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.
Before this change trying to run `nomad operator raft {info,logs}` on an
inuse raft.db would cause the command to block until the agent using
raft.db is closed.
After this change the command will block for 1s before returning a
(hopefully) helpful error message.
This change also sets the ReadOnly mode on the underlying BoltDb to
ensure diagnostics make no changes to the underlying store. We have no
evidence this has ever occurred, but it seems like a useful safety
measure.
No changelog added since this is a minor tweak in a "new" feature (it
was hidden in previous relases).
The `nomad operator raft logs` command uses a raft helper that reads
in the logs from raft and serializes them to JSON. The previous
implementation returned the slice of all logs and then serializes the
entire object. Update the helper to stream the log entries and then
serialize them as newline-delimited JSON.
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.
When a cluster doesn't have a leader, the `nomad operator debug`
command can safely use stale queries to gracefully degrade the
consistency of almost all its queries. The query parameter for these
API calls was not being set by the command.
Some `api` package queries do not include `QueryOptions` because
they target a specific agent, but they can potentially be forwarded to
other agents. If there is no leader, these forwarded queries will
fail. Provide methods to call these APIs with `QueryOptions`.
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.
