Log to Metrics

Generate metrics from logs

The log to metrics filter lets you generate log-derived metrics. It supports modes to count records, provide a guage for field values, or create a histogram. You can also match or exclude specific records based on regular expression patterns for values or nested values.

This filter does not actually act as a record filter and therefore does not change or drop records. All records will pass through this filter untouched, and any generated metrics will be emitted into a separate metric pipeline.

This filter is an experimental feature and is not recommended for production use. Configuration parameters and other capabilities are subject to change without notice.

Configuration parameters

The plugin supports the following configuration parameters:

Parameter

Description

Value format

tag

Required. Defines the tag for the generated metrics record.

metric_mode

Required. Defines the mode for the metric. Valid values are counter, gauge or histogram.

metric_name

Required. Sets the name of the metric.

metric_description

Required. Sets a description for the metric.

bucket

Required for mode histogram. Defines a bucket for histograms.

For example, 0.75

add_label

Adds a custom label NAME and set the value to the value of KEY.

label_field

Includes a record field as label dimension in the metric.

Name of record key. Supports record accessor notation for nested fields.

value_field

Required for modes gauge and histogram. Specifies the record field that holds a numerical value.

Name of record key. Supports record accessor notation for nested fields.

kubernetes_mode

If enabled, adds pod_id, pod_name, namespace_name, docker_id and container_name to the metric as labels. This option is intended to be used in combination with the kubernetes filter plugin, which fills those fields.

Regex

Includes records in which the content of KEY matches the regular expression.

KEY REGEX

Exclude

Excludes records in which the content of KEY matches the regular expression.

KEY REGEX

Flush_Interval_Sec

The interval for metrics emission, in seconds. If Flush_Interval_Sec and Flush_Interval_Nsec are either both unset or both set to 0, the filter emits metrics immediately after each filter match. Otherwise, if either parameter is set to a non-zero value, the filter emits metrics at the specified interval. Longer intervals help lower resource consumption in high-load situations. Default value: 0.

Flush_Interval_Nsec

The interval for metrics emission, in nanoseconds. This parameter works in conjunction with Flush_Interval_Sec. Default value: 0.

Examples

Counter

The following example takes records from two dummy inputs and counts all messages that pass through the log_to_metrics filter. It then generate metric records, which are provided to the prometheus_exporter output:

[SERVICE]
    flush              1
    log_level          info

[INPUT]
    Name               dummy
    Dummy              {"message":"dummy", "kubernetes":{"namespace_name": "default", "docker_id": "abc123", "pod_name": "pod1", "container_name": "mycontainer", "pod_id": "def456", "labels":{"app": "app1"}}, "duration": 20, "color": "red", "shape": "circle"}
    Tag                dummy.log

[INPUT]
    Name               dummy
    Dummy              {"message":"hello", "kubernetes":{"namespace_name": "default", "docker_id": "abc123", "pod_name": "pod1", "container_name": "mycontainer", "pod_id": "def456", "labels":{"app": "app1"}}, "duration": 60, "color": "blue", "shape": "square"}
    Tag                dummy.log2

[FILTER]
    name               log_to_metrics
    match              dummy.log*
    tag                test_metric
    metric_mode        counter
    metric_name        count_all_dummy_messages
    metric_description This metric counts dummy messages

[OUTPUT]
    name               prometheus_exporter
    match              *
    host               0.0.0.0
    port               2021

You can then use a tool like curl to retrieve the generated metric:

> curl -s http://127.0.0.1:2021/metrics


# HELP log_metric_counter_count_all_dummy_messages This metric counts dummy messages
# TYPE log_metric_counter_count_all_dummy_messages counter
log_metric_counter_count_all_dummy_messages 49

Gauge

The gauge mode needs a value_field to specify where to generate the metric values from. This example also applies a regex filter and enables the kubernetes_mode option:

[FILTER]
    name               log_to_metrics
    match              dummy.log*
    tag                test_metric
    metric_mode        gauge
    metric_name        current_duration
    metric_description This metric shows the current duration
    value_field        duration
    kubernetes_mode    on
    regex              message .*el.*
    add_label          app $kubernetes['labels']['app']
    label_field        color
    label_field        shape

You can then use a tool like curl to retrieve the generated metric:

> curl -s http://127.0.0.1:2021/metrics


# HELP log_metric_gauge_current_duration This metric shows the current duration
# TYPE log_metric_gauge_current_duration gauge
log_metric_gauge_current_duration{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="square"} 60

In the resulting output, only one line is printed. Records from the first input plugin are ignored because they don't match the regular expression.

This filter also lets you use multiple rules, which are applied in order. You can have as many regex and exclude entries as required (see Grep filter plugin).

If you execute the example curl command multiple times, the example metric value remains at 60 because the messages generated by the Dummy plugin don't change. In a real-world scenario, the values would change and return to the last processed value.

Metric `label_values`

The label sets defined by add_label and label_field are added to the metric. The lines in the metric represent every combination of labels. Only combinations that are actualy used are displayed here. To see this, you can add a dummy input to your configuration.

The metric output would then look like:

> curl -s http://127.0.0.1:2021/metrics

# HELP log_metric_gauge_current_duration This metric shows the current duration
# TYPE log_metric_gauge_current_duration gauge
log_metric_gauge_current_duration{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="square"} 60
log_metric_gauge_current_duration{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 20

You can also see that all Kubernetes labels have been attached to the metric accordingly.

Histogram

Similar to the gauge mode, the histogram mode needs a value_field to specify where to generate the metric values from. This example also applies a regex filter and enables the kubernetes_mode option:

[FILTER]
    name               log_to_metrics
    match              dummy.log*
    tag                test_metric
    metric_mode        histogram
    metric_name        current_duration
    metric_description This metric shows the request duration
    value_field        duration
    kubernetes_mode    on
    regex              message .*el.*
    add_label          app $kubernetes['labels']['app']
    label_field        color
    label_field        shape

You can then use a tool like curl to retrieve the generated metric:

> curl -s http://127.0.0.1:2021/metrics


# HELP log_metric_histogram_current_duration This metric shows the request duration
# TYPE log_metric_histogram_current_duration histogram
log_metric_histogram_current_duration_bucket{le="0.005",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.01",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.025",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.05",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.1",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.25",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.5",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="1.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="2.5",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="5.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="10.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="+Inf",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 28
log_metric_histogram_current_duration_sum{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 560
log_metric_histogram_current_duration_count{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="red",shape="circle"} 28
log_metric_histogram_current_duration_bucket{le="0.005",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.01",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.025",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.05",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.1",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.25",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="0.5",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="1.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="2.5",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="5.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="10.0",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 0
log_metric_histogram_current_duration_bucket{le="+Inf",namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 27
log_metric_histogram_current_duration_sum{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 1620
log_metric_histogram_current_duration_count{namespace_name="default",pod_name="pod1",container_name="mycontainer",docker_id="abc123",pod_id="def456",app="app1",color="blue",shape="circle"} 27

In the resulting output, there are several buckets by default: 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10.0 and +Inf. Values are sorted into these buckets. A sum and a counter are also part of this metric. You can specify own buckets in the configuration, like in the following example:

[FILTER]
    name               log_to_metrics
    match              dummy.log*
    tag                test_metric
    metric_mode        histogram
    metric_name        current_duration
    metric_description This metric shows the HTTP request duration as histogram in milliseconds
    value_field        duration
    kubernetes_mode    on
    bucket             1
    bucket             5
    bucket             10
    bucket             50
    bucket             100
    bucket             250
    bucket             500
    bucket             1000
    regex              message .*el.*
    label_field        color
    label_field        shape

The +Inf bucket will always be included regardless of the buckets you specify. The buckets in a histogram are cumulative, so a value added to one bucket will be added to all larger buckets, too.

This filter also attaches Kubernetes labels to each metric, identical to the behavior of label_field. This results in two sets for the histogram.

Last updated 1 month ago

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Configuration parameters

Examples

Counter

Gauge

Metric label_values

Histogram

Metric `label_values`