Define Additional Scripts via Separate Config Files (#116)

It is now possible to define additional scripts for the exporter via
separate config files. For that a new option `scripts_configs` was
added, which can be used to set a list of files, which are containing
additional script configuration.

The configuration must look as follows:

```
script_configs:
  - /path/to/file.yaml
```

The content of the additional scripts configuration file, can only
contain a list of scripts, e.g.

```yaml
- name: test
  command: ./examples/test.sh
```

Author: ricoberger

README.md

@@ -104,6 +104,9 @@ scripts:
       prefix: <string>
       scrape_interval: <duration>
       scrape_timeout: <duration>
+
+scripts_configs:
+  - <string>
 ```
 
 The `name` of the script must be a valid Prometheus label value. The `command` string is the script which is executed with all arguments specified in `args`. To add dynamic arguments you can pass the `params` query parameter with a list of query parameters which values should be added as argument. The program will be executed directly, without a shell being invoked, and it is recommended that it be specified by path instead of relying on ``$PATH``.
@@ -146,7 +149,7 @@ For testing purposes, the timeout can be specified directly as a URL parameter (
 
 The `cacheDuration` config can be used to cache the results from an execution of the script for the provided time. The provided duration must be parsable by the [`time.ParseDuration`](https://pkg.go.dev/time#ParseDuration) function. If no cache duration is provided or the provided cache duration can not be parsed, the output of an script will not be cached.
 
-You can fine tune the script discovery options via optional script `discovery`. All these options will go through prometheus configuration where you can change them via relabel mechanism. 
+You can fine tune the script discovery options via optional script `discovery`. All these options will go through prometheus configuration where you can change them via relabel mechanism.
 There are `params` to define dynamic script parameters (with reserved keys: `params`, `prefix`, `script` and `timeout`) where only value will be used during script invoking (similar to `args`), `prefix` to define prefix for all script metrics, `scrape_interval` to define how often the script scrape should run and `scrape_timeout` to define the scrape timeout for prometheus (similar to `timeout`).
 
 The global `discovery` configures the main discovery parameters. If not defined, the exporter will use `Host:` header from the request to decide how to present a `target` to prometheus.

examples/config.yaml

@@ -19,8 +19,6 @@ discovery:
   # path: /prefix-path
 
 scripts:
-  - name: test
-    command: ./examples/test.sh
   - name: ping
     command: ./examples/ping.sh
     cacheDuration: 1m
@@ -45,3 +43,6 @@ scripts:
     args:
       - test1
       - test2
+
+scripts_configs:
+  - ./examples/scripts_*.yaml

examples/scripts_test.yaml

@@ -0,0 +1,2 @@
+- name: test
+  command: ./examples/test.sh

pkg/config/config.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -47,6 +48,8 @@ type Config struct {
 
 	Scripts []ScriptConfig `yaml:"scripts"`
 
+	ScriptsConfigs []string `yaml:"scripts_configs"`
+
 	Discovery struct {
 		Host   string `yaml:"host"`
 		Port   string `yaml:"port"`
@@ -82,6 +85,32 @@ func (c *Config) LoadConfig(file string) error {
 		return err
 	}
 
+	// Additional scripts can also be defined via the `scripts_configs` field. This field can contain a list of glob
+	// patterns that will be expanded to a list of files. Each file contains a list of additional script configurations.
+	for _, scriptsConfig := range c.ScriptsConfigs {
+		files, err := filepath.Glob(scriptsConfig)
+		if err != nil {
+			return err
+		}
+
+		for _, file := range files {
+			data, err := os.ReadFile(file)
+			if err != nil {
+				return err
+			}
+
+			data = []byte(expandEnv(string(data)))
+
+			var additionalScriptConfigs []ScriptConfig
+			err = yaml.Unmarshal(data, &additionalScriptConfigs)
+			if err != nil {
+				return err
+			}
+
+			c.Scripts = append(c.Scripts, additionalScriptConfigs...)
+		}
+	}
+
 	return nil
 }