Send a node ID of vmstorage as a part of vmselect and vminsert handshakes.
Use vmstorage node ID as an identifier for consistent hashing at vminsert.
Cluster native endpoints calculate vminsert and vmselect node IDs as a hash of all underlying storage node IDs, so that it will also remain consistent in case of address changes.
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Generate random node ID on start if it is missing or load from disk. Save to storage on storage shutdown.
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
This reverts commit e280d90e9a.
Reason for revert: the updated code doesn't improve the performance of table.MustAddRows for the typical case
when rows contain timestamps belonging to ptws[0].
The performance may be improved in theory for the case when all the rows belong to partiton other than ptws[0],
but this partition is automatically moved to ptws[0] by the code at lines
6aad1d43e9/lib/storage/table.go (L287-L298) ,
so the next time the typical case will work.
Also the updated code makes the code harder to follow, since it introduces an additional level of indirection
with non-trivial semantics inside table.MustAddRows - the partition.TimeRangeInPartition() function.
This function needs to be inspected and understood when reading the code at table.MustAddRows().
This function depends on minTsInRows and maxTsInRows vars, which are defined and initialized
many lines above the partition.TimeRangeInPartition() call. This complicates reading and understanding
the code even more.
The previous code was using clearer loop over rows with the clear call to partition.HasTimestamp()
for every timestamp in the row. The partition.HasTimestamp() call is used in the table.MustAddRows()
function multiple times. This makes the use of partition.HasTimestamp() call more consistent,
easier to understand and easier to maintain comparing to the mix of partition.HasTimestamp() and partition.TimeRangeInPartition()
calls.
Aslo, there is no need in documenting some hardcore software engineering refactoring at docs/CHANGLELOG.md,
since the docs/CHANGELOG.md is intended for VictoriaMetrics users, who may not know software engineering.
The docs/CHANGELOG.md must document user-visible changes, and the docs must be concise and clear for VictoriaMetrics users.
See https://docs.victoriametrics.com/contributing/#pull-request-checklist for more details.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6629
### Describe Your Changes
The original logic is not only highly complex but also poorly readable,
so it can be modified to increase readability and reduce time
complexity.
---------
Co-authored-by: Zhu Jiekun <jiekun@victoriametrics.com>
- Mention that credentials can be configured via env variables at both vmbackup and vmrestore docs.
- Make clear that the AZURE_STORAGE_DOMAIN env var is optional at https://docs.victoriametrics.com/vmbackup/#providing-credentials-via-env-variables
- Use string literals as is for env variable names instead of indirecting them via string constants.
This makes easier to read and understand the code. These environment variable names aren't going to change
in the future, so there is no sense in hiding them under string constants with some other names.
- Refer to https://docs.victoriametrics.com/vmbackup/#providing-credentials-via-env-variables in error messages
when auth creds are improperly configured. This should simplify figuring out how to fix the error.
- Simplify the code a bit at FS.newClient(), so it is easier to follow it now.
While at it, remove the check when superflouos environment variables are set, since it is too fragile
and it looks like it doesn't help properly configuring vmbackup / vmrestore.
- Remove envLookuper indirection - just use 'func(name string) (string, bool)' type inline.
This simplifies code reading and understanding.
- Split TestFSInit() into TestFSInit_Failure() and TestFSInit_Success(). This simplifies the test code,
so it should be easier to maintain in the future.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6518
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5984
The %q formatter may result in incorrectly formatted JSON string if the original string
contains special chars such as \x1b . They must be encoded as \u001b , otherwise the resulting JSON string
cannot be parsed by JSON parsers.
This is a follow-up for c0caa69939
See https://github.com/VictoriaMetrics/victorialogs-datasource/issues/24
- Clarify the description of -graphite.sanitizeMetricName command-line flag at README.md
- Do not sanitize tag values - only metric names and tag names must be sanitized,
since they are treated specially by Grafana. Grafana doesn't apply any restrictions on tag values.
- Properly replace more than two consecutive dots with a single dot.
- Disallow unicode letters in metric names and tag names, since neither Prometheus nor Grafana
do not support them.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6489
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6077
`Storage.AddRows()` returns an error only in one case: when
`Storage.updatePerDateData()` fails to unmarshal a `metricNameRaw`. But
the same error is treated as a warning when it happens inside
`Storage.add()` or returned by `Storage.prefillNextIndexDB()`.
This commit fixes this inconsistency by treating the error returned by
`Storage.updatePerDateData()` as a warning as well. As a result
`Storage.add()` does not need a return value anymore and so doesn't
`Storage.AddRows()`.
Additionally, this commit adds a unit test that checks all cases that
result in a row not being added to the storage.
---------
Signed-off-by: Artem Fetishev <wwctrsrx@gmail.com>
Co-authored-by: Nikolay <nik@victoriametrics.com>
- Obtain IAM token via GCE-like API instead of Amazon EC2 IMDSv2 API,
since it looks like IMDBSv2 API isn't supported by Yandex Cloud
according to https://yandex.cloud/en/docs/security/standard/authentication#aws-token :
> So far, Yandex Cloud does not support version 2, so it is strongly recommended
> to technically disable getting a service account token via the Amazon EC2 metadata service.
- Try obtaining IAM token via GCE-like API at first and then fall back to the deprecated Amazon EC2 IMDBSv1.
This should prevent from auth errors for instances with disabled GCE-like auth API.
This addresses @ITD27M01 concern at https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5513#issuecomment-1867794884
- Make more clear the description of the change at docs/CHANGELOG.md , add reference to the related issue.
P.S. This change wasn't tested in prod because I have no access to Yandex Cloud.
It is recommended to test this change by @ITD27M01 and @vmazgo , who filed
the issue https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5513
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6524
- Rename GetStatDialFunc to NewStatDialFunc, since it returns new function with every call
- NewStatDialFunc isn't related to http in any way, so it must be moved from lib/httputils to lib/netutil
- Simplify the implementation of NewStatDialFunc by removing sync.Map from there.
- Use netutil.NewStatDialFunc at app/vmauth and lib/promscrape/discoveryutils
- Use gauge instead of counter type for *_conns metric
This is a follow-up for d7b5062917
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6299
- Move the remaining code responsible for stream aggregation initialization from remotewrite.go to streamaggr.go .
This improves code maintainability a bit.
- Properly shut down streamaggr.Aggregators initialized inside remotewrite.CheckStreamAggrConfigs().
This prevents from potential resource leaks.
- Use separate functions for initializing and reloading of global stream aggregation and per-remoteWrite.url stream aggregation.
This makes the code easier to read and maintain. This also fixes INFO and ERROR logs emitted by these functions.
- Add an ability to specify `name` option in every stream aggregation config. This option is used as `name` label
in metrics exposed by stream aggregation at /metrics page. This simplifies investigation of the exposed metrics.
- Add `path` label additionally to `name`, `url` and `position` labels at metrics exposed by streaming aggregation.
This label should simplify investigation of the exposed metrics.
- Remove `match` and `group` labels from metrics exposed by streaming aggregation, since they have little practical applicability:
it is hard to use these labels in query filters and aggregation functions.
- Rename the metric `vm_streamaggr_flushed_samples_total` to less misleading `vm_streamaggr_output_samples_total` .
This metric shows the number of samples generated by the corresponding streaming aggregation rule.
This metric has been added in the commit 861852f262 .
See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6462
- Remove the metric `vm_streamaggr_stale_samples_total`, since it is unclear how it can be used in practice.
This metric has been added in the commit 861852f262 .
See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6462
- Remove Alias and aggrID fields from streamaggr.Options struct, since these fields aren't related to optional params,
which could modify the behaviour of the constructed streaming aggregator.
Convert the Alias field to regular argument passed to LoadFromFile() function, since this argument is mandatory.
- Pass Options arg to LoadFromFile() function by reference, since this structure is quite big.
This also allows passing nil instead of Options when default options are enough.
- Add `name`, `path`, `url` and `position` labels to `vm_streamaggr_dedup_state_size_bytes` and `vm_streamaggr_dedup_state_items_count` metrics,
so they have consistent set of labels comparing to the rest of streaming aggregation metrics.
- Convert aggregator.aggrStates field type from `map[string]aggrState` to `[]aggrOutput`, where `aggrOutput` contains the corresponding
`aggrState` plus all the related metrics (currently only `vm_streamaggr_output_samples_total` metric is exposed with the corresponding
`output` label per each configured output function). This simplifies and speeds up the code responsible for updating per-output
metrics. This is a follow-up for the commit 2eb1bc4f81 .
See https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6604
- Added missing urls to docs ( https://docs.victoriametrics.com/stream-aggregation/ ) in error messages. These urls help users
figuring out why VictoriaMetrics or vmagent generates the corresponding error messages. The urls were removed for unknown reason
in the commit 2eb1bc4f81 .
- Fix incorrect update for `vm_streamaggr_output_samples_total` metric in flushCtx.appendSeriesWithExtraLabel() function.
While at it, reduce memory usage by limiting the maximum number of samples per flush to 10K.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5467
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6268
Pending rows and items unconditionally remain in memory for up to pending{Items,Rows}FlushInterval,
so there is no any sense in setting dataFlushInterval (the interval for guaranteed flush of in-memory data to disk)
to values smaller than pending{Items,Rows}FlushInterval, since this doesn't affect the interval
for flushing pending rows and items from memory to disk.
This is a follow-up for 4c80b17027
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6221
- Consistently enumerate stream aggregation outputs in alphabetical order across the source code and docs.
This should simplify future maintenance of the corresponding code and docs.
- Fix the link to `rate_sum()` at `see also` section of `rate_avg()` docs.
- Make more clear the docs for `rate_sum()` and `rate_avg()` outputs.
- Encapsulate output metric suffix inside rateAggrState. This eliminates possible bugs related
to incorrect suffix passing to newRateAggrState().
- Rename rateAggrState.total field to less misleading rateAggrState.increase name, since it calculates
counter increase in the current aggregation window.
- Set rateLastValueState.prevTimestamp on the first sample in time series instead of the second sample.
This makes more clear the code logic.
- Move the code for removing outdated entries at rateAggrState into removeOldEntries() function.
This make the code logic inside rateAggrState.flushState() more clear.
- Do not write output sample with zero value if there are no input series, which could be used
for calculating the rate, e.g. if only a single sample is registered for every input series.
- Do not take into account input series with a single registered sample when calculating rate_avg(),
since this leads to incorrect results.
- Move {rate,total}AggrState.flushState() function to the end of rate.go and total.go files, so they look more similar.
This shuld simplify future mantenance.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6243
- Drop samples and return true from remotewrite.TryPush() at fast path when all the remote storage
systems are configured with the disabled on-disk queue, every in-memory queue is full
and -remoteWrite.dropSamplesOnOverload is set to true. This case is quite common,
so it should be optimized. Previously additional CPU time was spent on per-remoteWriteCtx
relabeling and other processing in this case.
- Properly count the number of dropped samples inside remoteWriteCtx.pushInternalTrackDropped().
Previously dropped samples were counted only if -remoteWrite.dropSamplesOnOverload flag is set.
In reality, the samples are dropped when they couldn't be sent to the queue because in-memory queue is full
and on-disk queue is disabled.
The remoteWriteCtx.pushInternalTrackDropped() function is called by streaming aggregation for pushing
the aggregated data to the remote storage. Streaming aggregation cannot wait until the remote storage
processes pending data, so it drops aggregated samples in this case.
- Clarify the description for -remoteWrite.disableOnDiskQueue command-line flag at -help output,
so it is clear that this flag can be set individually per each -remoteWrite.url.
- Make the -remoteWrite.dropSamplesOnOverload flag global. If some of the remote storage systems
are configured with the disabled on-disk queue, then there is no sense in keeping samples
on some of these systems, while dropping samples on the remaining systems, since this
will result in global stall on the remote storage system with the disabled on-disk queue
and with the -remoteWrite.dropSamplesOnOverload=false flag. vmagent will always return false
from remotewrite.TryPush() in this case. This will result in infinite duplicate samples
written to the remaining remote storage systems. That's why the -remoteWrite.dropSamplesOnOverload
is forcibly set to true if more than one -remoteWrite.disableOnDiskQueue flag is set.
This allows proceeding with newly scraped / pushed samples by sending them to the remaining
remote storage systems, while dropping them on overloaded systems with the -remoteWrite.disableOnDiskQueue flag set.
- Verify that the remoteWriteCtx.TryPush() returns true in the TestRemoteWriteContext_TryPush_ImmutableTimeseries test.
- Mention in vmagent docs that the -remoteWrite.disableOnDiskQueue command-line flag can be set individually per each -remoteWrite.url.
See https://docs.victoriametrics.com/vmagent/#disabling-on-disk-persistence
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6248
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6065
This makes test code more clear and reduces the number of code lines by 500.
This also simplifies debugging tests. See https://itnext.io/f-tests-as-a-replacement-for-table-driven-tests-in-go-8814a8b19e9e
While at it, consistently use t.Fatal* instead of t.Error* across tests, since t.Error*
requires more boilerplate code, which can result in additional bugs inside tests.
While t.Error* allows writing logging errors for the same, this doesn't simplify fixing
broken tests most of the time.
This is a follow-up for a9525da8a4
We use `vm_streamaggr_flushed_samples_total` to show the number of
produced samples by aggregation rule, previously it was overcounted, and
doesn't account for `output_relabel_configs`.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6462
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit 2eb1bc4f81)
### Describe Your Changes
These changes support using Azure Managed Identity for the `vmbackup`
utility. It adds two new environment variables:
* `AZURE_USE_DEFAULT_CREDENTIAL`: Instructs the `vmbackup` utility to
build a connection using the [Azure Default
Credential](https://pkg.go.dev/github.com/Azure/azure-sdk-for-go/sdk/azidentity@v1.5.2#NewDefaultAzureCredential)
mode. This causes the Azure SDK to check for a variety of environment
variables to try and make a connection. By default, it tries to use
managed identity if that is set up.
This will close
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5984
### Checklist
The following checks are **mandatory**:
- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).
### Testing
However you normally test the `vmbackup` utility using Azure Blob should
continue to work without any changes. The set up for that is environment
specific and not listed out here.
Once regression testing has been done you can set up [Azure Managed
Identity](https://learn.microsoft.com/en-us/entra/identity/managed-identities-azure-resources/overview)
so your resource (AKS, VM, etc), can use that credential method. Once it
is set up, update your environment variables according to the updated
documentation.
I added unit tests to the `FS.Init` function, then made my changes, then
updated the unit tests to capture the new branches.
I tested this in our environment, but with SAS token auth and managed
identity and it works as expected.
---------
Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Co-authored-by: Justin Rush <jarush@epic.com>
Co-authored-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit 5fd3aef549)
'any' type is supported starting from Go1.18. Let's consistently use it
instead of 'interface{}' type across the code base, since `any` is easier to read than 'interface{}'.
This makes easier to read and debug these tests. This also reduces test lines count by 15% from 3K to 2.5K .
See https://itnext.io/f-tests-as-a-replacement-for-table-driven-tests-in-go-8814a8b19e9e .
While at it, consistently use t.Fatal* instead of t.Error*, since t.Error* usually leads
to more complicated and fragile tests, while it doesn't bring any practical benefits over t.Fatal*.
Reason for revert:
There are many statsd servers exist:
- https://github.com/statsd/statsd - classical statsd server
- https://docs.datadoghq.com/developers/dogstatsd/ - statsd server from DataDog built into DatDog Agent ( https://docs.datadoghq.com/agent/ )
- https://github.com/avito-tech/bioyino - high-performance statsd server
- https://github.com/atlassian/gostatsd - statsd server in Go
- https://github.com/prometheus/statsd_exporter - statsd server, which exposes the aggregated data as Prometheus metrics
These servers can be used for efficient aggregating of statsd data and sending it to VictoriaMetrics
according to https://docs.victoriametrics.com/#how-to-send-data-from-graphite-compatible-agents-such-as-statsd (
the https://github.com/prometheus/statsd_exporter can be scraped as usual Prometheus target
according to https://docs.victoriametrics.com/#how-to-scrape-prometheus-exporters-such-as-node-exporter ).
Adding support for statsd data ingestion protocol into VictoriaMetrics makes sense only if it provides
significant advantages over the existing statsd servers, while has no significant drawbacks comparing
to existing statsd servers.
The main advantage of statsd server built into VictoriaMetrics and vmagent - getting rid of additional statsd server.
The main drawback is non-trivial and inconvenient streaming aggregation configs, which must be used for the ingested statsd metrics (
see https://docs.victoriametrics.com/stream-aggregation/ ). These configs are incompatible with the configs for standalone statsd servers.
So you need to manually translate configs of the used statsd server to stream aggregation configs when migrating
from standalone statsd server to statsd server built into VictoriaMetrics (or vmagent).
Another important drawback is that it is very easy to shoot yourself in the foot when using built-in statsd server
with the -statsd.disableAggregationEnforcement command-line flag or with improperly configured streaming aggregation.
In this case the ingested statsd metrics will be stored to VictoriaMetrics as is without any aggregation.
This may result in high CPU usage during data ingestion, high disk space usage for storing all the unaggregated
statsd metrics and high CPU usage during querying, since all the unaggregated metrics must be read, unpacked and processed
during querying.
P.S. Built-in statsd server can be added to VictoriaMetrics and vmagent after figuring out more ergonomic
specialized configuration for aggregating of statsd metrics. The main requirements for this configuration:
- easy to write, read and update (ideally it should work out of the box for most cases without additional configuration)
- hard to misconfigure (e.g. hard to shoot yourself in the foot)
It would be great if this configuration will be compatible with the configuration of the most widely used statsd server.
In the mean time it is recommended continue using external statsd server.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6265
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5053
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5052
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/206
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4600
This reverts commit 5a3abfa041.
Reason for revert: exemplars aren't in wide use because they have numerous issues which prevent their adoption (see below).
Adding support for examplars into VictoriaMetrics introduces non-trivial code changes. These code changes need to be supported forever
once the release of VictoriaMetrics with exemplar support is published. That's why I don't think this is a good feature despite
that the source code of the reverted commit has an excellent quality. See https://docs.victoriametrics.com/goals/ .
Issues with Prometheus exemplars:
- Prometheus still has only experimental support for exemplars after more than three years since they were introduced.
It stores exemplars in memory, so they are lost after Prometheus restart. This doesn't look like production-ready feature.
See 0a2f3b3794/content/docs/instrumenting/exposition_formats.md (L153-L159)
and https://prometheus.io/docs/prometheus/latest/feature_flags/#exemplars-storage
- It is very non-trivial to expose exemplars alongside metrics in your application, since the official Prometheus SDKs
for metrics' exposition ( https://prometheus.io/docs/instrumenting/clientlibs/ ) either have very hard-to-use API
for exposing histograms or do not have this API at all. For example, try figuring out how to expose exemplars
via https://pkg.go.dev/github.com/prometheus/client_golang@v1.19.1/prometheus .
- It looks like exemplars are supported for Histogram metric types only -
see https://pkg.go.dev/github.com/prometheus/client_golang@v1.19.1/prometheus#Timer.ObserveDurationWithExemplar .
Exemplars aren't supported for Counter, Gauge and Summary metric types.
- Grafana has very poor support for Prometheus exemplars. It looks like it supports exemplars only when the query
contains histogram_quantile() function. It queries exemplars via special Prometheus API -
https://prometheus.io/docs/prometheus/latest/querying/api/#querying-exemplars - (which is still marked as experimental, btw.)
and then displays all the returned exemplars on the graph as special dots. The issue is that this doesn't work
in production in most cases when the histogram_quantile() is calculated over thousands of histogram buckets
exposed by big number of application instances. Every histogram bucket may expose an exemplar on every timestamp shown on the graph.
This makes the graph unusable, since it is litterally filled with thousands of exemplar dots.
Neither Prometheus API nor Grafana doesn't provide the ability to filter out unneeded exemplars.
- Exemplars are usually connected to traces. While traces are good for some
I doubt exemplars will become production-ready in the near future because of the issues outlined above.
Alternative to exemplars:
Exemplars are marketed as a silver bullet for the correlation between metrics, traces and logs -
just click the exemplar dot on some graph in Grafana and instantly see the corresponding trace or log entry!
This doesn't work as expected in production as shown above. Are there better solutions, which work in production?
Yes - just use time-based and label-based correlation between metrics, traces and logs. Assign the same `job`
and `instance` labels to metrics, logs and traces, so you can quickly find the needed trace or log entry
by these labes on the time range with the anomaly on metrics' graph.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5982
- Export streamaggr.LoadFromData() function, so it could be used in tests outside the lib/streamaggr package.
This allows removing a hack with creation of temporary files at TestRemoteWriteContext_TryPush_ImmutableTimeseries.
- Move common code for mustParsePromMetrics() function into lib/prompbmarshal package,
so it could be used in tests for building []prompbmarshal.TimeSeries from string.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6205
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6206
- Clarify docs for `Ignore aggregation intervals on start` feature.
- Make more clear the code dealing with ignoreFirstIntervals at aggregator.runFlusher() functions.
It is better from readability and maintainability PoV using distinct a.flush() calls
for distinct cases instead of merging them into a single a.flush() call.
- Take into account the first incomplete interval when tracking the number of skipped aggregation intervals,
since this behaviour is easier to understand by the end users.
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6137
### Describe Your Changes
- added stale metrics counters for input and output samples
- added labels for aggregator metrics =>
`name="{rwctx}:{aggrId}:{aggrSuffix}"`
- rwctx - global or number starting from 1
- aggrid - aggregator id starting from 1
- aggrSuffix - <interval>_(by|without)_label1_label2_labeln
e.g: `name="global:1:1m_without_instance_pod"`
### Checklist
The following checks are **mandatory**:
- [ ] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).
---------
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit 861852f262)
Signed-off-by: hagen1778 <roman@victoriametrics.com>
The set of log fields in the found logs may differ from the set of log fields present in the log stream.
So compare only the log fields in the found logs when searching for the matching log entry in the log stream.
While at it, return _stream field in the delimiter log entry, since this field is used by VictoriaLogs Web UI
for grouping logs by log streams.
