself
with the task.
When tasks are checked for script checks, we walk back through their
task group to see if there are script checks associated with the
task. If so, we'll spin off script check tasklets for them. The
group-level service and any restart behaviors it needs are entirely
encapsulated within the group service hook.
* connect: add unix socket to proxy grpc for envoy
Fixes#6124
Implement a L4 proxy from a unix socket inside a network namespace to
Consul's gRPC endpoint on the host. This allows Envoy to connect to
Consul's xDS configuration API.
* connect: pointer receiver on structs with mutexes
* connect: warn on all proxy errors
The ClientState being pending isn't a good criteria; as an alloc may
have been updated in-place before it was completed.
Also, updated the logic so we only check for task states. If an alloc
has deployment state but no persisted tasks at all, restore will still
fail.
* taskenv: add connect upstream env vars + test
* set taskenv upstreams instead of appending
* Update client/taskenv/env.go
Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>
This uses an alternative approach where we avoid restoring the alloc
runner in the first place, if we suspect that the alloc may have been
completed already.
This commit aims to help users running with clients suseptible to the
destroyed alloc being restrarted bug upgrade to latest. Without this,
such users will have their tasks run unexpectedly on upgrade and only
see the bug resolved after subsequent restart.
If, on restore, the client sees a pending alloc without any other
persisted info, then err on the side that it's an corrupt persisted
state of an alloc instead of the client happening to be killed right
when alloc is assigned to client.
Few reasons motivate this behavior:
Statistically speaking, corruption being the cause is more likely. A
long running client will have higher chance of having allocs persisted
incorrectly with pending state. Being killed right when an alloc is
about to start is relatively unlikely.
Also, delaying starting an alloc that hasn't started (by hopefully
seconds) is not as severe as launching too many allocs that may bring
client down.
More importantly, this helps customers upgrade their clients without
risking taking their clients down and destablizing their cluster. We
don't want existing users to force triggering the bug while they upgrade
and restart cluster.
Protect against a race where destroying and persist state goroutines
race.
The downside is that the database io operation will run while holding
the lock and may run indefinitely. The risk of lock being long held is
slow destruction, but slow io has bigger problems.
This fixes a bug where allocs that have been GCed get re-run again after client
is restarted. A heavily-used client may launch thousands of allocs on startup
and get killed.
The bug is that an alloc runner that gets destroyed due to GC remains in
client alloc runner set. Periodically, they get persisted until alloc is
gced by server. During that time, the client db will contain the alloc
but not its individual tasks status nor completed state. On client restart,
client assumes that alloc is pending state and re-runs it.
Here, we fix it by ensuring that destroyed alloc runners don't persist any alloc
to the state DB.
This is a short-term fix, as we should consider revamping client state
management. Storing alloc and task information in non-transaction non-atomic
concurrently while alloc runner is running and potentially changing state is a
recipe for bugs.
Fixes https://github.com/hashicorp/nomad/issues/5984
Related to https://github.com/hashicorp/nomad/pull/5890
Fixes a bug where we cpu is pigged at 100% due to collecting devices
statistics. The passed stats interval was ignored, and the default zero
value causes a very tight loop of stats collection.
FWIW, in my testing, it took 2.5-3ms to collect nvidia GPU stats, on a
`g2.2xlarge` ec2 instance.
The stats interval defaults to 1 second and is user configurable. I
believe this is too frequent as a default, and I may advocate for
reducing it to a value closer to 5s or 10s, but keeping it as is for
now.
Fixes https://github.com/hashicorp/nomad/issues/6057 .
* adds meta object to service in job spec, sends it to consul
* adds tests for service meta
* fix tests
* adds docs
* better hashing for service meta, use helper for copying meta when registering service
* tried to be DRY, but looks like it would be more work to use the
helper function
Fixes#6041
Unlike all other Consul operations, boostrapping requires Consul be
available. This PR tries Consul 3 times with a backoff to account for
the group services being asynchronously registered with Consul.
* nomad: add admission controller framework
* nomad: add admission controller framework and Consul Connect hooks
* run admission controllers before checking permissions
* client: add default node meta for connect configurables
* nomad: remove validateJob func since it has been moved to admission controller
* nomad: use new TaskKind type
* client: use consts for connect sidecar image and log level
* Apply suggestions from code review
Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>
* nomad: add job register test with connect sidecar
* Update nomad/job_endpoint_hooks.go
Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>
When rendering a task template, the `plugin` function is no longer
permitted by default and will raise an error. An operator can opt-in
to permitting this function with the new `template.function_blacklist`
field in the client configuration.
When rendering a task template, path parameters for the `file`
function will be treated as relative to the task directory by
default. Relative paths or symlinks that point outside the task
directory will raise an error. An operator can opt-out of this
protection with the new `template.disable_file_sandbox` field in the
client configuration.
When rendering a task consul template, ensure that only task environment
variables are used.
Currently, `consul-template` always falls back to host process
environment variables when key isn't a task env var[1]. Thus, we add
an empty entry for each host process env-var not found in task env-vars.
[1] bfa5d0e133/template/funcs.go (L61-L75)
Adds a new Prerun and Postrun hooks to manage set up of network namespaces
on linux. Work still needs to be done to make the code platform agnostic and
support Docker style network initalization.
There's a bug in go1.11 that causes some io operations on windows to
return incorrect errors for some cases when Stat-ing files. To avoid
upgrading to go1.12 in a point release, here we loosen up the cases
where we will attempt to create fifos, and add some logging of
underlying stat errors to help with debugging.
Previously, if a channel is closed, we retry the Stats call. But, if that call
fails, we go in a backoff loop without calling Stats ever again.
Here, we use a utility function for calling driverHandle.Stats call that retries
as one expects.
I aimed to preserve the logging formats but made small improvements as I saw fit.
When an alloc runner prestart hook fails, the task runners aren't invoked
and they remain in a pending state.
This leads to terrible results, some of which are:
* Lockup in GC process as reported in https://github.com/hashicorp/nomad/pull/5861
* Lockup in shutdown process as TR.Shutdown() waits for WaitCh to be closed
* Alloc not being restarted/rescheduled to another node (as it's still in
pending state)
* Unexpected restart of alloc on a client restart, potentially days/weeks after
alloc expected start time!
Here, we treat all tasks to have failed if alloc runner prestart hook fails.
This fixes the lockups, and permits the alloc to be rescheduled on another node.
While it's desirable to retry alloc runner in such failures, I opted to treat it
out of scope. I'm afraid of some subtles about alloc and task runners and their
idempotency that's better handled in a follow up PR.
This might be one of the root causes for
https://github.com/hashicorp/nomad/issues/5840 .
When fetching node alloc assignments, be defensive against a stale read before
killing local nodes allocs.
The bug is when both client and servers are restarting and the client requests
the node allocation for the node, it might get stale data as server hasn't
finished applying all the restored raft transaction to store.
Consequently, client would kill and destroy the alloc locally, just to fetch it
again moments later when server store is up to date.
The bug can be reproduced quite reliably with single node setup (configured with
persistence). I suspect it's too edge-casey to occur in production cluster with
multiple servers, but we may need to examine leader failover scenarios more closely.
In this commit, we only remove and destroy allocs if the removal index is more
recent than the alloc index. This seems like a cheap resiliency fix we already
use for detecting alloc updates.
A more proper fix would be to ensure that a nomad server only serves
RPC calls when state store is fully restored or up to date in leadership
transition cases.
Although this operation is safe on linux, it is not safe on Windows when
using the named pipe interface. To provide a ~reasonable common api
abstraction, here we switch to returning File exists errors on the unix
api.
On unix platforms, it is safe to re-open fifo's for reading after the
first creation if the file is already a fifo, however this is not
possible on windows where this triggers a permissions error on the
socket path, as you cannot recreate it.
We can't transparently handle this in the CreateAndRead handle, because
the Access Is Denied error is too generic to reliably be an IO error.
Instead, we add an explict API for opening a reader to an existing FIFO,
and check to see if the fifo already exists inside the calling package
(e.g logmon)
This change fixes a bug where nomad would avoid running alloc tasks if
the alloc is client terminal but the server copy on the client isn't
marked as running.
Here, we fix the case by having task runner uses the
allocRunner.shouldRun() instead of only checking the server updated
alloc.
Here, we preserve much of the invariants such that `tr.Run()` is always
run, and don't change the overall alloc runner and task runner
lifecycles.
Fixes https://github.com/hashicorp/nomad/issues/5883
Currently, if killTask results in the termination of a process before
calling WaitTask, Restart() will incorrectly return a TaskNotFound
error when using the raw_exec driver on Windows.
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)
We currently only run cleanup Service Hooks when a task is either
Killed, or Exited. However, due to the implementation of a task runner,
tasks are only Exited if they every correctly started running, which is
not true when you recieve an error early in the task start flow, such as
not being able to pull secrets from Vault.
This updates the service hook to also call consul deregistration
routines during a task Stop lifecycle event, to ensure that any
registered checks and services are cleared in such cases.
fixes#5770
When a client is running against an old server (e.g. running 0.8),
`alloc.AllocatedResources` may be nil, and we need to check the
deprecated `alloc.TaskResources` instead.
Fixes https://github.com/hashicorp/nomad/issues/5810
Alloc runner already tracks tasks associated with alloc. Here, we
become defensive by relying on the alloc runner tracked tasks, rather
than depend on server never updating the job unexpectedly.
This exposes a client flag to disable nomad remote exec support in
environments where access to tasks ought to be restricted.
I used `disable_remote_exec` client flag that defaults to allowing
remote exec. Opted for a client config that can be used to disable
remote exec globally, or to a subset of the cluster if necessary.
This fixes an issue where batch and service workloads would never be
restarted due to indefinitely blocking on a nil channel.
It also raises the restoration logging message to `Info` to simplify log
analysis.
Without this change, alloc_endpoint cancel the context passed to handler
when we detect EOF. This races driver in setting exit code; and we run
into a case where the exec process terminates cleanly yet we attempt to
mark it as failed with context error.
Here, we rely on the driver to handle errors returned from Stream and
without racing to set an error.
Registration and restoring allocs don't share state or depend on each
other in any way (syncing allocs with servers is done outside of
registration).
Since restoring is synchronous, start the registration goroutine first.
For nodes with lots of allocs to restore or close to their heartbeat
deadline, this could be the difference between becoming "lost" or not.
Refactoring of 104067bc2b2002a4e45ae7b667a476b89addc162
Switch the MarkLive method for a chan that is closed by the client.
Thanks to @notnoop for the idea!
The old approach called a method on most existing ARs and TRs on every
runAllocs call. The new approach does a once.Do call in runAllocs to
accomplish the same thing with less work. Able to remove the gate
abstraction that did much more than was needed.
Fixes#1795
Running restored allocations and pulling what allocations to run from
the server happen concurrently. This means that if a client is rebooted,
and has its allocations rescheduled, it may restart the dead allocations
before it contacts the server and determines they should be dead.
This commit makes tasks that fail to reattach on restore wait until the
server is contacted before restarting.
Related to #4280
This PR adds
`client.allocs.<job>.<group>.<alloc>.<task>.memory.allocated` as a gauge
in bytes to metrics to ease calculating how close a task is to OOMing.
```
'nomad.client.allocs.memory.allocated.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 268435456.000
'nomad.client.allocs.memory.cache.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 5677056.000
'nomad.client.allocs.memory.kernel_max_usage.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 0.000
'nomad.client.allocs.memory.kernel_usage.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 0.000
'nomad.client.allocs.memory.max_usage.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 8908800.000
'nomad.client.allocs.memory.rss.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 876544.000
'nomad.client.allocs.memory.swap.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 0.000
'nomad.client.allocs.memory.usage.example.cache.6d98cbaf-d6bc-2a84-c63f-bfff8905a9d8.redis.rusty': 8208384.000
```
Mahmood Ali