Nomad creates Consul ACL tokens and service registrations to support Consul
service mesh workloads, before bootstrapping the Envoy proxy. Nomad always talks
to the local Consul agent and never directly to the Consul servers. But the
local Consul agent talks to the Consul servers in stale consistency mode to
reduce load on the servers. This can result in the Nomad client making the Envoy
bootstrap request with a tokens or services that have not yet replicated to the
follower that the local client is connected to. This request gets a 404 on the
ACL token and that negative entry gets cached, preventing any retries from
succeeding.
To workaround this, we'll use a method described by our friends over on
`consul-k8s` where after creating the objects in Consul we try to read them from
the local agent in stale consistency mode (which prevents a failed read from
being cached). This cannot completely eliminate this source of error because
it's possible that Consul cluster replication is unhealthy at the time we need
it, but this should make Envoy bootstrap significantly more robust.
This changset adds preflight checks for the objects we create in Consul:
* We add a preflight check for ACL tokens after we login via via Workload
Identity and in the function we use to derive tokens in the legacy
workflow. We do this check early because we also want to use this token for
registering group services in the allocrunner hooks.
* We add a preflight check for services right before we bootstrap Envoy in the
taskrunner hook, so that we have time for our service client to batch updates
to the local Consul agent in addition to the local agent sync.
We've added the timeouts to be configurable via node metadata rather than the
usual static configuration because for most cases, users should not need to
touch or even know these values are configurable; the configuration is mostly
available for testing.
Fixes: https://github.com/hashicorp/nomad/issues/9307
Fixes: https://github.com/hashicorp/nomad/issues/10451
Fixes: https://github.com/hashicorp/nomad/issues/20516
Ref: https://github.com/hashicorp/consul-k8s/pull/887
Ref: https://hashicorp.atlassian.net/browse/NET-10051
Ref: https://hashicorp.atlassian.net/browse/NET-9273
Follow-up: https://hashicorp.atlassian.net/browse/NET-10138
Refactor the JWT token derivation logic to only take a single request
since it was only ever called with a map of length one.
The original implementation received multiple requets to match the
legacy flow, but but legacy flow requests were batched from the Nomad
client to the server, which doesn't happen for JWT. Each JWT request
goes directly from the Nomad client to the Consul agent, so there is no
batching involved.
Add a `Postrun` and `Destroy` hook to the allocrunner's `consul_hook` to ensure
that Consul tokens we've created via WI get revoked via the logout API when
we're done with them. Also add the logout to the `Prerun` hook if we've hit an
error.
This commit performs refactoring to pull out common service
registration objects into a new `client/serviceregistration`
package. This new package will form the base point for all
client specific service registration functionality.
The Consul specific implementation is not moved as it also
includes non-service registration implementations; this reduces
the blast radius of the changes as well.
This PR adds the common OSS changes for adding support for Consul Namespaces,
which is going to be a Nomad Enterprise feature. There is no new functionality
provided by this changeset and hopefully no new bugs.
When a job is configured with Consul Connect aware tasks (i.e. sidecar),
the Nomad Client should be able to request from Consul (through Nomad Server)
Service Identity tokens specific to those tasks.
* 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.
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.
Updated to hclog.
It exposed fields that required an unexported lock to access. Created a
getter methodn instead. Only old allocrunner currently used this
feature.
