为什么 ignite 客户端要打开一个端口？
Why does a the ignite client open a port?
我们已经开始使用 Apache Ignite 并且我们正在使用 TCP 通信。我们看到的是客户端像服务器一样打开一个端口进行通信。
我的第一个假设是我们不需要从服务器到客户端开放，一切似乎都运行良好。但是，在某些情况下，当拓扑发生变化时，我们会在日志中得到堆栈跟踪，表明服务器正在通过此端口启动与客户端的通信，但失败了。
我的问题是为什么服务器要尝试直接与客户端通信？我们是否需要让服务器与客户端通信，或者我们可以简单地忽略错误消息？
下面是堆栈跟踪的示例：
2016-07-04 16:02:32,298 ERROR [marshaller-cache-#67%PMCacheCluster%] [org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler] [NONE] - Failed to send event notification to node: ad8937b4-eb38-442a-8e06-9625c6246d7b
org.apache.ignite.IgniteCheckedException: Failed to send message (node may have left the grid or TCP connection cannot be established due to firewall issues) [node=TcpDiscoveryNode [id=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[xxx.xx.x.xxx], sockAddrs=[/xxx.xx.x.xxx:0, /xxx.xx.x.xxx:0], discPort=0, order=51, intOrder=29, lastExchangeTime=1467640045240, loc=false, ver=1.6.0#20160518-sha1:0b22c45b, isClient=true], topic=T4 [topic=TOPIC_CACHE, id1=ee261127-933b-36b7-b4ef-f5be9bb4bff2, id2=ad8937b4-eb38-442a-8e06-9625c6246d7b, id3=0], msg=GridContinuousMessage [type=MSG_EVT_NOTIFICATION, routineId=7107ffc5-9868-422f-8509-4739558869f7, data=null, futId=null], policy=2]
at org.apache.ignite.internal.managers.communication.GridIoManager.send(GridIoManager.java:1290)
at org.apache.ignite.internal.managers.communication.GridIoManager.sendOrderedMessage(GridIoManager.java:1508)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1229)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1200)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1182)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendNotification(GridContinuousProcessor.java:843)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.addNotification(GridContinuousProcessor.java:802)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.onEntryUpdate(CacheContinuousQueryHandler.java:787)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.access0(CacheContinuousQueryHandler.java:91)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.onEntryUpdated(CacheContinuousQueryHandler.java:412)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryManager.onEntryUpdated(CacheContinuousQueryManager.java:343)
at org.apache.ignite.internal.processors.cache.GridCacheMapEntry.innerUpdate(GridCacheMapEntry.java:2522)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateSingle(GridDhtAtomicCache.java:2246)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateAllAsyncInternal0(GridDhtAtomicCache.java:1644)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateAllAsyncInternal(GridDhtAtomicCache.java:1484)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.processNearAtomicUpdateRequest(GridDhtAtomicCache.java:2940)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.access0(GridDhtAtomicCache.java:129)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.apply(GridDhtAtomicCache.java:260)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.apply(GridDhtAtomicCache.java:258)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.processMessage(GridCacheIoManager.java:622)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.onMessage0(GridCacheIoManager.java:320)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.handleMessage(GridCacheIoManager.java:244)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.access[=10=]0(GridCacheIoManager.java:81)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.onMessage(GridCacheIoManager.java:203)
at org.apache.ignite.internal.managers.communication.GridIoManager.invokeListener(GridIoManager.java:1219)
at org.apache.ignite.internal.managers.communication.GridIoManager.processRegularMessage0(GridIoManager.java:847)
at org.apache.ignite.internal.managers.communication.GridIoManager.access00(GridIoManager.java:105)
at org.apache.ignite.internal.managers.communication.GridIoManager.run(GridIoManager.java:810)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.ignite.spi.IgniteSpiException: Failed to send message to remote node: TcpDiscoveryNode [id=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[xxx.xx.x.xxx], sockAddrs=[/xxx.xx.x.xxx:0, /xxx.xx.x.xxx:0], discPort=0, order=51, intOrder=29, lastExchangeTime=1467640045240, loc=false, ver=1.6.0#20160518-sha1:0b22c45b, isClient=true]
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage0(TcpCommunicationSpi.java:1993)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage(TcpCommunicationSpi.java:1933)
at org.apache.ignite.internal.managers.communication.GridIoManager.send(GridIoManager.java:1285)
... 30 common frames omitted
Caused by: org.apache.ignite.IgniteCheckedException: Failed to connect to node (is node still alive?). Make sure that each ComputeTask and GridCacheTransaction has a timeout set in order to prevent parties from waiting forever in case of network issues [nodeId=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[/xxx.xx.x.xxx:47100, /xxx.xx.x.xxx:47100]]
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2496)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createNioClient(TcpCommunicationSpi.java:2137)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.reserveClient(TcpCommunicationSpi.java:2031)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage0(TcpCommunicationSpi.java:1967)
... 32 common frames omitted
Suppressed: org.apache.ignite.IgniteCheckedException: Failed to connect to address: /xxx.xx.x.xxx:47100
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2501)
... 35 common frames omitted
Caused by: java.net.NoRouteToHostException: No route to host
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:111)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2360)
... 35 common frames omitted
Suppressed: org.apache.ignite.IgniteCheckedException: Failed to connect to address: /xxx.xx.x.xxx:47100
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2501)
... 35 common frames omitted
Caused by: java.net.ConnectException: Connection refused
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:111)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2360)
... 35 common frames omitted
2016-07-04 16:02:34,923 ERROR [marshaller-cache-#67%PMCacheCluster%] [org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler] [NONE] - Failed to send event notification to node: 95d9812d-4a16-4589-93a8-0bf2aa6b8413
客户端节点与服务器节点的主要区别在于它们不保存缓存数据并且不执行计算。
除此之外，客户端节点首先是 class 集群公民，并以与服务器相同的方式参与通信。所以是的，他们需要接受连接。
我们已经开始使用 Apache Ignite 并且我们正在使用 TCP 通信。我们看到的是客户端像服务器一样打开一个端口进行通信。 我的第一个假设是我们不需要从服务器到客户端开放，一切似乎都运行良好。但是，在某些情况下，当拓扑发生变化时，我们会在日志中得到堆栈跟踪，表明服务器正在通过此端口启动与客户端的通信，但失败了。
我的问题是为什么服务器要尝试直接与客户端通信？我们是否需要让服务器与客户端通信，或者我们可以简单地忽略错误消息？
下面是堆栈跟踪的示例：
2016-07-04 16:02:32,298 ERROR [marshaller-cache-#67%PMCacheCluster%] [org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler] [NONE] - Failed to send event notification to node: ad8937b4-eb38-442a-8e06-9625c6246d7b
org.apache.ignite.IgniteCheckedException: Failed to send message (node may have left the grid or TCP connection cannot be established due to firewall issues) [node=TcpDiscoveryNode [id=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[xxx.xx.x.xxx], sockAddrs=[/xxx.xx.x.xxx:0, /xxx.xx.x.xxx:0], discPort=0, order=51, intOrder=29, lastExchangeTime=1467640045240, loc=false, ver=1.6.0#20160518-sha1:0b22c45b, isClient=true], topic=T4 [topic=TOPIC_CACHE, id1=ee261127-933b-36b7-b4ef-f5be9bb4bff2, id2=ad8937b4-eb38-442a-8e06-9625c6246d7b, id3=0], msg=GridContinuousMessage [type=MSG_EVT_NOTIFICATION, routineId=7107ffc5-9868-422f-8509-4739558869f7, data=null, futId=null], policy=2]
at org.apache.ignite.internal.managers.communication.GridIoManager.send(GridIoManager.java:1290)
at org.apache.ignite.internal.managers.communication.GridIoManager.sendOrderedMessage(GridIoManager.java:1508)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1229)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1200)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendWithRetries(GridContinuousProcessor.java:1182)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.sendNotification(GridContinuousProcessor.java:843)
at org.apache.ignite.internal.processors.continuous.GridContinuousProcessor.addNotification(GridContinuousProcessor.java:802)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.onEntryUpdate(CacheContinuousQueryHandler.java:787)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.access0(CacheContinuousQueryHandler.java:91)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler.onEntryUpdated(CacheContinuousQueryHandler.java:412)
at org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryManager.onEntryUpdated(CacheContinuousQueryManager.java:343)
at org.apache.ignite.internal.processors.cache.GridCacheMapEntry.innerUpdate(GridCacheMapEntry.java:2522)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateSingle(GridDhtAtomicCache.java:2246)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateAllAsyncInternal0(GridDhtAtomicCache.java:1644)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.updateAllAsyncInternal(GridDhtAtomicCache.java:1484)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.processNearAtomicUpdateRequest(GridDhtAtomicCache.java:2940)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.access0(GridDhtAtomicCache.java:129)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.apply(GridDhtAtomicCache.java:260)
at org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.apply(GridDhtAtomicCache.java:258)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.processMessage(GridCacheIoManager.java:622)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.onMessage0(GridCacheIoManager.java:320)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.handleMessage(GridCacheIoManager.java:244)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.access[=10=]0(GridCacheIoManager.java:81)
at org.apache.ignite.internal.processors.cache.GridCacheIoManager.onMessage(GridCacheIoManager.java:203)
at org.apache.ignite.internal.managers.communication.GridIoManager.invokeListener(GridIoManager.java:1219)
at org.apache.ignite.internal.managers.communication.GridIoManager.processRegularMessage0(GridIoManager.java:847)
at org.apache.ignite.internal.managers.communication.GridIoManager.access00(GridIoManager.java:105)
at org.apache.ignite.internal.managers.communication.GridIoManager.run(GridIoManager.java:810)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.ignite.spi.IgniteSpiException: Failed to send message to remote node: TcpDiscoveryNode [id=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[xxx.xx.x.xxx], sockAddrs=[/xxx.xx.x.xxx:0, /xxx.xx.x.xxx:0], discPort=0, order=51, intOrder=29, lastExchangeTime=1467640045240, loc=false, ver=1.6.0#20160518-sha1:0b22c45b, isClient=true]
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage0(TcpCommunicationSpi.java:1993)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage(TcpCommunicationSpi.java:1933)
at org.apache.ignite.internal.managers.communication.GridIoManager.send(GridIoManager.java:1285)
... 30 common frames omitted
Caused by: org.apache.ignite.IgniteCheckedException: Failed to connect to node (is node still alive?). Make sure that each ComputeTask and GridCacheTransaction has a timeout set in order to prevent parties from waiting forever in case of network issues [nodeId=ad8937b4-eb38-442a-8e06-9625c6246d7b, addrs=[/xxx.xx.x.xxx:47100, /xxx.xx.x.xxx:47100]]
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2496)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createNioClient(TcpCommunicationSpi.java:2137)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.reserveClient(TcpCommunicationSpi.java:2031)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.sendMessage0(TcpCommunicationSpi.java:1967)
... 32 common frames omitted
Suppressed: org.apache.ignite.IgniteCheckedException: Failed to connect to address: /xxx.xx.x.xxx:47100
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2501)
... 35 common frames omitted
Caused by: java.net.NoRouteToHostException: No route to host
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:111)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2360)
... 35 common frames omitted
Suppressed: org.apache.ignite.IgniteCheckedException: Failed to connect to address: /xxx.xx.x.xxx:47100
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2501)
... 35 common frames omitted
Caused by: java.net.ConnectException: Connection refused
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at sun.nio.ch.SocketAdaptor.connect(SocketAdaptor.java:111)
at org.apache.ignite.spi.communication.tcp.TcpCommunicationSpi.createTcpClient(TcpCommunicationSpi.java:2360)
... 35 common frames omitted
2016-07-04 16:02:34,923 ERROR [marshaller-cache-#67%PMCacheCluster%] [org.apache.ignite.internal.processors.cache.query.continuous.CacheContinuousQueryHandler] [NONE] - Failed to send event notification to node: 95d9812d-4a16-4589-93a8-0bf2aa6b8413
客户端节点与服务器节点的主要区别在于它们不保存缓存数据并且不执行计算。
除此之外，客户端节点首先是 class 集群公民，并以与服务器相同的方式参与通信。所以是的，他们需要接受连接。