* vmalert: correctly re-instantinate HTTP req on retries
Previosly, request retry to datasource re-used existing HTTP request.
But if request object was already partially processed (body was read),
then retry will be unsuccessful.
The change re-instantinates HTTP request object before retry.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: review fix
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The deferred call's arguments are evaluated immediately, but the function call is not executed until the surrounding function returns.
Signed-off-by: Abirdcfly <fp544037857@gmail.com>
* rename `configErr` to `lastConfigErr` to reduce confusion
* add tests to verify metrics and msg are set properly
* fix mistake when config success metric wasn't restored after an error
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Value of `-dedup.minScrapeInterval` comand-line flag must be higher than `evaluation_interval` in order to make sure that only one sample on each evaluation will be left after deduplication.
Moreover, value of `-dedup.minScrapeInterval` must be a multiple of vmalert's `evaluation_interval` in order to make sure that samples will be aligned between deduplication window periods.
See: https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4774#issuecomment-1663940811
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Links of form `/api/v1/<groupID>/<alertID>/status` were deprecated
in favour of `/api/v1/alerts?group_id=<>&alert_id=<>` links in
v1.79.0. See more details here https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2825
This change removes code responsible for deprecated functionality.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* Revert "vmalert: unittest support stale datapoint (#4696)"
This reverts commit 0b44df7ec8.
* Revert "docs: specify min version and limitations for vmalert's unit tests"
This reverts commit a24541bd
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* Revert "vmalert: init unit test (#4596)"
This reverts commit da60a68d
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* docs: mention unittest revert in changelog
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The important change is to highlight that restore procedure happens
only once and only for already loaded rules. Config hot-reload
doesn't trigger the restore procedure.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmalert/datasource/graphite: allow overriding "from" parameter for datasource queries
Fixes construction of URL parameters for graphite render to allow overriding "from" parameter.
See: https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4685
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
* app/vmalert/datasource/graphite: update flow for building URL parameters
Makes flow of building URL parameters same as Prometheus datasource has:
1) Setting all default values
2) Merging those values with provided `extraParams`
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
* Update docs/CHANGELOG.md
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
---------
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
Add a break if gotAlert is nil
This removes the following golangci-lint warning:
app/vmalert/alerting_test.go:868:8: SA5011(related information): this check suggests that the pointer can be nil (staticcheck)
if gotAlert == nil {
^
It could happen for low evaluation intervals and irregular
delays during execution that evaluation time would get
a negative offset. This could result into cumulative
discrepancy between the actual time and evaluation time for rules.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* docs: make `httpAuth.*` flags description less ambiguous
Currently, it may confuse users whether `httpAuth.*` flags are used by HTTP client or server configuration(see https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4586 for example).
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
* docs: fix a typo
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
---------
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
vmalert: allow disabling of `step` param attached to instant queries
This might be useful for using vmalert with datasources that to not support this param,
unlike VictoriaMetrics.
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4573
Signed-off-by: hagen1778 <roman@victoriametrics.com>
By default, vmalert will make multiple retry attempts with exponential delay.
The total time spent during retry attempts shouldn't exceed `-remoteWrite.retryMaxTime` (default is 30s).
When retry time is exceeded vmalert drops the data dedicated for `-remoteWrite.url`.
Before, vmalert dropped data after 5 retry attempts with 1s delay between attempts (not configurable).
See `-remoteWrite.retryMinInterval` and `-remoteWrite.retryMaxTime` cmd-line flags.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Nikolay <nik@victoriametrics.com>
vmalert: retry all errors except 4XX status codes
Retry all errors except 4XX status codes while pushing via remote-write
to the remote storage. Previously, errors like broken connection could
prevent vmalert from retrying the request.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: fix nil map assignment
The storage instance with nil map params was created for remote-read purposes.
And before change 7a9ae9de0d this map was ignored in ApplyParams.
Now, it started to be used and vmalert panics in runtime.
The fix properly inits map for at `NewVMStorage` and verifies it is not nil
on assignment in `ApplyParams`.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: add to changelog
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: properly clone Storage params
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: properly clone Storage params
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: properly clone Storage params
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The fix addresses a case when vmalert is configured with a group
which has `name`, but doesn't have `rules` configured. In this
case it still returns a `nil` instead of `[]` slice.
Fixing this via current commit.
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4221
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Previously, metric `vmalert_alerting_rules_last_evaluation_series_fetched`
would be set to 0 for const expressions, because const expression do not match
any series. This may result into a confusion: no series were matched but response isn't empty.
The change updates the logic behind metric: if no series were matched but there are samples
in response - use amount of samples as number of series.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: expand rule groups on anchor click
before, anchor click was only updating the URL.
To expand the group, user had to click on rule's block.
Now, group will toggle automatically.
* vmalert: allow filtering group in web UI
The new filter allows to filter groups and rules within
groups by: errors only or noMatch only.
The filtering supposed to help navigating big numbers of groups/rules.
Filtering is reflected in URL, so can be shared as a link.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
app/vmalert: detect alerting rules which don't match any series at all
vmalert starts to understand /query responses which contain object:
```
"stats":{"seriesFetched": "42"}
```
If object is present, vmalert parses it and populates a new field
`SeriesFetched`. This field is then used to populate the new metric
`vmalert_alerting_rules_last_evaluation_series_fetched` and to
display warnings in the vmalert's UI.
If response doesn't contain the new object (Prometheus or
VictoriaMetrics earlier than v1.90), then `SeriesFetched=nil`.
In this case, UI will contain no additional warnings.
And `vmalert_alerting_rules_last_evaluation_series_fetched` will
be set to `-1`. Negative value of the metric will help to compile
correct alerting rule in follow-up.
Thanks for the initial implementation to @Haleygo
See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/4056
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4039
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Properly return empty slices instead of nil for `/api/v1/rules` and `/api/v1/alerts` API handlers.
This improves compatibility with Grafana.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4221
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Supports using `**` for `-rule` and `-rule.templates`: `dir/**/*.tpl` loads contents of dir and all subdirectories recursively.
See: #4041
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Co-authored-by: Artem Navoiev <tenmozes@gmail.com>
Co-authored-by: Nikolay <nik@victoriametrics.com>
Templating of `-external.alert.source` is not expected to have access to the query which was causing runtime error when query function was passed as nil.
See: #4181
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
* lib/httpserver: introduce `-http.maxConcurrentRequests` command-line flag
Introduce `-http.maxConcurrentRequests` command-line flag to protect
VM components from resource exhaustion during unexpected spikes of HTTP requests.
By default, the new flag's value is set to 0 which means no limits are applied.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* lib/httpserver: mention http.maxConcurrentRequests in docs
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: retry datasource requests with EOF or unexpected EOF errors
Retry failed read request on the closed connection one more time.
This may improve rules execution reliability when connection
between vmalert and datasource closes unexpectedly.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: fix old tests
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The change adds a new field `seriesFetched` to EvalConfig object.
Since EvalConfig object can be copied inside `Exec`,
`seriesFetched` is a pointer which can be updated by all copied
objects.
The reason for having stats is that other components, like vmalert,
could benefit from this information.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* vmalert: support logs suppressing during config reloads
The change is mostly required for ENT version of vmalert,
since it supports object-storage for config files.
Reading data from object storage could be time-consuming,
so vmalert emits logs to track the progress.
However, these logs are mostly needed on start or on
manual config reload. Printing these logs each time
`rule.configCheckInterval` is triggered would too verbose.
So the change allows to control logs emitting during
config reloads.
Now, logs are emitted during start up or when SIGHUP is receieved.
For periodicall config checks logs emitted by config pkg are suppressed.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: review fixes
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The change also introduces `List` method to `FS` interface.
The `List` method can be used for wildcard support in object storage FS.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Nikolay <nik@victoriametrics.com>
- Sync the description for -httpListenAddr.useProxyProtocol command-line flag at vmagent and vmauth,
so it is consistent with the description at vmauth and victoria-metrics
- Add a sample of panic text to docs/CHANGELOG.md, so it could be googled
- Mention the -httpListenAddr.useProxyProtocol command-line flag in the description for the bugfix
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3335
Each group in vmalert starts with an artifical delay to avoid
thundering herd problem. For some groups with high evaluation
intervals, the delay could be significant.
If during this delay user will remove the group from the config
and hot-reload it - vmalert will have to wait until the delay
ends. This results into slow config reloading and UI hang.
The change moves the start-delay logic back to the group's
`start` method. Now, group can immediately exit from the
delay when `group.close()` method is called.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
When group's update() or close() method is called, the group
still need to wait for its current evaluation to finish.
Sometimes, evaluation could take a significant amount of time
which slows configuration update or vmalert's graceful shutdown.
The change interrupts current evaluation in order to speed up
the graceful shutdown or config update procedures.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
- Document the change at docs/CHANGELOG.md
- Add `Reading rules from object storage` section to docs/vmalert.md
- Add `s3` prefix to command-line flags related to the configuration of s3 and gcs clients
- Explicitly mention that reading rules from object storage is supported only in enterprise version
* vmalert: support object storage for rules
Support loading of alerting and recording rules from object
storages `gcs://`, `gs://`, `s3://`.
* review fixes
* vmalert: use group's ID in UI to avoid collisions
Identical group names are allowed. So we should used IDs
for various groupings and aggregations in UI.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: prevent disabling state updates tracking
The minimum number of update states to track is now set to 1.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: properly update `debug` and `update_entries_limit` params on hot-reload
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: display `debug` field for rule in UI
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: exclude `updates` field from json marhsaling
This field isn't correctly marshaled right now.
And implementing the correct marshaling for it doesn't
seem right, since json representation is mostly used
by systems like Grafana. And Grafana doesn't expect this
field to be present.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* fix test for disabled state
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* fix test for disabled state
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: speed up state restore procedure on start
Alerts state restore procedure has been changed to become asynchronous.
It doesn't block groups start anymore which significantly improves vmalert's startup time.
Instead, state restore is called by each group in their goroutines after the first rules
evaluation.
While previously state restore attempt was made for all loaded alerting rules,
now it is called only for alerts which became active after the first evaluation.
This reduces the amount of API calls to the configured remote read URL.
This also means that `remoteRead.ignoreRestoreErrors` command-line flag becomes deprecated now
and will have no effect if configured.
See relevant issue https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2608
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* make lint happy
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* Apply suggestions from code review
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Stress the importance of specifying of all Alertmanager
URLs in vmalert's `-notifier.url` or `notifier.config`
if it runs in cluster mode.
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3547
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Allow configuring the default number of stored rule's update states in memory
via global `-rule.updateEntriesLimit` command-line flag or per-rule via rule's
`update_entries_limit` configuration param.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmbackupmanager: add metrics for better observability, include more information to `/api/v1/backups` API call response
* app/vmbackupmanager: drop old metrics before creating new ones
* app/vmbackupmanager: use `_total` postfix for counter metrics
* app/vmbackupmanager: remove `_total` postfix for gauge-like metrics
* app/vmbackupmanager: add `_last_run_failed` metrics for backups and retention
* app/vmbackupmanager: address review feedback
* app/vmbackupmanager: fix metric name
* app/vmbackupmanager: address review feedback, remove background updates of metrics, add restoring state of `_last_run_failed` metric from remote storage
* app/vmbackupmanager: improve performance for backup size calculation
* app/vmbackupmanager: refactor backup and retention runs to deduplicate each run logic
* {app/vmbackupmanager,lib/formatutil}: move HumanizeBytes into lib package
* app/vmbackupmanager: fix creating new metrics instead of reusing existing ones
* lit/formatutil: add comment to make linter happy
* app/vmbackupmanager: address review feedback
The system links are absolute, e.g. they start from `/`, so there are high chances
they won't work as expected when requested via proxy such as vmselect with -vmalert.proxyURL
command-line flag.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3424
http.Request was used as a part of state struct
for generating the curl command when viewing the rule's
state changes.
It appears, that holding a referencing is far more expensive
than generating the curl command immediately.
On the test with 40k rules, this change reduces memory
and CPU usage by 50%.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: correctly return error for RW failures
By mistake, in 0989649ad0 the error
for remote write failures weren't return to user.
This change fixes it.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Method `metrics()` now pre-allocates slices for labels
and results from query responses. This reduces the number
of allocations on the hot path for instant requests.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The recent change in modifying default value
of `datasource.queryStep` flag resulted in situation
where replay mode was always running queries with
step=`datasource.queryStep`. When it should always
use rule's evaluation interval.
The fix is related not to replay mode only, but
for all Range requests. Now step param is set
individually for each mode.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmalert: add `remoteWrite.sendTimeout` command-line flag to configure timeout for sending data to `remoteWrite.url`
* vmalert: remove WriteTimeout from clients Cfg
No need to have it as a part of configuration struct:
* the client isn't used by other packages;
* there are no internal tests to check the WriteTimeout.
* vmalert: remove DisablePathAppend from clients Cfg
No need to have it as a part of configuration struct:
* the client isn't used by other packages;
* there are no internal tests to check the DisablePathAppend.
Co-authored-by: hagen1778 <roman@victoriametrics.com>
- Return meta-labels for the discovered targets via promutils.Labels
instead of map[string]string. This improves the speed of generating
meta-labels for discovered targets by up to 5x.
- Remove memory allocations in hot paths during ScrapeWork generation.
The ScrapeWork contains scrape settings for a single discovered target.
This improves the service discovery speed by up to 2x.
* flag reference update
there is no flag `-datasource.disablePathAppend` and datasource actually checking for `-remoteRead.disablePathAppend`
* update source for doc as well
The default list of alerting rules contains the basic
rules for checking vmalert's health state and is recommended
to use for monitoring vmalert deployments.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Previously the `quotesEscape` function was escaping only double quotes.
This wasn't enough, since the input string could contain other special chars,
which must be escaped when put inside JSON string. For example, carriage return and line feed chars (\n\r),
backslash char, etc. This led to the following issues, which were improperly fixed:
- https://github.com/VictoriaMetrics/VictoriaMetrics/issues/890 - this issue
was "fixed" by introducing the `crlfEscape` function, which led to unnecessary
complications in user templates, while not fixing various corner cases
such as backslash chars in the input string.
See 1de15ad490
- https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3139 - this issue
was "fixed" by urlencoding the whole string passed to -external.alert.source
command-line flag. This led to invalid urls, which couldn't be parsed by Grafana.
See 00c838353d
and 4bd0244599
This commit properly encodes the input string passed to `quotesEscape`, so it can be safely embedded inside JSON strings.
This commit deprecates crlfEscape template function and adds the following new template functions:
- strvalue and stripDomain - these functions are supported by Prometheus, so they were added
for compatibility purposes.
- jsonEscape and htmlEscape for converting the input string to valid quoted JSON string
and for html-escaping the input string, so it could be safely embedded as a plaintext
into html.
This commit also documents all supported template functions at https://docs.victoriametrics.com/vmalert.html#template-functions
The deprecated crlfEscape function isn't documented on purpose, since its usefulness is negative in general case.
This reverts commit 00c838353d.
Reason for revert: it incorrectly fixes the issue https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3139 .
Now `-external.alert.source=explore?orgId=1&left=...` is converted to the following invalid url, which cannot be handled by Grafana:
https://grafana.example.com/explore%3ForgId%3D1%26left%3D...
The next commit will contain the correct fix of the issue - the `quotesEscape` function must
properly escape the string, so it could be embedded into JSON string. This function must
properly escape \n\r chars too. In this case the `crlfEscape` function becomes unnecessary.
Actually, the next commit makes the `crlfEscape` function deprecated.
The message about dropped data still remains at `error` level.
The change supposed to make log message more clear about how
serious it is.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The default value of `-datasource.queryStep` has changed, so we update
the troubleshooting docs accordingly.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Due to auto-refactoring, the filed `state` was automatically
renamed to `ruleState` when the entity with the same name
was renamed in other file. Reverting the change.
https://github.com/VictoriaMetrics/helm-charts/issues/391
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
vmalert: prevent duplicating label `alertname` for notifications
The issue has no impact on alerting procedure. But still needs to be fixed
for clarity.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3053
Signed-off-by: lihaowei <haoweili35@gmail.com>
Sort labels explicitly after calling the ParsedConfigs.Apply() when needed.
This reduces CPU usage when performing metric-level relabeling, where labels' sorting isn't needed.
* Use vm_account_id and vm_project_id labels to be consistent with https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html#multitenancy-via-labels
* Document the feature that vmalert now exposes vm_account_id and vm_project_id
labels if -clusterMode is set.
* Use literal strings instead of string constants for vm_account_id and vm_project_id.
This improves code readability.
The change is supposed to provide additional flexibility for generating alert's
source link based on label values.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Incorrect 301 redirects can be cached by user agents such as web browsers.
This can complicate recovery procedure after the incorrect redirect is fixed,
e.g. web browser cache must be reset.
The related issue - https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1752
Allow configuring authorization params per list of targets
in vmalert's notifier config for `static_configs`.
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2690
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
According to Ruler specification, only labels returned within time series
should be available for use in annotations.
For long time, vmalert didn't respect this rule. And in PR
https://github.com/VictoriaMetrics/VictoriaMetrics/pull/2403
this was fixed for the sake of compatibility. However, this resulted
into users confusion, as they expected all configured and extra labels
to be available - https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3013
This fix allows to use extra labels in Annotations. But in the case of conflicts
the original labels (extracted from time series) are preferred.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* lib/{httpserver,netutil}: allow to define min and max TLS version of the http server
* lib/httpserver: added descriptions about tls supported versions
* lib/netutil: check minimal tls version, added supported tls versions to error
* wip
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
- Clarify the description for -datasource.queryStep command-line flag
- Consistently use a single dash in front of -datasource.queryStep command-line flag
- Update -help output at docs/vmalert.md
- Consistently use single dash in front of command-line flags instead of double dashes.
- Add a warning that too small -search.latencyOffset may lead to incomplete query results.
