feat(serverless): coordinate early health checks once per container

ARCHITECTURE.md

@@ -599,12 +599,12 @@ log.error(message, job_id=None)
 
 ### Fitness Checks: `modules/rp_fitness.py`
 
-**Location**: `runpod/serverless/modules/rp_fitness.py`
+**Location**: `runpod/_health/fitness.py` (legacy `serverless.modules.rp_fitness` imports remain aliases)
 
 **Responsibilities**:
 - Validate worker health at startup before handler initialization
 - Support both synchronous and asynchronous check functions
-- Exit immediately with sys.exit(1) on any check failure
+- Exit immediately with os._exit(1) on any check failure
 - Enable fail-fast deployment validation
 
 **Key Functions**:
@@ -613,11 +613,11 @@ log.error(message, job_id=None)
 - `clear_fitness_checks()`: Clear registry (testing only)
 
 **Execution Flow**:
-1. Called from `worker.py:40` before heartbeat starts: `asyncio.run(run_fitness_checks())`
+1. The first top-level `import runpod` with both `RUNPOD_ENDPOINT_ID` and `RUNPOD_WEBHOOK_GET_JOB` runs the built-in hardware checks (RAM, disk, CUDA version, native GPU test), excluding `RUNPOD_TEST`, `--test_input`, and `--rp_serve_api` invocations. On success the process sets `RUNPOD_EARLY_FITNESS_CHECKS_DONE=1`, which child processes inherit so they skip the pass. Network, Python CUDA initialization, compute, and custom checks remain at worker start. `RUNPOD_DEFER_FITNESS_CHECKS=true` postpones early checks. No custom launcher or entrypoint changes are required.
 2. Runs only in production mode (skipped for local testing)
 3. Auto-detects sync vs async using `inspect.iscoroutinefunction()`
 4. Executes checks in registration order (list preserves order)
-5. On failure: log detailed error, call `sys.exit(1)`
+5. On health failure: log, best-effort unhealthy report, force-kill via `os._exit(1)`. Registration is atomic; early setup errors defer, unresolved worker-start setup errors report `fitness_check_setup` and force-exit.
 6. On success: log completion, proceed with worker startup
 
 **Performance**: ~0.5ms framework overhead per check, total depends on check logic
@@ -765,7 +765,7 @@ sequenceDiagram
             CHECK->>CHECK: Log success
         else Check fails
             CHECK->>SYS: Log error + traceback
-            CHECK->>SYS: sys.exit(1)
+            CHECK->>SYS: os._exit(1)
         end
     end
 

README.md

@@ -143,7 +143,9 @@ runpod.serverless.start({"handler": handler})
 
 **Key Features:**
 - Supports both synchronous and asynchronous check functions
-- Checks run only once at worker startup (production mode)
+- Hardware checks run once per process tree at the first Serverless import; child processes inherit the result via `RUNPOD_EARLY_FITNESS_CHECKS_DONE`
+- Local tests and non-worker imports remain exempt; network readiness and custom checks run at worker start
+- Successful early checks are reused at worker start unless their configuration changes
 - Runs before handler initialization and job processing begins
 - Any check failure exits with code 1 (worker marked unhealthy)
 

docs/serverless/worker_fitness_checks.md

@@ -41,6 +41,20 @@ if __name__ == "__main__":
     runpod.serverless.start({"handler": handler})
 ```
 
+## When Checks Run
+
+On Serverless, the first `import runpod` runs RAM, disk, CUDA-version, and native GPU health checks. Eligibility requires both `RUNPOD_ENDPOINT_ID` and `RUNPOD_WEBHOOK_GET_JOB`. Platform tests (`RUNPOD_TEST`), `--test_input`, and local `--rp_serve_api` invocations skip early checks.
+
+Each process tree runs these checks once. When the pass succeeds, the process sets `RUNPOD_EARLY_FITNESS_CHECKS_DONE=1` in its own environment. Child processes inherit it, so `multiprocessing` spawn workers that re-import the handler, subprocesses, and shell wrappers skip the early pass instead of repeating the hardware probes. A failed check exits before the marker is set, so the marker only ever means a parent process passed. Unrelated processes that do not inherit the environment run their own checks. The first import may occur after model loading; no earlier timing is guaranteed in that case.
+
+Network connectivity, Python CUDA initialization, GPU compute, and customer-registered checks run in the worker process at `.start()`, before accepting jobs. Network checks retry against the worker API with a bounded budget. Keeping Python CUDA initialization out of imports protects subsequent customer forks.
+
+`RUNPOD_DEFER_FITNESS_CHECKS=true` restores worker-start timing. `RUNPOD_SKIP_FITNESS_CHECKS=true` disables all checks. Set early thresholds before importing the SDK; late changes are applied at worker start. No launcher or Docker entrypoint changes are needed.
+
+### Rollout
+
+Validate in a small set of workers before broader rollout. The deferral variable provides a rollback of early timing without handler edits. This SDK change does not itself alter deployed platform configuration.
+
 ## Async Fitness Checks
 
 Fitness checks support both synchronous and asynchronous functions:
@@ -284,19 +298,17 @@ Disk space check passed: 50.00GB free (50.0% available)
 
 ### Network Connectivity
 
-Tests basic internet connectivity for API calls and job processing.
+Tests TCP reachability of the worker API host at worker start.
 
-- **Default**: 5 second timeout to 8.8.8.8:53
-- **Configure**: `RUNPOD_NETWORK_CHECK_TIMEOUT=10`
-
-What it checks:
-- Connection to Google DNS (8.8.8.8 port 53)
-- Response latency
-- Overall internet accessibility
+- **Default**: Up to three attempts within a 5-second total connection/cleanup budget.
+- **Configure**: `RUNPOD_NETWORK_CHECK_TIMEOUT=10` (positive seconds).
+- **Target**: Host and port from `RUNPOD_WEBHOOK_GET_JOB`; defaults to `api.runpod.ai:443` if absent. URL paths and credentials are not sent or logged by this probe.
+- Tests connection reachability, not API authentication or full application readiness.
+- Retries temporary connection failures; persistent failure exits through the worker failure path.
 
 Example log output:
 ```
-Network connectivity passed: Connected to 8.8.8.8 (45ms)
+Network connectivity passed: Connected to api.runpod.ai:443
 ```
 
 ### CUDA Version (GPU workers only)
@@ -343,15 +355,15 @@ ERROR  | Fitness check failed: _cuda_init_check | RuntimeError: Failed to initia
 
 Quick matrix multiplication to verify GPU compute functionality and responsiveness. Skips silently on CPU-only workers.
 
-- **Default**: 100ms maximum execution time
-- **Configure**: `RUNPOD_GPU_BENCHMARK_TIMEOUT=2`
+- **Default**: 2 seconds maximum execution time
+- **Configure**: `RUNPOD_GPU_BENCHMARK_TIMEOUT=2` (seconds)
 
 What it tests:
 - GPU compute capability (matrix multiplication)
 - GPU response time
 - Memory bandwidth to GPU
 
-If the operation takes longer than 100ms, the worker exits as the GPU is too slow for reliable job processing.
+If the operation takes longer than the timeout, the worker exits as the GPU is too slow for reliable job processing.
 
 Example log output:
 ```
@@ -371,13 +383,15 @@ ENV RUNPOD_NETWORK_CHECK_TIMEOUT=10
 ENV RUNPOD_GPU_BENCHMARK_TIMEOUT=2
 ```
 
-Or in Python:
+For deferred launches, settings can also be configured in Python before worker start:
 
 ```python
 import os
 
 os.environ["RUNPOD_MIN_MEMORY_GB"] = "8.0"
 os.environ["RUNPOD_MIN_DISK_PERCENT"] = "15.0"
+
+import runpod
 ```
 
 ### Disabling Built-in Checks
@@ -388,6 +402,8 @@ For testing or specialized deployments, built-in checks can be disabled via envi
 |---|---|
 | `RUNPOD_SKIP_AUTO_SYSTEM_CHECKS=true` | Skips auto-registration of memory, disk, network, CUDA version, CUDA init, and GPU benchmark checks |
 | `RUNPOD_SKIP_GPU_CHECK=true` | Skips auto-registration of the native GPU memory allocation test (`gpu_test` binary) |
+| `RUNPOD_SKIP_FITNESS_CHECKS=true` | Skips every fitness check, built-in **and** user-registered |
+| `RUNPOD_DEFER_FITNESS_CHECKS=true` | Keeps the checks but runs them only at `runpod.serverless.start()`, not at import |
 
 ```python
 import os
@@ -397,15 +413,19 @@ os.environ["RUNPOD_SKIP_AUTO_SYSTEM_CHECKS"] = "true"
 
 # Disable the automatic GPU memory allocation test
 os.environ["RUNPOD_SKIP_GPU_CHECK"] = "true"
+
+import runpod
 ```
 
-User-registered checks via `@register_fitness_check` still run regardless of these flags.
+For early checks, set these before launching the handler. For deferred launches, set them before worker start.
+
+User-registered checks via `@register_fitness_check` still run regardless of `RUNPOD_SKIP_AUTO_SYSTEM_CHECKS` and `RUNPOD_SKIP_GPU_CHECK`. Only `RUNPOD_SKIP_FITNESS_CHECKS` disables those too.
 
 ## Behavior
 
 ### Execution Timing
 
-- Fitness checks run **only once at worker startup**
+- Early checks run in eligible Serverless containers; the final pass runs before job processing. Successful checks are reused unless their configuration changes.
 - They run **before the first job is processed**
 - They run **only on the actual Runpod serverless platform**
 - Local development and testing modes skip fitness checks
@@ -555,7 +575,7 @@ async def check_api_with_retry():
 
 ## Testing
 
-When developing locally, fitness checks don't run. To test them, you can manually invoke the runner:
+When developing locally, fitness checks don't run. To test them, you can manually invoke the runner. Note that each check runs once per process: a second `run_fitness_checks()` call skips checks that already passed, so call `clear_fitness_checks()` (as below) between runs:
 
 ```python
 import asyncio

runpod/__init__.py

@@ -3,6 +3,10 @@
 import logging
 import os
 
+from ._startup import run_import_checks
+
+run_import_checks()
+
 from . import serverless
 from .api.ctl_commands import (
     create_container_registry_auth,

runpod/_health/__init__.py

@@ -0,0 +1,22 @@
+"""Lightweight Serverless environment detection; no SDK imports."""
+
+import os
+import sys
+
+
+def is_serverless_environment() -> bool:
+    """Recognize production worker configuration, excluding platform tests."""
+    return (
+        bool(os.environ.get("RUNPOD_ENDPOINT_ID", "").strip())
+        and bool(os.environ.get("RUNPOD_WEBHOOK_GET_JOB", "").strip())
+        and os.environ.get("RUNPOD_TEST", "").strip().lower()
+        not in ("1", "true", "yes", "on")
+    )
+
+
+def is_early_check_eligible() -> bool:
+    """Eligibility for shared early checks, not an assertion of process identity."""
+    return is_serverless_environment() and not any(
+        arg.split("=", 1)[0] in ("--test_input", "--rp_serve_api")
+        for arg in sys.argv[1:]
+    )

runpod/_health/cuda.py

@@ -0,0 +1,22 @@
+"""
+Provides some of the torch.cuda functionality without requiring torch.
+"""
+
+import subprocess
+
+
+def is_available():
+    """
+    Returns True if CUDA is available, False otherwise.
+    """
+    try:
+        # Bounded: this runs at `import runpod` on real workers, where a wedged
+        # nvidia-smi must not hang the boot forever.
+        output = subprocess.check_output(
+            ["nvidia-smi"], stderr=subprocess.DEVNULL, timeout=5
+        )
+        if "NVIDIA-SMI" in output.decode():
+            return True
+    except Exception:  # pylint: disable=broad-except
+        pass
+    return False