111 lines
3 KiB
Elixir
111 lines
3 KiB
Elixir
defmodule AprsmeWeb.Plugs.HealthCheck do
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@moduledoc """
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Health check plug that returns appropriate status based on application state.
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Used by Kubernetes liveness and readiness probes.
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"""
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import Plug.Conn
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alias Ecto.Adapters.SQL
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def init(opts), do: opts
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def call(%{request_path: "/health"} = conn, opts) do
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probe_type = opts[:probe_type] || :readiness
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case check_health(probe_type) do
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{:ok, message} ->
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conn
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|> put_resp_content_type("text/plain")
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|> send_resp(200, message)
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|> halt()
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{:error, message} ->
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conn
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|> put_resp_content_type("text/plain")
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|> send_resp(503, message)
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|> halt()
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end
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end
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def call(conn, _opts), do: conn
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defp check_health(:liveness) do
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# Liveness probe - only fails if the application is truly broken
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# Continue returning OK even during shutdown to prevent unnecessary restarts
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case basic_health_checks() do
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:ok -> {:ok, "OK"}
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{:error, reason} -> {:error, "Liveness check failed: #{reason}"}
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end
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end
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defp check_health(:readiness) do
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# Readiness probe - fails when shutting down to stop new traffic.
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health_status = Application.get_env(:aprsme, :health_status, :healthy)
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readiness_status(health_status, shutting_down?())
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end
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defp readiness_status(:draining, _shutting_down?), do: {:error, "Application is draining connections"}
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defp readiness_status(_status, true), do: {:error, "Application is shutting down"}
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defp readiness_status(_status, false) do
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case full_health_checks() do
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:ok -> {:ok, "OK"}
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{:error, reason} -> {:error, "Readiness check failed: #{reason}"}
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end
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end
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# Basic checks for liveness
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# Check if the application is running
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defp basic_health_checks do
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_ = Application.get_env(:aprsme, :env)
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:ok
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rescue
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_ -> {:error, "Application not responding"}
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end
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defp full_health_checks do
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# Comprehensive checks for readiness
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with :ok <- check_database_connection() do
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check_pubsub()
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end
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end
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defp check_database_connection do
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case SQL.query(Aprsme.Repo, "SELECT 1", [], timeout: 1000) do
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{:ok, _} -> :ok
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_ -> {:error, "Database connection failed"}
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end
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rescue
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_ -> {:error, "Database check failed"}
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end
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defp check_pubsub do
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_ = Phoenix.PubSub.broadcast(Aprsme.PubSub, "health_check", :ping)
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:ok
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rescue
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_ -> {:error, "PubSub check failed"}
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end
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defp shutting_down? do
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# Check if ShutdownHandler process exists and is shutting down
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Aprsme.ShutdownHandler |> Process.whereis() |> ask_shutting_down?()
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end
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# No ShutdownHandler process → definitely not shutting down.
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defp ask_shutting_down?(nil), do: false
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defp ask_shutting_down?(pid) when is_pid(pid) do
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ask_if_alive(Process.alive?(pid), pid)
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end
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defp ask_if_alive(false, _pid), do: false
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defp ask_if_alive(true, pid) do
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timeout = Application.get_env(:aprsme, :health_check_call_timeout_ms, 5000)
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GenServer.call(pid, :shutting_down?, timeout)
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catch
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_kind, _reason -> false
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end
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end
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