Switch CPU from field to tag in Interrupts input plugin (#4999)

plugins/inputs/interrupts/README.md

@@ -5,6 +5,9 @@ The interrupts plugin gathers metrics about IRQs from `/proc/interrupts` and `/p
 ### Configuration
 ```
 [[inputs.interrupts]]
+  # To report cpus as tags instead of fields use cpu_as_tags
+    # cpu_as_tags = false
+  #
   ## To filter which IRQs to collect, make use of tagpass / tagdrop, i.e.
   # [inputs.interrupts.tagdrop]
     # irq = [ "NET_RX", "TASKLET" ]
@@ -16,20 +19,32 @@ There are two measurements reported by this plugin.
 - `soft_interrupts` gathers metrics from the `/proc/softirqs` file
 
 ### Fields
-- CPUx: the amount of interrupts for the IRQ handled by that CPU
-- total: total amount of interrupts for all CPUs
+For cpu_as_tags=false (default):
+- CPUx: the amount of interrupts for the IRQ handled by the CPU
+- Total: sum of interrupts for the IRS for all CPUs
+For cpu_as_tags=true ():
+- Count: the amount of interrupts for the IRQ handled by CPU described in CPU tag
 
 ### Tags
 - irq: the IRQ
 - type: the type of interrupt
 - device: the name of the device that is located at that IRQ
+- cpu: the CPU (when cpus_as_tags=true)
 
 ### Example Output
 ```
 ./telegraf --config ~/interrupts_config.conf --test
+For cpus_as_tags=false (default):
 * Plugin: inputs.interrupts, Collection 1
-> interrupts,irq=0,type=IO-APIC,device=2-edge\ timer,host=hostname CPU0=23i,total=23i 1489346531000000000
-> interrupts,irq=1,host=hostname,type=IO-APIC,device=1-edge\ i8042 CPU0=9i,total=9i 1489346531000000000
-> interrupts,irq=30,type=PCI-MSI,device=65537-edge\ virtio1-input.0,host=hostname CPU0=1i,total=1i 1489346531000000000
-> soft_interrupts,irq=NET_RX,host=hostname CPU0=280879i,total=280879i 1489346531000000000
+> interrupts,irq=0,type=IO-APIC,device=2-edge\ timer,host=hostname,cpu=cpu0 count=23i 1489346531000000000
+> interrupts,irq=1,host=hostname,type=IO-APIC,device=1-edge\ i8042,cpu=cpu0 count=9i 1489346531000000000
+> interrupts,irq=30,type=PCI-MSI,device=65537-edge\ virtio1-input.0,host=hostname,cpu=cpu1 count=1i 1489346531000000000
+> soft_interrupts,irq=NET_RX,host=hostname,cpu=cpu0 count=280879i 1489346531000000000
+
+For cpus_as_tags=true:
+> interrupts,cpu=cpu6,host=hostname,irq=PIW,type=Posted-interrupt\ wakeup\ event count=0i 1543539773000000000
+> interrupts,cpu=cpu7,host=hostname,irq=PIW,type=Posted-interrupt\ wakeup\ event count=0i 1543539773000000000
+> soft_interrupts,cpu=cpu0,host=hostname,irq=HI count=246441i 1543539773000000000
+> soft_interrupts,cpu=cpu1,host=hostname,irq=HI count=159154i 1543539773000000000
+
 ```

plugins/inputs/interrupts/interrupts.go

@@ -12,7 +12,9 @@ import (
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
-type Interrupts struct{}
+type Interrupts struct {
+	CpuAsTags bool
+}
 
 type IRQ struct {
 	ID     string
@@ -27,6 +29,9 @@ func NewIRQ(id string) *IRQ {
 }
 
 const sampleConfig = `
+  ## To report cpus as tags instead of fields use cpu_as_tags
+    # cpu_as_tags = false
+  #
   ## To filter which IRQs to collect, make use of tagpass / tagdrop, i.e.
   # [inputs.interrupts.tagdrop]
     # irq = [ "NET_RX", "TASKLET" ]
@@ -92,7 +97,7 @@ func gatherTagsFields(irq IRQ) (map[string]string, map[string]interface{}) {
 	tags := map[string]string{"irq": irq.ID, "type": irq.Type, "device": irq.Device}
 	fields := map[string]interface{}{"total": irq.Total}
 	for i := 0; i < len(irq.Cpus); i++ {
-		cpu := fmt.Sprintf("CPU%d", i)
+		cpu := fmt.Sprintf("cpu%d", i)
 		fields[cpu] = irq.Cpus[i]
 	}
 	return tags, fields
@@ -111,12 +116,26 @@ func (s *Interrupts) Gather(acc telegraf.Accumulator) error {
 			acc.AddError(fmt.Errorf("Parsing %s: %s", file, err))
 			continue
 		}
-		for _, irq := range irqs {
-			tags, fields := gatherTagsFields(irq)
+		reportMetrics(measurement, irqs, acc, s.CpuAsTags)
+	}
+	return nil
+}
+
+func reportMetrics(measurement string, irqs []IRQ, acc telegraf.Accumulator, cpusAsTags bool) {
+	for _, irq := range irqs {
+		tags, fields := gatherTagsFields(irq)
+		if cpusAsTags {
+			for cpu, count := range irq.Cpus {
+				cpuTags := map[string]string{"cpu": fmt.Sprintf("cpu%d", cpu)}
+				for k, v := range tags {
+					cpuTags[k] = v
+				}
+				acc.AddFields(measurement, map[string]interface{}{"count": count}, cpuTags)
+			}
+		} else {
 			acc.AddFields(measurement, fields, tags)
 		}
 	}
-	return nil
 }
 
 func init() {