some loop optimizations, skip logging when there is no need to

code/core-api-consumer/src/main/java/com/redhat/training/kafka/coreapi/consumer/Consumer.java

@@ -121,12 +121,23 @@ public class Consumer {
         int recsSeen = 0;
         while (true) {
             ConsumerRecords<Integer, String> recs = kc.poll(Duration.ofMillis(pollPeriod));
-            try {
-                LOG.info("Received {} records. Sleeping for {} ms as per instructions...", recs.count(), waitAfterRecv);
-                Thread.sleep(waitAfterRecv);
-            } catch (InterruptedException ie) {
-                LOG.warn("Interrupted in sleep-after-recv: " + ie.getMessage());
+
+            // no records? skip the rest of this loop
+            if (recs.count() == 0) {
+                continue;
             }
+
+            // consumer.wait-after-recv
+            if (waitAfterRecv > 0) {
+                try {
+                    LOG.info("Received {} records. Sleeping for {} ms as per instructions...", recs.count(), waitAfterRecv);
+                    Thread.sleep(waitAfterRecv);
+                } catch (InterruptedException ie) {
+                    LOG.warn("Interrupted in sleep-after-recv: " + ie.getMessage());
+                }
+            }
+
+            // process records
             for (ConsumerRecord<Integer, String> rec : recs) {
                 recsSeen++;
                 if (rec.value().equals("quit")) {
@@ -153,25 +164,36 @@ public class Consumer {
                 pl.println(String.format("%s,%d,%d,%s", rec.topic(), rec.partition(), rec.key(), rec.value()));
                 pl.flush();
 
+                // consumer.ack-every-x-msgs
                 if (ackEveryNum != 0 && (recsSeen % ackEveryNum) == 0) {
                     LOG.info("Seen {} records, committing offsets as ackEveryNum == {}", recsSeen, ackEveryNum);
                     kc.commitSync();
                 }
-                try {
-                    LOG.info("Record processed. Sleeping for {} ms as per instructions...", waitAfterRecord);
-                    Thread.sleep(waitAfterRecord);
-                } catch (InterruptedException ie) {
-                    LOG.warn("Interrupted in sleep-after-record: " + ie.getMessage());
+
+                // consumer.wait-after-record
+                if (waitAfterRecord > 0) {
+                    try {
+                        LOG.info("Record processed. Sleeping for {} ms as per instructions...", waitAfterRecord);
+                        Thread.sleep(waitAfterRecord);
+                    } catch (InterruptedException ie) {
+                        LOG.warn("Interrupted in sleep-after-record: " + ie.getMessage());
+                    }
                 }
             }
+
+            // clean shutdown command?
             if (exitRequest) {
                 break;
             }
-            try {
-                LOG.info("Batch of {} processed. Sleeping for {} ms as per instructions...", recs.count(), waitAfterBatch);
-                Thread.sleep(waitAfterBatch);
-            } catch (InterruptedException ie) {
-                LOG.warn("Interrupted in sleep-after-batch: " + ie.getMessage());
+
+            // consumer.wait-after-batch
+            if (waitAfterBatch > 0) {
+                try {
+                    LOG.info("Batch of {} processed. Sleeping for {} ms as per instructions...", recs.count(), waitAfterBatch);
+                    Thread.sleep(waitAfterBatch);
+                } catch (InterruptedException ie) {
+                    LOG.warn("Interrupted in sleep-after-batch: " + ie.getMessage());
+                }
             }
         }
         kc.close();