TIBCO EMS Acknowledgement Modes - Interview Questions

                                        TIBCO EMS Acknowledgement Modes

TIBCO EMS has 8 different Acknowledgement Modes. The following are the different Acknowledgement Modes:

• Auto 
• Client 
• TIBCO EMS Explicit
• TIBCO EMS No 
• Dups Ok 
• TIBCO EMS Explicit Dups Ok
• Transactional
• Local Transactional

First of all, what is Message Acknowledgement Mode?

An Acknowledgement will be sent for an message when receiver received the message from the sender. Here, the receiver is JMS receiver and the sender is JMS sender. The medium on which they send or receive may be queue or topic.

what is the role of EMS server while acknowledging message?

EMS server acts an intermediate for both sender and receiver. Sender sends a message to EMS server and it gets the confirmation from the server that it is sent. After the confirmation, the message will be delivered to the receiver and depends upon the receiver's acknowledgement mode, it will be acknowledged. If the acknowledgement is not sent when it is expected, then it will be redelivered later to the receiver till acknowledging the message.

How it confirms the message?

JMS receiver acknowledges the message using Confirm activity. It will be added to the process and the corresponding JMS receiver should be selected in the configuration tab.

How do all acknowledgement mode work?

Auto

When sender sends an message, the message will be acknowledged immediately when it is received by the receiver. In process implementation, the message will be acknowledged when it is received by the JMS receiver before the execution of confirm activity.

Client 

Client ack mode is useful when your project needs session wise message processing. What is session? Session means that it would handle all the messages using a single thread. The project which has specification to use the limited no of threads, would use this ack mode. On this ack mode, when the sender sends, the receiver will acknowledge after the receipt of message. In process implementation, the message will be acknowledged when the confirm activity executes. 

It has two scenarios to work

When the session no > no of messages received, it will create each session for each messages and they all will be acknowledged at a time. If any message is not acknowledged, it will be redelivered to the receiver and the receiver will execute till it is acknowledged. If the message is not acknowledged till the end, it will go into an infinite loop.

When the session no < no of messaged received, it will create the max no of sessions specified in the JMS receiver and each session will process the messages. when one session gets free after execution, the session will process the other message. Like the first scenario, the message can be redelivered or get into an infinite loop.

TIBCO EMS explicit

Unlike client ack mode, it receives all the messages in one session and acknowledges the message after the execution of confirm activity in the process implementation. If even a single message is not acknowledged, then all the messages will be redelivered. This used to happen before TIBCO BW 5.10. After 5.10 version, the only message which is not acknowledged will be delivered and received. Most of the projects which has no limitation on number of threads, is using TIBCO EMS explicit ack mode.

TIBCO EMS No 

TIBCO EMS No will never send an acknowledgement for a message received by JMS receiver and will reduce the traffic. Durable JMS subscribers can't create sessions in no-acknowledgement mode. It can't be used in JMS receiver or subscriber when routing operation is performed.

Dups Ok

When the receiver has a lot of operations and performance issues, the acknowledgement will be sent for all the messages during a convenient timing.

TIBCO EMS Explicit Dups Ok

Unlike Dups Ok ack mode, it acknowledges for the individual message at a time.

Transactional

Transactional ack mode will be used when a transaction can process JMS messages. It will send acknowledgement when the transaction commits.

Local Transactional

This ack mode will consider JMS produced messages and consumed messages as a transaction. It will send a acknowledgement based on receipt of messages.