Configuring the Go Tracing Library

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After you set up the tracing library with your code, configure the Agent to collect APM data, and activate the Go integration, start the tracer and configure the library as desired.

Datadog recommends using DD_ENV, DD_SERVICE, and DD_VERSION to set env, service, and version for your services.

Read the Unified Service Tagging documentation for recommendations on how to configure these environment variables. These variables are available for versions 1.24.0+ of the Go tracer.

You may also elect to provide env, service, and version through the tracer’s API:

package main

import (
    "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)

func main() {
    tracer.Start(
        tracer.WithEnv("prod"),
        tracer.WithService("test-go"),
        tracer.WithServiceVersion("abc123"),
    )

    // When the tracer is stopped, it will flush everything it has to the Datadog Agent before quitting.
    // Make sure this line stays in your main function.
    defer tracer.Stop()

    // If you expect your application to be shut down by SIGTERM (for example, a container in Kubernetes),
    // you might want to listen for that signal and explicitly stop the tracer to ensure no data is lost
    sigChan := make(chan os.Signal, 1)
    signal.Notify(sigChan, syscall.SIGTERM)
    go func() {
        <-sigChan
        tracer.Stop()
    }()
}

The Go tracer supports additional environment variables and functions for configuration. See all available options in the configuration documentation.

Unified service tagging

DD_VERSION: Set the application’s version, for example: 1.2.3, 6c44da20, 2020.02.13
DD_SERVICE: The service name to be used for this application.
DD_ENV: Set the application’s environment, for example: prod, pre-prod, staging.

Traces

DD_TRACE_ENABLED

Default: true
Enable web framework and library instrumentation. When false, the application code doesn’t generate any traces.

DD_TRACE_AGENT_PORT

Default: 8126
Overrides the default trace Agent port for Datadog trace submission. If the Agent configuration sets receiver_port or DD_APM_RECEIVER_PORT to something other than the default 8126, then the library configuration DD_DOGSTATSD_PORT must match it.

DD_TRACE_SAMPLE_RATE

Default: nil
Enable ingestion rate control.
Note: DD_TRACE_SAMPLE_RATE is deprecated in favor of DD_TRACE_SAMPLING_RULES.

DD_TRACE_RATE_LIMIT

Maximum number of spans to sample per-second, per-Go process. Defaults to 100 when DD_TRACE_SAMPLE_RATE is set. Otherwise, delegates rate limiting to the Datadog Agent.

DD_TRACE_STARTUP_LOGS

Default: true
Enable startup configuration and the diagnostic log.

DD_TRACE_DEBUG

Default: false
Enable debug logging in the tracer.

DD_SERVICE_MAPPING

Default: null
Dynamically rename services through configuration. Services can be separated by commas or spaces, for example: mysql:mysql-service-name,postgres:postgres-service-name, mysql:mysql-service-name postgres:postgres-service-name.

DD_TRACE_PARTIAL_FLUSH_ENABLED

Default: false
Enables incrementally flushing large traces to the Datadog Agent, reducing the chance of rejection by the Agent. Use only when you have long-lived traces or traces with many spans. Valid values are true or false. Added in version 1.54.0. Only compatible with the Datadog Agent 7.26.0+.

DD_TRACE_PARTIAL_FLUSH_MIN_SPANS

Default: 1000
Number of spans within a trace that can be partially flushed to the Datadog Agent. DD_TRACE_PARTIAL_FLUSH_ENABLED must be true for partial flushing to occur. Added in version 1.54.0. Only compatible with the Datadog Agent 7.26.0+.

DD_TRACE_CLIENT_IP_ENABLED

Default: false
Enable client IP collection from relevant IP headers in HTTP request spans. Added in version 1.47.0

DD_TRACE_HEADER_TAGS

Default: null
List of comma-separated HTTP headers to be used as span tags. Optionally specify a “mapped” field to rename the request header as a tag. Configuration can be set globally with this environment variable, or at the integration level using the options specified in the Go documentation. This feature is compatible with HTTP1 headers.
Examples:

Capture request header my-header: "DD_TRACE_HEADER_TAGS=my-header"
Capture request headers my-header-1 and my-header-2: "DD_TRACE_HEADER_TAGS=my-header1,my-header-2"
Capture request header my-header and rename it to my-tag: "DD_TRACE_HEADER_TAGS=my-header:my-tag"

DD_TRACE_SAMPLING_RULES

Default: nil
A JSON array of objects. Each object must have a "sample_rate". The "name","service", "resource", and "tags" fields are optional. The "sample_rate" value must be between 0.0 and 1.0 (inclusive). Rules are applied in configured order to determine the trace’s sample rate.

Support for sampling by resource and tags is in Preview.

For more information, see Ingestion Mechanisms.
Examples:

Set the sample rate to 20%: '[{"sample_rate": 0.2}]'
Set the sample rate to 10% for services starting with ‘a’ and span name ‘b’ and set the sample rate to 20% for all other services: '[{"service": "a.*", "name": "b", "sample_rate": 0.1}, {"sample_rate": 0.2}]'.
Set the sample rate to 40% for services that have HTTP GET resource name: '[{"resource": "HTTP GET", "sample_rate": 0.4}]'.
Set the sample rate to 100% for services that have a tier tag with the value premium: '[{"tags": {"tier":"premium"}, "sample_rate": 1}]'.

DD_SPAN_SAMPLING_RULES

Default: nil
A JSON array of objects. Each object must have a "sample_rate". The "name","service", "resource", and "tags" fields are optional. Rules are applied in configured order to determine the span’s sample rate. The sample_rate value must be between 0.0 and 1.0 (inclusive).

Support for sampling by resource and tags is in Preview.

For more information, see Ingestion Mechanisms.
Example:

Set the span sample rate to 50% for the service my-service and operation name http.request, up to 50 traces per second: '[{"service": "my-service", "name": "http.request", "sample_rate":0.5, "max_per_second": 50}]'
Set the sample rate to 100% for services that have a priority tag with the value high: '[{"tags": {"priority":"high"}, "sample_rate": 1}]'.

DD_TAGS

Default: []
A list of default tags to be added to every span and profile. Tags can be separated by commas or spaces, for example: layer:api,team:intake,key:value or layer:api team:intake key:value.

Agent

DD_AGENT_HOST: Default: localhost
Override the default trace Agent host address for trace submission.
DD_DOGSTATSD_PORT: Default: 8125
Overrides the default trace Agent port for DogStatsD metric submission. If the Agent configuration sets dogstatsd_port or DD_DOGSTATSD_PORT to something other than the default 8125, then the library configuration DD_DOGSTATSD_PORT must match it.
DD_INSTRUMENTATION_TELEMETRY_ENABLED: Default: true
Datadog may collect environmental and diagnostic information about your system to improve the product. When false, this telemetry data will not be collected.

Runtime metrics

DD_RUNTIME_METRICS_ENABLED: Default: false
Enable runtime metric collection. Added in version 1.26.0.

Trace context propagation

DD_TRACE_PROPAGATION_STYLE: Default: datadog,tracecontext
Configures trace header injection and extraction style. See Propagating Go Trace Context for more information.