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Coolify Sentinel is a lightweight Rust agent that runs as the coolify-sentinel container on an eligible connected Docker server. Enable it from Servers > [server] > Sentinel > Configuration, select Enable Sentinel, then choose Sync (or Restart if it is already running). When the server header shows Sentinel In Sync, Coolify is receiving authenticated heartbeat, container-state, Docker-health, and root-filesystem usage data. CPU and memory history require the separate metrics collector, and public endpoint uptime or long-term log analytics still require an external monitoring system.
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What Coolify Sentinel is and how it works
Sentinel is Coolify’s server-side status agent. Coolify launches it as a container named coolify-sentinel on a connected Docker server. The agent authenticates to the Coolify control plane and periodically sends the server information needed for the panel to determine whether the host and its workloads are operating normally.
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In practical terms, Sentinel answers questions such as “Is this connected host still reporting?” and “Does Docker think this resource is running and healthy?” It does not answer every customer-facing question. A running web container can still return an error to users, a private network route can work while a public route fails, and a successful health check can omit a business dependency. Treat Sentinel as a platform signal, not a complete application test.
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Coolify stores the Sentinel credential in its instance database in encrypted form and supplies it to the agent through an environment variable. Treat that token like any other service credential: do not paste it into tickets, shell history, screenshots, or public configuration files. Anyone who obtains it may be able to impersonate the agent, so keep access to the Coolify instance and its backups restricted as well.
Check eligibility before enabling Sentinel
Sentinel is available for a supported, connected standard Docker server. Current Coolify documentation excludes build servers and Docker Swarm servers. If the server is one of those types, changing the Sentinel setting will not make the agent supported; place the workload on a standard Docker server instead.
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- Reachable Coolify address: the instance URL configured in Coolify must be non-empty and reachable from the server. This can be the normal instance URL or the custom URL configured for the server’s Sentinel settings.
- Valid generated credential: use the token Coolify creates for Sentinel. Do not invent a token or substitute an unrelated API key.
- Network path: outbound connectivity from the server to the Coolify URL must allow the agent’s authenticated status updates.
Check DNS resolution, firewall policy, reverse-proxy routing, and TLS behavior from the server itself, not only from your laptop. A URL that opens in an administrator’s browser may still be inaccessible to a host on a private network. If Coolify is behind a proxy, the address used by Sentinel must route to the instance and accept the agent’s requests.
Checking these conditions first separates an agent configuration problem from a server-type or network problem. A server can continue to be managed through Coolify’s existing mechanisms even when Sentinel is not active.
Enable Sentinel in the Coolify dashboard
- Open the server record. In Coolify, go to Servers and select the connected Docker server you want to observe.
- Open Sentinel settings. Select Sentinel > Configuration.
- Turn on the agent. Choose Enable Sentinel. Coolify prepares the generated token and the agent configuration for that server.
- Apply the configuration. Select Sync. If Sentinel is already running, the same action is labeled Restart; use it to reload the current configuration and credential.
- Confirm the state. Wait for the server header to display Sentinel In Sync. That status confirms that Coolify has received a current update from the agent.
Do not treat the presence of a running container alone as success. The useful test is the synchronization state in the server header, because it confirms communication with the Coolify control plane rather than merely local container creation. A first synchronization can take longer than the eventual reporting cadence while the container starts, resolves the URL, and performs its first authenticated push.
After changing the URL, enabling metrics, or regenerating a token, apply the change with Sync or Restart. Leaving an old container running can leave it with stale environment values, making the dashboard appear misconfigured even though the new setting is correct.
What Sentinel reports
| Signal | What it tells you | What it does not provide |
|---|---|---|
| Server heartbeat and synchronization state | Whether the agent is reaching Coolify and sending current status. | It is not an outside-in internet availability test. |
| Container running state | Whether Docker reports a workload container as running. | A running process does not prove that every user workflow succeeds. |
| Docker health information | The health result exposed by a container’s configured Docker health check. | Containers without a meaningful health check have less application-level coverage. |
| Root filesystem usage | Space consumption on the server’s root filesystem, useful for detecting storage pressure. | It is not a complete inventory of every mounted volume or remote storage system. |
| CPU and memory history (optional) | Charts and history collected when the separate metrics collector is enabled. | These charts do not appear merely because Sentinel status reporting is enabled. |
The distinction between running and healthy matters during incidents. Docker can report a process as running even when the application is stuck, returning errors, or unable to reach a database. A Docker health check adds another signal only when the image or Compose configuration defines a useful check and the check tests the condition that matters.
Root filesystem usage is a host-level warning, not a storage inventory. It can reveal a filling system partition caused by images, temporary files, or logs, but it does not describe every data volume, remote mount, or application quota. Investigate the affected mount directly before deleting files or pruning images.
Coolify’s built-in monitoring can also surface selected operational notifications and forward workload logs, depending on the resource and configuration. Those capabilities should not be confused with a long-term log platform: retention, querying, dashboards, and log-based alert rules beyond Coolify’s built-in scope need another system.
Sentinel timing and metrics settings
The standalone Sentinel repository documents defaults that explain the expected cadence, but a Coolify release can configure different values. Treat these as repository defaults, not a promise that every installation uses them.
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| Setting | Repository default | Interpretation |
|---|---|---|
PUSH_INTERVAL_SECONDS |
60 seconds | The agent pushes a status update about once per minute under the standalone configuration. |
| Collector refresh rate | 5 seconds | The metrics collector refreshes collected values at this interval when metrics are enabled. |
| Metric retention | 7 days | The standalone collector keeps metric history for seven days unless the deployment changes it. |
Because the values can be changed by the Coolify release or server configuration, use the settings shown for your installation when diagnosing timing. A one-minute push interval means a brief delay is normal; it does not by itself indicate a failed agent. Conversely, repeatedly seeing an old heartbeat well beyond the expected interval is meaningful evidence of a communication or process problem.
Collector refresh and push cadence are different concepts. The collector can sample values every five seconds while the agent publishes status less often. Enabling a faster collector therefore does not guarantee that the dashboard receives a new server heartbeat every five seconds, and extending retention does not create data that was never collected.
Understand “Sentinel In Sync” and “Sentinel Out of Sync”
Sentinel In Sync
This state means Coolify is receiving current authenticated updates from the agent. The dashboard can use those updates for heartbeat, container, Docker-health, and root-filesystem status, subject to the signals available on the server and its containers.
Sentinel Out of Sync
Coolify marks the server Sentinel Out of Sync when the expected heartbeat becomes stale. While the agent is unavailable, Coolify falls back to SSH-based checks for server operations. That fallback helps retain management visibility, but it does not restore the agent’s normal push path or optional metrics history.
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A transient out-of-sync state can occur during a restart or network interruption. If the state persists beyond the configured push cadence, follow the troubleshooting branches below rather than repeatedly clicking Sync without checking connectivity and credentials.
Troubleshoot Sentinel methodically
The header remains Sentinel Out of Sync
- Open the server’s Sentinel configuration and verify that the Coolify URL is present, correctly formed, and reachable from that server.
- Check for a DNS, firewall, reverse-proxy, TLS, or routing problem between the server and the Coolify instance.
- Use Sync when Sentinel is stopped, or Restart when it is already running.
- Wait through at least one expected push interval and check whether the header changes to Sentinel In Sync.
If the URL cannot be reached from the server, restarting the container will not solve the underlying path failure. Check the container’s startup and connection logs, but avoid exposing its token while collecting diagnostics. If only one server is affected, compare its URL, DNS path, and egress policy with a known-good connected server.
Logs show an authorization error
Regenerate the Sentinel token in Coolify rather than creating a replacement by hand. After regeneration, synchronize or restart Sentinel so the container receives the new credential. A token that was copied incorrectly, revoked, or associated with another server will continue to fail until the Coolify-generated value is applied.
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No CPU or memory charts appear
Sentinel status reporting and metrics collection are separate features. Open the server’s Charts page and confirm that metrics are enabled. If Sentinel is in sync but charts are empty, first correct the metrics setting and then allow the collector to gather data; a healthy heartbeat alone does not create historical CPU or memory series.
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Also check the selected history window and the release’s effective refresh and retention values. A newly enabled collector has no historical backlog, so an empty chart immediately after activation is expected. If data never appears after collection time has elapsed, treat metrics enablement and collector health as a separate troubleshooting path from Sentinel synchronization.
The server is a build or Swarm server
Those server types are outside Sentinel’s supported scope. Do not spend time rotating tokens or changing push intervals for an unsupported host. Move the workload to a supported standard Docker server when Sentinel-based status reporting is required.
You need endpoint uptime or alert thresholds
Sentinel does not probe a public URL from outside your infrastructure, and Coolify’s built-in monitoring does not provide chart-based CPU or memory threshold alerting. Add an external uptime or observability system for those requirements.
When Coolify monitoring is enough—and when it is not
The right design depends on where a check runs, which signal it evaluates, and how long the resulting data must be retained. Sentinel is strongest for Coolify-aware infrastructure status; an external service is necessary when the question must be answered from outside the server or across systems.
| Capability | Coolify with Sentinel | External monitoring system |
|---|---|---|
| Monitoring location | Agent runs inside the connected Coolify server and reports to the Coolify control plane. | Checks can originate outside your infrastructure or from multiple regions and networks. |
| Primary signals | Server heartbeat, container running state, Docker health, and root filesystem usage. | Public endpoint availability, TLS or DNS checks, workflow transactions, and broader infrastructure signals. |
| CPU and memory | Historical charts are available when the separate metrics collector is enabled. | Provider-specific dashboards and threshold rules can evaluate collected metrics. |
| Alerting | Coolify notifications and operational status for supported resources. | Threshold, synthetic-check, escalation, and log-based rules, depending on the service. |
| Retention | Standalone collector default is seven days; an actual Coolify release may configure another value. | Retention is controlled by the provider or your storage configuration and can be longer-term. |
| Logs | Coolify can forward workload logs within its built-in feature set. | Long-term storage, search, dashboards, correlation, and log-derived alerts. |
| Application workflows | Visibility is tied to the health endpoint and resource checks configured in Coolify. | Can execute multi-step or business-transaction checks beyond a single health endpoint. |
Use Sentinel alone when
- Your main question is whether the Coolify server is reachable and whether deployed containers are running and healthy.
- Root filesystem pressure is the storage condition you need to watch.
- Short-lived operational history and Coolify-native notifications meet your response requirements.
Add external monitoring when
- Customers must be checked from outside the hosting network.
- You need CPU or memory threshold alerts instead of manually reviewing charts.
- Incident response requires long-term logs, searchable dashboards, or log-based alert rules.
- The application has workflows that can fail even while its container and configured health endpoint remain healthy.
A common production pattern is to use both layers: Sentinel gives the deployment platform an authenticated host and container view, while an external service checks the public URL and sends independent alerts. Keeping those paths independent helps distinguish a server outage from a Coolify control-plane, proxy, DNS, or monitoring-path outage.
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Automate Sentinel settings through the API
Coolify exposes authenticated API operations to retrieve and update per-server Sentinel settings. The settings model includes Sentinel enablement, metrics enablement, token fields, metric refresh rate, history duration, push interval, a custom URL, and traffic-analytics controls. This makes it possible to standardize configuration across servers or apply changes through infrastructure automation instead of the dashboard.
Design automation around least privilege. Reading sensitive token fields requires the read:sensitive ability or a root token, so a routine configuration job should not receive that access unless it genuinely needs to handle credentials. Store any token returned by an authorized operation in a secret manager, pass it only to the intended server configuration, and avoid writing it to build logs.
Before changing intervals or retention programmatically, confirm which values your Coolify release supports. The repository defaults of 60 seconds, 5 seconds, and seven days describe the standalone service and may not match your instance. A configuration pipeline should also verify the resulting synchronization state rather than assuming that an accepted API response means the agent is communicating.
When applying settings to several servers, identify each server explicitly and verify the resulting URL and enablement state per host. A successful update to one server does not imply that another server has the same network reachability or supported type. Keep configuration changes auditable, and separate ordinary settings access from the permission needed to read sensitive token fields.
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A practical operating checklist
- Record the server type and confirm it is a connected standard Docker server.
- Verify that the Coolify URL resolves and is reachable from the server.
- Enable Sentinel under Servers > [server] > Sentinel > Configuration.
- Use Sync, or Restart after a configuration or token change.
- Wait for Sentinel In Sync before treating the setup as complete.
- Check heartbeat, container state, Docker health, and root filesystem usage for the signals relevant to the workload.
- Enable metrics separately on the server’s Charts page when CPU or memory history is required.
- Keep the generated token confidential and rotate it through Coolify if authorization fails.
- Pair Sentinel with external checks for public uptime, threshold alerting, long-term logs, or workflow monitoring.
Configured this way, Sentinel gives Coolify a timely, authenticated view of the server and its Docker workloads without pretending to be a complete external observability system.
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Frequently Asked Questions
How do I monitor my server with Coolify Sentinel?
Use a supported connected standard Docker server, verify that its Coolify URL is reachable, then open Servers > [server] > Sentinel > Configuration. Enable Sentinel, select Sync (or Restart), and wait for Sentinel In Sync.
What does Coolify Sentinel monitor?
It reports the server heartbeat, container running state, Docker health information, and root filesystem usage. CPU and memory history are collected only when the separate metrics collector is enabled.
Why is Sentinel out of sync?
The heartbeat has become stale. Check that the Coolify URL is non-empty and reachable from the server, inspect DNS, firewall, proxy, TLS, and routing, then synchronize or restart Sentinel and wait through the expected push interval.
Do I need an external uptime monitor with Coolify?
Use one when you need public endpoint checks from outside your infrastructure, synthetic workflow tests, independent alerting, or long-term observability. Sentinel is focused on Coolify-side server and container status.
Can Sentinel run on a build server or Docker Swarm server?
No. Current Coolify documentation excludes build servers and Docker Swarm servers. Use a supported standard Docker server for Sentinel-based monitoring.
Why are CPU and memory charts empty when Sentinel is in sync?
Sentinel status reporting and metrics collection are separate. Enable metrics on the server’s Charts page and allow the collector to gather data; an in-sync heartbeat does not create charts by itself.
What should I do if Sentinel logs show an authorization error?
Regenerate the Sentinel token in Coolify, then use Sync or Restart so the container receives the new credential. Never replace it with an invented or unrelated API key.
How long does Sentinel retain metrics?
The standalone repository default is seven days, with a five-second collector refresh and a 60-second push interval. A Coolify release or server configuration can use different values, so verify the effective settings on your installation.
The Bottom Line
Bottom line: Enable Sentinel on a supported connected Docker server, verify the Coolify URL and generated token, and wait for Sentinel In Sync. It provides lightweight heartbeat, container, Docker-health, and root-filesystem visibility; enable metrics separately for CPU and memory history. Add external uptime, alerting, and log systems when you need public checks, thresholds, long-term retention, or workflow-level monitoring.
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