“No Available Server” means Traefik cannot find a healthy container for the HTTPS router behind your Coolify domain. The server itself may be online, DNS may be correct, and a TLS certificate may be valid while the application container is stopped, failing its health check, listening on the wrong port, bound only to localhost, or missing the labels Traefik needs. Diagnose the container and router in that order instead of changing DNS or certificates first.
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What the Coolify error actually means
Coolify uses Traefik as a reverse proxy. When a browser requests your secured domain, Traefik selects the router for that hostname and then forwards the request to a healthy application container. “No Available Server” is returned when Traefik has no usable backend for that router. Coolify’s troubleshooting guidance describes the condition as Traefik being unable to find any healthy container to route traffic to under the provided HTTPS URL.
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Use this diagnostic order
Work from the application outward. Each step either fixes the issue or gives you evidence for the next layer.
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- Confirm deployment state. Open the application’s deployment logs and Runtime Logs in Coolify. Verify that the latest deployment completed and that the process did not exit immediately after startup.
- Check container state. On the server, run the status command below. The target container should be running and should not show
(unhealthy). - Reproduce the health check inside the container. Use the application’s Terminal and run the same command or HTTP request configured in Coolify. Check the path, response, tool availability, and internal port.
- Verify the listening address and port. The application must listen on the port entered in Coolify’s Ports Exposes setting and normally bind to
0.0.0.0, not only loopback. - Verify domain and DNS assignment. Match the requested hostname exactly, including any
wwwvariant, and confirm the DNS record points to the server running this service. - Inspect Traefik logs and generated labels. Look for Docker API compatibility errors, router errors, or a missing
loadbalancer.server.portlabel. - If it happens only during updates, inspect replacement timing. Review health-check timeouts and rolling-update behavior before making proxy-wide changes.
Check whether the container is running and healthy
SSH to the Coolify server and run:
docker ps --format "table {{.Names}}t{{.Status}}t{{.Ports}}"Find the container associated with the affected application. A normal result includes an “Up” status and the expected exposed port. A status containing (unhealthy) means Docker is running the container but its configured health check is failing. A missing container, an “Exited” status, or a restart loop points to an application or deployment failure rather than a DNS problem.
Open Runtime Logs and the deployment logs in Coolify. Look for an exception during boot, a missing environment variable, a failed database connection, a migration that never completes, a process that exits after binding, or a command that is not present in the image. Fix the first startup error you see, then redeploy or restart the service and run the status command again.
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Do not treat a running container as proof that the web service is reachable. A container can remain “Up” while the application process has failed, is listening on another port, or is returning a failure response to every health check.
Fix health-check failures
Understand where the check runs
Dashboard-configured HTTP health checks run inside the application container. The final image therefore needs a request utility such as curl or wget. Installing either tool on the deployment server does not make it available inside the image. When every application container is unhealthy, Traefik may return “No available server” or a 404 response because it has no healthy backend.
For Docker Compose applications, define the health check in the Compose service or in the image’s Dockerfile. Do not assume that a generic application Healthcheck page is automatically used for a Compose service; the command and endpoint must be present in the service configuration that is actually deployed.
Run the exact check manually
Open the application’s Terminal in Coolify and execute the same command configured for the check. For an HTTP check, confirm all of the following:
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- The path exists in the deployed version.
- The request uses the container’s internal listening port, not a host-published port.
- The response is the success status expected by the check.
- The command uses a utility installed in the final image.
- The application is ready by the time the health-check interval and timeout expire.
If the endpoint requires authentication, redirects unexpectedly, depends on a database that is not ready, or returns a non-success status while warming up, choose a lightweight readiness endpoint that accurately indicates whether the service can accept traffic. Do not simply disable health checks to hide a startup failure: that can send users to a container that is running but unable to serve requests.
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Correct a bad command or image
Install curl or wget in the image used at runtime, not only in a build stage that is discarded. Then ensure the check’s URL and port match the process. Rebuild and redeploy so the running container contains the tool and the corrected endpoint. Re-run the command in the Coolify Terminal before testing the public domain.
Align the internal port with the process and domain
The port Traefik needs is the port where the process listens inside the container. It is not necessarily the host-published port shown in a local Docker tutorial. A mapping such as host port 8080 to container port 3000 still requires the proxy and health check to use the service’s internal port, 3000.
Verify all four port values
- Application process: the port passed to the framework or server command.
- Coolify Ports Exposes: the internal port entered for the resource.
- Health check: the port used by its command or URL.
- Domain configuration: the internal port appended to the domain when it is not 80.
These values must describe the same listener. Coolify’s Compose guidance requires the internal listening port in the domain value when the service does not listen on port 80. The first-application example uses nginx:alpine with Ports Exposes set to 80; that is an example of matching the container’s actual listener, not a requirement that every application use port 80.
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Check the application startup command and its framework configuration. In the container Terminal, inspect the process or listening sockets with the diagnostic tools available in the image. If the image is minimal and lacks those tools, use the application’s own startup output or temporarily add a diagnostic utility to a debugging build. The important result is the actual container port, not the port you intended to use.
After changing Ports Exposes or the domain, redeploy the resource so Coolify regenerates the proxy configuration. Test the health endpoint from inside the container and then request the public hostname.
Make the process reachable from Traefik
A web process bound to 127.0.0.1 accepts requests only from the same network namespace. A local test inside the container can therefore succeed while Traefik, connecting through the container network, receives a connection refusal or timeout. Coolify’s Dockerfile and Compose guidance recommends binding the service to 0.0.0.0.
Set the framework bind address
Use the framework’s host or bind option to set 0.0.0.0. The exact setting varies by runtime, so check the command used by your image rather than changing an unrelated operating-system setting. Keep the internal port unchanged unless you also update Coolify’s port and domain settings.
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Retest from both locations
- From the Coolify Terminal, request the service on its internal port and confirm a success response.
- Confirm the process is listening on
0.0.0.0:internal-port, not only127.0.0.1:internal-port. - Redeploy, wait for the health check to pass, and request the public HTTPS domain.
Check the domain, DNS, and service assignment
Compare the hostname in the browser with the hostname configured for the Coolify resource character for character. Differences between the apex name and a www name, a typo, or an unassigned subdomain can select a different router or no router at all.
- Confirm the DNS record resolves to the public IP address of the Coolify server.
- Confirm the domain is assigned to the intended application or Compose service.
- Confirm the assigned internal port matches the process.
- Test each hostname you publish separately; a certificate for one name does not configure another name.
A valid certificate proves that the TLS handshake completed for a hostname. It does not prove that the application container is healthy or that the router has a reachable backend. If HTTPS loads a certificate and then shows “No Available Server,” continue with container, health-check, port, and proxy diagnostics rather than replacing the certificate.
Distinguish deployment downtime from a persistent failure
Coolify lists brief deployment downtime as a possible cause. During a replacement, the old container may be removed while the new container is still starting or failing its health check. The public router can temporarily have no healthy target.
If the error appears only while updating, record how long it lasts and inspect the deployment logs. Review the resource’s rolling-update and health-check timing. A health check allows Coolify to wait for a ready replacement and can preserve the healthy version when the new check fails. Increasing a readiness timeout or correcting a slow startup can be appropriate; changing DNS or disabling the proxy is not.
If the error remains after the deployment reports success, treat it as a persistent routing problem and continue through the port, bind-address, domain, and Traefik checks. A one-time replacement gap and a container that never becomes healthy require different fixes.
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Read the proxy logs in Coolify
In Coolify, open Servers → [Your Server] → Proxy → Logs. You can also inspect the proxy container’s logs on the server. Search around the time of a request for Docker API compatibility errors, router creation errors, backend connection failures, or messages indicating that a service has no available server.
A Docker API version mismatch can prevent Traefik from discovering containers even when the application itself is healthy. Resolve the compatibility issue shown in the logs and then restart or redeploy the affected proxy only after recording the error and confirming the scope of the change.
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Check generated labels for custom domains
A documented Coolify issue records custom-domain failures when the generated label traefik.http.services.*.loadbalancer.server.port is missing. That label tells Traefik which internal port to use. If the affected resource has no correct service-port label, compare its generated labels with those of a newly deployed test service that routes successfully.
Label problems are version- or resource-specific. Avoid applying broad, manual proxy edits to every application before confirming the generated configuration on the affected container. Correct the resource’s port or deployment configuration where possible, redeploy, and then verify that the expected router and service labels are present.
Match the symptom to the most useful evidence
| Observed symptom | Most useful evidence | Likely layer | Next action |
|---|---|---|---|
| Container is absent or shows Exited | Deployment and Runtime Logs | Application startup or deployment | Fix the first crash, missing variable, or failed dependency and redeploy. |
| Container is Up but unhealthy | Health-check command and its response in the container | Health check, readiness, or image tools | Correct the path, port, expected status, startup timing, or install curl/wget. |
| Container is healthy but public domain fails | Process bind address, Ports Exposes, and domain value | Internal connectivity or routing target | Use the actual internal port and bind to 0.0.0.0. |
| Only one hostname fails | Hostname spelling, DNS record, and resource assignment | Domain or DNS | Correct the exact hostname and its record or service assignment. |
| Failure occurs only during updates | Deployment timeline and health-check timing | Replacement window | Review rolling-update behavior and readiness delays. |
| Several healthy services fail together | Proxy logs and Docker API errors | Traefik discovery or compatibility | Investigate the proxy and generated labels before changing applications individually. |
Targeted fixes by cause
The container stopped or crashes
Read the deployment and Runtime Logs, correct the startup command, environment variable, image entrypoint, or dependency that caused the exit, and deploy again. Confirm the status changes to running and healthy before testing the domain.
The health check is wrong
Run the configured check manually in the container. Correct its URL, internal port, path, expected response, or timeout. Ensure the final image contains the command-line tool it invokes. Redeploy and wait for a healthy status.
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Identify the process’s real internal listener, set that value in Ports Exposes, and include it in the domain configuration when it is not 80. Remove assumptions based solely on a host-published port.
The process binds to localhost
Change the framework’s bind setting to 0.0.0.0, redeploy, and confirm the listener and health check from the container before requesting the public URL.
The hostname is wrong
Correct the Coolify domain and DNS record so both point to the intended service. Test apex and www names independently if both are published.
Traefik cannot discover the service
Use the proxy logs to identify Docker API incompatibility or label generation errors. Compare the affected resource with a working deployment, correct the resource configuration, and redeploy. Make proxy-wide changes only when the logs show a proxy-wide fault.
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- Keep a lightweight readiness endpoint that reports success only when the application can serve real traffic.
- Ensure the runtime image includes every executable used by its health check, including
curlorwgetwhen required. - Document the internal listening port beside the application start command and keep it synchronized with Coolify’s Ports Exposes value.
- Bind web processes to
0.0.0.0inside containers unless the architecture intentionally uses another reachable address. - Test the exact production hostname, including each published
wwwor subdomain variant. - Watch deployment logs during replacements and allow enough time for dependencies and migrations before health checks begin failing.
- Keep a record of proxy-log errors and generated labels when diagnosing custom domains; this makes it possible to distinguish one-resource configuration errors from a proxy or Docker API incident.
What not to infer from “No Available Server”
The message does not identify one universal root cause. Do not infer that DNS is broken because the page is unavailable, that TLS is broken because the application is unreachable, or that the server needs a replacement simply because Traefik has no backend. Collect container status, health-check output, listening-port information, domain assignment, and proxy logs first. Changing several layers at once removes the evidence needed to tell which fix worked and can create a second configuration problem.
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