MySQL-JDBC Loadbalance 深入解析

Table 1 LoadBalancedConnectionProxy.pickNewConnection()   synchronized void pickNewConnection() throws SQLException {       if (this.isClosed && this.closedExplicitly) {           return;       }       if (this.currentConnection == null) { // startup           this.currentConnection = this.balancer.pickConnection(this, Collections.unmodifiableList(this.hostList),                   Collections.unmodifiableMap(this.liveConnections), this.responseTimes.clone(), this.retriesAllDown);           return;       }       if (this.currentConnection.isClosed()) {           invalidateCurrentConnection();       }       int pingTimeout = this.currentConnection.getLoadBalancePingTimeout();       boolean pingBeforeReturn = this.currentConnection.getLoadBalanceValidateConnectionOnSwapServer();       for (int hostsTried = 0, hostsToTry = this.hostList.size(); hostsTried < hostsToTry; hostsTried++) {           ConnectionImpl newConn = null;           try {               newConn = this.balancer.pickConnection(this, Collections.unmodifiableList(this.hostList), Collections.unmodifiableMap(this.liveConnections), this.responseTimes.clone(), this.retriesAllDown);               if (this.currentConnection != null) {                   if (pingBeforeReturn) {                       if (pingTimeout == 0) {                           newConn.ping();                       } else {                           newConn.pingInternal(true, pingTimeout);                       }                   }                   syncSessionState(this.currentConnection, newConn);
               }               this.currentConnection = newConn;               return;           } catch (SQLException e) {               if (shouldExceptionTriggerConnectionSwitch(e) && newConn != null) {                   // connection error, close up shop on current connection                   invalidateConnection(newConn);               }           }       }       // no hosts available to swap connection to, close up.       this.isClosed = true;       this.closedReason = "Connection closed after inability to pick valid new connection during load-balance.";   }


Table 2 MultiHostConnectionProxy.syncSessionState()   static void syncSessionState(Connection source, Connection target, boolean readOnly) throws SQLException {       if (target != null) {           target.setReadOnly(readOnly);       }       if (source == null || target == null) {           return;       }target.setAutoCommit(source.getAutoCommit());       target.setCatalog(source.getCatalog());       target.setTransactionIsolation(source.getTransactionIsolation());       target.setSessionMaxRows(source.getSessionMaxRows());   }