Logging for upstream selection strategy.

Log strategy loading, warn of deprecation of ConnectRandomlyWithinServerGroupStrategy.java, log bad configs of ConnectRandomlyToServerGroupStrategy.java and UserDefinedConfigurationStrategy.java. Additionally parse config in UserDefinedConfigurationStrategy.java once at initialisation.

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/readreplica/ConnectRandomlyToServerGroupStrategy.java

@@ -21,20 +21,21 @@
 
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 import org.neo4j.causalclustering.core.CausalClusteringSettings;
 import org.neo4j.causalclustering.identity.MemberId;
 import org.neo4j.helpers.Service;
 
-// TODO deprecation warning
 @Service.Implementation( UpstreamDatabaseSelectionStrategy.class )
 public class ConnectRandomlyToServerGroupStrategy extends UpstreamDatabaseSelectionStrategy
 {
+    static final String NAME = "connect-randomly-to-server-group";
     private ConnectRandomlyToServerGroupImpl strategyImpl;
 
     public ConnectRandomlyToServerGroupStrategy()
     {
-        super( "connect-randomly-to-server-group" );
+        super( NAME );
     }
 
     @Override
@@ -43,6 +44,16 @@ void init()
         List<String> groups = config.get( CausalClusteringSettings.connect_randomly_to_server_group_strategy );
         strategyImpl = new ConnectRandomlyToServerGroupImpl( groups, topologyService,
                 myself );
+
+        if (groups.isEmpty())
+        {
+            log.warn( "No server groups configured for upstream strategy " + readableName + ". Strategy will not find upstream servers." );
+        }
+        else
+        {
+            String readableGroups = groups.stream().collect( Collectors.joining( ", " ) );
+            log.info( "Upstream selection strategy " + readableName + " configured with server groups " + readableGroups );
+        }
     }
 
     @Override

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/readreplica/ConnectRandomlyWithinServerGroupStrategy.java

@@ -42,6 +42,7 @@ void init()
     {
         List<String> groups = config.get( CausalClusteringSettings.server_groups );
         strategyImpl = new ConnectRandomlyToServerGroupImpl( groups, topologyService, myself );
+        log.warn( "Upstream selection strategy " + readableName + " is deprecated. Consider using " + ConnectRandomlyToServerGroupStrategy.NAME + " instead." );
     }
 
     @Override

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/readreplica/UpstreamDatabaseSelectionStrategy.java

@@ -36,6 +36,7 @@ public abstract class UpstreamDatabaseSelectionStrategy extends Service
     protected Config config;
     protected Log log;
     protected MemberId myself;
+    protected String readableName;
 
     public UpstreamDatabaseSelectionStrategy( String key, String... altKeys )
     {
@@ -50,6 +51,8 @@ void inject( TopologyService topologyService, Config config, LogProvider logProv
         this.log = logProvider.getLog( this.getClass() );
         this.myself = myself;
 
+        readableName = StreamSupport.stream( getKeys().spliterator(), false ).collect( Collectors.joining( ", " ) );
+        log.info( "Using upstream selection strategy " + readableName );
         init();
     }
 

enterprise/causal-clustering/src/main/java/org/neo4j/causalclustering/readreplica/UserDefinedConfigurationStrategy.java

@@ -39,29 +39,47 @@
 @Service.Implementation( UpstreamDatabaseSelectionStrategy.class )
 public class UserDefinedConfigurationStrategy extends UpstreamDatabaseSelectionStrategy
 {
+
+    // Empty if provided filter config cannot be parsed.
+    // Ideally this class would not be created until config has been successfully parsed
+    // in which case there would be no need for Optional
+    private Optional<Filter<ServerInfo>> filters;
+
     public UserDefinedConfigurationStrategy()
     {
         super( "user-defined" );
     }
 
     @Override
-    public Optional<MemberId> upstreamDatabase() throws UpstreamDatabaseSelectionException
+    void init()
     {
+        String filterConfig = config.get( CausalClusteringSettings.user_defined_upstream_selection_strategy );
         try
         {
-            Filter<ServerInfo> filters = FilterConfigParser.parse( config.get( CausalClusteringSettings.user_defined_upstream_selection_strategy ) );
+            Filter<ServerInfo> parsed = FilterConfigParser.parse( filterConfig );
+            filters = Optional.of( parsed );
+            log.info( "Upstream selection strategy " + readableName + " configured with " + filterConfig );
+        }
+        catch ( InvalidFilterSpecification invalidFilterSpecification )
+        {
+            filters = Optional.empty();
+            log.warn( "Cannot parse configuration '" + filterConfig + "' for upstream selection strategy "
+                    + readableName + ". " + invalidFilterSpecification.getMessage() );
+        }
+    }
 
+    @Override
+    public Optional<MemberId> upstreamDatabase() throws UpstreamDatabaseSelectionException
+    {
+        return filters.flatMap( filters ->
+        {
             Set<ServerInfo> possibleServers = possibleServers();
 
             return filters.apply( possibleServers ).stream()
                     .map( ServerInfo::memberId )
                     .filter( memberId -> !Objects.equals( myself, memberId ) )
                     .findFirst();
-        }
-        catch ( InvalidFilterSpecification invalidFilterSpecification )
-        {
-            return Optional.empty();
-        }
+        } );
     }
 
     private Set<ServerInfo> possibleServers()