我在AWS中运行多DC Cassandra（开源，而不是DSE）群集，其中一个DC（us-west-2）设置用于分析，另一个（us-east）是事务存储。我使用NetworkTopologyStrategy和EC2 snitch，以及我的Hadoop配置中的LOCAL_ONE的一致性级别。 Hadoop 可以在没有问题的情况下从Cassandra中读取，但尝试写入会产生超时异常。
运行nodetool status表示已正确配置DC：
Datacenter: us-west-2
=====================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Owns Host ID Token Rack
UN x.x.x.x 1.01 GB 9.9% 9e7f4393-7ac9-4559-b3ff-de48be50016f -9127921345534057723 2a
UN x.x.x.x 1001.16 MB 11.4% d0760383-c3dd-474c-9261-239b71dba3f1 -9221279003374097975 2b
UN x.x.x.x 1.05 GB 11.7% 3f09fbf5-0d85-4283-9009-0ec0e29223c0 -9140104347498952504 2c
Datacenter: us-east
===================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Owns Host ID Token Rack
UN x.x.x.x 1.1 GB 11.3% 5bbd2de4-e1d2-4a17-9f40-034f60b35954 -9061054426204373981 1b
UN x.x.x.x 1.15 GB 11.5% e34c590e-6176-45b2-a8f9-18b4a9a80032 -9216519687724118609 1c
UN x.x.x.x 1.18 GB 10.9% fa0b0a1a-f156-40fc-a267-970d1eb9cddb -9207673937991303291 1a
UN x.x.x.x 1.46 GB 10.7% b18ae406-c9ec-42b7-a365-b0c6e2fe582f -9206671929961171506 1a
UN x.x.x.x 1.13 GB 11.4% 1ac9c1c5-55ad-4048-b1ba-3b9768933ecc -9146100851344467112 1c
UN x.x.x.x 1.53 GB 11.2% dad665bb-68d9-4811-b421-f33333261867 -9178920986366339267 1b
使用ColumnFamilyOutputFormat：
进行堆栈跟踪java.io.IOException: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection timed out
at org.apache.cassandra.hadoop.ColumnFamilyRecordWriter$RangeClient.run(ColumnFamilyRecordWriter.java:224)
Caused by: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection timed out
at org.apache.thrift.transport.TSocket.open(TSocket.java:185)
at org.apache.thrift.transport.TFramedTransport.open(TFramedTransport.java:81)
at org.apache.cassandra.thrift.TFramedTransportFactory.openTransport(TFramedTransportFactory.java:41)
at org.apache.cassandra.hadoop.AbstractColumnFamilyOutputFormat.createAuthenticatedClient(AbstractColumnFamilyOutputFormat.java:123)
at org.apache.cassandra.hadoop.ColumnFamilyRecordWriter$RangeClient.run(ColumnFamilyRecordWriter.java:215)
Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at org.apache.thrift.transport.TSocket.open(TSocket.java:180)
... 4 more
...并使用CqlOutputFormat：
java.io.IOException: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection timed out
at org.apache.cassandra.hadoop.cql3.CqlRecordWriter$RangeClient.run(CqlRecordWriter.java:271)
Caused by: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection timed out
at org.apache.thrift.transport.TSocket.open(TSocket.java:185)
at org.apache.thrift.transport.TFramedTransport.open(TFramedTransport.java:81)
at org.apache.cassandra.thrift.TFramedTransportFactory.openTransport(TFramedTransportFactory.java:41)
at org.apache.cassandra.hadoop.AbstractColumnFamilyOutputFormat.createAuthenticatedClient(AbstractColumnFamilyOutputFormat.java:123)
at org.apache.cassandra.hadoop.cql3.CqlRecordWriter$RangeClient.run(CqlRecordWriter.java:262)
Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at org.apache.thrift.transport.TSocket.open(TSocket.java:180)
... 4 more
两条痕迹最终都指向AbstractColumnFamilyOutputFormat.createAuthenticatedClient(host, port, conf)。
然后我打开了该源并向异常添加了一些细节，因此它将输出它连接的主机名，从而产生了这个跟踪：
java.io.IOException: java.lang.Exception: Unable to connect to host [hostname]
at org.apache.cassandra.hadoop.cql3.CqlRecordWriter$RangeClient.run(CqlRecordWriter.java:271)
Caused by: java.lang.Exception: Unable to connect to host [hostname]
at org.apache.cassandra.hadoop.AbstractColumnFamilyOutputFormat.createAuthenticatedClient(AbstractColumnFamilyOutputFormat.java:139)
at org.apache.cassandra.hadoop.cql3.CqlRecordWriter$RangeClient.run(CqlRecordWriter.java:262)
Caused by: org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection timed out
at org.apache.thrift.transport.TSocket.open(TSocket.java:185)
at org.apache.thrift.transport.TFramedTransport.open(TFramedTransport.java:81)
at org.apache.cassandra.thrift.TFramedTransportFactory.openTransport(TFramedTransportFactory.java:41)
at org.apache.cassandra.hadoop.AbstractColumnFamilyOutputFormat.createAuthenticatedClient(AbstractColumnFamilyOutputFormat.java:124)
... 1 more
Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at org.apache.thrift.transport.TSocket.open(TSocket.java:180)
... 4 more
问题是[hostname]是一台不在分析群集中的机器（它位于我们东部）。为什么它不能自动地知道这一点，特别是当读取工作正常时？无论DC如何，它似乎都在尝试环中的所有节点。
对于记录，使用CqlOutputFormat，ColumnFamilyOutputFormat和使用CqlStorage和CassandraStorage的Pig通过写入失败。
答案 0 :(得分：0)
我会说，尝试将cassandra.yaml中的write_request_timeout_in_ms设置为某个非常高的数字，看看是否有帮助。节点本身可能存在问题，当它仍然显示为正在响应时没有响应。如果它仍然超时，请重新启动您怀疑导致该问题的节点上的服务。
答案 1 :(得分：0)
这个问题归结为两件事：
对于多区域EC2设置，Cassandra要求将broadcast_address设置为公共IP，将listen_address设置为内部IP。在大多数情况下，你会希望rpc_address是内部IP，但这可能会破坏Cassandra的Hadoop客户端，该客户端根据broadcast_address确定要与之通信的端点。
Cassandra的Hadoop客户端（特别是RingCache）不尊重节点发现的数据中心，并试图发现环中的所有节点 - 包括非本地节点。它尊重实际写入的一致性级别，但在我们的情况下，由于＃1，它从未到达那里。
我提交了一张票并提交了一个补丁来解决这些问题：