public void run()

in wrapper/src/main/java/software/amazon/jdbc/hostlistprovider/monitoring/ClusterTopologyMonitorImpl.java [827:915]
66 lines of code
15 McCabe index (conditional complexity)

    public void run() {
      Connection connection = null;
      boolean updateTopology = false;

      final long start = System.nanoTime();
      try {
        while (!this.monitor.nodeThreadsStop.get()) {

          if (connection == null) {

            try {
              connection = this.monitor.pluginService.forceConnect(
                  hostSpec, this.monitor.monitoringProperties);
              this.monitor.pluginService.setAvailability(
                  hostSpec.asAliases(), HostAvailability.AVAILABLE);
            } catch (SQLException ex) {
              // connect issues
              this.monitor.pluginService.setAvailability(
                  hostSpec.asAliases(), HostAvailability.NOT_AVAILABLE);
            }
          }

          if (connection != null) {

            String writerId = null;
            try {
              writerId = this.monitor.getWriterNodeId(connection);

            } catch (SQLSyntaxErrorException ex) {
              LOGGER.severe(() -> Messages.get("NodeMonitoringThread.invalidWriterQuery",
                  new Object[] {ex.getMessage()}));
              throw new RuntimeException(ex);

            } catch (SQLException ex) {
              this.monitor.closeConnection(connection);
              connection = null;
            }

            if (!StringUtils.isNullOrEmpty(writerId)) {
              // this prevents closing connection in finally block
              if (!this.monitor.nodeThreadsWriterConnection.compareAndSet(null, connection)) {
                // writer connection is already setup
                this.monitor.closeConnection(connection);

              } else {
                // writer connection is successfully set to writerConnection
                LOGGER.fine(Messages.get("NodeMonitoringThread.detectedWriter", new Object[]{writerId}));
                // When nodeThreadsWriterConnection and nodeThreadsWriterHostSpec are both set, the topology monitor may
                // set ignoreNewTopologyRequestsEndTimeNano, in which case other threads will use the cached topology
                // for the ignore duration, so we need to update the topology before setting nodeThreadsWriterHostSpec.
                this.monitor.fetchTopologyAndUpdateCache(connection);
                this.monitor.nodeThreadsWriterHostSpec.set(hostSpec);
                this.monitor.nodeThreadsStop.set(true);
                LOGGER.fine(Utils.logTopology(
                    this.monitor.topologyMap.get(this.monitor.clusterId)));
              }

              // Setting the connection to null here prevents the final block
              // from closing nodeThreadsWriterConnection.
              connection = null;
              return;

            } else if (connection != null) {
              // this connection is a reader connection
              if (this.monitor.nodeThreadsWriterConnection.get() == null) {
                // while writer connection isn't yet established this reader connection may update topology
                if (updateTopology) {
                  this.readerThreadFetchTopology(connection, writerHostSpec);
                } else if (this.monitor.nodeThreadsReaderConnection.get() == null) {
                  if (this.monitor.nodeThreadsReaderConnection.compareAndSet(null, connection)) {
                    // let's use this connection to update topology
                    updateTopology = true;
                    this.readerThreadFetchTopology(connection, writerHostSpec);
                  }
                }
              }
            }
          }
          TimeUnit.MILLISECONDS.sleep(100);
        }
      } catch (InterruptedException ex) {
        Thread.currentThread().interrupt();
      } finally {
        this.monitor.closeConnection(connection);
        final long end = System.nanoTime();
        LOGGER.finest(() -> Messages.get("NodeMonitoringThread.threadCompleted",
            new Object[] {TimeUnit.NANOSECONDS.toMillis(end - start)}));
      }
    }