org.apache.kafka.common.network
Class Selector

java.lang.Object
  org.apache.kafka.common.network.Selector

All Implemented Interfaces:

Selectable

public class Selector
extends java.lang.Object
implements Selectable

A selector interface for doing non-blocking multi-connection network I/O.

This class works with NetworkSend and NetworkReceive to transmit size-delimited network requests and responses.

A connection can be added to the selector associated with an integer id by doing

 selector.connect(42, new InetSocketAddress("google.com", server.port), 64000, 64000);
 

The connect call does not block on the creation of the TCP connection, so the connect method only begins initiating the connection. The successful invocation of this method does not mean a valid connection has been established. Sending requests, receiving responses, processing connection completions, and disconnections on the existing connections are all done using the poll() call.

 List<NetworkRequest> requestsToSend = Arrays.asList(new NetworkRequest(0, myBytes), new NetworkRequest(1, myOtherBytes));
 selector.poll(TIMEOUT_MS, requestsToSend);
 

The selector maintains several lists that are reset by each call to poll() which are available via various getters. These are reset by each call to poll(). This class is not thread safe!

Constructor Summary

Selector(Metrics metrics, Time time)
Create a new selector

Method Summary

void	close() Close this selector and all associated connections
java.util.List<NetworkReceive>	completedReceives() The list of receives that completed on the last poll() call.
java.util.List<NetworkSend>	completedSends() The list of sends that completed on the last poll() call.
void	connect(int id, java.net.InetSocketAddress address, int sendBufferSize, int receiveBufferSize) Begin connecting to the given address and add the connection to this selector associated with the given id number.
java.util.List<java.lang.Integer>	connected() The list of connections that completed their connection on the last poll() call.
void	disconnect(int id) Disconnect any connections for the given id (if there are any).
java.util.List<java.lang.Integer>	disconnected() The list of connections that finished disconnecting on the last poll() call.
void	poll(long timeout, java.util.List<NetworkSend> sends) Do whatever I/O can be done on each connection without blocking.
void	wakeup() Interrupt the selector if it is blocked waiting to do I/O.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Selector

public Selector(Metrics metrics,
                Time time)

Create a new selector

Method Detail

connect

public void connect(int id,
                    java.net.InetSocketAddress address,
                    int sendBufferSize,
                    int receiveBufferSize)
             throws java.io.IOException

Begin connecting to the given address and add the connection to this selector associated with the given id number.

Note that this call only initiates the connection, which will be completed on a future poll(long, List) call. Check connected() to see which (if any) connections have completed after a given poll call.

Specified by:

connect in interface Selectable

Parameters:

id - The id for the new connection

address - The address to connect to

sendBufferSize - The send buffer for the new connection

receiveBufferSize - The receive buffer for the new connection

Throws:

java.lang.IllegalStateException - if there is already a connection for that id

java.io.IOException - if DNS resolution fails on the hostname or if the broker is down

disconnect

public void disconnect(int id)

Disconnect any connections for the given id (if there are any). The disconnection is asynchronous and will not be processed until the next poll() call.

Specified by:

disconnect in interface Selectable

wakeup

public void wakeup()

Interrupt the selector if it is blocked waiting to do I/O.

Specified by:

wakeup in interface Selectable

close

public void close()

Close this selector and all associated connections

Specified by:

close in interface Selectable

poll

public void poll(long timeout,
                 java.util.List<NetworkSend> sends)
          throws java.io.IOException

Do whatever I/O can be done on each connection without blocking. This includes completing connections, completing disconnections, initiating new sends, or making progress on in-progress sends or receives.

The provided network sends will be started. When this call is completed the user can check for completed sends, receives, connections or disconnects using completedSends(), completedReceives(), connected(), disconnected(). These lists will be cleared at the beginning of each poll(long, List) call and repopulated by the call if any completed I/O.

Specified by:

poll in interface Selectable

Parameters:

timeout - The amount of time to wait, in milliseconds. If negative, wait indefinitely.

sends - The list of new sends to begin

Throws:

java.lang.IllegalStateException - If a send is given for which we have no existing connection or for which there is already an in-progress send

java.io.IOException

completedSends

public java.util.List<NetworkSend> completedSends()

Description copied from interface: Selectable

The list of sends that completed on the last poll() call.

Specified by:

completedSends in interface Selectable

completedReceives

public java.util.List<NetworkReceive> completedReceives()

Description copied from interface: Selectable

The list of receives that completed on the last poll() call.

Specified by:

completedReceives in interface Selectable

disconnected

public java.util.List<java.lang.Integer> disconnected()

Description copied from interface: Selectable

The list of connections that finished disconnecting on the last poll() call.

Specified by:

disconnected in interface Selectable

connected

public java.util.List<java.lang.Integer> connected()

Description copied from interface: Selectable

The list of connections that completed their connection on the last poll() call.

Specified by:

connected in interface Selectable