Works with Phoenix and with plain Plug/Cowboy applications. Request spans are published by a Plug in your endpoint pipeline, inside the recorded process.
Record your server
ct record --server --lang elixir -o ./trace -- mix phx.serveror, for a plain Plug application:
ct record --server --lang elixir -o ./trace -- mix run --no-haltFlags after the program name are passed through unchanged. Stop with Ctrl-C, which is a normal end.
Watch requests arrive
In a second terminal:
ct replay -t ./traceSend traffic and rows appear:
curl http://localhost:4000/users/7Double-click a row to jump to the code that handled the request.
Open a recording later
ct replay ./traceWhat gets recorded
- **The route from your router**, so parameterised routes group correctly.
- **Status and duration** per request.
- **Errors**, including the exception message.
A note on BEAM concurrency
The BEAM serves each request in its own lightweight process. These map onto *threads* within a single recording rather than separate recordings, so a burst of concurrent requests is one recording containing many overlapping intervals. The Request Panel shows them as separate rows even though they ran at the same time, and the recording preserves which ones genuinely overlapped.
Double-clicking a request row currently lands you at the request boundary rather than inside your handler function for some .ex modules. The span itself is correct — method, route, status and duration are all accurate, and the recording contains the handler — but the seek target may be earlier than you expect. Compiled .exs scripts are unaffected.
Requirements
Elixir 1.15 or newer, or Erlang/OTP 26 or newer for plain Erlang servers.
