Add possibility for GroupValueRead at startup

README.md

@@ -92,12 +92,14 @@ Connection:
     Endpoint: "192.168.1.15:3671"
     PhysicalAddress: 2.0.1
 MetricsPrefix: knx_
+ReadStartupInterval: 200ms
 AddressConfigs:
     0/0/1:
         Name: dummy_metric
         DPT: 1.*
         Export: true
         MetricType: "counter"
+        ReadStartup: true
         ReadActive: true
         MaxAge: 10m
         Comment: dummy comment
@@ -125,6 +127,12 @@ The `MetricsPrefix` defines a single string that will be added to all your expor
 format must be compliant with the
 [prometheus metrics names](https://prometheus.io/docs/practices/naming/#metric-names).
 
+#### The `ReadStartupInterval`
+It is possible to send `GroupValueRead` telegrams to specific group addresses at startup.
+Sending out all `GroupValueRead` telegrams at once on startup can overwhelm the KNX bus.
+The `ReadStartupInterval` defines the interval between the `GroupValueRead` telegrams sent out at startup.
+If not specified, `ReadStartupInterval` is set to 200ms by default.
+
 #### The `AddressConfigs` section
 
 The `AddressConfigs` section defines all the information about the group addresses which should be
@@ -136,6 +144,7 @@ exported to prometheus. It contains the following structure for every exported g
       DPT: 1.*
       Export: true
       MetricType: "counter"
+      ReadStartup: true
       ReadActive: true
       MaxAge: 10m
       Comment: dummy comment
@@ -164,6 +173,9 @@ Next it defines the actual information for a single group address:
 - `MetricType` defines the type of the exported metric. Can be either `counter` or `gauge`. See
   [Prometheus documentation counter vs. gauge](https://prometheus.io/docs/practices/instrumentation/#counter-vs-gauge-summary-vs-histogram)
   for more information about it.
+- `ReadStartup` can either be `true` or `false`. If set to `true` the KNX Prometheus Exporter will
+  send a `GroupValueRead` telegram to the group address to actively ask for a new value once after startup.
+  In contrast to `ReadActive` this sends out a `GroupValueRead` telegram at startup once.
 - `ReadActive` can either be `true` or `false`. If set to `true` the KNX Prometheus Exporter will
   send a `GroupValueRead` telegram to the group address to active ask for a new value if the last
   received value is older than `MaxAge`.

pkg/knx/config.go

@@ -15,60 +15,62 @@
 package knx
 
 import (
-    "encoding/json"
-    "fmt"
-    "os"
-    "strings"
-    "time"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
 
-    "github.com/ghodss/yaml"
+	"github.com/ghodss/yaml"
 )
 
 // Config defines the structure of the configuration file which defines which
 // KNX Group Addresses were mapped into prometheus metrics.
 type Config struct {
-    Connection Connection `json:",omitempty"`
-    // MetricsPrefix is a short prefix which will be added in front of the actual metric name.
-    MetricsPrefix  string
-    AddressConfigs GroupAddressConfigSet
+	Connection Connection `json:",omitempty"`
+	// MetricsPrefix is a short prefix which will be added in front of the actual metric name.
+	MetricsPrefix  string
+	AddressConfigs GroupAddressConfigSet
+	// ReadStartupInterval is the intervall to wait between read of group addresses after startup.
+	ReadStartupInterval Duration `json:",omitempty"`
 }
 
 // ReadConfig reads the given configuration file and returns the parsed Config object.
 func ReadConfig(configFile string) (*Config, error) {
-    content, err := os.ReadFile(configFile)
-    if err != nil {
-        return nil, fmt.Errorf("can not read group address configuration: %s", err)
-    }
-    config := Config{}
-    err = yaml.Unmarshal(content, &config)
-    if err != nil {
-        return nil, fmt.Errorf("can not read config file %s: %s", configFile, err)
-    }
-    return &config, nil
+	content, err := os.ReadFile(configFile)
+	if err != nil {
+		return nil, fmt.Errorf("can not read group address configuration: %s", err)
+	}
+	config := Config{}
+	err = yaml.Unmarshal(content, &config)
+	if err != nil {
+		return nil, fmt.Errorf("can not read config file %s: %s", configFile, err)
+	}
+	return &config, nil
 }
 
 // NameForGa returns the full metric name for the given GroupAddress.
 func (c *Config) NameForGa(address GroupAddress) string {
-    gaConfig, ok := c.AddressConfigs[address]
-    if !ok {
-        return ""
-    }
-    return c.NameFor(gaConfig)
+	gaConfig, ok := c.AddressConfigs[address]
+	if !ok {
+		return ""
+	}
+	return c.NameFor(gaConfig)
 }
 
 // NameFor return s the full metric name for the given GroupAddressConfig.
 func (c *Config) NameFor(gaConfig GroupAddressConfig) string {
-    return c.MetricsPrefix + gaConfig.Name
+	return c.MetricsPrefix + gaConfig.Name
 }
 
 // Connection contains the information about how to connect to the KNX system and how to identify itself.
 type Connection struct {
-    // Type of the actual connection. Can be either Tunnel or Router
-    Type ConnectionType
-    // Endpoint defines the IP address or hostname and port to where it should connect.
-    Endpoint string
-    // PhysicalAddress defines how the knx-exporter should identify itself within the KNX system.
-    PhysicalAddress PhysicalAddress
+	// Type of the actual connection. Can be either Tunnel or Router
+	Type ConnectionType
+	// Endpoint defines the IP address or hostname and port to where it should connect.
+	Endpoint string
+	// PhysicalAddress defines how the knx-exporter should identify itself within the KNX system.
+	PhysicalAddress PhysicalAddress
 }
 
 type ConnectionType string
@@ -77,62 +79,64 @@ const Tunnel = ConnectionType("Tunnel")
 const Router = ConnectionType("Router")
 
 func (t ConnectionType) MarshalJSON() ([]byte, error) {
-    return json.Marshal(string(t))
+	return json.Marshal(string(t))
 }
 
 func (t *ConnectionType) UnmarshalJSON(data []byte) error {
-    var str string
-    if err := json.Unmarshal(data, &str); err != nil {
-        return err
-    }
-    switch strings.ToLower(str) {
-    case "tunnel":
-        *t = Tunnel
-    case "router":
-        *t = Router
-    default:
-        return fmt.Errorf("invalid connection type given: \"%s\"", str)
-    }
-    return nil
+	var str string
+	if err := json.Unmarshal(data, &str); err != nil {
+		return err
+	}
+	switch strings.ToLower(str) {
+	case "tunnel":
+		*t = Tunnel
+	case "router":
+		*t = Router
+	default:
+		return fmt.Errorf("invalid connection type given: \"%s\"", str)
+	}
+	return nil
 }
 
 type Duration time.Duration
 
 func (d Duration) MarshalJSON() ([]byte, error) {
-    return json.Marshal(time.Duration(d).String())
+	return json.Marshal(time.Duration(d).String())
 }
 
 func (d *Duration) UnmarshalJSON(data []byte) error {
-    var str string
-    if err := json.Unmarshal(data, &str); err != nil {
-        return err
-    }
-    duration, err := time.ParseDuration(str)
-    if err != nil {
-        return err
-    }
-    *d = Duration(duration)
-    return nil
+	var str string
+	if err := json.Unmarshal(data, &str); err != nil {
+		return err
+	}
+	duration, err := time.ParseDuration(str)
+	if err != nil {
+		return err
+	}
+	*d = Duration(duration)
+	return nil
 }
 
 // GroupAddressConfig defines all information to map a KNX group address to a prometheus metric.
 type GroupAddressConfig struct {
-    // Name defines the prometheus metric name without the MetricsPrefix.
-    Name string
-    // Comment to identify the group address.
-    Comment string `json:",omitempty"`
-    // DPT defines the DPT at the knx bus. This is required to parse the values correctly.
-    DPT string
-    // MetricType is the type that prometheus uses when exporting it. i.e. gauge or counter
-    MetricType string
-    // Export the metric to prometheus
-    Export bool
-    // ReadActive allows the exporter to actively send `GroupValueRead` telegrams to actively poll the value instead waiting for it.
-    ReadActive bool `json:",omitempty"`
-    // MaxAge of a value until it will actively send a `GroupValueRead` telegram to read the value if ReadActive is set to true.
-    MaxAge Duration `json:",omitempty"`
-    // Labels defines static labels that should be set when exporting the metric using prometheus.
-    Labels map[string]string `json:",omitempty"`
+	// Name defines the prometheus metric name without the MetricsPrefix.
+	Name string
+	// Comment to identify the group address.
+	Comment string `json:",omitempty"`
+	// DPT defines the DPT at the knx bus. This is required to parse the values correctly.
+	DPT string
+	// MetricType is the type that prometheus uses when exporting it. i.e. gauge or counter
+	MetricType string
+	// Export the metric to prometheus
+	Export bool
+	// ReadStartup allows the exporter to actively send `GroupValueRead` telegrams to actively read the value at startup instead waiting for it.
+	ReadStartup bool `json:",omitempty"`
+	// ReadActive allows the exporter to actively send `GroupValueRead` telegrams to actively poll the value instead waiting for it.
+	ReadActive bool `json:",omitempty"`
+	// MaxAge of a value until it will actively send a `GroupValueRead` telegram to read the value if ReadActive is set to true.
+	MaxAge Duration `json:",omitempty"`
+	// Labels defines static labels that should be set when exporting the metric using prometheus.
+	Labels map[string]string `json:",omitempty"`
 }
 
 // GroupAddressConfigSet is a shortcut type for the group address config map.

pkg/knx/exporter.go

@@ -37,6 +37,7 @@ type metricsExporter struct {
 	metrics        MetricSnapshotHandler
 	listener       Listener
 	messageCounter *prometheus.CounterVec
+	startupReader  StartupReader
 	poller         Poller
 	health         error
 }
@@ -64,6 +65,9 @@ func (e *metricsExporter) Run() error {
 		return err
 	}
 
+	e.startupReader = NewStartupReader(e.config, e.client, e.metrics, e.messageCounter)
+	e.startupReader.Run()
+
 	e.poller = NewPoller(e.config, e.client, e.metrics, e.messageCounter)
 	e.poller.Run()
 
@@ -75,6 +79,9 @@ func (e *metricsExporter) Run() error {
 }
 
 func (e *metricsExporter) Close() {
+	if e.startupReader != nil {
+		e.startupReader.Close()
+	}
 	if e.poller != nil {
 		e.poller.Close()
 	}

pkg/knx/fixtures/readConfig.yaml

@@ -3,32 +3,37 @@ Connection:
   Endpoint: "224.0.0.120:3672"
   PhysicalAddress: 2.0.1
 MetricsPrefix: knx_
+ReadStartupInterval: 250ms
 AddressConfigs:
   0/0/1:
     Name: dummy_metric
     DPT: 1.*
     Export: true
     MetricType: "counter"
+    ReadStartup: true
     ReadActive: true
     MaxAge: 5s
   0/0/2:
     Name: dummy_metric1
     DPT: 1.*
     Export: true
     MetricType: "counter"
+    ReadStartup: true
     ReadActive: true
     MaxAge: 5s
   0/0/3:
     Name: dummy_metric2
     DPT: 1.*
     Export: true
     MetricType: "counter"
+    ReadStartup: true
     ReadActive: true
     MaxAge: 5s
   0/0/4:
     Name: dummy_metric3
     DPT: 1.*
     Export: true
     MetricType: "counter"
+    ReadStartup: false
     ReadActive: false
     MaxAge: 5s