Hi,
*Usecases*
Sending messages To TCP backend via a persistent connection in ESB. ESB
will use TCPTransportSender class to send TCP messages when send mediator
used with TCP protocol.
This messages will send after adding message length to the front of the
message. Back end also should send messages by adding message length to the
front of the messages for the purpose of reading easily.
Messages can be concatenated in TCP layer even though application layer
send messages separately. There can be delay in message reading from TCP
axi2 end and that delay will lead to concatenation of messages. Even though
messages concatenated message should be retrieved separately and send
separately to the original caller.
ESB should recognized disconnection of TCP links immediately and retry in
configured time interval for configured number of times and if failed even
after, should report to the client about the error.
*Solution for persistent connection.*
TCPTransportSender {
private Map<String, Socket> persistentConnectionsMap = new HashMap<>();
}
This map holds a unique client id and a socket instance. Whenever a message
comes to TCPTransportSender it retrieves the relevant socket instance to
the relevant client id and will send messages via that socket.
*How to prevent message concatenation in TCP layer.*
Existing methods flow is as follows for messages
sendMessage() --> writeMessageOut() --> waitForReply() --> getMessage()
According to the current implementation getMessage() will receive messages
from TCP backend and after receiving messages it will read bytes for
message length which is in front of the message ,via a buffer. After that
it will read the actual message by message length via the same buffer.
Since getMessage will return after reading the first message, it will lost
the second message or snippet from it which is remaining in the buffer.
Then what kind of mechanism should we implement to process the subsequent
messages also and send them separately to the original caller (websocket
inbound, tcp client, etc )?
*Solution to retry mechanism.*
To provide two separate configurations,
retryInterval - in seconds - default 3 seconds
noOfRetries - default 3
and finally send an exception report to the client.
Your suggestions are highly appreciated.
Thanks.
--
Lakshman Udayakantha
WSO2 Inc. www.wso2.com
lean.enterprise.middleware
Mobile: *0717429601*
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