Add workaround to sleep after connect

config/config.go

@@ -15,6 +15,7 @@ package config
 
 import (
 	"fmt"
+	"time"
 
 	multierror "github.com/hashicorp/go-multierror"
 )
@@ -59,14 +60,19 @@ type ListTargets map[string]*Module
 
 // Module defines the configuration parameters of a modbus module.
 type Module struct {
-	Name     string         `yaml:"name"`
-	Protocol ModbusProtocol `yaml:"protocol"`
-	Timeout  int            `yaml:"timeout"`
-	Baudrate int            `yaml:"baudrate"`
-	Databits int            `yaml:"databits"`
-	Stopbits int            `yaml:"stopbits"`
-	Parity   string         `yaml:"parity"`
-	Metrics  []MetricDef    `yaml:"metrics"`
+	Name        string         `yaml:"name"`
+	Protocol    ModbusProtocol `yaml:"protocol"`
+	Timeout     int            `yaml:"timeout"`
+	Baudrate    int            `yaml:"baudrate"`
+	Databits    int            `yaml:"databits"`
+	Stopbits    int            `yaml:"stopbits"`
+	Parity      string         `yaml:"parity"`
+	Metrics     []MetricDef    `yaml:"metrics"`
+	Workarounds Workarounds    `yaml:"workarounds"`
+}
+
+type Workarounds struct {
+	SleepAfterConnect time.Duration `yaml:"sleepAfterConnect"`
 }
 
 // RegisterAddr specifies the register in the possible output of _digital

modbus.yml

@@ -3,6 +3,10 @@ modules:
     # Module name, needs to be passed as parameter by Prometheus.
   - name: "fake"
     protocol: 'tcp/ip'
+    # Certain modbus devices need special timing workarounds
+    workarounds:
+      # Sleep a certain time after the TCP connection is established
+      sleepAfterConnect: "1s"
     metrics:
         # Name of the metric.
       - name: "power_consumption_total"

modbus/modbus.go

@@ -63,6 +63,10 @@ func (e *Exporter) Scrape(targetAddress string, subTarget byte, moduleName strin
 			targetAddress, module.Name)
 	}
 
+	if module.Workarounds.SleepAfterConnect > 0 {
+		time.Sleep(module.Workarounds.SleepAfterConnect)
+	}
+
 	// TODO: Should we reuse this?
 	c := modbus.NewClient(handler)