The Cluster Sender object
Table of Contents
Introduction
The channel sender component is responsible for delivering outgoing cluster messages over
the network.
In the default implementation, org.apache.catalina.tribes.transport.ReplicationTransmitter,
the sender is a fairly empty shell with not much logic around a fairly complex <Transport>
component the implements the actual delivery mechanism.
Concurrent Parallel Delivery
In the default transport implementation, org.apache.catalina.tribes.transport.nio.PooledParallelSender,
Apache Tribes implements what we like to call "Concurrent Parallel Delivery".
This means that we can send a message to more than one destination at the same
time(parallel), and
deliver two messages to the same destination at the same time(concurrent). Combine these two
and we have
"Concurrent Parallel Delivery".
When is this useful? The simplest example we can think of is when part of your code is sending a 10MB message, like a war file being deployed, and you need to push through a small 10KB message, say a session being replicated, you don't have to wait for the 10MB message to finish, as a separate thread will push in the small message transmission at the same time. Currently there is no interrupt, pause or priority mechanism available, but check back soon.
Nested Elements
The nested element <Transport> is not required, but encouraged, as this
is where
you would set all the socket options for the outgoing messages. Please see its attributes
below.
There are two implementations, in a similar manner to the receiver,
one is non-blocking
based and the other is built using blocking IO.
org.apache.catalina.tribes.transport.bio.PooledMultiSender is the blocking
implementation and
org.apache.catalina.tribes.transport.nio.PooledParallelSender.
Parallel delivery is not available for the blocking implementation due to the fact that it
is blocking a thread on sending data.
Attributes
Common Sender Attributes
| Attribute | Description |
|---|---|
className |
Required, only available implementation is org.apache.catalina.tribes.transport.ReplicationTransmitter
|
Common Transport Attributes
| Attribute | Description |
|---|---|
className |
Required, an implementation of the org.apache.catalina.tribes.transport.MultiPointSender.Non-blocking implementation is org.apache.catalina.tribes.transport.nio.PooledParallelSenderBlocking implementation is org.apache.catalina.tribes.transport.bio.PooledMultiSender
|
rxBufSize |
The receive buffer size on the socket.
Default value is 25188 bytes.
|
txBufSize |
The send buffer size on the socket.
Default value is 43800 bytes.
|
udpRxBufSize |
The receive buffer size on the datagram socket.
Default value is 25188 bytes.
|
udpTxBufSize |
The send buffer size on the datagram socket.
Default value is 43800 bytes.
|
directBuffer |
Possible values are true or false.
Set to true if you want the receiver to use direct bytebuffers when writing
data
to the sockets. Default value is false
|
keepAliveCount |
The number of requests that can go through the socket before the socket is
closed, and reopened
for the next request. The default value is -1, which is
unlimited.
|
keepAliveTime |
The number of milliseconds a connection is kept open after its been opened.
The default value is -1, which is unlimited.
|
timeout |
Sets the SO_TIMEOUT option on the socket. The value is in milliseconds and
the default value is 3000
milliseconds.(3 seconds) This timeout starts when a message send attempt is
starting, until the transfer has been completed.
For the NIO sockets, this will mean, that the caller can guarantee that we
will not attempt sending the message
longer than this timeout value. For the blocking IO implementation, this
translated directly to the soTimeout.A timeout will not spawn a retry attempt, in order to guarantee the return of the application thread. |
maxRetryAttempts |
How many times do we retry a failed message, that received a IOException at
the socket level.
The default value is 1, meaning we will retry a message that
has failed once.
In other words, we will attempt a message send no more than twice. One is
the original send, and one is the
maxRetryAttempts.
|
ooBInline |
Boolean value for the socket OOBINLINE option. Possible values are true
or false.
|
soKeepAlive |
Boolean value for the socket SO_KEEPALIVE option. Possible values are true
or false.
|
soLingerOn |
Boolean value to determine whether to use the SO_LINGER socket option.
Possible values are true or false. Default value
is true.
|
soLingerTime |
Sets the SO_LINGER socket option time value. The value is in seconds.
The default value is 3 seconds.
|
soReuseAddress |
Boolean value for the socket SO_REUSEADDR option. Possible values are true
or false.
|
soTrafficClass |
Sets the traffic class level for the socket, the value is between 0 and 255.
Default value is int soTrafficClass = 0x04 | 0x08 | 0x010;
Different values are defined in
java.net.Socket#setTrafficClass(int).
|
tcpNoDelay |
Boolean value for the socket TCP_NODELAY option. Possible values are true
or false.
The default value is true
|
throwOnFailedAck |
Boolean value, default value is true.
If set to true, the sender will throw a org.apache.catalina.tribes.RemoteProcessException
when we receive a negative ack from the remote member.
Set to false, and Tribes will treat a positive ack the same way as a
negative ack, that the message was received.
|
Common PooledSender Attributes
| Attribute | Description |
|---|---|
poolSize |
The maximum number of concurrent connections from A to B.
The value is based on a per-destination count.
The default value is 25
|
maxWait |
The maximum number of milliseconds that the senderPool will wait when
there are no available senders. The default value is 3000
milliseconds.(3 seconds).
|