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PromQL: Always enable negative offset and @ modifier

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This follows the line of argument that the invariant of not looking
ahead of the query time was merely emerging behavior and not a
documented stable feature. Any query that looks ahead of the query
time was simply invalid before the introduction of the negative offset
and the @ modifier.

Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
beorn7 2022-01-11 17:01:02 +01:00
parent 61509fc840
commit b39f2739e5
9 changed files with 33 additions and 70 deletions
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16
cmd/prometheus/main.go
View file

@ -149,8 +149,6 @@ type flagConfig struct {
featureList []string
// These options are extracted from featureList
// for ease of use.
enablePromQLAtModifier bool
enablePromQLNegativeOffset bool
enableExpandExternalLabels bool
enableNewSDManager bool
@ -166,12 +164,6 @@ func (c *flagConfig) setFeatureListOptions(logger log.Logger) error {
opts := strings.Split(f, ",")
for _, o := range opts {
switch o {
case "promql-at-modifier":
c.enablePromQLAtModifier = true
level.Info(logger).Log("msg", "promql-at-modifier enabled")
case "promql-negative-offset":
c.enablePromQLNegativeOffset = true
level.Info(logger).Log("msg", "promql-negative-offset enabled")
case "remote-write-receiver":
c.web.EnableRemoteWriteReceiver = true
level.Warn(logger).Log("msg", "Remote write receiver enabled via feature flag remote-write-receiver. This is DEPRECATED. Use --web.enable-remote-write-receiver.")
@ -195,6 +187,8 @@ func (c *flagConfig) setFeatureListOptions(logger log.Logger) error {
level.Info(logger).Log("msg", "Experimental agent mode enabled.")
case "":
continue
case "promql-at-modifier", "promql-negative-offset":
level.Warn(logger).Log("msg", "This option for --enable-feature is now permanently enabled and therefore a no-op.", "option", o)
default:
level.Warn(logger).Log("msg", "Unknown option for --enable-feature", "option", o)
}
@ -570,8 +564,10 @@ func main() {
ActiveQueryTracker: promql.NewActiveQueryTracker(localStoragePath, cfg.queryConcurrency, log.With(logger, "component", "activeQueryTracker")),
LookbackDelta: time.Duration(cfg.lookbackDelta),
NoStepSubqueryIntervalFn: noStepSubqueryInterval.Get,
EnableAtModifier: cfg.enablePromQLAtModifier,
EnableNegativeOffset: cfg.enablePromQLNegativeOffset,
// EnableAtModifier and EnableNegativeOffset have to be
// always on for regular PromQL as of Prometheus v2.33.
EnableAtModifier: true,
EnableNegativeOffset: true,
}
queryEngine = promql.NewEngine(opts)

15
cmd/promtool/main.go
View file

@ -203,17 +203,14 @@ func main() {
p = &promqlPrinter{}
}
var queryOpts promql.LazyLoaderOpts
for _, f := range *featureList {
opts := strings.Split(f, ",")
for _, o := range opts {
switch o {
case "promql-at-modifier":
queryOpts.EnableAtModifier = true
case "promql-negative-offset":
queryOpts.EnableNegativeOffset = true
case "":
continue
case "promql-at-modifier", "promql-negative-offset":
fmt.Printf(" WARNING: Option for --enable-feature is a no-op after promotion to a stable feature: %q\n", o)
default:
fmt.Printf(" WARNING: Unknown option for --enable-feature: %q\n", o)
}
@ -258,7 +255,13 @@ func main() {
os.Exit(QueryLabels(*queryLabelsServer, *queryLabelsName, *queryLabelsBegin, *queryLabelsEnd, p))
case testRulesCmd.FullCommand():
os.Exit(RulesUnitTest(queryOpts, *testRulesFiles...))
os.Exit(RulesUnitTest(
promql.LazyLoaderOpts{
EnableAtModifier: true,
EnableNegativeOffset: true,
},
*testRulesFiles...),
)
case tsdbBenchWriteCmd.FullCommand():
os.Exit(checkErr(benchmarkWrite(*benchWriteOutPath, *benchSamplesFile, *benchWriteNumMetrics, *benchWriteNumScrapes)))

31
docs/feature_flags.md
View file

@ -11,18 +11,6 @@ Their behaviour can change in future releases which will be communicated via the
You can enable them using the `--enable-feature` flag with a comma separated list of features.
They may be enabled by default in future versions.
## `@` Modifier in PromQL
`--enable-feature=promql-at-modifier`
The `@` modifier lets you specify the evaluation time for instant vector selectors,
range vector selectors, and subqueries. More details can be found [here](querying/basics.md#modifier).
This feature is considered stable, but since it breaks the invariant that
PromQL does not look ahead of the evaluation time, it still needs to be enabled
via this feature flag. The feature will be permanently enabled (and the feature
flag ignored) upon major release v3.
## Expand environment variables in external labels
`--enable-feature=expand-external-labels`
@ -31,25 +19,6 @@ Replace `${var}` or `$var` in the [`external_labels`](configuration/configuratio
values according to the values of the current environment variables. References
to undefined variables are replaced by the empty string.
## Negative offset in PromQL
This negative offset is disabled by default since it breaks the invariant
that PromQL does not look ahead of the evaluation time for samples.
`--enable-feature=promql-negative-offset`
In contrast to the positive offset modifier, the negative offset modifier lets
one shift a vector selector into the future. An example in which one may want
to use a negative offset is reviewing past data and making temporal comparisons
with more recent data.
More details can be found [here](querying/basics.md#offset-modifier).
This feature is considered stable, but since it breaks the invariant that
PromQL does not look ahead of the evaluation time, it still needs to be enabled
via this feature flag. The feature will be permanently enabled (and the feature
flag ignored) upon major release v3.
## Remote Write Receiver
`--enable-feature=remote-write-receiver`

10
docs/querying/basics.md
View file

@ -209,9 +209,7 @@ can be specified:
rate(http_requests_total[5m] offset -1w)
This feature is enabled by setting `--enable-feature=promql-negative-offset`
flag. See [feature flags](../feature_flags.md) for more details about
this flag.
Note that this allows a query to look ahead of its evaluation time.
### @ modifier
@ -249,10 +247,6 @@ These 2 queries will produce the same result.
# offset before @
http_requests_total offset 5m @ 1609746000
This modifier is disabled by default since it breaks the invariant that PromQL
does not look ahead of the evaluation time for samples. It can be enabled by setting
`--enable-feature=promql-at-modifier` flag. See [feature flags](../feature_flags.md) for more details about this flag.
Additionally, `start()` and `end()` can also be used as values for the `@` modifier as special values.
For a range query, they resolve to the start and end of the range query respectively and remain the same for all steps.
@ -262,6 +256,8 @@ For an instant query, `start()` and `end()` both resolve to the evaluation time.
http_requests_total @ start()
rate(http_requests_total[5m] @ end())
Note that the `@` modifier allows a query to look ahead of its evaluation time.
## Subquery
Subquery allows you to run an instant query for a given range and resolution. The result of a subquery is a range vector.

2
go.mod
View file

@ -64,7 +64,7 @@ require (
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e
golang.org/x/time v0.0.0-20211116232009-f0f3c7e86c11
golang.org/x/tools v0.1.8
golang.org/x/tools v0.1.9-0.20211209172050-90a85b2969be
google.golang.org/api v0.64.0
google.golang.org/genproto v0.0.0-20211223182754-3ac035c7e7cb
google.golang.org/protobuf v1.27.1

4
go.sum
View file

@ -1785,8 +1785,8 @@ golang.org/x/tools v0.1.3/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
golang.org/x/tools v0.1.4/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
golang.org/x/tools v0.1.5/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
golang.org/x/tools v0.1.6-0.20210726203631-07bc1bf47fb2/go.mod h1:o0xws9oXOQQZyjljx8fwUC0k7L1pTE6eaCbjGeHmOkk=
golang.org/x/tools v0.1.8 h1:P1HhGGuLW4aAclzjtmJdf0mJOjVUZUzOTqkAkWL+l6w=
golang.org/x/tools v0.1.8/go.mod h1:nABZi5QlRsZVlzPpHl034qft6wpY4eDcsTt5AaioBiU=
golang.org/x/tools v0.1.9-0.20211209172050-90a85b2969be h1:JRBiPXZpZ1FsceyPRRme0vX394zXC3xlhqu705k9nzM=
golang.org/x/tools v0.1.9-0.20211209172050-90a85b2969be/go.mod h1:nABZi5QlRsZVlzPpHl034qft6wpY4eDcsTt5AaioBiU=
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

11
promql/engine.go
View file

@ -222,10 +222,17 @@ type EngineOpts struct {
// a subquery in milliseconds if no step in range vector was specified `[30m:<step>]`.
NoStepSubqueryIntervalFn func(rangeMillis int64) int64
// EnableAtModifier if true enables @ modifier. Disabled otherwise.
// EnableAtModifier if true enables @ modifier. Disabled otherwise. This
// is supposed to be enabled for regular PromQL (as of Prometheus v2.33)
// but the option to disable it is still provided here for those using
// the Engine outside of Prometheus.
EnableAtModifier bool
// EnableNegativeOffset if true enables negative (-) offset values. Disabled otherwise.
// EnableNegativeOffset if true enables negative (-) offset
// values. Disabled otherwise. This is supposed to be enabled for
// regular PromQL (as of Prometheus v2.33) but the option to disable it
// is still provided here for those using the Engine outside of
// Prometheus.
EnableNegativeOffset bool
}

4
promql/test.go
View file

@ -680,7 +680,9 @@ type LazyLoader struct {
// LazyLoaderOpts are options for the lazy loader.
type LazyLoaderOpts struct {
// Disabled PromQL engine features.
// Both of these must be set to true for regular PromQL (as of
// Prometheus v2.33). They can still be disabled here for legacy and
// other uses.
EnableAtModifier, EnableNegativeOffset bool
}

10
web/api/v1/api.go
View file

@ -378,11 +378,6 @@ func (api *API) query(r *http.Request) (result apiFuncResult) {
}
qry, err := api.QueryEngine.NewInstantQuery(api.Queryable, r.FormValue("query"), ts)
if err == promql.ErrValidationAtModifierDisabled {
err = errors.New("@ modifier is disabled, use --enable-feature=promql-at-modifier to enable it")
} else if err == promql.ErrValidationNegativeOffsetDisabled {
err = errors.New("negative offset is disabled, use --enable-feature=promql-negative-offset to enable it")
}
if err != nil {
return invalidParamError(err, "query")
}
@ -458,11 +453,6 @@ func (api *API) queryRange(r *http.Request) (result apiFuncResult) {
}
qry, err := api.QueryEngine.NewRangeQuery(api.Queryable, r.FormValue("query"), start, end, step)
if err == promql.ErrValidationAtModifierDisabled {
err = errors.New("@ modifier is disabled, use --enable-feature=promql-at-modifier to enable it")
} else if err == promql.ErrValidationNegativeOffsetDisabled {
err = errors.New("negative offset is disabled, use --enable-feature=promql-negative-offset to enable it")
}
if err != nil {
return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
}