Use PID to assign rainbow colors to console output prefixes. (ray-pro…

…ject#26900)

When I use tune.run, different processes are distinguished by the number corresponding to their pid:

doc/source/ray-observability/ray-logging.rst

@@ -109,6 +109,15 @@ This produces the following output:
  (MyActor(index=2) pid=482120) hello there
  (MyActor(index=1) pid=482119) hello there
 
+Coloring Actor log prefixes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+By default Ray prints Actor logs prefixes in light blue:
+Users may instead activate multi-color prefixes by setting the environment variable ``RAY_COLOR_PREFIX=1``.
+This will index into an array of colors modulo the PID of each process.
+
+.. image:: images/images/coloring-actor-log-prefixes.png
+ :align: center
+
 Distributed progress bars (tqdm)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

python/ray/_private/worker.py

@@ -1859,6 +1859,28 @@ def color_for(data: Dict[str, str], line: str) -> str:
  return colorama.Style.BRIGHT + colorama.Fore.YELLOW
  else:
  return colorama.Style.BRIGHT + colorama.Fore.CYAN
+ elif os.getenv("RAY_COLOR_PREFIX") == "1":
+ colors = [
+ # colorama.Fore.BLUE, # Too dark
+ colorama.Fore.MAGENTA,
+ colorama.Fore.CYAN,
+ colorama.Fore.GREEN,
+ # colorama.Fore.WHITE, # Too light
+ # colorama.Fore.RED,
+ colorama.Fore.LIGHTBLACK_EX,
+ colorama.Fore.LIGHTBLUE_EX,
+ # colorama.Fore.LIGHTCYAN_EX, # Too light
+ # colorama.Fore.LIGHTGREEN_EX, # Too light
+ colorama.Fore.LIGHTMAGENTA_EX,
+ # colorama.Fore.LIGHTWHITE_EX, # Too light
+ # colorama.Fore.LIGHTYELLOW_EX, # Too light
+ ]
+ pid = data.get("pid", 0)
+ try:
+ i = int(pid)
+ except ValueError:
+ i = 0
+ return colors[i % len(colors)]
  else:
  return colorama.Fore.CYAN