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https://github.com/muxinc/certificate-expiry-monitor

Utility that exposes the expiry of TLS certificates as Prometheus metrics
https://github.com/muxinc/certificate-expiry-monitor

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Utility that exposes the expiry of TLS certificates as Prometheus metrics

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Utility that exposes the expiry of TLS certificates as Prometheus metrics



## Building

To build the Docker image, simply run `docker build`:

```

docker build . -t muxinc/certificate-expiry-monitor:latest

```



## Running

Run the Docker image using the executable at `/app`:

```

→ docker run muxinc/certificate-expiry-monitor:latest /app --help

Usage of ./certificate-expiry-monitor:

  -domains string

        Comma-separated SNI domains to query

  -frequency duration

        Frequency at which the certificate expiry times are polled (default 1m0s)

  -hostIP

        If true, then connect to the host that the pod is running on rather than to the pod itself.

  -ignoredDomains string

        Comma-separated list of domains to exclude from the discovered set. This can be a regex if the string is wrapped in forward-slashes like /.*\.domain\.com$/ which would exclude all domain.com subdomains.

  -ingressNamespaces string

        If provided, a comma-separated list of namespaces that will be searched for ingresses with domains to automatically query

  -insecure

        If true, then the InsecureSkipVerify option will be used with the TLS connection, and the remote certificate and hostname will be trusted without verification (default true)

  -kubeconfig string

        Path to kubeconfig file if running outside the Kubernetes cluster

  -labels string

        Label selector that identifies pods to query

  -logformat string

        Log format (text or json) (default "text")

  -loglevel string

        Log-level threshold for logging messages (debug, info, warn, error, fatal, or panic) (default "error")

  -metricsPort int

        TCP port that the Prometheus metrics listener should use (default 8888)

  -namespaces string

        Comma-separated Kubernetes namespaces to query (default "default")

  -port int

        TCP port to connect to each pod on (default 443)

```



### Kubernetes Manifest

You're probably going to want to run the certificate-expiry monitor in a Kubernetes cluster. The following manifest shows how you might monitor a set of ingress pods matching the label `k8s-app=my-ingresses` in the `default` namespace for the `foobar.example.com` domain:



```yaml

apiVersion: extensions/v1beta1

kind: Deployment

metadata:

  name: certificate-expiry-monitor

  namespace: default

spec:

  minReadySeconds: 5

  revisionHistoryLimit: 3

  strategy:

    rollingUpdate:

      maxSurge: 1

      maxUnavailable: 0

  template:

    metadata:

      labels:

        app: certificate-expiry-monitor

    spec:

      containers:

      - command:

        - /app

        - -labels

        - k8s-app=my-ingresses

        - -namespaces

        - default

        - -frequency

        - 1m

        - -domains

        - foobar.example.com

        image: muxinc/certificate-expiry-monitor:latest

        imagePullPolicy: Always

        livenessProbe:

          httpGet:

            path: /healthz

            port: 8888

          initialDelaySeconds: 5

          timeoutSeconds: 5

        name: certificate-expiry-monitor

        resources:

          limits:

            cpu: 20m

            memory: 50Mi

          requests:

            cpu: 20m

            memory: 50Mi

```



## Monitoring

A Prometheus endpoint is available at `/metrics` on TCP port `:8888` (customizable with `metricsPort`).



### Labels

| Name  | Description  |

|---|---|

| `ns` | Namespace of the pod that was queried |

| `pod` | Pod being queried for TLS certificates |

| `domain` | Domain being verified against TLS certificates |

| `status` | Certificate is either `valid`, `expired`, `soon` (not yet valid), or `notfound` |



### Gauges

| Name  | Labels | Description  |

|---|---|---|

| `certificate_expiry_monitor_matching_pods` | `ns` | Number of pods that match the label filter in a namespace  |

| `certificate_expiry_monitor_certificate`  | `ns`, `pod`, `domain`, `status` | Number of pods with a certificate in a given status for the domain |

| `certificate_expiry_monitor_seconds_since_cert_issued`  | `ns`, `pod`, `domain` | Seconds since the certificate was issued  |

| `certificate_expiry_monitor_seconds_until_cert_expires`  | `ns`, `pod`, `domain` | Seconds until the certificate expires  |



### Counters

| Name  | Labels | Description  |

|---|---|---|

| `certificate_expiry_monitor_tls_open_connection_error`  | `ns`, `pod`, `domain` | Number of times an error occurred while opening a TLS connection to a pod |

| `certificate_expiry_monitor_tls_close_connection_error`  | `ns`, `pod`, `domain` | Number of times an error occurred while closing a TLS connection to a pod |



## Healthcheck

A simple healthcheck is available at `/healthz` on the TCP port `:8888` (customizable with `metricsPort`):



```

→ curl -v http://localhost:8888/healthz

*   Trying ::1...

* TCP_NODELAY set

* Connection failed

* connect to ::1 port 8888 failed: Connection refused

*   Trying 127.0.0.1...

* TCP_NODELAY set

* Connected to localhost (127.0.0.1) port 8888 (#0)

> GET /healthz HTTP/1.1

> Host: localhost:8888

> User-Agent: curl/7.52.1

> Accept: */*

>

< HTTP/1.1 200 OK

< Date: Mon, 04 Mar 2019 17:56:45 GMT

< Content-Length: 7

< Content-Type: text/plain; charset=utf-8

<

* Curl_http_done: called premature == 0

* Connection #0 to host localhost left intact

Healthy

```