View Source NewRelic.Tracer (New Relic Elixir Agent v1.34.0)

Function Tracing

To enable function tracing in a particular module, use NewRelic.Tracer, and annotate the functions you want to trace with @trace.

Traced functions will report as:

Segments in Transaction Traces
Span Events in Distributed Traces
Special custom attributes on Transaction Events

Warning

Traced functions will not be tail-call-recursive. Don't use this for recursive functions.

Example

Trace a function:

defmodule MyModule do
  use NewRelic.Tracer

  @trace :my_function
  def my_function do
    # Will report as `MyModule.my_function/0`
  end

  @trace :alias
  def my_function do
    # Will report as `MyModule.my_function:alias/0`
  end
end

Arguments

By default, arguments are inspected and recorded along with traces. You can opt-out of function argument tracing on individual tracers:

defmodule SecretModule do
  use NewRelic.Tracer

  @trace {:login, args: false}
  def login(username, password) do
    # do something secret...
  end
end

This will prevent the argument values from becoming part of Transaction Traces.

This may also be configured globally via Application config. See NewRelic.Config for details.

External Service calls

Finch

Finch requests are auto-instrumented, so you don't need to use category: :external tracers or call set_span if you use Finch. You may still want to use a normal tracer for functions that make HTTP requests if they do additional work worth instrumenting. Automatic Finch instrumentation can not inject Distributed Trace headers, so that must still be done manually.

To manually instrument External Service calls you must give the trace annotation a category.

You may also call NewRelic.set_span/2 to provide better naming for metrics & spans, and additionally annotate the outgoing HTTP headers with the Distributed Tracing context to track calls across services.

defmodule MyExternalService do
  use NewRelic.Tracer

  @trace {:request, category: :external}
  def request(method, url, headers) do
    NewRelic.set_span(:http, url: url, method: method, component: "HttpClient")
    headers ++ NewRelic.distributed_trace_headers(:http)
    HttpClient.request(method, url, headers)
  end
end