feat(ml): make http keep-alive configurable

Closes #12064

docs/docs/install/environment-variables.md

@@ -168,6 +168,7 @@ Redis (Sentinel) URL example JSON before encoding:
 | `MACHINE_LEARNING_MODEL_INTER_OP_THREADS`        | Number of parallel model operations                                                                 |                  `1`                  | machine learning |
 | `MACHINE_LEARNING_MODEL_INTRA_OP_THREADS`        | Number of threads for each model operation                                                          |                  `2`                  | machine learning |
 | `MACHINE_LEARNING_WORKERS`<sup>\*2</sup>         | Number of worker processes to spawn                                                                 |                  `1`                  | machine learning |
+| `MACHINE_LEARNING_HTTP_KEEPALIVE_TIMEOUT_S`<sup>\*3</sup>      | HTTP Keep-alive time in seconds                                                               |                  `2`                  | machine learning |
 | `MACHINE_LEARNING_WORKER_TIMEOUT`                | Maximum time (s) of unresponsiveness before a worker is killed                                      | `120` (`300` if using OpenVINO image) | machine learning |
 | `MACHINE_LEARNING_PRELOAD__CLIP`                 | Name of a CLIP model to be preloaded and kept in cache                                              |                                       | machine learning |
 | `MACHINE_LEARNING_PRELOAD__FACIAL_RECOGNITION`   | Name of a facial recognition model to be preloaded and kept in cache                                |                                       | machine learning |
@@ -179,6 +180,8 @@ Redis (Sentinel) URL example JSON before encoding:
 
 \*2: Since each process duplicates models in memory, changing this is not recommended unless you have abundant memory to go around.
 
+\*3: For scenarios like HPA in K8S. https://github.com/immich-app/immich/discussions/12064
+
 :::info
 
 Other machine learning parameters can be tuned from the admin UI.

machine-learning/start.sh

@@ -13,11 +13,13 @@ fi
 : "${IMMICH_HOST:=[::]}"
 : "${IMMICH_PORT:=3003}"
 : "${MACHINE_LEARNING_WORKERS:=1}"
+: "${MACHINE_LEARNING_HTTP_KEEPALIVE_TIMEOUT_S:=2}"
 
 gunicorn app.main:app \
 	-k app.config.CustomUvicornWorker \
 	-b "$IMMICH_HOST":"$IMMICH_PORT" \
 	-w "$MACHINE_LEARNING_WORKERS" \
 	-t "$MACHINE_LEARNING_WORKER_TIMEOUT" \
 	--log-config-json log_conf.json \
+	--keep-alive "$MACHINE_LEARNING_HTTP_KEEPALIVE_TIMEOUT_S" \
 	--graceful-timeout 0