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Metrics

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Prometheus

Flipt exposes Prometheus metrics by default at the /metrics HTTP endpoint. To see which metrics are currently supported, point your browser to FLIPT_HOST/metrics (ex: localhost:8080/metrics).

You should see a bunch of metrics being recorded such as:

flipt_cache_hit_total{cache="memory",type="flag"} 1
flipt_cache_miss_total{cache="memory",type="flag"} 1
---
go_gc_duration_seconds{quantile="0"} 8.641e-06
go_gc_duration_seconds{quantile="0.25"} 2.499e-05
go_gc_duration_seconds{quantile="0.5"} 3.5359e-05
go_gc_duration_seconds{quantile="0.75"} 6.6594e-05
go_gc_duration_seconds{quantile="1"} 0.00026651 go_gc_duration_seconds_sum
0.000402094 go_gc_duration_seconds_count 5

An example showing how to set up Flipt with Prometheus can be found in the GitHub repository.

You can disable the Prometheus metrics collection by setting the metrics.enabled configuration option to false.

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OTLP

Flipt supports sending metrics to an OTLP collector.

OTLP supports additional configuration such as specifying the protocol to use (gRPC or HTTP) as well as providing custom headers to send with the request.

Custom headers can be used to provide authentication information to the collector which may be required if you are using a hosted collector such as NewRelic, DataDog, or Honeycomb.

These can be configured via the metrics.otlp configuration section.

metrics:
  enabled: true
  exporter: "otlp"
  otlp:
    endpoint: "https://{your-collector-url}"
    headers:
      "X-Some-Header": "some-value"

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Dashboards

We provide a set of Grafana dashboards that you can use to visualize the metrics collected by Flipt, including both server health and flag evaluation metrics.

You can find the dashboards in our grafana-dashboards repository.

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Logging

Flipt writes logs to STDOUT in two formats:

The format can be configured via the log.encoding configuration option.

log:
  encoding: json

For production deployments, we recommend using the JSON format as it’s easier to parse and ingest into log aggregation systems such as Elasticsearch, Splunk, Loki, or Datadog.

We’ve prepared an example showing how to set up Flipt with Grafana Loki and Promtail to ingest and query logs.

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JSON

{
  "L": "INFO",
  "T": "2024-01-20T21:59:49-05:00",
  "M": "finished unary call with code OK",
  "server": "grpc",
  "grpc.start_time": "2024-01-20T21:59:49-05:00",
  "system": "grpc",
  "span.kind": "server",
  "grpc.service": "flipt.evaluation.EvaluationService",
  "grpc.method": "Boolean",
  "peer.address": "127.0.0.1:52635",
  "grpc.code": "OK",
  "grpc.time_ms": 0.146
}

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Log Key Descriptions

  • L: Level (log level). Possible values include: debug, info, warn, error, fatal, and panic.
  • T: Timestamp. The timestamp is in ISO 8601 format, widely used for representing date and time. It includes the date, time, and time zone information. For example, “2024-01-20T21:59:49-05:00” represents the date and time in the Eastern Time Zone (UTC-5).
  • M: Message. The message describes the log event. It can include information about the operation, errors encountered, or other relevant details.

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Console

2024-01-20T22:04:18-05:00	INFO	finished unary call with code OK	{"server": "grpc", "grpc.start_time": "2024-01-20T22:04:18-05:00", "system": "grpc", "span.kind": "server", "grpc.service": "flipt.evaluation.EvaluationService", "grpc.method": "Boolean", "peer.address": "127.0.0.1:53714", "grpc.code": "OK", "grpc.time_ms": 0.373}

More information about the available configuration options can be found in the Logging configuration section.

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Tracing

Flipt supports distributed tracing via the OpenTelemetry project.

Currently, we support the following tracing backends:

Enable tracing via the values described in the Tracing configuration and point Flipt to your configured collector to record spans.

Examples showing how to set up Flipt with each of the supported tracing backends can be found in the main GitHub repository .

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OTLP

OTLP supports additional configuration such as specifying the protocol to use (gRPC or HTTP) as well as providing custom headers to send with the request.

Custom headers can be used to provide authentication information to the collector which may be required if you are using a hosted collector such as NewRelic, Datadog, or Honeycomb.

These can be configured via the tracing.otlp configuration section.

tracing:
  enabled: true
  exporter: "otlp"
  otlp:
    endpoint: "https://{your-collector-url}"
    headers:
      "X-Some-Header": "some-value"

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Environment Variables

Flipt supports OTLP specific resource environment variables that are part of the OTLP spec.

The following environment variables are supported:

  • OTEL_SERVICE_NAME - Sets the value of the service.name resource attribute (default: flipt)
  • OTEL_RESOURCE_ATTRIBUTES - Key-value pairs to be used as resource attributes.