Usually the number of blocks returned per each time series during queries is around 4.
So it is a good idea to pre-allocate 4 block references per time series
in order to reduce the number of memory allocations.
Previously the -maxConcurrentInserts was limiting the number of established client connections,
which write data to VictoriaMetrics. Some of these connections could be idle.
Such connections do not consume big amounts of CPU and RAM, so there is a little sense in limiting
the number of such connections. So now the -maxConcurrentInserts command-line option
limits the number of concurrently executed insert requests, not including idle connections.
It is recommended removing -maxConcurrentInserts command-line option, since the default value
for this option should work good for most cases.
- Show in the line tooltip the number of the query which generates the given line.
This simplifies comparison of lines generated by multiple queries.
- Show metric name as __name__ label in the line tooltip in the same way as other labels are shown there.
This makes the label information in the tooltip more consistent.
- Properly quote label values with JSON.stringify(). This prevents from improper formatting
when label values contain doublequote chars.
- Remove double curly braces artifact at graph legend for lines without names and labels.
- Properly use modifier for regular expressions across the code.
There is no need to manually call `queryDuration.UpdateDuration(startTime)`, because `defer queryDuration.UpdateDuration(startTime)` is executed at the beginning of the function(L660).
This simplifies manual usage of the APIs. For example, the following query
would return the results over the 2022 year.
/api/v1/query_range?start=2022&end=2023&step=1d&query=...
This is equivalent to:
/api/v1/query_range?start=2022-01-01T00:00:00Z&end=2023-01-01T00:00:00Z&step=1d&query=...
- Document the feature at docs/CHANGELOG.md.
- Document the metrics explorer at https://docs.victoriametrics.com/#metrics-explorer .
- Properly set `start` and `end` args for the selected time range
when performing the request, which returns metric names.
- Improve queries, so they return lower number of lines and labels.
This should improve metrics' exploration.
- Properly encode label filters and query args before passing them to VictoriaMetrics.
- Various cosmetic fixes.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3386
Previously too short lookbehind window d for rate(m[d]) could be automatically extended
if it didn't cover at least two raw samples. This was needed in order to guarantee
non-empty results from rate(m[d]) on short time ranges.
Now the lookbehind window isn't extended if it is set explicitly,
since it is expected that the user knows what he is doing.
The lookbehind window continues to be extended when needed if it isn't set explicitly.
For example, in the case of rate(m).
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3483
support overriding of `-search.latencyOffset` value via
URL param `latency_offset`.
See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3481
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
This fixes handling of values bigger than 2GiB for the following command-line flags:
- -storage.minFreeDiskSpaceBytes
- -remoteWrite.maxDiskUsagePerURL
* feat: add maximum display series by tabs
* feat: add warning on PredefinedPanels.tsx
* docs/CHANGELOG.md: vmui limit number of plotted series
* docs/CHANGELOG.md: vmui limit number of plotted series
* wip
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* Optimize fast path for /api/v1/import when importing numeric values
* Move the docs about the change from features to bugfixes at docs/CHANGELOG.md
* Update tests at lib/protoparser/vmimport
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3161
* app/vmselect: properly work when export import json from `api/v1/{export, import}` API
* app/vmselect: update convert function
* app/vmselect: export null if `math.IsNaN(v)`
* app/vmselect: get float from json
* lib/protoparser: add test
* docs: add change log
* lib/protoparser: make export import api compatible
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
Previously empty series (e.g. series with all NaN samples) were passed to aggregate functions.
Such series must be ingored by all the aggregate functions.
So it is better from consistency PoV filtering out empty series before applying aggregate functions.
* app/vmselect: ignore empty series for `limit_offset`
VictoriaMetrics doesn't return empty series (with all NaN values) to
the user. But such series are filtered after transform functions.
It means `limit_offset` will account for empty series as well.
For example, let's consider following data set:
```
time series:
foo{label="1"} NaN, NaN, NaN, NaN // empty series
foo{label="2"} 1, 2, 3, 4
foo{label="3"} 4, 3, 2, 1
```
When user requests all series for metric `foo` the empty series
will be filtered out:
```
/query=foo:
foo{label="v2"} 1, 2, 3, 4
foo{label="v3"} 4, 3, 2, 1
```
But `limit_offset(1, 1, foo)` is applied to original series, not filtered yet.
So it will return `foo{label="v2"}` (skips the first in list)
```
/query=limit_offset(1, 1, foo):
foo{label="v2"} 1, 2, 3, 4
```
Expected result would be to apply `limit_offset` to already filtered list,
so in result we receive `foo{label="v3"}`:
```
/query=limit_offset(1, 1, foo):
foo{label="v3"} 4, 3, 2, 1
```
The change does exactly that - filters empty series before applying `limit_offset`.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmselect: ignore empty series for `limit_offset`
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The workaround was introduced to fix https://github.com/VictoriaMetrics/VictoriaMetrics/issues/962.
However, it didn't prove itself useful. Instead, it is recommended using `increase_pure` function.
Removing the workaround makes VM to produce accurate results when calculating
`delta` or `increase` functions over slow-changing counters with vary intervals
between data points.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmselect/promql: add alphanumeric sort by label (sort_by_label_numeric)
* vmselect/promql: fix tests, add documentation
* vmselect/promql: update test
* vmselect/promql: update for alphanumeric sorting, fix tests
* vmselect/promql: remove comments
* vmselect/promql: cleanup
* vmselect/promql: avoid memory allocations, update functions descriptions
* vmselect/promql: make linter happy (remove ineffectual assigment)
* vmselect/promql: add test case, fix behavior when strings are equal
* vendor: update github.com/VictoriaMetrics/metricsql from v0.44.1 to v0.45.0
this adds support for sort_by_label_numeric and sort_by_label_numeric_desc functions
* wip
* lib/promscrape: read response body into memory in stream parsing mode before parsing it
This reduces scrape duration for targets returning big responses.
The response body was already read into memory in stream parsing mode before this change,
so this commit shouldn't increase memory usage.
* wip
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
- Add getCommonParamsWithDefaultDuration function and use it at /api/v1/series, /api/v1/labels and /api/v1/label/.../values
- Document the default behaviour for setting 5 minutes time range if start arg isn't passed to /api/v1/series, /api/v1/labels and /api/v1/label/.../values
- Document the change at docs/CHANGELOG.md
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3052
Note that the parallel execution of `union()` args may take more memory and CPU time
than the sequential execution if args contain heavy queries, which may load all the available CPU,
disk and memory resources and vmselect and vmstorage levels.
- Use getScalar() function for obtaining the expected scalar from phi arg
- Reduce the error message returned to the user when incorrect phi is passed to histogram_quantiles
- Improve the description of this bugfix in the docs/CHANGELOG.md
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3026
The io/ioutil package is deprecated since Go1.16 - see https://tip.golang.org/doc/go1.16#ioutil
VictoriaMetrics requires at least Go1.18, so it is time to remove the io/ioutil from source code
This is a follow-up for 02ca2342ab
The ioutil.{Read|Write}File is deprecated since Go1.16 -
see https://tip.golang.org/doc/go1.16#ioutil
VictoriaMetrics needs at least Go1.18, so it is safe to remove ioutil usage
from source code.
This is a follow-up for 02ca2342ab
* Explicitly store a pointer to UserReadableError in the error interface.
Previously Go automatically converted the value to a pointer before storing in the error interface.
* Add Unwrap() method to UserReadableError, so it can be used transparently with the other code,
which calls errors.Is() and errors.As().
* Document the change in docs/CHANGELOG.md
When read query fails, VM returns rich error message with
all the details. While these details might be useful
for debugging specific cases, they're usually too verbose
for users.
Introducing a new error type `UserReadableError` is supposed
to allow to return to user only the most important parts
of the error trace. This supposed to improve error readability
in web interfaces such as VMUI or Grafana.
The full error trace is still logged with the full context
and can be found in vmselect logs.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Reduce inter-CPU communications when processing the query over big number of time series.
This should improve performance for queries over big number of time series
on systems with many CPU cores.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2896
Based on b596ac3745
Thanks to @zqyzyq for the idea.
The change allows to specify default value for `getScrapeInterval`
function when actual interval can't be calculated.
Before the change, function were returning `maxSilenceInterval` (5m)
in such cases, which may be not correct for instant queries processing.
The specific scenario where using `maxSilenceInterval` caused issues
is the following:
1. Series becomes stale;
2. Client (in this case vmalert) continues to request series every 15s;
3. Database returns empty results as expected;
4. But at some specific moment of time database returns datapoints from `now()-5m`,
because lookback window was extended to `maxSilenceInterval`.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmselect: cover special cases for vmalert's routing in single-node version
* remove trailing `/` from requests
* redirect to vmalert's home page when `/vmalert` is requested.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* vmalert: fix review comments
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* Update app/vmselect/main.go
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
- Use binary search instead of linear scan when locating the run of smallest timestamps
in blocks with intersected time ranges. This should improve performance
when merging blocks with big number of samples
- Skip samples with duplicate timestamps. This should increase query performance
in cluster version of VictoriaMetrics with the enabled replication.
- show dates in human-readable format, e.g. 2022-05-07, instead of a numeric value
- limit the maximum length of queries and filters shown in trace messages
Production experience shows that 100k is too big for /api/v1/series .
It leads to increased CPU usage when Grafana queries /api/v1/series over VictoriaMetrics
with big number of time series during auto-completion and when modifying template variables.
Previously SearchMetricNames was returning unmarshaled metric names.
This wasn't great for vmstorage, which should spend additional CPU time
for marshaling the metric names before sending them to vmselect.
While at it, remove possible duplicate metric names, which could occur when
multiple samples for new time series are ingested via concurrent requests.
Also sort the metric names before returning them to the client.
This simplifies debugging of the returned metric names across repeated requests to /api/v1/series
querytracer has been added to the following storage.Storage methods:
- RegisterMetricNames
- DeleteMetrics
- SearchTagValueSuffixes
- SearchGraphitePaths
* vmselect: limit `end` param max value by 2d in future
The change is applied only to service handlers like `/labels` or `/series`
and limits the `end` param by max value <= now() + 2 days. The same limit
is applied for the ingested data, so no reason to allow to request data
in future far than that.
The change is also needed for corner cases like https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2669
where too high `end` value triggers inefficient global index search.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* docs/CHANGELOG.md: document the bugfix
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
This allows filling the seriesCountByFocusLabelValue list in the /api/v1/status/tsdb response
with label values for the specified focusLabel, which contain the highest number of time series.
TODO: add this to Cardinality explorer at VMUI - https://docs.victoriametrics.com/#cardinality-explorer
* feat: make datepicker to be set to last 30 min by default
* fix: correct spinner while loading data
* feat: change legend style
* app/vmselect: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
- Remove unused js bloatware from /targets page. This strips down binary size by more than 100Kb
- Add /service-discovery page for API compatibility with Prometheus
- Properly load bootstrap.min.css from /prometheus/targets
- Serve static contents for /targets page from app/vminsert instead of app/vmselect, because /targets page is served from there
* app/vmselect: adds proxy for rules and alerts API
It allows to visualization for rules at grafana
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1739
* Update app/vmselect/main.go
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
* Export "null" in jsonl instead of NaN
The NaN appeared because of staleness markers that were added for compatibility. I think it's better to use json `null`, implemented here.
Also maybe it also makes sense to add a flag like `?skip-staleness-markers=true` to `/export`, to skip nulls at all?
* Update app/vmselect/prometheus/export.qtpl
* app/vmselect/prometheus/export.qtpl.go: `make quicktemplate-gen`
* docs/CHANGELOG.md: document the change
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* app/vmselect: adds API /api/v1/status/buildinfo
it should fix an compability error with grafana 8.5 prometheus datasource
https://github.com/grafana/grafana/pull/46771
* Update main.go
This should prevent from `duplicate time series` errors when executing the following query:
kube_pod_container_resource_requests{resource="cpu"} * on (namespace,pod) group_left() (kube_pod_status_phase{phase=~"Pending|Running"}==1)
where `kube_pod_status_phase{phase=~"Pending|Running"}==1` filters out diplicate time series
* Remove unneeded dependency on `numeral` package
* Properly parse numbers obtained from /api/v1/query_range according to
https://prometheus.io/docs/prometheus/latest/querying/api/#expression-query-result-formats
* Optimize updating processing the received data from /api/v1/query_range
* Make smoother zoom on `ctrl+scroll`
* Reduce the number of points received from /api/v1/query_range by 2x in order to reduce load on backend
* lib/promscrape: support prometheus-like duration in scrape configs
The change allows to specify duration values like `1d`, `1w`
for fields `scrape_interval`, `scrape_timeout`, etc.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/817#issuecomment-1033384766
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* lib/blockcache: make linter happy
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* lib/promscrape: support prometheus-like duration in scrape configs
* add support for extra fields `scrape_align_interval` and `scrape_offset`;
* support Prometheus duration parsing for `__scrape_interval__`
and `__scrape_duration__` labels;
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* wip
* wip
* docs/CHANGELOG.md: document the feature
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Previously bytesutil.Resize() was copying the original byte slice contents to a newly allocated slice.
This wasted CPU cycles and memory bandwidth in some places, where the original slice contents wasn't needed
after slize resizing. Switch such places to bytesutil.ResizeNoCopy().
Rename the original bytesutil.Resize() function to bytesutil.ResizeWithCopy() for the sake of improved readability.
Additionally, allocate new slice with `make()` instead of `append()`. This guarantees that the capacity of the allocated slice
exactly matches the requested size. The `append()` could return a slice with bigger capacity as an optimization for further `append()` calls.
This could result in excess memory usage when the returned byte slice was cached (for instance, in lib/blockcache).
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2007
* fix: add date validate for time range
* app/vmselect/vmui: `make vmui-update`
* docs/CHANGELOG.md: document the bugfix
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* feat: replace @codemirror to text field
* feat: switch to Preact from React
* fix: optimize mui imports
* fix: remove unused vars
* update package-lock.json
* app/vmselect/vmui: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* feat: add a reset query by clicking the logo
* feat: add sequence number for query fields
* feat: invert behavior on the graph's legend
* app/vmselect/vmui: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Grafana expects `data` in response to be a slice and logs an err
if it is not:
```
err="[]v1.ExemplarQueryResult: decode slice: expect [ or n, but found , error found in #0 byte of ...||..., bigger context ...||..."
```
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1999
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* fix: remove disabling custom step when zooming
* feat: add a dynamic calc of the width of the graph
* fix: add validate y-axis limits
* fix: correct axis limits for value 0
* fix: change logic create time series
* fix: change types for tooltip
* fix: correct points on the line
* fix: change the logic for set graph width
* fix: stop checking the period when auto-refresh is enabled
* app/vmselect/vmui: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* Document changes_prometheus(), increase_prometheus() and delta_prometheus() functions.
* Simplify their implementation
* Mention these functions in docs/CHANGELOG.md
* feat: add a label for the Query field
* fix: change zoom position
* fix: add description and error code to alerts
* fix: correct logic query history
* fix: correct update query history
* feat: add custom step
* update package-lock.json
* docs: document that VMUI now supports overriding of `step` query arg, which is passed to `/api/v1/query_range`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* feat: change duration by "enter"
* fix: optimize data processing for chart
* feat: set minimum step to 1ms
* update dependencies
* feat: remove save the last query to local storage
* fix: handle an error in a table with subqueries
* feat: store display type in URL
* Revert "feat: store display type in URL"
This reverts commit ccc242c69a.
* feat: store display type in URL
* refactor: move the time setting to a folder
* refactor: move the query configurator to a folder
* refactor: move the auth settings to a folder
* feat: improve styles
* feat: add multi query
* update package-lock
* feat: add display multiple queries
* feat: add limits for multiple queries
* update dependencies
* feat: add history for multiple queries
* feat: add line type to legend
* feat: change style for switch
* feat: change the logic for axes limits for multiple queries
* update package-lock.json
* update dependencies
* feat: add the filter to legend
* wip
* lib/httpserver: add missing 127.0.0.1 hostname to the logged address for http and pprof server if the address starts with ':'
This allows copy-pasting the url to http server from logs.
* lib/httpserver: add missing 127.0.0.1 hostname to the logged address for http and pprof server if the address starts with ':'
This allows copy-pasting the url to http server from logs.
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* feat: add query history
* fix: change detect keyUp for nav query history
* feat: set default query history
* feat: change graph legend
* update dependencies
* update codemirror version
* fix: correct update period time after zoom/pan
* fix: optimize data processing for the graph
* fix: eliminate memory leaks related to mouse events
* fix: correct display of straight line
* Merge branch 'master' into vmui-fix-reset-graph
* app/vmselect: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
* feat: add query history
* fix: change detect keyUp for nav query history
* feat: set default query history
* app/vmselect/vmui: `make vmui-update`
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
Sort series by a hash calculated from the series labels. This should guarantee "random" selection of the returned time series.
Previously the selection could be biased, since time series were sorted alphabetically by label names and label values.
The list of functions, which can adjust lookbehind window is more limited than the rest of functions,
so it is better from maintainability and readability PoV using the allowlist instead of blocklist.
It is expected that the `deriv(m[d])` returns non-empty value if the lookbehind window `d`
contains less than 2 samples in the same way as `rate()` does.
This is a follow-up after 3e084be06b .
Previously, `predict_linear` returned slightly different results comparing
to Prometheus. The change makes linear regression algorithm compatible
with Prometheus.
`deriv` was excluded from the list of functions which can adjust the time
window for the same reasons.
The fix makes the binary comparison func to check for NaNs
before executing the actual comparison. This prevents VM
to return values for non-existing samples for expressions
which contain bool comparisons. Please see added test
for example.
It appeared, that `testRowsEqual` NaN comparison was incorrect.
The fix caused some tests to fail. Please see the change and
tests updated.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Adjustment results into discrepancy between Prometheus and VM on time windows
smaller than scrape interval.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The fix will always return zero if received set of items consists of one
element only, which also means no deviation.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The change affects `count/stddev/stdvar_over_time` funcs and makes
them to return NaN instead of zero when there is no datapoints
in a time window.
This is needed for improving compatibility with Prometheus.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The removed fast path optimisations weren't consistent with
`quantile` function behavior and results into discrepancy.
Specifically, results didn't match in cases when:
* 0 < phi > 1;
* values contain only one element.
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmselect: `quantile` func compatiblity with Prometheus
The `quantile` func was previously calculated by https://github.com/valyala/histogram
package. The result of such calculation was always the closest real value to
requested quantile. While in Prometheus implementation interpolation is used.
Such difference may result into discrepancy in output between Prometheus and
VictoriaMetrics.
This commit adds a Prometheus-like `quantile` function. It also used by other
functions which depend on it, such as `quantiles`, `quantile_over_time`, `median` etc.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1625
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmselect: `quantile` review fixes
* quantile functions were split into multiple to provide
different API for already sorted data;
* float64sPool is used for reducing allocations. Items in pool may have
different sizes, but defining a new pool was complicates due to name collisions;
Signed-off-by: hagen1778 <roman@victoriametrics.com>
* app/vmselect: make sorting for query result similar to Prometheus
Updated sorting allows to get the order of series in result similar or equal
to what Prometheus returns.
The change is needed for compatibility reasons.
* Update app/vmselect/promql/exec_test.go
Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>
The commit contains the following changes:
- Show vmui when requesting /graph page in order to be compatible with Prometheus datasource in Grafana.
- Properly encode query args at vmui url.
- Set the number of points on the graph to the number of horizontal pixels divided by 2. Previously it was hardcoded to 30.
- Do not save server url to persistent storage at browser, since it should be always obtained from the url.
- Run `make vmui-update` for updating vmui embedded into VictoriaMetrics.
Before, metric `vm_request_duration_seconds` was update only on successful
attempts which could be misleading. For example, timeout errors on netstorage
request may be not accounted in the metric and won't be visible on dashboards.
Using `defer` statement to update the metric after query arguments validation
may improve the situation.
This option allows reducing CPU usage a bit when VictoriaMetrics is used
for collecting and processing non-Prometheus data. For example, InfluxDB line protocol, Graphite, OpenTSDB, CSV, etc.
This reverts commit 94dfcb6747a3b29a11d14e71bea21a2312bb6346.
It is better to remove staleness marks (decimal.StaleNaN) before calling rollupConfig.Do, e.g. in preFunc
Prometheus stalenss marks shouldn't be changed in removeCounterResets. Otherwise they will be converted to an ordinary NaN values,
which couldn't be removed in dropStaleNaNs() function later. This may result in incorrect calculations for rollup functions.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1526
* Rename -search.maxMetricsPointSearch to -search.maxSamplesPerQuery, so it is more consistent with the existing -search.maxSamplesPerSeries
* Move the -search.maxSamplesPerQuery from vmstorage to vmselect, so it could effectively limit the number of raw samples obtained from all the vmstorage nodes
* Document the -search.maxSamplesPerQuery in docs/CHANGELOG.md
