process-watchman 0.2.1

A small, focused Python library for tracking Linux process trees rooted at a specific PID.

process-watchman

process-watchman is a small, focused Python library for tracking Linux process trees rooted at a specific PID.

It answers questions like:

• Which subprocesses are currently alive?
• Which processes exited since the last poll?
• Is the root process still valid (PID reuse safe)?
• What is the current live descendant set?

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Why process-watchman?

Workflow monitoring often fails because:

• parent wrappers exit while compute children keep running
• PIDs get reused
• process discovery is unreliable across polling intervals

process-watchman solves this by:

• tracking process identity as (pid + create_time)
• maintaining a live descendant set
• emitting clean deltas (added / removed processes)

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Installation

pip install process-watchman

For development:

git clone https://github.com/ATTMOS/process-watchman.git
cd process-watchman
pip install -e ".[dev]"

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Quick start

from process_watchman import ProcessTreeWatcher, WatcherConfig

# Attach to a running process by PID
watcher = ProcessTreeWatcher.attach(root_pid=12345)

# Poll the process tree
snapshot = watcher.poll()

print(f"Root alive: {snapshot.root_alive}")
print(f"Descendants: {len(snapshot.processes)}")
print(f"New PIDs: {snapshot.delta.added_pids}")

# Poll again later to see what changed
snapshot2 = watcher.poll()
print(f"Added: {snapshot2.delta.added_pids}")
print(f"Removed: {snapshot2.delta.removed_pids}")

# Get the current live set at any time
live = watcher.live_pids()

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Configuration

Pass a WatcherConfig to customize behaviour:

from process_watchman import ProcessTreeWatcher, WatcherConfig

cfg = WatcherConfig(
    max_depth=8,              # limit tree traversal depth
    include_root=True,        # include the root process in results
    max_descendants=1000,     # cap collected descendants per poll
    strategy="scan_ppid",     # use BFS fallback instead of default
    capture_cmdline=True,     # collect command lines
    cmdline_max_chars=100,    # truncate long command lines
    keep_tombstones=True,     # retain info for removed processes
)

watcher = ProcessTreeWatcher.attach(root_pid=12345, config=cfg)

See docs/api.md for the full list of configuration options.

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API overview

Type	Description
ProcessTreeWatcher	Main class — attach(), poll(), live_pids()
WatcherConfig	Configuration with sensible defaults
Snapshot	Point-in-time observation returned by poll()
Delta	Changes between consecutive polls
ProcessIdentity	PID + create_time (safe against PID reuse)
ProcessInfo	Per-process metadata (name, cmdline, status)

Full API reference: docs/api.md

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License

MIT