In #12324 we made it so that plugins wait until the node drain is
complete, as we do for system jobs. But we neglected to mark the node
drain as complete once only plugins (or system jobs) remaining, which
means that the node drain is left in a draining state until the
`deadline` time expires. This was incorrectly documented as expected
behavior in #12324.
notably:
- name of the compiled binary is 'nomad-device-nvidia', not 'nvidia-gpu'
- link to Nvidia docs for installing the container runtime toolkit
- list docker v19.03 as minimum version, to track with nvidia's new container runtime toolkit
The capacity fields for `create volume` set bounds on the resulting
size of the volume, but the ultimate size of the volume will be
determined by the storage provider (between the min and max). Clarify
this in the documentation and provide a suggestion for how to set a
exact size.
This test exercises upgrades between 0.8 and Nomad versions greater
than 0.9. We have not supported 0.8.x in a very long time and in any
case the test has been marked to skip because the downloader doesn't
work.
* docs: update json jobs docs
Did you know that Nomad has not 1 but 2 JSON formats for jobs? 2½ if you
want to acknowledge that sometimes our JSON job representations have a
Job top-level wrapper and sometimes do not.
The 2½ formats are:
```
1. HCL JSON
2. Input API JSON (top-level Job field)
2.5. Output API JSON (lacks top-level Job field)
```
`#2` is what our docs consider our API JSON. `#2.5` seems to be an
accident of history we can't fix with breaking API compatibility.
`#1` is an even more interesting accident of history: the `jobspec2`
package automatically detects if the input to Parse is JSON and switches
to a JSON parser. This behavior is undocumented, the format is
unspecified, and there is no official HashiCorp tooling to produce this
JSON from HCL. The plot thickens when you discover popular third party
tools like hcl2json.com and https://github.com/tmccombs/hcl2json seem to
produce JSON that `nomad run` accepts!
Since we have no telemetry around whether or not anyone passes HCL JSON
to `nomad run`, and people don't file bugs around features that Just
Work, I'm choosing to leave that code path in place and *acknowledged
but not suggested* in documentation.
See https://github.com/hashicorp/hcl/issues/498 for a more comprehensive
discussion of what officially supporting HCL JSON in Nomad would look
like.
(I also added some of the missing fields to the (Input API flavor) JSON
Job documentation, but it still needs a lot of work to be
comprehensive.)
Co-authored-by: Tim Gross <tgross@hashicorp.com>
After a more detailed analysis of this feature, the approach taken in
PR #12449 was found to be not ideal due to poor UX (users are
responsible for setting the entity alias they would like to use) and
issues around jobs potentially masquerading itself as another Vault
entity.
This PR introduces the `address` field in the `service` block so that Nomad
or Consul services can be registered with a custom `.Address.` to advertise.
The address can be an IP address or domain name. If the `address` field is
set, the `service.address_mode` must be set in `auto` mode.
* cli: add -json flag to support job commands
While the CLI has always supported running JSON jobs, its support has
been via HCLv2's JSON parsing. I have no idea what format it expects the
job to be in, but it's absolutely not in the same format as the API
expects.
So I ignored that and added a new -json flag to explicitly support *API*
style JSON jobspecs.
The jobspecs can even have the wrapping {"Job": {...}} envelope or not!
* docs: fix example for `nomad job validate`
We haven't been able to validate inside driver config stanzas ever since
the move to task driver plugins. 😭
The new `namespace apply` feature that allows for passing a namespace
specification file detects the difference between an empty namespace
and a namespace specification by checking if the file exists. For most
cases, the file will have an extension like `.hcl` and so there's
little danger that a user will apply a file spec when they intended to
apply a file name.
But because directory names typically don't include an extension,
you're much more likely to collide when trying to `namespace apply` by
name only, and then you get a confusing error message of the form:
Failed to read file: read $namespace: is a directory
Detect the case where the namespace name collides with a directory in
the current working directory, and skip trying to load the directory.
This PR updates the changelog, adds notes the 1.3 upgrade guide, and
updates the connect integration docs with documentation about the new
requirement on Consul ACL policies of Consul agent default anonymous ACL
tokens.
* Add os to NodeListStub struct.
Signed-off-by: Shishir Mahajan <smahajan@roblox.com>
* Add os as a query param to /v1/nodes.
Signed-off-by: Shishir Mahajan <smahajan@roblox.com>
* Add test: os as a query param to /v1/nodes.
Signed-off-by: Shishir Mahajan <smahajan@roblox.com>
- Moved federation docs to the bottom since *everyone* is potentially
affected by the other sections on the page, but only users of
federation are affected by it.
- Added section on the plan for node rejected bug since it is fairly
easy to diagnose and removing affected nodes is a fairly reliable
workaround.
- Mention 5s cliff for wait_for_index.
- Remove the lie that we do not have job status metrics! How old was
that?!
- Reinforce the importance of monitoring basic system resources
This PR expands on the work done in #12543 to
- prefix the tag, so it is now "nomad.alloc_id" to be more consistent with Consul tags
- merge into pre-existing envoy_stats_tags fields
- update the upgrade guide docs
- update changelog
* services: add pagination and filter support to info RPC.
* cli: add filter flag to service info command.
* docs: add pagination and filter details to services info API.
* paginator: minor updates to comment and func signature.
Many of our scripts have a non-portable interpreter line for bash and
use bash-specific variables like `BASH_SOURCE`. Update the interpreter
line to be portable between various Linuxes and macOS without
complaint from posix shell users.
Custom variable validation is a useful feature that is supported by
Nomad and not just Terraform. As such it should be documented on the
input variable page.
I've cribbed the content from the terraform docs so this should be
consistent across projects
We introduced a `pprof-interval` argument to `operator debug` in #11938, and unfortunately this has resulted in a lot of test flakes. The actual command in use is mostly fine (although I've fixed some quirks here), so what's really happened is that the change has revealed some existing issues in the tests. Summary of changes:
* Make first pprof collection synchronous to preserve the existing
behavior for the common case where the pprof interval matches the
duration.
* Clamp `operator debug` pprof timing to that of the command. The
`pprof-duration` should be no more than `duration` and the
`pprof-interval` should be no more than `pprof-duration`. Clamp the
values rather than throwing errors, which could change the commands
that existing users might already have in debugging scripts
* Testing: remove test parallelism
The `operator debug` tests that stand up servers can't be run in
parallel, because we don't have a way of canceling the API calls for
pprof. The agent will still be running the last pprof when we exit,
and that breaks the next test that talks to that same agent.
(Because you can only run one pprof at a time on any process!)
We could split off each subtest into its own server, but this test
suite is already very slow. In future work we should fix this "for
real" by making the API call cancelable.
* Testing: assert against unexpected errors in `operator debug` tests.
If we assert there are no unexpected error outputs, it's easier for
the developer to debug when something is going wrong with the tests
because the error output will be presented as a failing test, rather
than just a failing exit code check. Or worse, no failing exit code
check!
This also forces us to be explicit about which tests will return 0
exit codes but still emit (presumably ignorable) error outputs.
Additional minor bug fixes (mostly in tests) and test refactorings:
* Fix text alignment on pprof Duration in `operator debug` output
* Remove "done" channel from `operator debug` event stream test. The
goroutine we're blocking for here already tells us it's done by
sending a value, so block on that instead of an extraneous channel
* Event stream test timer should start at current time, not zero
* Remove noise from `operator debug` test log output. The `t.Logf`
calls already are picked out from the rest of the test output by
being prefixed with the filename.
* Remove explicit pprof args so we use the defaults clamped from
duration/interval
This PR injects the 'NOMAD_CPU_CORES' environment variable into
tasks that have been allocated reserved cpu cores. The value uses
normal cpuset notation, as found in cpuset.cpu cgroup interface files.
Note this value is not necessiarly the same as the content of the actual
cpuset.cpus interface file, which will also include shared cpu cores when
using cgroups v2. This variable is a workaround for users who used to be
able to read the reserved cgroup cpuset file, but lose the information
about distinct reserved cores when using cgroups v2.
Side discussion in: https://github.com/hashicorp/nomad/issues/12374
Move some common Vault API data struct decoding out of the Vault client
so it can be reused in other situations.
Make Vault job validation its own function so it's easier to expand it.
Rename the `Job.VaultPolicies` method to just `Job.Vault` since it
returns the full Vault block, not just their policies.
Set `ChangeMode` on `Vault.Canonicalize`.
Add some missing tests.
Allows specifying an entity alias that will be used by Nomad when
deriving the task Vault token.
An entity alias assigns an indentity to a token, allowing better control
and management of Vault clients since all tokens with the same indentity
alias will now be considered the same client. This helps track Nomad
activity in Vault's audit logs and better control over Vault billing.
Add support for a new Nomad server configuration to define a default
entity alias to be used when deriving Vault tokens. This default value
will be used if the task doesn't have an entity alias defined.
This PR adds support for the raw_exec driver on systems with only cgroups v2.
The raw exec driver is able to use cgroups to manage processes. This happens
only on Linux, when exec_driver is enabled, and the no_cgroups option is not
set. The driver uses the freezer controller to freeze processes of a task,
issue a sigkill, then unfreeze. Previously the implementation assumed cgroups
v1, and now it also supports cgroups v2.
There is a bit of refactoring in this PR, but the fundamental design remains
the same.
Closes#12351#12348
The client configuration options for drivers have been deprecated
since 0.9. We haven't torn them out completely but because they're
deprecated it's been hard to guarantee correct behavior. Remove the
documentation so that users aren't misled about their viability.
Resolves#12095 by WONTFIXing it.
This approach disables `writeToFile` as it allows arbitrary host
filesystem writes and is only a small quality of life improvement over
multiple `template` stanzas.
This approach has the significant downside of leaving people who have
altered their `template.function_denylist` *still vulnerable!* I added
an upgrade note, but we should have implemented the denylist as a
`map[string]bool` so that new funcs could be denied without overriding
custom configurations.
This PR also includes a bug fix that broke enabling all consul-template
funcs. We repeatedly failed to differentiate between a nil (unset)
denylist and an empty (allow all) one.
Pass-through the `-secret` and `-parameter` flags to allow setting
parameters for the snapshot and overriding the secrets we've stored on
the CSI volume in the state store.
This PR introduces support for using Nomad on systems with cgroups v2 [1]
enabled as the cgroups controller mounted on /sys/fs/cgroups. Newer Linux
distros like Ubuntu 21.10 are shipping with cgroups v2 only, causing problems
for Nomad users.
Nomad mostly "just works" with cgroups v2 due to the indirection via libcontainer,
but not so for managing cpuset cgroups. Before, Nomad has been making use of
a feature in v1 where a PID could be a member of more than one cgroup. In v2
this is no longer possible, and so the logic around computing cpuset values
must be modified. When Nomad detects v2, it manages cpuset values in-process,
rather than making use of cgroup heirarchy inheritence via shared/reserved
parents.
Nomad will only activate the v2 logic when it detects cgroups2 is mounted at
/sys/fs/cgroups. This means on systems running in hybrid mode with cgroups2
mounted at /sys/fs/cgroups/unified (as is typical) Nomad will continue to
use the v1 logic, and should operate as before. Systems that do not support
cgroups v2 are also not affected.
When v2 is activated, Nomad will create a parent called nomad.slice (unless
otherwise configured in Client conifg), and create cgroups for tasks using
naming convention <allocID>-<task>.scope. These follow the naming convention
set by systemd and also used by Docker when cgroups v2 is detected.
Client nodes now export a new fingerprint attribute, unique.cgroups.version
which will be set to 'v1' or 'v2' to indicate the cgroups regime in use by
Nomad.
The new cpuset management strategy fixes#11705, where docker tasks that
spawned processes on startup would "leak". In cgroups v2, the PIDs are
started in the cgroup they will always live in, and thus the cause of
the leak is eliminated.
[1] https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.htmlCloses#11289Fixes#11705#11773#11933
When a node is drained, system jobs are left until last so that
operators can rely on things like log shippers running even as their
applications are getting drained off. Include CSI plugins in this set
so that Controller plugins deployed as services can be handled as
gracefully as Node plugins that are running as system jobs.
The previous output of the `nomad server members` command would output a
column named `Protocol` that displayed the Serf protocol being currently
used by servers.
This is not a configurable option, so it holds very little value to
operators. It is also easy to confuse it with the Raft Protocol version,
which is configurable and highly relevant to operators.
This commit replaces the previous `Protocol` column with the new `Raft
Version`. It also updates the `-detailed` flag to be called `-verbose`
so it matches other commands. The detailed output now also outputs the
same information as the standard output with the addition of the
previous `Protocol` column and `Tags`.
The `related` query param is used to indicate that the request should
return a list of related (next, previous, and blocked) evaluations.
Co-authored-by: Jasmine Dahilig <jasmine@hashicorp.com>
When a Nomad server becomes the Raft leader, it must perform several
actions defined in the establishLeadership function. If any of these
actions fail, Raft will think the node is the leader, but it will not
actually be able to act as a Nomad leader.
In this scenario, leadership must be revoked and transferred to another
server if possible, or the node should retry the establishLeadership
steps.
Clarify the behavior of `restart` inheritance with respect to Connect
sidecar tasks. Remove incorrect language about the scheduler being
involved in restart decisions. Try to make the `delay` mode
documentation more clear, and provide examples of delay vs fail.
The Docker DNS configuration options are not compatible with a
group-level network in `bridge` mode. Warn users about this in the
Docker task configuration docs.
The RPC for listing volume snapshots requires a plugin ID. Update the
`volume snapshot list` command to find the specific plugin from the
provided prefix.
The advertise.rpc config option is not intuitive. At first glance you'd
assume it works like advertise.http or advertise.serf, but it does not.
The current behavior is working as intended, but the documentation is
very hard to parse and doesn't draw a clear picture of what the setting
actually does.
Closes https://github.com/hashicorp/nomad/issues/11075
* chore: bump to latest docs-page
* fix: bump to react-consent-manager patch
* chore: bump to consent-manager with events dep
* chore: bump to stable consent-manager release
The dynamic plugin registry assumes that plugins are singletons, which
matches the behavior of other Nomad plugins. But because dynamic
plugins like CSI are implemented by allocations, we need to handle the
possibility of multiple allocations for a given plugin type + ID, as
well as behaviors around interleaved allocation starts and stops.
Update the data structure for the dynamic registry so that more recent
allocations take over as the instance manager singleton, but we still
preserve the previous running allocations so that restores work
without racing.
Multiple allocations can run on a client for the same plugin, even if
only during updates. Provide each plugin task a unique path for the
control socket so that the tasks don't interfere with each other.
Nomad inherited protocol version numbering configuration from Consul and
Serf, but unlike those projects Nomad has never used it. Nomad's
`protocol_version` has always been `1`.
While the code is effectively unused and therefore poses no runtime
risks to leave, I felt like removing it was best because:
1. Nomad's RPC subsystem has been able to evolve extensively without
needing to increment the version number.
2. Nomad's HTTP API has evolved extensively without increment
`API{Major,Minor}Version`. If we want to version the HTTP API in the
future, I doubt this is the mechanism we would choose.
3. The presence of the `server.protocol_version` configuration
parameter is confusing since `server.raft_protocol` *is* an important
parameter for operators to consider. Even more confusing is that
there is a distinct Serf protocol version which is included in `nomad
server members` output under the heading `Protocol`. `raft_protocol`
is the *only* protocol version relevant to Nomad developers and
operators. The other protocol versions are either deadcode or have
never changed (Serf).
4. If we were to need to version the RPC, HTTP API, or Serf protocols, I
don't think these configuration parameters and variables are the best
choice. If we come to that point we should choose a versioning scheme
based on the use case and modern best practices -- not this 6+ year
old dead code.
These API endpoints now return results in chronological order. They
can return results in reverse chronological order by setting the
query parameter ascending=true.
- Eval.List
- Deployment.List
The examples for `nomad volume create` and `nomad volume register` are
not setting `mount_flags` using an array of strings.
This fixes the issue by changing the example to be `mount_flags =
["noatime"]`.
This PR exposes the following existing`consul-template` configuration options to Nomad jobspec authors in the `{job.group.task.template}` stanza.
- `wait`
It also exposes the following`consul-template` configuration to Nomad operators in the `{client.template}` stanza.
- `max_stale`
- `block_query_wait`
- `consul_retry`
- `vault_retry`
- `wait`
Finally, it adds the following new Nomad-specific configuration to the `{client.template}` stanza that allows Operators to set bounds on what `jobspec` authors configure.
- `wait_bounds`
Co-authored-by: Tim Gross <tgross@hashicorp.com>
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>
Client endpoints such as `alloc exec` are enforced on the client if
the API client or CLI has "line of sight" to the client. This is
already in the Learn guide but having it in the ACL configuration docs
would be helpful.
* Fixed name of `nomad.scheduler.allocs.reschedule` metric
* Added new metrics to metrics reference documentation
* Expanded definitions of "waiting" metrics
* Changelog entry for #10236 and #10237
## Development Environment Changes
* Added stringer to build deps
## New HTTP APIs
* Added scheduler worker config API
* Added scheduler worker info API
## New Internals
* (Scheduler)Worker API refactor—Start(), Stop(), Pause(), Resume()
* Update shutdown to use context
* Add mutex for contended server data
- `workerLock` for the `workers` slice
- `workerConfigLock` for the `Server.Config.NumSchedulers` and
`Server.Config.EnabledSchedulers` values
## Other
* Adding docs for scheduler worker api
* Add changelog message
Co-authored-by: Derek Strickland <1111455+DerekStrickland@users.noreply.github.com>
When the scheduler picks a node for each evaluation, the
`LimitIterator` provides at most 2 eligible nodes for the
`MaxScoreIterator` to choose from. This keeps scheduling fast while
producing acceptable results because the results are binpacked.
Jobs with a `spread` block (or node affinity) remove this limit in
order to produce correct spread scoring. This means that every
allocation within a job with a `spread` block is evaluated against
_all_ eligible nodes. Operators of large clusters have reported that
jobs with `spread` blocks that are eligible on a large number of nodes
can take longer than the nack timeout to evaluate (60s). Typical
evaluations are processed in milliseconds.
In practice, it's not necessary to evaluate every eligible node for
every allocation on large clusters, because the `RandomIterator` at
the base of the scheduler stack produces enough variation in each pass
that the likelihood of an uneven spread is negligible. Note that
feasibility is checked before the limit, so this only impacts the
number of _eligible_ nodes available for scoring, not the total number
of nodes.
This changeset sets the iterator limit for "large" `spread` block and
node affinity jobs to be equal to the number of desired
allocations. This brings an example problematic job evaluation down
from ~3min to ~10s. The included tests ensure that we have acceptable
spread results across a variety of large cluster topologies.
* Mesh Gateway doc enhancements
1. I believe this line should be corrected to add mesh as one of the choices
2. I found that we are not setting this meta, and it is a required element for wan federation. I believe it would be helpful and potentially time saving to note that right here.
The `nomad operator raft` and `nomad operator snapshot state`
subcommands for inspecting on-disk raft state were hidden and
undocumented. Expose and document these so that advanced operators
have support for these tools.
Use the new filtering and pagination capabilities of the `Eval.List`
RPC to provide filtering and pagination at the command line.
Also includes note that `nomad eval status -json` is deprecated and
will be replaced with a single evaluation view in a future version of
Nomad.
Some operators use very long group/task `shutdown_delay` settings to
safely drain network connections to their workloads after service
deregistration. But during incident response, they may want to cause
that drain to be skipped so they can quickly shed load.
Provide a `-no-shutdown-delay` flag on the `nomad alloc stop` and
`nomad job stop` commands that bypasses the delay. This sets a new
desired transition state on the affected allocations that the
allocation/task runner will identify during pre-kill on the client.
Note (as documented here) that using this flag will almost always
result in failed inbound network connections for workloads as the
tasks will exit before clients receive updated service discovery
information and won't be gracefully drained.
API queries can request pagination using the `NextToken` and `PerPage`
fields of `QueryOptions`, when supported by the underlying API.
Add a `NextToken` field to the `structs.QueryMeta` so that we have a
common field across RPCs to tell the caller where to resume paging
from on their next API call. Include this field on the `api.QueryMeta`
as well so that it's available for future versions of List HTTP APIs
that wrap the response with `QueryMeta` rather than returning a simple
list of structs. In the meantime callers can get the `X-Nomad-NextToken`.
Add pagination to the `Eval.List` RPC by checking for pagination token
and page size in `QueryOptions`. This will allow resuming from the
last ID seen so long as the query parameters and the state store
itself are unchanged between requests.
Add filtering by job ID or evaluation status over the results we get
out of the state store.
Parse the query parameters of the `Eval.List` API into the arguments
expected for filtering in the RPC call.
This changeset adds more specific recommendations as to what metrics
to monitor, and what resources should be examined during incident
response.
It also renames the "Telemetry" section to "Monitoring Nomad" to
surface the material better and distinguish it from the "Metric
Reference".
Co-authored-by: Charlie Voiselle <464492+angrycub@users.noreply.github.com>
During incident response, operators may find that automated processes
elsewhere in the organization can be generating new workloads on Nomad
clusters that are unable to handle the workload. This changeset adds a
field to the `SchedulerConfiguration` API that causes all job
registration calls to be rejected unless the request has a management
ACL token.
Give ourselves some room for extension in the UI configuration block
by naming the field `ui_url`, which will let us have an `api_url`.
Fix the template path to ensure we're getting the right value from the
API.
This change modifies the Nomad job register and deregister RPCs to
accept an updated option set which includes eval priority. This
param is optional and override the use of the job priority to set
the eval priority.
In order to ensure all evaluations as a result of the request use
the same eval priority, the priority is shared to the
allocReconciler and deploymentWatcher. This creates a new
distinction between eval priority and job priority.
The Nomad agent HTTP API has been modified to allow setting the
eval priority on job update and delete. To keep consistency with
the current v1 API, job update accepts this as a payload param;
job delete accepts this as a query param.
Any user supplied value is validated within the agent HTTP handler
removing the need to pass invalid requests to the server.
The register and deregister opts functions now all for setting
the eval priority on requests.
The change includes a small change to the DeregisterOpts function
which handles nil opts. This brings the function inline with the
RegisterOpts.
The QEMU driver allows arbitrary command line options, but many of
these options give access to host resources that operators may not
want to expose such as devices. Add an optional allowlist to the
plugin configuration so that operators can limit the resources for
QEMU.
While it *is* clarified toward the bottom of this page, I've seen people
go to great lengths to configure tokens for clients anyway, so I think
it's worth noting on the parameter's docs as well.
Enhance the CLI in order to return the host network in two flavors
(default, verbose) of the `node status` command.
Fixes: #11223.
Signed-off-by: Alessandro De Blasis <alex@deblasis.net>
Fixes#2522
Skip embedding client.alloc_dir when building chroot. If a user
configures a Nomad client agent so that the chroot_env will embed the
client.alloc_dir, Nomad will happily infinitely recurse while building
the chroot until something horrible happens. The best case scenario is
the filesystem's path length limit is hit. The worst case scenario is
disk space is exhausted.
A bad agent configuration will look something like this:
```hcl
data_dir = "/tmp/nomad-badagent"
client {
enabled = true
chroot_env {
# Note that the source matches the data_dir
"/tmp/nomad-badagent" = "/ohno"
# ...
}
}
```
Note that `/ohno/client` (the state_dir) will still be created but not
`/ohno/alloc` (the alloc_dir).
While I cannot think of a good reason why someone would want to embed
Nomad's client (and possibly server) directories in chroots, there
should be no cause for harm. chroots are only built when Nomad runs as
root, and Nomad disables running exec jobs as root by default. Therefore
even if client state is copied into chroots, it will be inaccessible to
tasks.
Skipping the `data_dir` and `{client,server}.state_dir` is possible, but
this PR attempts to implement the minimum viable solution to reduce risk
of unintended side effects or bugs.
When running tests as root in a vm without the fix, the following error
occurs:
```
=== RUN TestAllocDir_SkipAllocDir
alloc_dir_test.go:520:
Error Trace: alloc_dir_test.go:520
Error: Received unexpected error:
Couldn't create destination file /tmp/TestAllocDir_SkipAllocDir1457747331/001/nomad/test/testtask/nomad/test/testtask/.../nomad/test/testtask/secrets/.nomad-mount: open /tmp/TestAllocDir_SkipAllocDir1457747331/001/nomad/test/.../testtask/secrets/.nomad-mount: file name too long
Test: TestAllocDir_SkipAllocDir
--- FAIL: TestAllocDir_SkipAllocDir (22.76s)
```
Also removed unused Copy methods on AllocDir and TaskDir structs.
Thanks to @eveld for not letting me forget about this!
FailoverHeartbeatTTL is the amount of time to wait after a server leader failure
before considering reallocating client tasks. This TTL should be fairly long as
the new server leader needs to rebuild the entire heartbeat map for the
cluster. In deployments with a small number of machines, the default TTL (5m)
may be unnecessary long. Let's allow operators to configure this value in their
config files.
