Improve procstat

closes #799

plugins/inputs/procstat/README.md

@@ -35,6 +35,10 @@ The above configuration would result in output like:
 # Measurements
 Note: prefix can be set by the user, per process.
 
+
+Threads related measurement names:
+- procstat_[prefix_]num_threads value=5
+
 File descriptor related measurement names:
 - procstat_[prefix_]num_fds value=4
 

plugins/inputs/procstat/spec_processor.go

@@ -52,6 +52,7 @@ func NewSpecProcessor(
 }
 
 func (p *SpecProcessor) pushMetrics() {
+	p.pushNThreadsStats()
 	p.pushFDStats()
 	p.pushCtxStats()
 	p.pushIOStats()
@@ -60,6 +61,15 @@ func (p *SpecProcessor) pushMetrics() {
 	p.flush()
 }
 
+func (p *SpecProcessor) pushNThreadsStats() error {
+	numThreads, err := p.proc.NumThreads()
+	if err != nil {
+		return fmt.Errorf("NumThreads error: %s\n", err)
+	}
+	p.add("num_threads", numThreads)
+	return nil
+}
+
 func (p *SpecProcessor) pushFDStats() error {
 	fds, err := p.proc.NumFDs()
 	if err != nil {