Plan rejections occur when the scheduler work and the leader plan
applier disagree on the feasibility of a plan. This may happen for valid
reasons: since Nomad does parallel scheduling, it is expected that
different workers will have a different state when computing placements.
As the final plan reaches the leader plan applier, it may no longer be
valid due to a concurrent scheduling taking up intended resources. In
these situations the plan applier will notify the worker that the plan
was rejected and that they should refresh their state before trying
again.
In some rare and unexpected circumstances it has been observed that
workers will repeatedly submit the same plan, even if they are always
rejected.
While the root cause is still unknown this mitigation has been put in
place. The plan applier will now track the history of plan rejections
per client and include in the plan result a list of node IDs that should
be set as ineligible if the number of rejections in a given time window
crosses a certain threshold. The window size and threshold value can be
adjusted in the server configuration.
To avoid marking several nodes as ineligible at one, the operation is rate
limited to 5 nodes every 30min, with an initial burst of 10 operations.
* core: allow pause/un-pause of eval broker on region leader.
* agent: add ability to pause eval broker via scheduler config.
* cli: add operator scheduler commands to interact with config.
* api: add ability to pause eval broker via scheduler config
* e2e: add operator scheduler test for eval broker pause.
* docs: include new opertor scheduler CLI and pause eval API info.
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.
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.
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.
This PR implements a new "System Batch" scheduler type. Jobs can
make use of this new scheduler by setting their type to 'sysbatch'.
Like the name implies, sysbatch can be thought of as a hybrid between
system and batch jobs - it is for running short lived jobs intended to
run on every compatible node in the cluster.
As with batch jobs, sysbatch jobs can also be periodic and/or parameterized
dispatch jobs. A sysbatch job is considered complete when it has been run
on all compatible nodes until reaching a terminal state (success or failed
on retries).
Feasibility and preemption are governed the same as with system jobs. In
this PR, the update stanza is not yet supported. The update stanza is sill
limited in functionality for the underlying system scheduler, and is
not useful yet for sysbatch jobs. Further work in #4740 will improve
support for the update stanza and deployments.
Closes#2527
This PR introduces the /v1/search/fuzzy API endpoint, used for fuzzy
searching objects in Nomad. The fuzzy search endpoint routes requests
to the Nomad Server leader, which implements the Search.FuzzySearch RPC
method.
Requests to the fuzzy search API are based on the api.FuzzySearchRequest
object, e.g.
{
"Text": "ed",
"Context": "all"
}
Responses from the fuzzy search API are based on the api.FuzzySearchResponse
object, e.g.
{
"Index": 27,
"KnownLeader": true,
"LastContact": 0,
"Matches": {
"tasks": [
{
"ID": "redis",
"Scope": [
"default",
"example",
"cache"
]
}
],
"evals": [],
"deployment": [],
"volumes": [],
"scaling_policy": [],
"images": [
{
"ID": "redis:3.2",
"Scope": [
"default",
"example",
"cache",
"redis"
]
}
]
},
"Truncations": {
"volumes": false,
"scaling_policy": false,
"evals": false,
"deployment": false
}
}
The API is tunable using the new server.search stanza, e.g.
server {
search {
fuzzy_enabled = true
limit_query = 200
limit_results = 1000
min_term_length = 5
}
}
These values can be increased or decreased, so as to provide more
search results or to reduce load on the Nomad Server. The fuzzy search
API can be disabled entirely by setting `fuzzy_enabled` to `false`.
