Fix NPE when namenode transition to active during startup by adding checkNNStartup() in NameNodeRpcServer

Start NN
Let NN standby services be started.
Before the editLogTailer is initialised start ZKFC and allow the activeservices start to proceed further.

Here editLogTailer.catchupDuringFailover() will throw NPE.

void startActiveServices() throws IOException {
LOG.info("Starting services required for active state");
writeLock();
try {
FSEditLog editLog = dir.fsImage.getEditLog();

if (!editLog.isOpenForWrite())

2012-05-18 16:51:27,585 WARN org.apache.hadoop.ipc.Server: IPC Server Responder, call org.apache.hadoop.ha.HAServiceProtocol.getServiceStatus from XX.XX.XX.55:58003: output error
2012-05-18 16:51:27,586 WARN org.apache.hadoop.ipc.Server: IPC Server handler 8 on 8020, call org.apache.hadoop.ha.HAServiceProtocol.transitionToActive from XX.XX.XX.55:58004: error: java.lang.NullPointerException
java.lang.NullPointerException
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startActiveServices(FSNamesystem.java:602)
at org.apache.hadoop.hdfs.server.namenode.NameNode$NameNodeHAContext.startActiveServices(NameNode.java:1287)
at org.apache.hadoop.hdfs.server.namenode.ha.ActiveState.enterState(ActiveState.java:61)
at org.apache.hadoop.hdfs.server.namenode.ha.HAState.setStateInternal(HAState.java:63)
at org.apache.hadoop.hdfs.server.namenode.ha.StandbyState.setState(StandbyState.java:49)
at org.apache.hadoop.hdfs.server.namenode.NameNode.transitionToActive(NameNode.java:1219)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.transitionToActive(NameNodeRpcServer.java:978)
at org.apache.hadoop.ha.protocolPB.HAServiceProtocolServerSideTranslatorPB.transitionToActive(HAServiceProtocolServerSideTranslatorPB.java:107)
at org.apache.hadoop.ha.proto.HAServiceProtocolProtos$HAServiceProtocolService$2.callBlockingMethod(HAServiceProtocolProtos.java:3633)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:427)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:916)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1692)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1688)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1686)
2012-05-18 16:51:27,586 INFO org.apache.hadoop.ipc.Server: IPC Server handler 9 on 8020 caught an exception
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.ensureWriteOpen(SocketChannelImpl.java:133)
at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:324)
at org.apache.hadoop.ipc.Server.channelWrite(Server.java:2092)
at org.apache.hadoop.ipc.Server.access$2000(Server.java:107)
at org.apache.hadoop.ipc.Server$Responder.processResponse(Server.java:930)
at org.apache.hadoop.ipc.Server$Responder.doRespond(Server.java:994)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1738)