Add some debug logging in ConfigSubscriber

To be able to see what is going on when getting config in client,
how long it takes and to help when rewriting this code

1 files changed, 5 insertions, 0 deletions

diff --git a/config/src/main/java/com/yahoo/config/subscription/ConfigSubscriber.java b/config/src/main/java/com/yahoo/config/subscription/ConfigSubscriber.java
index f5ed79a1d44..07132c460f9 100644
--- a/config/src/main/java/com/yahoo/config/subscription/ConfigSubscriber.java
+++ b/config/src/main/java/com/yahoo/config/subscription/ConfigSubscriber.java
@@ -14,6 +14,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CopyOnWriteArrayList;
 
+import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.FINE;
@@ -293,10 +294,13 @@ public class ConfigSubscriber implements AutoCloseable {
             // Keep on polling the subscriptions until we have a new generation across the board, or it times out
             for (ConfigHandle<? extends ConfigInstance> h : subscriptionHandles) {
                 ConfigSubscription<? extends ConfigInstance> subscription = h.subscription();
+                log.log(Level.FINEST, () -> "Calling nextConfig for " + subscription.getKey());
                 if ( ! subscription.nextConfig(timeLeftMillis)) {
                     // This subscriber has no new state and we know it has exhausted all time
+                    log.log(Level.FINEST, () -> "No new config for " + subscription.getKey());
                     return false;
                 }
+                log.log(Level.FINEST, () -> "Got new generation or config for " + subscription.getKey());
                 throwIfExceptionSet(subscription);
                 ConfigSubscription.ConfigState<? extends ConfigInstance> config = subscription.getConfigState();
                 if (currentGen == null) currentGen = config.getGeneration();
@@ -322,6 +326,7 @@ public class ConfigSubscriber implements AutoCloseable {
         if (reconfigDue) {
             // This indicates the clients will possibly reconfigure their services, so "reset" changed-logic in subscriptions.
             // Also if appropriate update the changed flag on the handler, which clients use.
+            log.log(Level.FINE, () -> "Reconfig will happen for generation " + generation);
             markSubsChangedSeen(currentGen);
             synchronized (monitor) {
                 generation = currentGen;