117 lines
2.9 KiB
Elixir
117 lines
2.9 KiB
Elixir
defmodule Tesla.Middleware.OpenTelemetry do
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@moduledoc """
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Creates OpenTelemetry spans and injects tracing headers into HTTP requests
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When used with `Tesla.Middleware.PathParams`, the span name will be created
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based on the provided path. Without it, the span name follow OpenTelemetry
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standards and use just the method name, if not being overriden by opts.
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NOTE: This middleware needs to come before `Tesla.Middleware.PathParams`
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## Options
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- `:span_name` - override span name. Can be a `String` for a static span name,
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or a function that takes the `Tesla.Env` and returns a `String`
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"""
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require OpenTelemetry.Tracer
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@behaviour Tesla.Middleware
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def call(env, next, opts) do
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span_name = get_span_name(env, Keyword.get(opts, :span_name))
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OpenTelemetry.Tracer.with_span span_name, %{kind: :client} do
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env
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|> Tesla.put_headers(:otel_propagator_text_map.inject([]))
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|> Tesla.run(next)
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|> set_span_attributes()
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|> handle_result()
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end
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end
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defp get_span_name(_env, span_name) when is_binary(span_name) do
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span_name
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end
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defp get_span_name(env, span_name_fun) when is_function(span_name_fun, 1) do
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span_name_fun.(env)
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end
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defp get_span_name(env, _) do
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case env.opts[:path_params] do
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nil -> "HTTP #{http_method(env.method)}"
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_ -> URI.parse(env.url).path
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end
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end
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defp set_span_attributes({_, %Tesla.Env{} = env} = result) do
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OpenTelemetry.Tracer.set_attributes(build_attrs(env))
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result
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end
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defp set_span_attributes(result) do
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result
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end
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defp handle_result({:ok, %Tesla.Env{status: status} = env}) when status > 400 do
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OpenTelemetry.Tracer.set_status(OpenTelemetry.status(:error, ""))
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{:ok, env}
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end
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defp handle_result({:error, {Tesla.Middleware.FollowRedirects, :too_many_redirects}} = result) do
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OpenTelemetry.Tracer.set_status(OpenTelemetry.status(:error, ""))
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result
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end
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defp handle_result({:ok, env}) do
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{:ok, env}
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end
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defp handle_result(result) do
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OpenTelemetry.Tracer.set_status(OpenTelemetry.status(:error, ""))
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result
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end
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defp build_attrs(%Tesla.Env{
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method: method,
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url: url,
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status: status_code,
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headers: headers,
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query: query
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}) do
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url = Tesla.build_url(url, query)
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uri = URI.parse(url)
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attrs = %{
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"http.method": http_method(method),
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"http.url": url,
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"http.target": uri.path,
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"http.host": uri.host,
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"http.scheme": uri.scheme,
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"http.status_code": status_code
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}
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maybe_append_content_length(attrs, headers)
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end
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defp maybe_append_content_length(attrs, headers) do
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case Enum.find(headers, fn {k, _v} -> k == "content-length" end) do
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nil ->
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attrs
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{_key, content_length} ->
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Map.put(attrs, :"http.response_content_length", content_length)
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end
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end
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defp http_method(method) do
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method
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|> Atom.to_string()
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|> String.upcase()
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end
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end
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