![Gatus](.github/assets/logo-with-name.png)

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Gatus is a health dashboard that gives you the ability to monitor your services using HTTP, ICMP, TCP, and even DNS
queries as well as evaluate the result of said queries by using a list of conditions on values like the status code,
the response time, the certificate expiration, the body and many others. The icing on top is that each of these health
checks can be paired with alerting via Slack, PagerDuty, Discord and even Twilio.

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

<details>
  <summary><b>Quick start</b></summary>

```
docker run -p 8080:8080 --name gatus twinproduction/gatus
```
For more details, see [Usage](#usage)
</details>


## Table of Contents

- [Why Gatus?](#why-gatus)
- [Features](#features)
- [Usage](#usage)
- [Configuration](#configuration)
  - [Conditions](#conditions)
    - [Placeholders](#placeholders)
    - [Functions](#functions)
  - [Alerting](#alerting)
    - [Configuring Slack alerts](#configuring-slack-alerts)
    - [Configuring Discord alerts](#configuring-discord-alerts)
    - [Configuring PagerDuty alerts](#configuring-pagerduty-alerts)
    - [Configuring Twilio alerts](#configuring-twilio-alerts)
    - [Configuring Mattermost alerts](#configuring-mattermost-alerts)
    - [Configuring Messagebird alerts](#configuring-messagebird-alerts)    
    - [Configuring Telegram alerts](#configuring-telegram-alerts)
    - [Configuring custom alerts](#configuring-custom-alerts)
  - [Kubernetes (ALPHA)](#kubernetes-alpha)
    - [Auto Discovery](#auto-discovery)
    - [Deploying](#deploying)
- [Docker](#docker)
- [Running the tests](#running-the-tests)
- [Using in Production](#using-in-production)
- [FAQ](#faq)
  - [Sending a GraphQL request](#sending-a-graphql-request)
  - [Recommended interval](#recommended-interval)
  - [Default timeouts](#default-timeouts)
  - [Monitoring a TCP service](#monitoring-a-tcp-service)
  - [Monitoring a service using ICMP](#monitoring-a-service-using-icmp)
  - [Monitoring a service using DNS queries](#monitoring-a-service-using-dns-queries)
  - [Monitoring a service using STARTTLS](#monitoring-a-service-using-starttls)
  - [Basic authentication](#basic-authentication)
  - [disable-monitoring-lock](#disable-monitoring-lock)
  - [Reloading configuration on the fly](#reloading-configuration-on-the-fly)
  - [Service groups](#service-groups)
  - [Exposing Gatus on a custom port](#exposing-gatus-on-a-custom-port)
  - [Uptime Badges (ALPHA)](#uptime-badges)
  - [API](#API)


## Why Gatus?

Before getting into the specifics, I want to address the most common question:
> Why would I use Gatus when I can just use Prometheus’ Alertmanager, Cloudwatch or even Splunk?

Neither of these can tell you that there’s a problem if there are no clients actively calling the endpoint.
In other words, it's because monitoring metrics mostly rely on existing traffic, which effectively means that unless
your clients are already experiencing a problem, you won't be notified.

Gatus, on the other hand, allows you to configure health checks for each of your features, which in turn allows it to
monitor these features and potentially alert you before any clients are impacted.

A sign you may want to look into Gatus is by simply asking yourself whether you'd receive an alert if your load balancer
was to go down right now. Will any of your existing alerts by triggered? Your metrics won’t report an increase in errors
if there’s no traffic that makes it to your applications. This puts you in a situation where your clients are the ones
that will notify you about the degradation of your services rather than you reassuring them that you're working on
fixing the issue before they even know about it.


## Features

![Gatus dark mode](.github/assets/dark-mode.png)

The main features of Gatus are:
- **Highly flexible health check conditions**: While checking the response status may be enough for some use cases, Gatus goes much further and allows you to add conditions on the response time, the response body and even the IP address.
- **Ability to use Gatus for user acceptance tests**: Thanks to the point above, you can leverage this application to create automated user acceptance tests.
- **Very easy to configure**: Not only is the configuration designed to be as readable as possible, it's also extremely easy to add a new service or a new endpoint to monitor.
- **Alerting**: While having a pretty visual dashboard is useful to keep track of the state of your application(s), you probably don't want to stare at it all day. Thus, notifications via Slack, Mattermost, Messagebird, PagerDuty and Twilio are supported out of the box with the ability to configure a custom alerting provider for any needs you might have, whether it be a different provider or a custom application that manages automated rollbacks. 
- **Metrics**
- **Low resource consumption**: As with most Go applications, the resource footprint that this application requires is negligibly small.
- **GitHub uptime badges**: ![Uptime 1h](https://status.twinnation.org/api/v1/badges/uptime/1h/core_twinnation-external.svg) ![Uptime 24h](https://status.twinnation.org/api/v1/badges/uptime/24h/core_twinnation-external.svg) ![Uptime 7d](https://status.twinnation.org/api/v1/badges/uptime/7d/core_twinnation-external.svg)


## 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: 60s)
    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: 5m
    conditions:
      - "[STATUS] == 200"
```

This example would look like this:

![Simple example](.github/assets/example.png)

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

If you want to test it locally, see [Docker](#docker).


## Configuration

| Parameter                                | Description                                                                   | Default        |
|:---------------------------------------- |:----------------------------------------------------------------------------- |:-------------- |
| `debug`                                  | Whether to enable debug logs                                                  | `false`        |
| `metrics`                                | Whether to expose metrics at /metrics                                         | `false`        |
| `storage`                                | Storage configuration                                                         | `{}`           |
| `storage.file`                           | File to persist the data in. If not set, storage is in-memory only.           | `""`           |
| `services`                               | List of services to monitor                                                   | Required `[]`  |
| `services[].name`                        | Name of the service. Can be anything.                                         | Required `""`  |
| `services[].group`                       | Group name. Used to group multiple services together on the dashboard. See [Service groups](#service-groups). | `""`           |
| `services[].url`                         | URL to send the request to                                                    | Required `""`  |
| `services[].method`                      | Request method                                                                | `GET`          |
| `services[].insecure`                    | Whether to skip verifying the server's certificate chain and host name        | `false`        |
| `services[].conditions`                  | Conditions used to determine the health of the service. See [Conditions](#conditions). | `[]`           |
| `services[].interval`                    | Duration to wait between every status check                                   | `60s`          |
| `services[].graphql`                     | Whether to wrap the body in a query param (`{"query":"$body"}`)               | `false`        |
| `services[].body`                        | Request body                                                                  | `""`           |
| `services[].headers`                     | Request headers                                                               | `{}`           |
| `services[].dns`                         | Configuration for a service of type DNS. See [Monitoring a service using DNS queries](#monitoring-a-service-using-dns-queries). | `""`           |
| `services[].dns.query-type`              | Query type for DNS service                                                    | `""`           |
| `services[].dns.query-name`              | Query name for DNS service                                                    | `""`           |
| `services[].alerts[].type`               | Type of alert. Valid types: `slack`, `discord`, `pagerduty`, `twilio`, `mattermost`, `messagebird`, `custom` | Required `""`  |
| `services[].alerts[].enabled`            | Whether to enable the alert                                                   | `false`        |
| `services[].alerts[].failure-threshold`  | Number of failures in a row needed before triggering the alert                | `3`            |
| `services[].alerts[].success-threshold`  | Number of successes in a row before an ongoing incident is marked as resolved | `2`            |
| `services[].alerts[].send-on-resolved`   | Whether to send a notification once a triggered alert is marked as resolved   | `false`        |
| `services[].alerts[].description`        | Description of the alert. Will be included in the alert sent                  | `""`           |
| `alerting`                               | Configuration for alerting. See [Alerting](#alerting).                        | `{}`           |
| `security`                               | Security configuration                                                        | `{}`           |
| `security.basic`                         | Basic authentication security configuration                                   | `{}`           |
| `security.basic.username`                | Username for Basic authentication                                             | Required `""`  |
| `security.basic.password-sha512`         | Password's SHA512 hash for Basic authentication                               | Required `""`  |
| `disable-monitoring-lock`                | Whether to [disable the monitoring lock](#disable-monitoring-lock)            | `false`        |
| `skip-invalid-config-update`             | Whether to ignore invalid configuration update. See [Reloading configuration on the fly](#reloading-configuration-on-the-fly).
| `web`                                    | Web configuration                                                             | `{}`           |
| `web.address`                            | Address to listen on                                                          | `0.0.0.0`      |
| `web.port`                               | Port to listen on                                                             | `8080`         |

- For Kubernetes configuration, see [Kubernetes](#kubernetes-alpha).
- For alerting configuration, see [Alerting](#alerting).


### 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, ...  |
| `[STATUS] < 300`             | Status must lower than 300                              | 200, 201, 299              | 301, 302, ...  |
| `[STATUS] <= 299`            | Status must be less than or equal to 299                | 200, 201, 299              | 301, 302, ...  |
| `[STATUS] > 400`             | Status must be greater than 400                         | 401, 402, 403, 404         | 400, 200, ...  |
| `[STATUS] == any(200, 429)`  | Status must be either 200 or 429                        | 200, 429                   | 201, 400, ...  |
| `[CONNECTED] == true`        | Connection to host must've been successful              | true, false                |  |
| `[RESPONSE_TIME] < 500`      | Response time must be below 500ms                       | 100ms, 200ms, 300ms        | 500ms, 501ms   |
| `[IP] == 127.0.0.1`          | Target IP must be 127.0.0.1                             | 127.0.0.1                  | 0.0.0.0        |
| `[BODY] == 1`                | The body must be equal to 1                             | 1                          | `{}`, `2`, ... |
| `[BODY].user.name == john`   | JSONPath value of `$.user.name` is equal to `john`      | `{"user":{"name":"john"}}` |  |
| `[BODY].data[0].id == 1`     | JSONPath value of `$.data[0].id` is equal to 1          | `{"data":[{"id":1}]}`      |  |
| `[BODY].age == [BODY].id`    | JSONPath value of `$.age` is equal JSONPath `$.id`      | `{"age":1,"id":1}`         |  |
| `len([BODY].data) < 5`       | Array at JSONPath `$.data` has less than 5 elements     | `{"data":[{"id":1}]}`      |  |
| `len([BODY].name) == 8`      | String at JSONPath `$.name` has a length of 8           | `{"name":"john.doe"}`      | `{"name":"bob"}` |
| `has([BODY].errors) == false` | JSONPath `$.errors` does not exist                     | `{"name":"john.doe"}`      | `{"errors":[]}` |
| `has([BODY].users) == true`  | JSONPath `$.users` exists                               | `{"users":[]}`             | `{}` |
| `[BODY].name == pat(john*)`  | String at JSONPath `$.name` matches pattern `john*`     | `{"name":"john.doe"}`      | `{"name":"bob"}` |
| `[BODY].id == any(1, 2)`     | Value at JSONPath `$.id` is equal to `1` or `2`         | 1, 2                       | 3, 4, 5 |
| `[CERTIFICATE_EXPIRATION] > 48h` | Certificate expiration is more than 48h away        | 49h, 50h, 123h             | 1h, 24h, ... |


#### Placeholders

| Placeholder                | Description                                                     | Example of resolved value |
|:-------------------------- |:--------------------------------------------------------------- |:------------------------- |
| `[STATUS]`                 | Resolves into the HTTP status of the request                    | 404
| `[RESPONSE_TIME]`          | Resolves into the response time the request took, in ms         | 10
| `[IP]`                     | Resolves into the IP of the target host                         | 192.168.0.232
| `[BODY]`                   | Resolves into the response body. Supports JSONPath.             | `{"name":"john.doe"}`
| `[CONNECTED]`              | Resolves into whether a connection could be established         | `true`
| `[CERTIFICATE_EXPIRATION]` | Resolves into the duration before certificate expiration        | `24h`, `48h`, 0 (if not using HTTPS)
| `[DNS_RCODE]`              | Resolves into the DNS status of the response                    | NOERROR


#### Functions

| Function   | Description                                                                                                      | Example                    |
|:-----------|:---------------------------------------------------------------------------------------------------------------- |:-------------------------- |
| `len`      | Returns the length of the object/slice. Works only with the `[BODY]` placeholder.                                | `len([BODY].username) > 8`
| `has`      | Returns `true` or `false` based on whether a given path is valid. Works only with the `[BODY]` placeholder.      | `has([BODY].errors) == false`
| `pat`      | Specifies that the string passed as parameter should be evaluated as a pattern. Works only with `==` and `!=`.   | `[IP] == pat(192.168.*)`
| `any`      | Specifies that any one of the values passed as parameters is a valid value. Works only with `==` and `!=`.       | `[BODY].ip == any(127.0.0.1, ::1)`

**NOTE**: Use `pat` only when you need to. `[STATUS] == pat(2*)` is a lot more expensive than `[STATUS] < 300`.


### Alerting

Gatus supports multiple alerting providers, such as Slack and PagerDuty, and supports different alerts for each
individual services with configurable descriptions and thresholds.

Note that if an alerting provider is not configured properly, all alerts configured with the provider's type will be
ignored.

| Parameter                                | Description                                                                   | Default        |
|:---------------------------------------- |:----------------------------------------------------------------------------- |:-------------- |
| `alerting.slack`                         | Configuration for alerts of type `slack`                                      | `{}`           |
| `alerting.slack.webhook-url`             | Slack Webhook URL                                                             | Required `""`  |
| `alerting.discord`                       | Configuration for alerts of type `discord`                                    | `{}`           |
| `alerting.discord.webhook-url`           | Discord Webhook URL                                                           | Required `""`  |
| `alerting.pagerduty`                     | Configuration for alerts of type `pagerduty`                                  | `{}`           |
| `alerting.pagerduty.integration-key`     | PagerDuty Events API v2 integration key.                                      | Required `""`  |
| `alerting.twilio`                        | Settings for alerts of type `twilio`                                          | `{}`           |
| `alerting.twilio.sid`                    | Twilio account SID                                                            | Required `""`  |
| `alerting.twilio.token`                  | Twilio auth token                                                             | Required `""`  |
| `alerting.twilio.from`                   | Number to send Twilio alerts from                                             | Required `""`  |
| `alerting.twilio.to`                     | Number to send twilio alerts to                                               | Required `""`  |
| `alerting.mattermost`                    | Configuration for alerts of type `mattermost`                                 | `{}`           |
| `alerting.mattermost.webhook-url`        | Mattermost Webhook URL                                                        | Required `""`  |
| `alerting.mattermost.insecure`           | Whether to skip verifying the server's certificate chain and host name        | `false`        |
| `alerting.messagebird`                   | Settings for alerts of type `messagebird`                                     | `{}`           |
| `alerting.messagebird.access-key`        | Messagebird access key                                                        | Required `""`  |
| `alerting.messagebird.originator`        | The sender of the message                                                     | Required `""`  |
| `alerting.messagebird.recipients`        | The recipients of the message                                                 | Required `""`  |
| `alerting.telegram`                      | Configuration for alerts of type `telegram`                                   | `{}`           |
| `alerting.telegram.token`                | Telegram Bot Token                                                            | Required `""`  |
| `alerting.telegram.id`                   | Telegram User ID                                                              | Required `""`  |
| `alerting.custom`                        | Configuration for custom actions on failure or alerts                         | `{}`           |
| `alerting.custom.url`                    | Custom alerting request url                                                   | Required `""`  |
| `alerting.custom.method`                 | Request method                                                                | `GET`          |
| `alerting.custom.insecure`               | Whether to skip verifying the server's certificate chain and host name        | `false`        |
| `alerting.custom.body`                   | Custom alerting request body.                                                 | `""`           |
| `alerting.custom.headers`                | Custom alerting request headers                                               | `{}`           |
| `alerting.*.default-alert.enabled`            | Whether to enable the alert                                                   | N/A       |
| `alerting.*.default-alert.failure-threshold`  | Number of failures in a row needed before triggering the alert                | N/A       |
| `alerting.*.default-alert.success-threshold`  | Number of successes in a row before an ongoing incident is marked as resolved | N/A       |
| `alerting.*.default-alert.send-on-resolved`   | Whether to send a notification once a triggered alert is marked as resolved   | N/A       |
| `alerting.*.default-alert.description`        | Description of the alert. Will be included in the alert sent                  | N/A       |


#### Configuring Slack alerts

```yaml
alerting:
  slack: 
    webhook-url: "https://hooks.slack.com/services/**********/**********/**********"

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

Here's an example of what the notifications look like:

![Slack notifications](.github/assets/slack-alerts.png)


#### Configuring Discord alerts

```yaml
alerting:
  discord: 
    webhook-url: "https://discord.com/api/webhooks/**********/**********"

services:
  - name: twinnation
    url: "https://twinnation.org/health"
    interval: 30s
    alerts:
      - type: discord
        enabled: true
        description: "healthcheck failed"
        send-on-resolved: true
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```


#### Configuring PagerDuty alerts

It is highly recommended to set `services[].alerts[].send-on-resolved` to `true` for alerts 
of type `pagerduty`, because unlike other alerts, the operation resulting from setting said 
parameter to `true` will not create another incident, but mark the incident as resolved on 
PagerDuty instead. 

```yaml
alerting:
  pagerduty: 
    integration-key: "********************************"

services:
  - name: twinnation
    url: "https://twinnation.org/health"
    interval: 30s
    alerts:
      - type: pagerduty
        enabled: true
        failure-threshold: 3
        success-threshold: 5
        send-on-resolved: true
        description: "healthcheck failed"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```


#### Configuring Twilio alerts

```yaml
alerting:
  twilio:
    sid: "..."
    token: "..."
    from: "+1-234-567-8901"
    to: "+1-234-567-8901"

services:
  - name: twinnation
    interval: 30s
    url: "https://twinnation.org/health"
    alerts:
      - type: twilio
        enabled: true
        failure-threshold: 5
        send-on-resolved: true
        description: "healthcheck failed"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```


#### Configuring Mattermost alerts

```yaml
alerting:
  mattermost: 
    webhook-url: "http://**********/hooks/**********"
    insecure: true

services:
  - name: twinnation
    url: "https://twinnation.org/health"
    interval: 30s
    alerts:
      - type: mattermost
        enabled: true
        description: "healthcheck failed"
        send-on-resolved: true
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```

Here's an example of what the notifications look like:

![Mattermost notifications](.github/assets/mattermost-alerts.png)


#### Configuring Messagebird alerts

Example of sending **SMS** text message alert using Messagebird:

```yaml
alerting:
  messagebird:
    access-key: "..."
    originator: "31619191918"
    recipients: "31619191919,31619191920"
services:
  - name: twinnation
    interval: 30s
    url: "https://twinnation.org/health"
    alerts:
      - type: messagebird
        enabled: true
        failure-threshold: 3
        send-on-resolved: true
        description: "healthcheck failed"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```


#### Configuring Telegram alerts

```yaml
alerting:
  telegram: 
    token: "123456:ABC-DEF1234ghIkl-zyx57W2v1u123ew11"
    id: "0123456789"

services:
  - name: twinnation
    url: "https://twinnation.org/health"
    interval: 30s
    alerts:
      - type: telegram
        enabled: true
        send-on-resolved: true
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
```

Here's an example of what the notifications look like:

![Telegram notifications](.github/assets/telegram-alerts.png)


#### 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 placeholders `[ALERT_DESCRIPTION]` and `[SERVICE_NAME]` are automatically substituted for the alert description and
the service name. These placeholders can be used in the body (`alerting.custom.body`) and in the url (`alerting.custom.url`).

If you have an alert using the `custom` provider with `send-on-resolved` set to `true`, you can use the
`[ALERT_TRIGGERED_OR_RESOLVED]` placeholder to differentiate the notifications. 
The aforementioned placeholder will be replaced by `TRIGGERED` or `RESOLVED` accordingly, though it can be modified
(details at the end of this section).

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"
    insecure: true
    body: |
      {
        "text": "[ALERT_TRIGGERED_OR_RESOLVED]: [SERVICE_NAME] - [ALERT_DESCRIPTION]"
      }
services:
  - name: twinnation
    url: "https://twinnation.org/health"
    interval: 30s
    alerts:
      - type: custom
        enabled: true
        failure-threshold: 10
        success-threshold: 3
        send-on-resolved: true
        description: "healthcheck failed"
    conditions:
      - "[STATUS] == 200"
      - "[BODY].status == UP"
      - "[RESPONSE_TIME] < 300"
```

Note that you can customize the resolved values for the `[ALERT_TRIGGERED_OR_RESOLVED]` placeholder like so:
```yaml
alerting:
  custom:
    placeholders:
      ALERT_TRIGGERED_OR_RESOLVED:
        TRIGGERED: "partial_outage"
        RESOLVED: "operational"
```
As a result, the `[ALERT_TRIGGERED_OR_RESOLVED]` in the body of first example of this section would be replaced by 
`partial_outage` when an alert is triggered and `operational` when an alert is resolved.


#### Setting a default provider alert

While you can specify the alert configuration directly in the service definition, it's tedious and may lead to a very
long configuration file.

To avoid such problem, you can use the `default-alert` parameter present in each provider configuration:
```yaml
alerting:
  slack: 
    webhook-url: "https://hooks.slack.com/services/**********/**********/**********"
    default-alert:
      enabled: true
      description: "healthcheck failed"
      send-on-resolved: true
      failure-threshold: 5
      success-threshold: 5
```

As a result, your service configuration looks a lot tidier:
```yaml
services:
  - name: example
    url: "https://example.org"
    alerts:
      - type: slack
    conditions:
      - "[STATUS] == 200"

  - name: other-example
    url: "https://example.com"
    alerts:
      - type: slack
    conditions:
      - "[STATUS] == 200"
```

It also allows you to do things like this:
```yaml
services:
  - name: twinnation
    url: "https://twinnation.org/health"
    alerts:
      - type: slack
        failure-threshold: 5
      - type: slack
        failure-threshold: 10
      - type: slack
        failure-threshold: 15
    conditions:
      - "[STATUS] == 200"
```


### Kubernetes (ALPHA)

> **WARNING**: This feature is in ALPHA. This means that it is very likely to change in the near future, which means that
> while you can use this feature as you see fit, there may be breaking changes in future releases.

| Parameter                                   | Description                                                                   | Default        |
|:------------------------------------------- |:----------------------------------------------------------------------------- |:-------------- |
| `kubernetes`                                | Kubernetes configuration                                                      | `{}`           |
| `kubernetes.auto-discover`                  | Whether to enable auto discovery                                              | `false`        |
| `kubernetes.cluster-mode`                   | Cluster mode to use for authenticating. Supported values: `in`, `out`         | Required `""`  |
| `kubernetes.service-template`               | Service template. See `services[]` in [Configuration](#configuration)         | Required `nil` |
| `kubernetes.excluded-service-suffixes`      | List of service suffixes to not monitor (e.g. `canary`)                       | `[]`           |
| `kubernetes.namespaces`                     | List of configurations for the namespaces from which services will be discovered | `[]`        |
| `kubernetes.namespaces[].name`              | Namespace name                                                                | Required `""`  |
| `kubernetes.namespaces[].hostname-suffix`   | Suffix to append to the service name before calling `target-path`             | Required `""`  |
| `kubernetes.namespaces[].target-path`       | Path that will be called on the discovered service for the health check       | `""`           |
| `kubernetes.namespaces[].excluded-services` | List of services to not monitor in the given namespace                        | `[]`           |


#### Auto Discovery

Auto discovery works by reading all `Service` resources from the configured `namespaces` and appending the `hostname-suffix` as 
well as the configured `target-path` to the service name and making an HTTP call.

All auto-discovered services will have the service configuration populated from the `service-template`.

You can exclude certain services from the dashboard by using `kubernetes.excluded-service-suffixes` or `kubernetes.namespaces[].excluded-services`.

```yaml
kubernetes:
  auto-discover: true
  # out: Gatus is deployed outside of the K8s cluster.
  # in: Gatus is deployed in the K8s cluster
  cluster-mode: "out"                                              
  excluded-service-suffixes:
    - canary
  service-template:
    interval: 30s
    conditions:
      - "[STATUS] == 200"
  namespaces:
    - name: default
      # If cluster-mode is out, you should use an externally accessible hostname suffix (e.g.. .example.com)
      # This will result in gatus generating services with URLs like <service-name>.example.com
      # If cluster-mode is in, you can use either an externally accessible hostname suffix (e.g.. .example.com)
      # or an internally accessible hostname suffix (e.g. .default.svc.cluster.local)
      hostname-suffix: ".default.svc.cluster.local"
      target-path: "/health"
      # If some services cannot be or do not need to be monitored, you can exclude them by explicitly defining them
      # in the following list.
      excluded-services:
        - gatus
        - kubernetes
```

Note that `hostname-suffix` could also be something like `.yourdomain.com`, in which case the endpoint that would be 
monitored would be `potato.example.com/health`, assuming you have a service named `potato` and a matching ingress
to map `potato.example.com` to the `potato` service.

#### Deploying

See [example/kubernetes-with-auto-discovery](example/kubernetes-with-auto-discovery)


## Docker

To run Gatus locally with Docker:
```
docker run -p 8080:8080 --name gatus twinproduction/gatus
```

Other than using one of the examples provided in the `examples` folder, you can also try it out locally by 
creating a configuration file, we'll call it `config.yaml` for this example, and running the following 
command:
```
docker run -p 8080:8080 --mount type=bind,source="$(pwd)"/config.yaml,target=/config/config.yaml --name gatus twinproduction/gatus
```

If you're on Windows, replace `"$(pwd)"` by the absolute path to your current directory, e.g.:
```
docker run -p 8080:8080 --mount type=bind,source=C:/Users/Chris/Desktop/config.yaml,target=/config/config.yaml --name gatus twinproduction/gatus
```

To build the image locally:
```
docker build . -t twinproduction/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: |
      {
        users(gender: "female") {
          id
          name
          gender
          avatar
        }
      }
    conditions:
      - "[STATUS] == 200"
      - "[BODY].data.users[0].gender == female"
```

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


### Recommended interval

**NOTE**: This does not _really_ apply if `disable-monitoring-lock` is set to `true`, as the monitoring lock is what
tells Gatus to only evaluate one service at a time.

To ensure that Gatus provides reliable and accurate results (i.e. response time), Gatus only evaluates one service at a time
In other words, even if you have multiple services with the exact same interval, they will not execute at the same time.

You can test this yourself by running Gatus with several services configured with a very short, unrealistic interval, 
such as 1ms. You'll notice that the response time does not fluctuate - that is because while services are evaluated on
different goroutines, there's a global lock that prevents multiple services from running at the same time.

Unfortunately, there is a drawback. If you have a lot of services, including some that are very slow or prone to time out (the default
time out is 10s for HTTP and 5s for TCP), then it means that for the entire duration of the request, no other services can be evaluated.

**This does mean that Gatus will be unable to evaluate the health of other services**. 
The interval does not include the duration of the request itself, which means that if a service has an interval of 30s 
and the request takes 2s to complete, the timestamp between two evaluations will be 32s, not 30s. 

While this does not prevent Gatus' from performing health checks on all other services, it may cause Gatus to be unable 
to respect the configured interval, for instance:
- Service A has an interval of 5s, and times out after 10s to complete 
- Service B has an interval of 5s, and takes 1ms to complete
- Service B will be unable to run every 5s, because service A's health evaluation takes longer than its interval

To sum it up, while Gatus can really handle any interval you throw at it, you're better off having slow requests with 
higher interval.

As a rule of the thumb, I personally set interval for more complex health checks to `5m` (5 minutes) and 
simple health checks used for alerting (PagerDuty/Twilio) to `30s`.


### Default timeouts

| Protocol | Timeout |
|:-------- |:------- |
| HTTP     | 10s
| TCP      | 5s


### Monitoring a TCP service

By prefixing `services[].url` with `tcp:\\`, you can monitor TCP services at a very basic level:

```yaml
services:
  - name: redis
    url: "tcp://127.0.0.1:6379"
    interval: 30s
    conditions:
      - "[CONNECTED] == true"
```

Placeholders `[STATUS]` and `[BODY]` as well as the fields `services[].body`, `services[].insecure`, 
`services[].headers`, `services[].method` and `services[].graphql` are not supported for TCP services.

**NOTE**: `[CONNECTED] == true` does not guarantee that the service itself is healthy - it only guarantees that there's 
something at the given address listening to the given port, and that a connection to that address was successfully 
established.


### Monitoring a service using ICMP

By prefixing `services[].url` with `icmp:\\`, you can monitor services at a very basic level using ICMP, or more 
commonly known as "ping" or "echo":

```yaml
services:
  - name: ping-example
    url: "icmp://example.com"
    conditions:
      - "[CONNECTED] == true"
```

Only the placeholders `[CONNECTED]`, `[IP]` and `[RESPONSE_TIME]` are supported for services of type ICMP.
You can specify a domain prefixed by `icmp://`, or an IP address prefixed by `icmp://`.


### Monitoring a service using DNS queries

Defining a `dns` configuration in a service will automatically mark that service as a service of type DNS:
```yaml
services:
  - name: example-dns-query
    url: "8.8.8.8" # Address of the DNS server to use
    interval: 30s
    dns:
      query-name: "example.com"
      query-type: "A"
    conditions:
      - "[BODY] == 93.184.216.34"
      - "[DNS_RCODE] == NOERROR"
```

There are two placeholders that can be used in the conditions for services of type DNS:
- The placeholder `[BODY]` resolves to the output of the query. For instance, a query of type `A` would return an IPv4.
- The placeholder `[DNS_RCODE]` resolves to the name associated to the response code returned by the query, such as 
`NOERROR`, `FORMERR`, `SERVFAIL`, `NXDOMAIN`, etc.


### Monitoring a service using STARTTLS

If you have an email server that you want to ensure there are no problems with, monitoring it through STARTTLS 
will serve as a good initial indicator:
```yaml
services:
  - name: starttls-smtp-example
    url: "starttls://smtp.gmail.com:587"
    interval: 30m
    conditions:
      - "[CONNECTED] == true"
      - "[CERTIFICATE_EXPIRATION] > 48h"
```


### Basic authentication

You can require Basic authentication by leveraging the `security.basic` configuration:
```yaml
security:
  basic:
    username: "john.doe"
    password-sha512: "6b97ed68d14eb3f1aa959ce5d49c7dc612e1eb1dafd73b1e705847483fd6a6c809f2ceb4e8df6ff9984c6298ff0285cace6614bf8daa9f0070101b6c89899e22"
```

The example above will require that you authenticate with the username `john.doe` as well as the password `hunter2`.


### disable-monitoring-lock

Setting `disable-monitoring-lock` to `true` means that multiple services could be monitored at the same time.

While this behavior wouldn't generally be harmful, conditions using the `[RESPONSE_TIME]` placeholder could be impacted 
by the evaluation of multiple services at the same time, therefore, the default value for this parameter is `false`.

There are three main reasons why you might want to disable the monitoring lock:
- You're using Gatus for load testing (each services are periodically evaluated on a different goroutine, so 
technically, if you create 100 services with a 1 seconds interval, Gatus will send 100 requests per second)
- You have a _lot_ of services to monitor
- You want to test multiple services at very short interval (< 5s)


### Reloading configuration on the fly

For the sake on convenience, Gatus automatically reloads the configuration on the fly if the loaded configuration file
is updated while Gatus is running.

By default, the application will exit if the updating configuration is invalid, but you can configure
Gatus to continue running if the configuration file is updated with an invalid configuration by
setting `skip-invalid-config-update` to `true`.

Keep in mind that it is in your best interest to ensure the validity of the configuration file after each update you
apply to the configuration file while Gatus is running by looking at the log and making sure that you do not see the
following message:
```
The configuration file was updated, but it is not valid. The old configuration will continue being used.
```
Failure to do so may result in Gatus being unable to start if the application is restarted for whatever reason.

I recommend not setting `skip-invalid-config-update` to `true` to avoid a situation like this, but the choice is yours
to make.

Note that if you are not using a file storage, updating the configuration while Gatus is running is effectively
the same as restarting the application.


### Service groups

Service groups are used for grouping multiple services together on the dashboard.

```yaml
services:
  - name: frontend
    group: core
    url: "https://example.org/"
    interval: 5m
    conditions:
      - "[STATUS] == 200"

  - name: backend
    group: core
    url: "https://example.org/"
    interval: 5m
    conditions:
      - "[STATUS] == 200"

  - name: monitoring
    group: internal
    url: "https://example.org/"
    interval: 5m
    conditions:
      - "[STATUS] == 200"

  - name: nas
    group: internal
    url: "https://example.org/"
    interval: 5m
    conditions:
      - "[STATUS] == 200"

  - name: random service that isn't part of a group
    url: "https://example.org/"
    interval: 5m
    conditions:
      - "[STATUS] == 200"
```

The configuration above will result in a dashboard that looks like this:

![Gatus Service Groups](.github/assets/service-groups.png)


### Exposing Gatus on a custom port

By default, Gatus is exposed on port `8080`, but you may specify a different port by setting the `web.port` parameter:
```yaml
web:
  port: 8081
```

If you're using a PaaS like Heroku that doesn't let you set a custom port and exposes it through an environment
variable instead, you can use that environment variable directly in the configuration file:
```yaml
web:
  port: ${PORT}
```

### Uptime badges
![Uptime 1h](https://status.twinnation.org/api/v1/badges/uptime/1h/core_twinnation-external.svg)
![Uptime 24h](https://status.twinnation.org/api/v1/badges/uptime/24h/core_twinnation-external.svg)
![Uptime 7d](https://status.twinnation.org/api/v1/badges/uptime/7d/core_twinnation-external.svg)

Gatus can automatically generate a SVG badge for one of your monitored services.
This allows you to put badges in your individual services' README or even create your own status page, if you 
desire.

The endpoint to generate a badge is the following:
```
/api/v1/badges/uptime/{duration}/{identifier}.svg
```
Where:
- `{duration}` is `7d`, `24h` or `1h`
- `{identifier}` has the pattern `<GROUP_NAME>_<SERVICE_NAME>.svg` in which both variables have ` `, `/`, `_`, `,` and `.` replaced by `-`.

For instance, if you want the uptime during the last 24 hours from the service `frontend` in the group `core`, 
the URL would look like this:
```
http://example.com/api/v1/badges/uptime/7d/core_frontend.svg
```

If you want to display a service that is not part of a group, you must leave the group value empty:
```
http://example.com/api/v1/badges/uptime/7d/_frontend.svg
```

Example: ![Uptime 24h](https://status.twinnation.org/api/v1/badges/uptime/24h/core_twinnation-external.svg)
```
![Uptime 24h](https://status.twinnation.org/api/v1/badges/uptime/24h/core_twinnation-external.svg)
```

If you'd like to see a visual example of each badges available, you can simply navigate to the service's detail page.

### API
Gatus provides a simple read-only API which can be queried in order to programmatically determine service status and history.

All services are available via a GET request to the following endpoint:
```
/api/v1/statuses
````

Example: https://status.twinnation.org/api/v1/statuses

Specific services can also be queried by using the following pattern:
```
/api/v1/statuses/{group}_{service}
```

Example: https://status.twinnation.org/api/v1/statuses/core_twinnation-home

Gzip compression will be used if the `Accept-Encoding` HTTP header contains `gzip`.

The API will return a JSON payload with the `Content-Type` response header set to `application/json`. 
No such header is required to query the API.
