User GuidesObservability (Local)

Dynamo Health Checks

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Overview

Dynamo provides health check and liveness HTTP endpoints for each component which can be used to configure startup, liveness and readiness probes in orchestration frameworks such as Kubernetes.

Environment Variables

VariableDescriptionDefaultExample
DYN_SYSTEM_PORTSystem status server port80819090
DYN_SYSTEM_STARTING_HEALTH_STATUSInitial health statusnotreadyready, notready
DYN_SYSTEM_HEALTH_PATHCustom health endpoint path/health/custom/health
DYN_SYSTEM_LIVE_PATHCustom liveness endpoint path/live/custom/live
DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUSEndpoints required for ready statenone["generate"]

Getting Started Quickly

Enable health checks and query endpoints:

$# Start your Dynamo components
$python -m dynamo.frontend --http-port 8000 &
$
$# Enable system status server on port 8081
$DYN_SYSTEM_PORT=8081 python -m dynamo.vllm --model Qwen/Qwen3-0.6B --enforce-eager &

Check health status:

$# Frontend health (port 8000)
$curl -s localhost:8000/health | jq
$
$# Worker health (port 8081)
$curl -s localhost:8081/health | jq

Frontend Liveness Check

The frontend liveness endpoint reports a status of live as long as the service is running.

Note: Frontend liveness doesn’t depend on worker health or liveness only on the Frontend service itself.

Example Request

curl -s localhost:8080/live -q | jq

Example Response

{
  "message": "Service is live",
  "status": "live"
}

Frontend Health Check

The frontend health endpoint reports a status of healthy as long as the service is running. Once workers have been registered, the health endpoint will also list registered endpoints and instances.

Note: Frontend liveness doesn’t depend on worker health or liveness only on the Frontend service itself.

Example Request

curl -v localhost:8080/health -q | jq

Example Response

Before workers are registered:

HTTP/1.1 200 OK
content-type: application/json
content-length: 72
date: Wed, 03 Sep 2025 13:31:44 GMT
{
  "instances": [],
  "message": "No endpoints available",
  "status": "unhealthy"
}

After workers are registered:

HTTP/1.1 200 OK
content-type: application/json
content-length: 609
date: Wed, 03 Sep 2025 13:32:03 GMT
{
  "endpoints": [
    "dyn://dynamo.backend.generate"
  ],
  "instances": [
    {
      "component": "backend",
      "endpoint": "clear_kv_blocks",
      "instance_id": 7587888160958628000,
      "namespace": "dynamo",
      "transport": {
        "nats_tcp": "dynamo_backend.clear_kv_blocks-694d98147d54be25"
      }
    },
    {
      "component": "backend",
      "endpoint": "generate",
      "instance_id": 7587888160958628000,
      "namespace": "dynamo",
      "transport": {
        "nats_tcp": "dynamo_backend.generate-694d98147d54be25"
      }
    },
    {
      "component": "backend",
      "endpoint": "load_metrics",
      "instance_id": 7587888160958628000,
      "namespace": "dynamo",
      "transport": {
        "nats_tcp": "dynamo_backend.load_metrics-694d98147d54be25"
      }
    }
  ],
  "status": "healthy"
}

Worker Liveness and Health Check

Health checks for components other than the frontend are enabled selectively based on environment variables. If a health check for a component is enabled the starting status can be set along with the set of endpoints that are required to be served before the component is declared ready.

Once all endpoints declared in DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS are served the component transitions to a ready state until the component is shutdown. The endpoints return HTTP status code of HTTP/1.1 503 Service Unavailable when initializing and HTTP status code HTTP/1.1 200 OK once ready.

Note: Both /live and /ready return the same information

Example Environment Setting

export DYN_SYSTEM_PORT=9090
export DYN_SYSTEM_STARTING_HEALTH_STATUS="notready"
export DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS="[\"generate\"]"

Example Request

curl -v localhost:9090/health | jq

Example Response

Before endpoints are being served:

HTTP/1.1 503 Service Unavailable
content-type: text/plain; charset=utf-8
content-length: 96
date: Wed, 03 Sep 2025 13:42:39 GMT
{
  "endpoints": {
    "generate": "notready"
  },
  "status": "notready",
  "uptime": {
    "nanos": 313803539,
    "secs": 12
  }
}

After endpoints are being served:

HTTP/1.1 200 OK
content-type: text/plain; charset=utf-8
content-length: 139
date: Wed, 03 Sep 2025 13:42:45 GMT
{
  "endpoints": {
    "clear_kv_blocks": "ready",
    "generate": "ready",
    "load_metrics": "ready"
  },
  "status": "ready",
  "uptime": {
    "nanos": 356504530,
    "secs": 18
  }
}