Graham McIntire
9af50a9e34
PromEx.Plug's internal path check doesn't match when forwarded under /metrics (conn.path_info is [] after the forward strips the prefix), so it silently returned without sending a response. Call PromEx.get_metrics/1 directly and send the text body ourselves — tested, returns 200 with all 23 registered event handlers producing proper Prometheus histogram output.
56 lines
1.3 KiB
Elixir
56 lines
1.3 KiB
Elixir
defmodule MicrowavepropWeb.MetricsPlug do
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@moduledoc """
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Serves PromEx metrics at `/metrics`. Optionally gated by a bearer
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token via `config :microwaveprop, :prometheus_auth_token`, sourced
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from the `PROMETHEUS_AUTH_TOKEN` env var in `runtime.exs`.
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"""
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@behaviour Plug
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import Plug.Conn
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@impl true
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def init(opts), do: opts
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@impl true
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def call(conn, _opts) do
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case authorized?(conn) do
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:ok ->
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body = PromEx.get_metrics(Microwaveprop.PromEx)
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conn
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|> put_resp_content_type("text/plain; version=0.0.4")
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|> send_resp(200, body)
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|> halt()
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:denied ->
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conn
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|> put_resp_header("www-authenticate", ~s(Bearer realm="metrics"))
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|> send_resp(401, "unauthorized")
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|> halt()
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end
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end
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defp authorized?(conn) do
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case Application.get_env(:microwaveprop, :prometheus_auth_token) do
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token when is_binary(token) and token != "" ->
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check_token(conn, token)
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_ ->
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:ok
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end
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end
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defp check_token(conn, expected) do
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conn
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|> get_req_header("authorization")
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|> List.first()
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|> case do
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"Bearer " <> token ->
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if Plug.Crypto.secure_compare(token, expected), do: :ok, else: :denied
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_ ->
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:denied
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end
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end
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end
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