VictoriaMetrics/docs/VictoriaLogs/querying/README.md at a7e1575ebea17ab64015d293c4b8388b5235b354

mirror of https://github.com/VictoriaMetrics/VictoriaMetrics.git synced 2024-12-01 14:47:38 +00:00

Aliaksandr Valialkin 2818ce29f8

app/vlselect/logsql: add an ability to delay returning matching logs from live tailing via offset query arg

By default the delay equals to 1 second.

While at it, document refresh_interval query arg at /select/logsql/tail endpoint.

Thanks to @Fusl for the idea and the initial implementation at https://github.com/VictoriaMetrics/VictoriaMetrics/pull/7428

(cherry picked from commit a44787372f)

2024-11-08 17:07:57 +01:00

45 KiB

Raw Blame History

VictoriaLogs can be queried with LogsQL via the following ways:

vlogscli
Command-line interface
HTTP API
Web UI - a web-based UI for querying logs
Grafana plugin

HTTP API

VictoriaLogs provides the following HTTP endpoints:

/select/logsql/query for querying logs.
/select/logsql/tail for live tailing of query results.
/select/logsql/hits for querying log hits stats over the given time range.
/select/logsql/stats_query for querying log stats at the given time.
/select/logsql/stats_query_range for querying log stats over the given time range.
/select/logsql/stream_ids for querying _stream_id values of log streams.
/select/logsql/streams for querying log streams.
/select/logsql/stream_field_names for querying log stream field names.
/select/logsql/stream_field_values for querying log stream field values.
/select/logsql/field_names for querying log field names.
/select/logsql/field_values for querying log field values.

Querying logs

Logs stored in VictoriaLogs can be queried at the /select/logsql/query HTTP endpoint. The LogsQL query must be passed via query argument. For example, the following query returns all the log entries with the error word:

curl http://localhost:9428/select/logsql/query -d 'query=error'

The response by default contains all the fields for the selected logs. Use fields pipe for selecting only the needed fields.

The query argument can be passed either in the request url itself (aka HTTP GET request) or via request body with the x-www-form-urlencoded encoding (aka HTTP POST request). The HTTP POST is useful for sending long queries when they do not fit the maximum url length of the used clients and proxies.

See LogsQL docs for details on what can be passed to the query arg. The query arg must be properly encoded with percent encoding when passing it to curl or similar tools.

By default the /select/logsql/query returns all the log entries matching the given query. The response size can be limited in the following ways:

By closing the response stream at any time. VictoriaLogs stops query execution and frees all the resources occupied by the request as soon as it detects closed client connection. So it is safe running * query, which selects all the logs, even if trillions of logs are stored in VictoriaLogs.
By specifying the maximum number of log entries, which can be returned in the response via limit query arg. For example, the following command returns up to 10 most recently added log entries with the error word in the _msg field:
```
curl http://localhost:9428/select/logsql/query -d 'query=error' -d 'limit=10'
```
By adding limit pipe to the query. For example, the following command returns up to 10 random log entries with the error word in the _msg field:
```
curl http://localhost:9428/select/logsql/query -d 'query=error | limit 10'
```
By adding _time filter. The time range for the query can be specified via optional start and end query args formatted according to these docs.
By adding more specific filters to the query, which select lower number of logs.

The /select/logsql/query endpoint returns a stream of JSON lines, where each line contains JSON-encoded log entry in the form {field1="value1",...,fieldN="valueN"}. Example response:

{"_msg":"error: disconnect from 19.54.37.22: Auth fail [preauth]","_stream":"{}","_time":"2023-01-01T13:32:13Z"}
{"_msg":"some other error","_stream":"{}","_time":"2023-01-01T13:32:15Z"}

Logs lines are sent to the response stream as soon as they are found in VictoriaLogs storage. This means that the returned response may contain billions of lines for queries matching too many log entries. The response can be interrupted at any time by closing the connection to VictoriaLogs server. This allows post-processing the returned lines at the client side with the usual Unix commands such as grep, jq, less, head, etc., without worrying about resource usage at VictoriaLogs side. See these docs for more details.

The returned lines aren't sorted by default, since sorting disables the ability to send matching log entries to response stream as soon as they are found. Query results can be sorted in the following ways:

By passing limit=N query arg to /select/logsql/query. The up to N most recent matching log entries are returned in the response.
By adding sort pipe to the query.
By using Unix sort command at client side according to these docs.

The maximum query execution time is limited by -search.maxQueryDuration command-line flag value. This limit can be overridden to smaller values on a per-query basis by passing the needed timeout via timeout query arg. For example, the following command limits query execution time to 4.2 seconds:

curl http://localhost:9428/select/logsql/query -d 'query=error' -d 'timeout=4.2s'

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query searches for log messages at (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/query -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=error'

The number of requests to /select/logsql/query can be monitored with vl_http_requests_total{path="/select/logsql/query"} metric.

See also:

vlogscli
Extra filters
Live tailing
Querying hits stats
Querying log stats
Querying log range stats
Querying streams
Querying stream field names
Querying stream field values
Querying field names
Querying field values

Live tailing

VictoriaLogs provides /select/logsql/tail?query=<query> HTTP endpoint, which returns live tailing results for the given <query>, e.g. it works in the way similar to tail -f unix command. For example, the following command returns live tailing logs with the error word:

curl -N http://localhost:9428/select/logsql/tail -d 'query=error'

The -N command-line flag is essential to pass to curl during live tailing, since otherwise curl may delay displaying matching logs because of internal response buffering. It is recommended using vlogscli for live tailing - see these docs.

The <query> must conform the following rules:

It cannot contain the following pipes:
- pipes, which calculate stats over the logs - stats, uniq, top
- pipes, which change the order of logs - sort
- pipes, which limit or ignore some logs - limit, offset.
It must select _time field.
It is recommended to return _stream_id field for more accurate live tailing across multiple streams.

Live tailing supports returning historical logs, which were ingested into VictoriaLogs before the start of live tailing. Pass start_offset=<d> query arg to /select/logsql/tail where <d> is the duration for returning historical logs. For example, the following command returns historical logs which were ingested into VictoriaLogs during the last hour, before starting live tailing:

curl -N http://localhost:9428/select/logsql/tail -d 'query=*' -d 'start_offset=1h'

Live tailing delays delivering new logs for one second, so they could be properly delivered from log collectors to VictoriaLogs. This delay can be changed via offset query arg. For example, the following command delays delivering new logs for 30 seconds:

curl -N http://localhost:9428/select/logsql/tail -d 'query=*' -d 'offset=30s'

Live tailing checks for new logs every second. The frequency for the check can be changed via refresh_interval query arg. For example, the following command instructs live tailing to check for new logs every 10 seconds:

curl -N http://localhost:9428/select/logsql/tail -d 'query=*' -d 'refresh_interval=10s'

It isn't recommended setting too low value for refresh_interval query arg, since this may increase load on VictoriaLogs without measurable benefits.

Performance tip: live tailing works the best if it matches newly ingested logs at relatively slow rate (e.g. up to 1K matching logs per second), e.g. it is optimized for the case when real humans inspect the output of live tailing in the real time. If live tailing returns logs at too high rate, then it is recommended adding more specific filters to the <query>, so it matches less logs.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query performs live tailing for (AccountID=12, ProjectID=34) tenant:

curl -N http://localhost:9428/select/logsql/tail -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=error'

The number of currently executed live tailing requests to /select/logsql/tail can be monitored with vl_live_tailing_requests metric.

See also:

Live tailing in vlogscli
Extra filters
Querying logs
Querying streams

Querying hits stats

VictoriaLogs provides /select/logsql/hits?query=<query>&start=<start>&end=<end>&step=<step> HTTP endpoint, which returns the number of matching log entries for the given <query> on the given [<start> ... <end>] time range grouped by <step> buckets. The returned results are sorted by time.

The <start> and <end> args can contain values in any supported format. If <start> is missing, then it equals to the minimum timestamp across logs stored in VictoriaLogs. If <end> is missing, then it equals to the maximum timestamp across logs stored in VictoriaLogs.

The <step> arg can contain values in the format specified here. If <step> is missing, then it equals to 1d (one day).

For example, the following command returns per-hour number of log messages with the error word over logs for the last 3 hours:

curl http://localhost:9428/select/logsql/hits -d 'query=error' -d 'start=3h' -d 'step=1h'

Below is an example JSON output returned from this endpoint:

{
  "hits": [
    {
      "fields": {},
      "timestamps": [
        "2024-01-01T00:00:00Z",
        "2024-01-01T01:00:00Z",
        "2024-01-01T02:00:00Z"
      ],
      "values": [
        410339,
        450311,
        899506
      ],
      "total": 1760176
    }
  ]
}

Additionally, the offset=<offset> arg can be passed to /select/logsql/hits in order to group buckets according to the given timezone offset. The <offset> can contain values in the format specified here. For example, the following command returns per-day number of logs with error word over the last week in New York time zone (-4h):

curl http://localhost:9428/select/logsql/hits -d 'query=error' -d 'start=1w' -d 'step=1d' -d 'offset=-4h'

Additionally, any number of field=<field_name> args can be passed to /select/logsql/hits for grouping hits buckets by the mentioned <field_name> fields. For example, the following query groups hits by level field additionally to the provided step:

curl http://localhost:9428/select/logsql/hits -d 'query=*' -d 'start=3h' -d 'step=1h' -d 'field=level'

The grouped fields are put inside "fields" object:

{
  "hits": [
    {
      "fields": {
        "level": "error"
      },
      "timestamps": [
        "2024-01-01T00:00:00Z",
        "2024-01-01T01:00:00Z",
        "2024-01-01T02:00:00Z"
      ],
      "values": [
        25,
        20,
        15
      ],
      "total": 60
    },
    {
      "fields": {
        "level": "info"
      },
      "timestamps": [
        "2024-01-01T00:00:00Z",
        "2024-01-01T01:00:00Z",
        "2024-01-01T02:00:00Z"
      ],
      "values": [
        25625,
        35043,
        25230
      ],
      "total": 85898
    }
  ]
}

Optional fields_limit=N query arg can be passed to /select/logsql/hits for limiting the number of unique "fields" groups to return to N. If more than N unique "fields" groups is found, then top N "fields" groups with the maximum number of "total" hits are returned. The remaining hits are returned in "fields": {} group.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns hits stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/hits -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=error'

See also:

Extra filters
Querying logs
Querying log stats
Querying log range stats
Querying streams
HTTP API

Querying log stats

VictoriaLogs provides /select/logsql/stats_query?query=<query>&time=<t> HTTP endpoint, which returns log stats for the given query at the given timestamp t in the format compatible with Prometheus querying API.

The <query> must contain stats pipe. The calculated stats is converted into metrics with labels from by(...) clause of the | stats by(...) pipe.

The <t> arg can contain values in any supported format. If <t> is missing, then it equals to the current time.

For example, the following command returns the number of logs per each level field across logs over 2024-01-01 day by UTC:

curl http://localhost:9428/select/logsql/stats_query -d 'query=_time:1d | stats by (level) count(*)' -d 'time=2024-01-02Z'

Below is an example JSON output returned from this endpoint:

{
  "status": "success",
  "data": {
    "resultType": "vector",
    "result": [
      {
        "metric": {
          "__name__": "count(*)",
          "level": "info"
        },
        "value": [
          1704153600,
          "20395342"
        ]
      },
      {
        "metric": {
          "__name__": "count(*)",
          "level": "warn"
        },
        "value": [
          1704153600,
          "1239222"
        ]
      },
      {
        "metric": {
          "__name__": "count(*)",
          "level": "error"
        },
        "value": [
          1704153600,
          "832"
        ]
      },
    ]
  }
}

The /select/logsql/stats_query API is useful for generating Prometheus-compatible alerts and calculating recording rules results.

See also:

Extra filters
Querying log range stats
Querying logs
Querying hits stats
HTTP API

Querying log range stats

VictoriaLogs provides /select/logsql/stats_query_range?query=<query>&start=<start>&end=<end>&step=<step> HTTP endpoint, which returns log stats for the given query on the given [start ... end] time range with the given step interval. The stats is returned in the format compatible with Prometheus querying API.

The <query> must contain stats pipe. The calculated stats is converted into metrics with labels from by(...) clause of the | stats by(...) pipe.

The <step> arg can contain values in the format specified here. If <step> is missing, then it equals to 1d (one day).

For example, the following command returns the number of logs per each level field across logs over 2024-01-01 day by UTC with 6-hour granularity:

curl http://localhost:9428/select/logsql/stats_query_range -d 'query=* | stats by (level) count(*)' -d 'start=2024-01-01Z' -d 'end=2024-01-02Z' -d 'step=6h'

Below is an example JSON output returned from this endpoint:

{
  "status": "success",
  "data": {
    "resultType": "matrix",
    "result": [
      {
        "metric": {
          "__name__": "count(*)",
          "level": "info"
        },
        "values": [
          [
            1704067200,
            "103125"
          ],
          [
            1704088800,
            "102500"
          ],
          [
            1704110400,
            "103125"
          ],
          [
            1704132000,
            "102500"
          ]
        ]
      },
      {
        "metric": {
          "__name__": "count(*)",
          "level": "error"
        },
        "values": [
          [
            1704067200,
            "31"
          ],
          [
            1704088800,
            "25"
          ],
          [
            1704110400,
            "31"
          ],
          [
            1704132000,
            "125"
          ]
        ]
      }
    ]
  }
}

The /select/logsql/stats_query_range API is useful for generating Prometheus-compatible graphs in Grafana.

See also:

Extra filters
Querying log stats
Querying logs
Querying hits stats
HTTP API

Querying stream_ids

VictoriaLogs provides /select/logsql/stream_ids?query=<query>&start=<start>&end=<end> HTTP endpoint, which returns _stream_id values for the log streams from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every _stream_id.

For example, the following command returns _stream_id values across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/stream_ids -d 'query=error' -d 'start=5m'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "0000000000000000106955b1744a71b78bd3a88c755751e8",
      "hits": 442953
    },
    {
      "value": "0000000000000000b80988e6012df3520a8e20cd5353c52b",
      "hits": 59349
    },
    {
      "value": "0000000000000000f8d02151e40a6cbbb1edb2050ea910ba",
      "hits": 59277
    }
  ]
}

The /select/logsql/stream_ids endpoint supports optional limit=N query arg, which allows limiting the number of returned _stream_id values to N. The endpoint returns arbitrary subset of _stream_id values if their number exceeds N, so limit=N cannot be used for pagination over big number of _stream_id values. When the limit is reached, hits are zeroed, since they cannot be calculated reliably.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns _stream_id stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/stream_ids -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying streams
Querying logs
Querying hits stats
HTTP API

Querying streams

VictoriaLogs provides /select/logsql/streams?query=<query>&start=<start>&end=<end> HTTP endpoint, which returns streams from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every _stream.

For example, the following command returns streams across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/streams -d 'query=error' -d 'start=5m'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "{host=\"host-123\",app=\"foo\"}",
      "hits": 34980
    },
    {
      "value": "{host=\"host-124\",app=\"bar\"}",
      "hits": 32892
    },
    {
      "value": "{host=\"host-125\",app=\"baz\"}",
      "hits": 32877
    }
  ]
}

The /select/logsql/streams endpoint supports optional limit=N query arg, which allows limiting the number of returned streams to N. The endpoint returns arbitrary subset of streams if their number exceeds N, so limit=N cannot be used for pagination over big number of streams. When the limit is reached, hits are zeroed, since they cannot be calculated reliably.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns stream stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/streams -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying stream_ids
Querying logs
Querying hits stats
HTTP API

Querying stream field names

VictoriaLogs provides /select/logsql/stream_field_names?query=<query>&start=<start>&end=<end> HTTP endpoint, which returns log stream field names from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every field name.

For example, the following command returns stream field names across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/stream_field_names -d 'query=error' -d 'start=5m'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "app",
      "hits": 1033300623
    },
    {
      "value": "container",
      "hits": 1033300623
    },
    {
      "value": "datacenter",
      "hits": 1033300623
    }
  ]
}

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns stream field names stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/stream_field_names -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying stream field names
Querying field values
Querying streams
HTTP API

Querying stream field values

VictoriaLogs provides /select/logsql/stream_field_values?query=<query>&start=<start>&<end>&field=<fieldName> HTTP endpoint, which returns log stream field values for the field with the given <fieldName> name from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every field value.

For example, the following command returns values for the stream field host across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/stream_field_values -d 'query=error' -d 'start=5m' -d 'field=host'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "host-1",
      "hits": 69426656
    },
    {
      "value": "host-2",
      "hits": 66507749
    }
  ]
}

The /select/logsql/stream_field_values endpoint supports optional limit=N query arg, which allows limiting the number of returned values to N. The endpoint returns arbitrary subset of values if their number exceeds N, so limit=N cannot be used for pagination over big number of field values. When the limit is reached, hits are zeroed, since they cannot be calculated reliably.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns stream field values stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/stream_field_values -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying stream field values
Querying field names
Querying streams
HTTP API

Querying field names

VictoriaLogs provides /select/logsql/field_names?query=<query>&start=<start>&end=<end> HTTP endpoint, which returns field names from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every field name.

For example, the following command returns field names across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/field_names -d 'query=error' -d 'start=5m'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "_msg",
      "hits": 1033300623
    },
    {
      "value": "_stream",
      "hits": 1033300623
    },
    {
      "value": "_time",
      "hits": 1033300623
    }
  ]
}

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns field names stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/field_names -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying stream field names
Querying field values
Querying streams
HTTP API

Querying field values

VictoriaLogs provides /select/logsql/field_values?query=<query>&field=<fieldName>&start=<start>&end=<end> HTTP endpoint, which returns unique values for the given <fieldName> field from results of the given <query> on the given [<start> ... <end>] time range. The response also contains the number of log results per every field value.

For example, the following command returns unique values for host field across logs with the error word for the last 5 minutes:

curl http://localhost:9428/select/logsql/field_values -d 'query=error' -d 'field=host' -d 'start=5m'

Below is an example JSON output returned from this endpoint:

{
  "values": [
    {
      "value": "host-1",
      "hits": 69426656
    },
    {
      "value": "host-2",
      "hits": 66507749
    },
    {
      "value": "host-3",
      "hits": 65454351
    }
  ]
}

The /select/logsql/field_values endpoint supports optional limit=N query arg, which allows limiting the number of returned values to N. The endpoint returns arbitrary subset of values if their number exceeds N, so limit=N cannot be used for pagination over big number of field values. When the limit is reached, hits are zeroed, since they cannot be calculated reliably.

By default the (AccountID=0, ProjectID=0) tenant is queried. If you need querying other tenant, then specify it via AccountID and ProjectID http request headers. For example, the following query returns field values stats for (AccountID=12, ProjectID=34) tenant:

curl http://localhost:9428/select/logsql/field_values -H 'AccountID: 12' -H 'ProjectID: 34' -d 'query=_time:5m'

See also:

Extra filters
Querying stream field values
Querying field names
Querying streams
HTTP API

Extra filters

All the HTTP querying APIs provided by VictoriaLogs support the following optional query args:

extra_filters - this arg may contain extra field:=value filters, which must be applied to the query before returning the results.
extra_stream_filters - this arg may contain extra {field="value"} filters, which must be applied to the query before returning results.

The filters must be passed as JSON object with "field":"value" entries. For example, the following JSON object applies namespace:=my-app and env:prod filter to the query passed to HTTP querying APIs:

{
  "namespace":"my-app",
  "env":"prod"
}

The JSON object must be properly encoded with percent encoding before being passed to VictoriaLogs.

Web UI

VictoriaLogs provides Web UI for logs querying and exploration at http://localhost:9428/select/vmui.

There are three modes of displaying query results:

Group - results are displayed as a table with rows grouped by stream fields.
Table - displays query results as a table.
JSON - displays raw JSON response from /select/logsql/query HTTP API.

Visualization in Grafana

VictoriaLogs Grafana Datasource allows you to query and visualize VictoriaLogs data in Grafana

Command-line

VictoriaLogs provides vlogsqcli interactive command-line tool for querying logs. See these docs.

VictoriaLogs querying API integrates well with curl and other Unix command-line tools because of the following features:

Matching log entries are sent to the response stream as soon as they are found. This allows forwarding the response stream to arbitrary Unix pipes without waiting until the response finishes.
Query execution speed is automatically adjusted to the speed of the client, which reads the response stream. For example, if the response stream is piped to less command, then the query is suspended until the less command reads the next block from the response stream.
Query is automatically canceled when the client closes the response stream. For example, if the query response is piped to head command, then VictoriaLogs stops executing the query when the head command closes the response stream.

These features allow executing queries at command-line interface, which potentially select billions of rows, without the risk of high resource usage (CPU, RAM, disk IO) at VictoriaLogs.

For example, the following query can return very big number of matching log entries (e.g. billions) if VictoriaLogs contains many log messages with the error word:

curl http://localhost:9428/select/logsql/query -d 'query=error'

If the command above returns "never-ending" response, then just press ctrl+C at any time in order to cancel the query. VictoriaLogs notices that the response stream is closed, so it cancels the query and stops consuming CPU, RAM and disk IO for this query.

Then use head command for investigating the returned log messages and narrowing down the query:

curl http://localhost:9428/select/logsql/query -d 'query=error' | head -10

The head -10 command reads only the first 10 log messages from the response and then closes the response stream. This automatically cancels the query at VictoriaLogs side, so it stops consuming CPU, RAM and disk IO resources.

Alternatively, you can limit the number of returned logs at VictoriaLogs side via limit pipe:

curl http://localhost:9428/select/logsql/query -d 'query=error | limit 10'

Sometimes it may be more convenient to use less command instead of head during the investigation of the returned response:

curl http://localhost:9428/select/logsql/query -d 'query=error' | less

The less command reads the response stream on demand, when the user scrolls down the output. VictoriaLogs suspends query execution when less stops reading the response stream. It doesn't consume CPU and disk IO resources during this time. It resumes query execution after the less continues reading the response stream.

Suppose that the initial investigation of the returned query results helped determining that the needed log messages contain cannot open file phrase. Then the query can be narrowed down to error AND "cannot open file" (see these docs about AND operator). Then run the updated command in order to continue the investigation:

curl http://localhost:9428/select/logsql/query -d 'query=error AND "cannot open file"' | head

Note that the query arg must be properly encoded with percent encoding when passing it to curl or similar tools. It is highly recommended to use vlogscli - it automatically performs all the needed encoding.

The pipe the query to "head" or "less" -> investigate the results -> refine the query iteration can be repeated multiple times until the needed log messages are found.

The returned VictoriaLogs query response can be post-processed with any combination of Unix commands, which are usually used for log analysis - grep, jq, awk, sort, uniq, wc, etc.

For example, the following command uses wc -l Unix command for counting the number of log messages with the error word received from streams with app="nginx" field during the last 5 minutes:

curl http://localhost:9428/select/logsql/query -d 'query={app="nginx"} AND _time:5m AND error' | wc -l

See these docs about _stream filter, these docs about _time filter and these docs about AND operator.

Alternatively, you can count the number of matching logs at VictoriaLogs side with stats pipe:

curl http://localhost:9428/select/logsql/query -d 'query={app="nginx"} AND _time:5m AND error | stats count() logs_with_error'

The following example shows how to sort query results by the _time field with traditional Unix tools:

curl http://localhost:9428/select/logsql/query -d 'query=error' | jq -r '._time + " " + ._msg' | sort | less

This command uses jq for extracting _time and _msg fields from the returned results, and piping them to sort command.

Note that the sort command needs to read all the response stream before returning the sorted results. So the command above can take non-trivial amounts of time if the query returns too many results. The solution is to narrow down the query before sorting the results. See these tips on how to narrow down query results.

Alternatively, sorting of matching logs can be performed at VictoriaLogs side via sort pipe:

curl http://localhost:9428/select/logsql/query -d 'query=error | sort by (_time)' | less

The following example calculates stats on the number of log messages received during the last 5 minutes grouped by log.level field with traditional Unix tools:

curl http://localhost:9428/select/logsql/query -d 'query=_time:5m log.level:*' | jq -r '."log.level"' | sort | uniq -c

The query selects all the log messages with non-empty log.level field via "any value" filter, then pipes them to jq command, which extracts the log.level field value from the returned JSON stream, then the extracted log.level values are sorted with sort command and, finally, they are passed to uniq -c command for calculating the needed stats.

Alternatively, all the stats calculations above can be performed at VictoriaLogs side via stats by(...):

curl http://localhost:9428/select/logsql/query -d 'query=_time:5m log.level:* | stats by (log.level) count() matching_logs'

See also:

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HTTP API

Querying logs

Live tailing

Querying hits stats

Querying log stats

Querying log range stats

Querying stream_ids

Querying streams

Querying stream field names

Querying stream field values

Querying field names

Querying field values

Extra filters

Web UI

Visualization in Grafana

Command-line

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