twin-gatus/README.md

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A service health dashboard in Go that is meant to be used as a docker 
image with a custom configuration file.

I personally deploy it in my Kubernetes cluster and have it monitor the status of my
core applications: https://status.twinnation.org/


## Table of Contents

- [Usage](#usage)
  - [Configuration](#configuration)
  - [Conditions](#conditions)
- [Docker](#docker)
- [Running the tests](#running-the-tests)
- [Using in Production](#using-in-production)
- [FAQ](#faq)
  - [Sending a GraphQL request](#sending-a-graphql-request)
  - [Configuring Slack alerts](#configuring-slack-alerts)
  - [Configuring custom alert](#configuring-custom-alerts)


## Usage

By default, the configuration file is expected to be at `config/config.yaml`.

You can specify a custom path by setting the `GATUS_CONFIG_FILE` environment variable.

Here's a simple example:

```yaml
metrics: true         # Whether to expose metrics at /metrics
services:
  - name: twinnation  # Name of your service, can be anything
    url: "https://twinnation.org/health"
    interval: 30s     # Duration to wait between every status check (default: 10s)
    conditions:
      - "[STATUS] == 200"         # Status must be 200
      - "[BODY].status == UP"     # The json path "$.status" must be equal to UP
      - "[RESPONSE_TIME] < 300"   # Response time must be under 300ms
  - name: example
    url: "https://example.org/"
    interval: 30s
    conditions:
      - "[STATUS] == 200"
```

Note that you can also add environment variables in the your configuration file (i.e. `$DOMAIN`, `${DOMAIN}`)


### Configuration

| Parameter                         | Description                                                     | Default        |
| --------------------------------- | --------------------------------------------------------------- | -------------- |
| `metrics`                         | Whether to expose metrics at /metrics                           | `false`        |
| `services`                        | List of services to monitor                                     | Required `[]`  |
| `services[].name`                 | Name of the service. Can be anything.                           | Required `""`  |
| `services[].url`                  | URL to send the request to                                      | Required `""`  |
| `services[].conditions`           | Conditions used to determine the health of the service          | `[]`           |
| `services[].interval`             | Duration to wait between every status check                     | `10s`          |
| `services[].method`               | Request method                                                  | `GET`          |
| `services[].graphql`              | Whether to wrap the body in a query param (`{"query":"$body"}`) | `false`        |
| `services[].body`                 | Request body                                                    | `""`           |
| `services[].headers`              | Request headers                                                 | `{}`           |
| `services[].alerts[].type`        | Type of alert. Valid types: `slack`, `custom`                   | Required `""`  |
| `services[].alerts[].enabled`     | Whether to enable the alert                                     | `false`        |
| `services[].alerts[].threshold`   | Number of failures in a row needed before triggering the alert  | `3`            |
| `services[].alerts[].description` | Description of the alert. Will be included in the alert sent    | `""`           |
| `alerting`                        | Configuration for alerting                                      | `{}`           |
| `alerting.slack`                  | Webhook to use for alerts of type `slack`                       | `""`           |
| `alerting.custom`                 | Configuration for custom actions on failure or alerts           | `""`           |
| `alerting.custom.url`             | Custom alerting request url                                     | `""`           |
| `alerting.custom.body`            | Custom alerting request body.                                   | `""`           |
| `alerting.custom.headers`         | Custom alerting request headers                                 | `{}`           |


### Conditions

Here are some examples of conditions you can use:

| Condition                    | Description                                             | Passing values           | Failing values          |
| -----------------------------| ------------------------------------------------------- | ------------------------ | ----------------------- |
| `[STATUS] == 200`            | Status must be equal to 200                             | 200                      | 201, 404, 500           |
| `[STATUS] < 300`             | Status must lower than 300                              | 200, 201, 299            | 301, 302, 400, 500      |
| `[STATUS] <= 299`            | Status must be less than or equal to 299                | 200, 201, 299            | 301, 302, 400, 500      |
| `[STATUS] > 400`             | Status must be greater than 400                         | 401, 402, 403, 404       | 200, 201, 300, 400      |
| `[RESPONSE_TIME] < 500`      | Response time must be below 500ms                       | 100ms, 200ms, 300ms      | 500ms, 1500ms           |
| `[BODY] == 1`                | The body must be equal to 1                             | 1                        | literally anything else |
| `[BODY].data.id == 1`        | The jsonpath `$.data.id` is equal to 1                  | `{"data":{"id":1}}`      | literally anything else |
| `[BODY].data[0].id == 1`     | The jsonpath `$.data[0].id` is equal to 1               | `{"data":[{"id":1}]}`    | literally anything else |
| `len([BODY].data) > 0`       | Array at jsonpath `$.data` has less than 5 elements     | `{"data":[{"id":1}]}`    | `{"data":[{"id":1}]}`   |
| `len([BODY].name) == 8`      | String at jsonpath `$.name` has a length of 8           | `{"name":"john.doe"}`    | `{"name":"bob"}`        |

**NOTE**: `[BODY]` with JSON path (i.e. `[BODY].id == 1`) is currently in BETA. For the most part, the only thing that doesn't work is arrays.


## Docker

Building the Docker image is done as following:

```
docker build . -t gatus
```

You can then run the container with the following command:

```
docker run -p 8080:8080 --name gatus gatus
```


## Running the tests

```
go test ./... -mod vendor
```


## Using in Production

See the [example](example) folder.


## FAQ

### Sending a GraphQL request

By setting `services[].graphql` to true, the body will automatically be wrapped by the standard GraphQL `query` parameter.

For instance, the following configuration:
```yaml
services:
  - name: filter users by gender
    url: http://localhost:8080/playground
    method: POST
    graphql: true
    body: |
      {
        user(gender: "female") {
          id
          name
          gender
          avatar
        }
      }
    headers:
      Content-Type: application/json
    conditions:
      - "[STATUS] == 200"
      - "[BODY].data.user[0].gender == female"
```

will send a `POST` request to `http://localhost:8080/playground` with the following body:
```json
{"query":"      {\n        user(gender: \"female\") {\n          id\n          name\n          gender\n          avatar\n        }\n      }"}
```


### Configuring Slack alerts

```yaml
alerting:
  slack: "https://hooks.slack.com/services/**********/**********/**********"
services:
  - name: twinnation
    interval: 30s
    url: "https://twinnation.org/health"
    alerts:
      - type: slack
        enabled: true
        description: "healthcheck failed 3 times in a row"
      - type: slack
        enabled: true
        threshold: 5
        description: "healthcheck failed 5 times in a row"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```


### Configuring custom alerts

While they're called alerts, you can use this feature to call anything. 

For instance, you could automate rollbacks by having an application that keeps tracks of new deployments, and by 
leveraging Gatus, you could have Gatus call that application endpoint when a service starts failing. Your application
would then check if the service that started failing was recently deployed, and if it was, then automatically 
roll it back.

The values `[ALERT_DESCRIPTION]` and `[SERVICE_NAME]` are automatically substituted for the alert description and the 
service name respectively in the body (`alerting.custom.body`) and the url (`alerting.custom.url`).

For all intents and purpose, we'll configure the custom alert with a Slack webhook, but you can call anything you want.

```yaml
alerting:
  custom:
    url: "https://hooks.slack.com/services/**********/**********/**********"
    method: "POST"
    body: |
      {
        "text": "[SERVICE_NAME] - [ALERT_DESCRIPTION]"
      }
services:
  - name: twinnation
    interval: 30s
    url: "https://twinnation.org/health"
    alerts:
      - type: custom
        enabled: true
        threshold: 10
        description: "healthcheck failed 10 times in a row"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```