| name | dial9-red-flags |
| description | Automated health checks for dial9 Tokio runtime traces. Detects long polls, task leaks, scheduling delays, blocking calls, queue buildup, worker imbalance, CPU contention, and span anomalies. Use when you want a quick automated assessment of trace health. |
Red Flags: Automated Health Checks
Run scripts/red_flag_scan.js against any trace to surface common Tokio runtime problems.
node scripts/red_flag_scan.js <trace.bin or directory>
Each finding has a severity: critical, warning, or info.
Checks performed
long-poll
A single .poll() call took too long. This blocks the worker from processing other tasks. The fixed >10ms warning / >50ms critical cutoffs here are a coarse default, not a universal truth — "long" is really relative to this runtime's own poll distribution. In a service whose p99 poll is 500µs, a 1ms poll is a severe tail outlier these cutoffs miss entirely; in a batch job whose p99 is 40ms, a 20ms poll is normal. Calibrate against pollDurationByLoc (p50/p99 per spawn location) before trusting an absolute threshold. Look at poll.cpuSamples and poll.schedSamples for stack traces. To root-cause why a flagged poll was long — especially an off-CPU one with no scheduling stacks — use the dial9-diagnose-long-poll skill (which thresholds on p99 by default), and dial9-zoom-window to inspect the surrounding instant.
task-leak
Active task count grows without bound. Tasks are spawned but never complete. Check taskSpawnLocs for spawn locations of unterminated tasks.
sched-delay
Time between Waker::wake() and the task being polled exceeds 5ms. All workers are busy. Fix: shorter polls, more workers, or yield points.
blocking-calls
Scheduling samples (source=1) reveal blocking system calls (file I/O, DNS resolution, mutex contention) on the async runtime. These should use spawn_blocking or a dedicated thread.
queue-depth
Global injection queue exceeds 100 (warning) or 1000 (critical). The runtime cannot keep up with incoming work.
worker-imbalance
Poll counts differ by more than 3x across workers. Work-stealing may not be distributing evenly, or one worker is stuck on long polls.
cpu-contention
Workers are active but spending less than 50% of wall time on CPU. The kernel is descheduling them due to CPU contention.
kernel-sched-wait
Worker unpark takes more than 1ms of kernel scheduling wait. Indicates CPU contention at the OS level.
many-spans-per-poll
A single poll contains more than 20 span enter/exit pairs. Usually a tight loop without yielding.
span-duration-outlier
A span whose duration exceeds 10x the P50 for its name. Flags individual slow operations.
unmatched-spans
Spans with enter but no exit. Small counts are normal at segment boundaries. Large counts may indicate task cancellation or a bug in span instrumentation.
