Log to Metrics

Generate metrics from logs

Log To Metrics

The Log To Metrics Filter plugin allows you to generate log-derived metrics. It currently supports modes to count records, provide a gauge 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 plugin does not actually act as a record filter and does not change or drop records. All records will pass this filter untouched and generated metrics will be emitted into a seperate metric pipeline.

Please note that this plugin is an experimental feature and is not recommended for production use. Configuration parameters and plugin functionality are subject to change without notice.

Configuration Parameters

The plugin supports the following configuration parameters:

Key	Description	Mandatory	Value Format
tag	Defines the tag for the generated metrics record	Yes
metric_mode	Defines the mode for the metric. Valid values are [counter, gauge or histogram]	Yes
metric_name	Sets the name of the metric.	Yes
metric_description	Sets a help text for the metric.	Yes
bucket	Defines a bucket for histogram	Yes, for mode histogram	e.g. 0.75
add_label	Add 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	Specify the record field that holds a numerical value	Yes, for modes [gauge and histogram]	Name of record key. Supports Record Accessor notation for nested fields.
kubernetes_mode	If enabled, it will automatically put pod_id, pod_name, namespace_name, docker_id and container_name into the metric as labels. This option is intended to be used in combination with the kubernetes filter plugin, which fills those fields.
Regex	Include records in which the content of KEY matches the regular expression.		KEY REGEX
Exclude	Exclude 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.

Getting Started

The following example takes records from two dummy inputs and counts all messages passing through the log_to_metrics filter. It then generates metric records which are provided to the prometheus_exporter:

Configuration - Counter

[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 e.g. curl command 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

Configuration - Gauge

The gauge mode needs a value_field specified, where the current metric values are generated from. In this example we also apply a regex filter and enable 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 e.g. curl command 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

As you can see in the output, only one line is printed, as the records from the first input plugin are ignored, as they do not match the regex.

The filter also allows to use multiple rules which are applied in order, you can have many Regex and Exclude entries as required (see grep filter plugin).

If you execute the above curl command multiple times, you see, that in this example the metric value stays at 60, as the messages generated by the dummy plugin are not changing. In a real-world scenario the values would change and return the last processed value.

Metric label_values

As you can see, 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 actually used combinations are displayed here. To see this, you can add a dummy 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 the kubernetes labels have been attached to the metric, accordingly.

Configuration - Histogram

Similar to the gauge mode, histogram needs a value_field specified, where the current metric values are generated from. In this example we also apply a regex filter and enable 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 e.g. curl command 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

As you can see in the output, there are per default the buckets 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10.0 and +Inf, in which values are sorted into. A sum and a counter are also part of this metric. You can specify own buckets in the config, 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

Please note, that the +Inf bucket will always be included implicitly. The buckets in a histogram are cumulative, so a value added to one bucket will add 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.