feat: Nats Jetstream consumer add simple support for jetstream subjects (#11373)

plugins/inputs/nats_consumer/README.md

@@ -15,8 +15,19 @@ instances of telegraf can read from a NATS cluster in parallel.
   servers = ["nats://localhost:4222"]
 
   ## subject(s) to consume
+  ## If you use jetstream you need to set the subjects
+  ## in jetstream_subjects
   subjects = ["telegraf"]
 
+  ## jetstream subjects
+  ## jetstream is a streaming technology inside of nats.
+  ## With jetstream the nats-server persists messages and 
+  ## a consumer can consume historical messages. This is
+  ## useful when telegraf needs to restart it don't miss a 
+  ## message. You need to configure the nats-server:
+  ## https://docs.nats.io/nats-concepts/jetstream.
+  jetstream_subjects = ["js_telegraf"]
+
   ## name a queue group
   queue_group = "telegraf_consumers"
 
@@ -62,3 +73,12 @@ instances of telegraf can read from a NATS cluster in parallel.
 [nats]: https://www.nats.io/about/
 [input data formats]: /docs/DATA_FORMATS_INPUT.md
 [queue group]: https://www.nats.io/documentation/concepts/nats-queueing/
+
+## Metrics
+
+Which data you will get depends on the subjects you consume from nats
+
+## Example Output
+
+Depends on the nats subject input
+nats_consumer,host=[] value=1.9 1655972309339341000

plugins/inputs/nats_consumer/nats_consumer.go

@@ -46,6 +46,7 @@ type natsConsumer struct {
 	Username    string   `toml:"username"`
 	Password    string   `toml:"password"`
 	Credentials string   `toml:"credentials"`
+	JsSubjects  []string `toml:"jetstream_subjects"`
 
 	tls.ClientConfig
 
@@ -59,7 +60,9 @@ type natsConsumer struct {
 	MetricBuffer           int `toml:"metric_buffer" deprecated:"0.10.3;2.0.0;option is ignored"`
 
 	conn   *nats.Conn
+	jsConn nats.JetStreamContext
 	subs   []*nats.Subscription
+	jsSubs []*nats.Subscription
 
 	parser parsers.Parser
 	// channel for all incoming NATS messages
@@ -142,6 +145,33 @@ func (n *natsConsumer) Start(acc telegraf.Accumulator) error {
 
 			n.subs = append(n.subs, sub)
 		}
+
+		if len(n.JsSubjects) > 0 {
+			var connErr error
+			n.jsConn, connErr = n.conn.JetStream(nats.PublishAsyncMaxPending(256))
+			if connErr != nil {
+				return connErr
+			}
+
+			if n.jsConn != nil {
+				for _, jsSub := range n.JsSubjects {
+					sub, err := n.jsConn.QueueSubscribe(jsSub, n.QueueGroup, func(m *nats.Msg) {
+						n.in <- m
+					})
+					if err != nil {
+						return err
+					}
+
+					// set the subscription pending limits
+					err = sub.SetPendingLimits(n.PendingMessageLimit, n.PendingBytesLimit)
+					if err != nil {
+						return err
+					}
+
+					n.jsSubs = append(n.jsSubs, sub)
+				}
+			}
+		}
 	}
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -154,8 +184,8 @@ func (n *natsConsumer) Start(acc telegraf.Accumulator) error {
 		go n.receiver(ctx)
 	}()
 
-	n.Log.Infof("Started the NATS consumer service, nats: %v, subjects: %v, queue: %v",
+	n.Log.Infof("Started the NATS consumer service, nats: %v, subjects: %v, jssubjects: %v, queue: %v",
-		n.conn.ConnectedUrl(), n.Subjects, n.QueueGroup)
+		n.conn.ConnectedUrl(), n.Subjects, n.JsSubjects, n.QueueGroup)
 
 	return nil
 }
@@ -201,7 +231,14 @@ func (n *natsConsumer) clean() {
 	for _, sub := range n.subs {
 		if err := sub.Unsubscribe(); err != nil {
 			n.Log.Errorf("Error unsubscribing from subject %s in queue %s: %s",
-				sub.Subject, sub.Queue, err.Error())
+				sub.Subject, sub.Queue, err)
+		}
+	}
+
+	for _, sub := range n.jsSubs {
+		if err := sub.Unsubscribe(); err != nil {
+			n.Log.Errorf("Error unsubscribing from subject %s in queue %s: %s",
+				sub.Subject, sub.Queue, err)
 		}
 	}
 

plugins/inputs/nats_consumer/sample.conf

@@ -4,8 +4,19 @@
   servers = ["nats://localhost:4222"]
 
   ## subject(s) to consume
+  ## If you use jetstream you need to set the subjects
+  ## in jetstream_subjects
   subjects = ["telegraf"]
 
+  ## jetstream subjects
+  ## jetstream is a streaming technology inside of nats.
+  ## With jetstream the nats-server persists messages and 
+  ## a consumer can consume historical messages. This is
+  ## useful when telegraf needs to restart it don't miss a 
+  ## message. You need to configure the nats-server.
+  ## https://docs.nats.io/nats-concepts/jetstream.
+  jetstream_subjects = ["js_telegraf"]
+
   ## name a queue group
   queue_group = "telegraf_consumers"