;; marking those as data-only so that CIs and other automated systems don't try

;; to build

(data_only_dirs examples)

In this directory is a demo for live-monitoring runtime-events and detecting

stalls (extended periods of time when the Lwt main loop is not entered).

Stalls happen when too many of the promises make too many blocking calls. In the

example here (`Stallerlib.stall`) it's one promise which does increasingly long

blocking calls to `Unix.sleepf`. Stalls can also happen with many short blocking

calls (e.g., many promises logging to a file in a blocking way). Stalls

can also happen if promises execute long computations.

The detection relies on two mechanism. The first mechanism polls the runtime

event ring to record the latest occurrence of Lwt scheduler's events. The second

mechanism checks that this latest occurrence is recent enough.

The `selfdetector.ml` file shows how to run the detector in the same process as

the Lwt code. It runs in a separate domain so it executes in parallel.

The `stall-detect.sh` runs separate processes for the Lwt-based program which

stalls and a program which monitors the events of the first process.

This is a demo for producing a tail-trace for an Lwt program. The Lwt program

emits tracing events as introduced by the ppx. A separate program monitors the

execution of the Lwt program process and, upon a crash, it gets the content of

the events ring-buffer and dumps it into a perfetto-compatible format.

The produced trace shows the trace of execution for the end of the program, the

part leading to its crash. This is called "tail tracing."