Remove stacktrace from connection acquisition attempts in LoadBalancer

This is to reduce the noise in the logs when connection acquisition errors occur. Complete acquisitions failures are expected to be reported separately.

Author: injectives

driver/src/main/java/org/neo4j/driver/internal/cluster/RediscoveryImpl.java

@@ -58,7 +58,7 @@ public class RediscoveryImpl implements Rediscovery
     private static final String RECOVERABLE_ROUTING_ERROR = "Failed to update routing table with server '%s'.";
     private static final String RECOVERABLE_DISCOVERY_ERROR_WITH_SERVER = "Received a recoverable discovery error with server '%s', " +
                                                                           "will continue discovery with other routing servers if available. " +
-                                                                          "Complete routing failures will be reported separately from this warning.";
+                                                                          "Complete failure is reported separately from this entry.";
 
     private final BoltServerAddress initialRouter;
     private final RoutingSettings settings;

driver/src/main/java/org/neo4j/driver/internal/cluster/loadbalancing/LoadBalancer.java

@@ -20,6 +20,7 @@
 
 import io.netty.util.concurrent.EventExecutorGroup;
 
+import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
@@ -62,6 +63,12 @@
 public class LoadBalancer implements ConnectionProvider
 {
     private static final String LOAD_BALANCER_LOG_NAME = "LoadBalancer";
+    private static final String CONNECTION_ACQUISITION_COMPLETION_FAILURE_MESSAGE = "Connection acquisition failed for all available addresses.";
+    private static final String CONNECTION_ACQUISITION_COMPLETION_EXCEPTION_MESSAGE =
+            "Failed to obtain connection towards %s server. Known routing table is: %s";
+    private static final String CONNECTION_ACQUISITION_ATTEMPT_FAILURE_MESSAGE =
+            "Failed to obtain a connection towards address %s, will try other addresses if available. Complete failure is reported separately from this entry.";
+    private static final String CONNECTION_ACQUISITION_ATTEMPT_EXCEPTION_MESSAGE = "Server at %s is no longer available";
     private final ConnectionPool connectionPool;
     private final RoutingTableRegistry routingTables;
     private final LoadBalancingStrategy loadBalancingStrategy;
@@ -181,19 +188,23 @@ private CompletionStage<Connection> acquire( AccessMode mode, RoutingTable routi
     {
         AddressSet addresses = addressSet( mode, routingTable );
         CompletableFuture<Connection> result = new CompletableFuture<>();
-        acquire( mode, routingTable, addresses, result );
+        List<Throwable> attemptExceptions = new LinkedList<>();
+        acquire( mode, routingTable, addresses, result, attemptExceptions );
         return result;
     }
 
-    private void acquire( AccessMode mode, RoutingTable routingTable, AddressSet addresses, CompletableFuture<Connection> result )
+    private void acquire( AccessMode mode, RoutingTable routingTable, AddressSet addresses, CompletableFuture<Connection> result,
+                          List<Throwable> attemptExceptions )
     {
         BoltServerAddress address = selectAddress( mode, addresses );
 
         if ( address == null )
         {
-            result.completeExceptionally( new SessionExpiredException(
-                    "Failed to obtain connection towards " + mode + " server. " +
-                    "Known routing table is: " + routingTable ) );
+            SessionExpiredException completionError =
+                    new SessionExpiredException( format( CONNECTION_ACQUISITION_COMPLETION_EXCEPTION_MESSAGE, mode, routingTable ) );
+            attemptExceptions.forEach( completionError::addSuppressed );
+            log.error( CONNECTION_ACQUISITION_COMPLETION_FAILURE_MESSAGE, completionError );
+            result.completeExceptionally( completionError );
             return;
         }
 
@@ -204,10 +215,14 @@ private void acquire( AccessMode mode, RoutingTable routingTable, AddressSet add
             {
                 if ( error instanceof ServiceUnavailableException )
                 {
-                    SessionExpiredException errorToLog = new SessionExpiredException( format( "Server at %s is no longer available", address ), error );
-                    log.warn( "Failed to obtain a connection towards address " + address, errorToLog );
+                    String attemptMessage = format( CONNECTION_ACQUISITION_ATTEMPT_FAILURE_MESSAGE, address );
+                    log.warn( attemptMessage );
+                    SessionExpiredException attemptException =
+                            new SessionExpiredException( format( CONNECTION_ACQUISITION_ATTEMPT_EXCEPTION_MESSAGE, address ), error );
+                    attemptExceptions.add( attemptException );
+                    log.debug( attemptMessage, attemptException );
                     routingTable.forget( address );
-                    eventExecutorGroup.next().execute( () -> acquire( mode, routingTable, addresses, result ) );
+                    eventExecutorGroup.next().execute( () -> acquire( mode, routingTable, addresses, result, attemptExceptions ) );
                 }
                 else
                 {