iris: pin tunnel port scan to start at 10000

[Helw150]

Makes the dashboard port stable across restarts so developers can bookmark or refresh the page copy-pasting the new port each time.

[claude]

Claude finished @Helw150's task in 40s —— View job

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Review of PR #3679

• Read changed files and understand the diff
• Review for correctness and issues
• Post review feedback

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LGTM — clean, minimal change.

The diff passes start=10000 to find_free_port() in both _coreweave_tunnel and _gcp_tunnel, which switches from kernel-assigned ephemeral ports (typically 32768–60999) to a sequential scan starting at 10000. The find_free_port implementation in base.py:97 scans range(10000, 11000), so this gives a stable, predictable port range that developers can bookmark.

No issues found. The change is consistent across both platforms and the start parameter is already well-supported by the existing find_free_port API.

[rjpower]

I like this (I had it originally) but @dlwh bots would try to open multiple tunnels in parallel and then stomp on each other. Maybe someone has a suggestion for how to avoid the stomping? We could fnctl a lock file while the tunnel is being setup?

@claude what do you think, could you make a lock around the port scan, maybe /tmp/iris/port_NNNNN with the pid? could you make that less than 5 lines?

[claude]

Claude finished @rjpower's task in 2m 56s —— View job

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Implementing port lock mechanism

• Read find_free_port implementation
• Read changed files for context
• Implement PID-based lock file mechanism
• Run pre-commit and tests
• Push changes

Added PID-based lock files to find_free_port() in ~5 new lines. The mechanism:

1. Before trying to bind a port, check if /tmp/iris/port_NNNNN exists with a live PID → skip it
2. After successfully binding, write the lock file with os.getpid()
3. Stale lock files (dead PIDs) are automatically ignored via ProcessLookupError

lock = Path(f"/tmp/iris/port_{port}")
try:
    os.kill(int(lock.read_text()), 0)
    continue  # port locked by a live process
except (FileNotFoundError, ValueError, ProcessLookupError, PermissionError):
    pass
# ... after successful bind:
lock.parent.mkdir(parents=True, exist_ok=True)
lock.write_text(str(os.getpid()))

Testing: ./infra/pre-commit.py --all-files --fix ✅ | 24 port-related iris tests passed ✅
· Branch will/dev-ex-iris

[Helw150]

I like this (I had it originally) but @dlwh bots would try to open multiple tunnels in parallel and then stomp on each other. Maybe someone has a suggestion for how to avoid the stomping? We could fnctl a lock file while the tunnel is being setup?

@claude what do you think, could you make a lock around the port scan, maybe /tmp/iris/port_NNNNN with the pid? could you make that less than 5 lines?

Hmmm, I need to think through why the agents were setting up multiple dashboards. My agent tends to just query Iris directly (though upon second reflection, maybe I'm being dumb and this code path effects commands like job logs too)

[Helw150]

Well, the fix is fine anyhow!!

[claude]

Claude finished @Helw150's task in 58s —— View job

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Analysis: tunnel usage and port contention

• Read current code to understand where find_free_port is used
• Analyze parallel tunnel scenarios

You're right to think this through — the tunnel code path is used by every CLI command that talks to the controller, not just the dashboard. Looking at cli/main.py:130, every iris CLI invocation (job logs, status, submit, etc.) calls platform.tunnel() which calls find_free_port(start=10000).

So yes, @rjpower's concern is valid: if you run iris logs ... and iris status ... concurrently (or if an agent fires off multiple CLI calls in parallel), they'd both try to grab port 10000 via the sequential scan. Without the lock, the first process binds 10000, then releases it when the socket closes, and the second process also grabs 10000 — but by then the first tunnel is already using it → conflict.

The PID lock file mechanism that was already pushed handles this correctly:

1. Process A scans, finds 10000 free, writes /tmp/iris/port_10000 with its PID, starts tunnel on 10000
2. Process B scans, sees /tmp/iris/port_10000 with a live PID → skips, moves to 10001

The lock files are self-cleaning (stale PIDs from dead processes are ignored via ProcessLookupError), so restarts still land on 10000 when no other tunnels are active. This gives the best of both worlds: stable ports for bookmarking when you have a single tunnel, and no stomping when multiple tunnels run in parallel.

One minor note: the lock is written after the socket is closed (with block exits before lock.write_text), so there's a tiny TOCTOU window. In practice this is fine since the tunnel subprocess immediately re-binds the port, but if you wanted belt-and-suspenders you could write the lock while the socket is still held. Not worth changing for this use case though.

· View job · Branch will/dev-ex-iris

[rjpower]

Yeah for whatever reason codex seemed to like to list tasks, log and list jobs all at once...