support host_pattern in config devices list

README.md

@@ -69,6 +69,14 @@ devices:
   - host: host2.example.com:2233
     username: exporter
     password: secret
+  - host: router.*.example.com
+    # Tell the exporter that this hostname should be used as a pattern when loading
+    # device-specific configurations. This example would match against a hostname
+    # like "router1.example.com".
+    host_pattern: true
+    username: exporter
+    password: secret
+
 
 features:
   bgp: true

config/config.go

@@ -3,6 +3,7 @@ package config
 import (
 	"io"
 	"io/ioutil"
+	"regexp"
 	"strings"
 
 	"gopkg.in/yaml.v2"
@@ -31,6 +32,8 @@ type DeviceConfig struct {
 	Timeout       *int           `yaml:"timeout,omitempty"`
 	BatchSize     *int           `yaml:"batch_size,omitempty"`
 	Features      *FeatureConfig `yaml:"features,omitempty"`
+	IsHostPattern bool           `yaml:"host_pattern,omitempty"`
+	HostPattern   *regexp.Regexp
 }
 
 // FeatureConfig is the list of collectors enabled or disabled
@@ -66,6 +69,13 @@ func Load(reader io.Reader) (*Config, error) {
 	}
 
 	for _, d := range c.Devices {
+		if d.IsHostPattern {
+			hostPattern, err := regexp.Compile(d.Host)
+			if err != nil {
+				return nil, err
+			}
+			d.HostPattern = hostPattern
+		}
 		if d.Features == nil {
 			continue
 		}

devices.go

@@ -10,26 +10,31 @@ import (
 )
 
 func devicesForConfig(cfg *config.Config) ([]*connector.Device, error) {
-	devs := make([]*connector.Device, len(cfg.Devices))
-	var err error
-	for i, d := range cfg.Devices {
-		devs[i], err = deviceFromDeviceConfig(d, cfg)
+	devs := make([]*connector.Device, 0)
+	for _, d := range cfg.Devices {
+		if d.IsHostPattern {
+			continue
+		}
+
+		dev, err := deviceFromDeviceConfig(d, d.Host, cfg)
 		if err != nil {
 			return nil, err
 		}
+
+		devs = append(devs, dev)
 	}
 
 	return devs, nil
 }
 
-func deviceFromDeviceConfig(device *config.DeviceConfig, cfg *config.Config) (*connector.Device, error) {
+func deviceFromDeviceConfig(device *config.DeviceConfig, hostname string, cfg *config.Config) (*connector.Device, error) {
 	auth, err := authForDevice(device, cfg)
 	if err != nil {
 		return nil, errors.Wrapf(err, "could not initialize config for device %s", device.Host)
 	}
 
 	port := "22"
-	host := device.Host
+	host := hostname
 	if strings.Contains(host, ":") {
 		d := strings.Split(host, ":")
 		host = d[0]

main.go

@@ -144,9 +144,16 @@ func startServer() {
 }
 
 func handleMetricsRequest(w http.ResponseWriter, r *http.Request) {
+
 	reg := prometheus.NewRegistry()
 
-	c := newCiscoCollector(devices)
+	devs, err := devicesForRequest(r)
+	if err != nil {
+		http.Error(w, err.Error(), 400)
+		return
+	}
+
+	c := newCiscoCollector(devs)
 	reg.MustRegister(c)
 
 	l := log.New()
@@ -156,3 +163,33 @@ func handleMetricsRequest(w http.ResponseWriter, r *http.Request) {
 		ErrorLog:      l,
 		ErrorHandling: promhttp.ContinueOnError}).ServeHTTP(w, r)
 }
+
+func devicesForRequest(r *http.Request) ([]*connector.Device, error) {
+	reqTarget := r.URL.Query().Get("target")
+	if reqTarget == "" {
+		return devices, nil
+	}
+
+	for _, d := range devices {
+		if d.Host == reqTarget {
+			return []*connector.Device{d}, nil
+		}
+	}
+
+	for _, dc := range cfg.Devices {
+		if !dc.IsHostPattern {
+			continue
+		}
+
+		if dc.HostPattern.MatchString(reqTarget) {
+			d, err := deviceFromDeviceConfig(dc, reqTarget, cfg)
+			if err != nil {
+				return nil, err
+			}
+
+			return []*connector.Device{d}, nil
+		}
+	}
+
+	return nil, fmt.Errorf("the target '%s' is not defined in the configuration file", reqTarget)
+}