Graham McIntire
52a32032a3
The ingress + Grafana pipeline parses JSON-formatted log lines; Elixir's default text formatter was the odd format everywhere else, forcing Loki to fall back to free-text parsing. Swap the `:default` :logger handler's formatter to `LoggerJSON.Formatters.Basic` when `LOG_FORMAT=json`. Defaults: `LOG_FORMAT=text` for dev/test (no behaviour change), `json` for prod. Whitelisted metadata covers the fields we actually correlate on — `request_id`, `trace_id`, `worker`, `queue`, `job_id`. OTP 28 / Elixir 1.19 exposes `Logger.Formatter.new/1` but ships no JSON encoder of its own, so `logger_json` (~> 7.0) carries the rendering. The test pokes the formatter directly rather than round-tripping through ExUnit's capture_log, which replaces the handler and so can't see the installed formatter's output.
59 lines
2.1 KiB
Elixir
59 lines
2.1 KiB
Elixir
defmodule Microwaveprop.LoggerFormatTest do
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# async: false — we briefly swap the global :default :logger handler's
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# formatter and forward its output to a self()-bound IO device so the
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# test can capture the JSON-encoded output. Restored on exit.
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use ExUnit.Case, async: false
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alias LoggerJSON.Formatters.Basic
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require Logger
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describe "structured JSON formatter" do
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setup do
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{:ok, handler_cfg} = :logger.get_handler_config(:default)
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prev_formatter = handler_cfg.formatter
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new_formatter =
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Basic.new(metadata: [:request_id, :trace_id, :worker, :queue, :job_id])
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:ok = :logger.update_handler_config(:default, :formatter, new_formatter)
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on_exit(fn ->
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:logger.update_handler_config(:default, :formatter, prev_formatter)
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end)
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{:ok, formatter: new_formatter}
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end
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test "Basic formatter encodes an info log as a valid JSON object",
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%{formatter: {formatter_mod, formatter_cfg}} do
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# Build a `:logger` log event the same shape the handler feeds the
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# formatter, then assert the formatter's output is valid JSON with
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# the expected message and metadata fields.
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log_event = %{
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level: :info,
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msg: {:string, "hello-json"},
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meta: %{
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time: :os.system_time(:microsecond),
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request_id: "abc-123",
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worker: "TestWorker"
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}
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}
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rendered = formatter_mod.format(log_event, formatter_cfg)
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payload = rendered |> IO.iodata_to_binary() |> String.trim_trailing("\n")
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assert {:ok, decoded} = Jason.decode(payload)
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assert decoded["message"] == "hello-json"
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assert get_in(decoded, ["metadata", "request_id"]) == "abc-123"
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assert get_in(decoded, ["metadata", "worker"]) == "TestWorker"
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end
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test "swapping the :default handler formatter takes effect" do
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# Smoke test that the setup actually attached our JSON formatter
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# to the :default handler (i.e. the runtime.exs swap would land).
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{:ok, cfg} = :logger.get_handler_config(:default)
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assert match?({Basic, _}, cfg.formatter)
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end
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end
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end
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