Enterprise Messaging Service · TIBCO

Tibco EMS FAQs

 

What are the messaging models does EMS support?
Point-to-Point (Queue)
b. Publish and Subscribe (Topic)
c. Multicast (Topic)

There are two major models for messaging supported by JMS: queues and topics. Queues are based on a point-to-point messaging model. Topics make use of the new publish-and-subscribe messaging model.

Regardless whether queues or topics are used, the messages are not sent directly peer-to-peer. Messages are forwarded to a JMS infrastructure that is composed of one or more JMS servers. The servers are responsible for providing the quality-of-services to JMS and responsible for implementing all the components not addressed by JMS Specification.

When determining when to use queues versus topics consider the two fundamental messaging mechanisms. The first is point-to-point messaging, in which a message is sent by one publisher (sender) and received by one subscriber (receiver). The second is publish-subscribe messaging, in which a message is sent by one or more publishers and received by one or more subscribers. The messaging model as listed below will dictate when to use a queue or a topic:

One-to-one messaging                   Queue    point-to-point
One-to-many messaging   Topic   publish-subscribe
Many-to-many messaging   Topic    publish-subscribe model

What is the difference between a topic and queue?
Answer:

Topic-synchronous mode of communication.
-publisher and subscriber model.
-broad cast type messaging.
-there is no guarantee of delivery.
Queue-asynchronous mode of communication.
-point to point model.
-unidirectional type of messaging.
-there is guarantee of delivery.
When will u use a topic and when will u use a queue?
Answer: 1.only one producer and only one consumer is there then “Queues” are used. Simply “Queue” is of type “Point to Point”. One or more than one publishers and one or more than one subscriber is there than “Topic”. Simply “Topic” is of type “Broadcast messaging”.
Can queues be shared between two consumers?
Answer: Yes. If queue is non-exclusive (default) it can be shared by any number of consumers. Non-exclusive queues are useful for balancing the load of incoming messages across multiple receivers.
What is an exclusive queue? When would u use it?
Answer: If queue is exclusive, then all queue messages can only be retrieved by the first consumer specified for the queue. Exclusive queues are useful when we want only one application to receive messages for a specific queue.
A message in a queue can be consumed by how many consumers?
Answer: if all are non-exclusive queue any number of consumers will receive messages. If exclusive queue, the first consumer will get messages.
How will you grant privileges to topics and queues?
Answer: Only EMS admin have privilege
What are the protocols supported by JMS/EMS?
Answer: 1.SSL (HTTP) 2. TCP

What are the limitations of the Durable Subscriber?

As long as the durable subscriber exists
• Expiration time of the message
• Storage limit of that Topic

What is the difference between “Multicasting” and “publish and subscribe” messaging model?

BROADCAST-
Many publishers can publish to the same topic, and a message from a single publisher can be received by many subscribers. Subscribers subscribe to topics,
and all messages published to the topic are received by all subscribers to the topic.This type of message protocol is also known a broadcast messaging because
messages are sent over the network and received by all interested subscribers,similar to how radio or television signals are broadcast and received.

MULTICAST-
Multicast messaging allows one message producer to send a message to multiple subscribed consumers simultaneously.It is similar to publish and subscribe in that it
also addresses message to a topic. Instead of delivering a copy of the message to each individual subscriber over TCP,however, the EMS server broadcasts the message
over Pragmatic General Multicast (PGM). A daemon running on the machine with the subscribed EMS client receives the multicast message and delivers it to the message
consumer.
Multicast is highly scalable because of the reduction in bandwidth used to broadcast messages & it also uses less EMS resources.
However,one drawback of this model is that it does not guarantee the delivery of messages to all subscribers.

What are the EMS Destination features?
• Secure Property
• Trace Property
• Store Property
• Redelivery policy
• Flow control
• Exclusive property for queues

What are the extra features are available in EMS apart from JMS?

The JMS standard specifies two delivery modes for messages, PERSISTENT and NON_PERSISTENT. EMS also includes a RELIABLE_DELIVERY mode that eliminates some of the overhead associated with the other delivery modes.
• For consumer sessions, you can specify a NO_ACKNOWLEDGE mode so that consumers do not need to acknowledge receipt of messages, if desired. EMS also provides an EXPLICIT_CLIENT_ACKNOWLEDGE and EXPLICIT_CLIENT_DUPS_OK_ACKNOWLEDGE mode that restricts the acknowledgement to single messages
• EMS extends the MapMessage and StreamMessage body types. These extensions allow EMS to exchange messages with TIBCO Rendezvous and ActiveEnterprise formats that have certain features not available within the JMS MapMessage and StreamMessage

What is structure of JMS Message?

Header(Required)
• Properties(optional)
• Body(optional)

Where does the undelivered messages will be stored?

If a message expires or has exceeded the value specified by the maxRedelivery property on a queue, the server checks the message’s JMS_TIBCO_PRESERVE_UNDELIVERED property. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to true, the server moves the message to the undelivered message queue, $sys.undelivered. This undelivered message queue is a system queue that is always present and cannot be deleted. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to false, the message will be deleted by the server
• You can only set the undelivered property on individual messages, there is no way to set the undelivered message queue as an option at the per-topic or per-queue level

What are the messages bodies are supported by the EMS?
• Map Message
• Text Message
• Stream Message
• Bytes Message
• Object Message

What is the Maximum message size is supported by EMS?

EMS supports messages up to a maximum size of 512MB. However, we recommend that application programs use smaller messages, since messages approaching this maximum size will strain the performance limits of most current hardware and operating system platforms

What are the different delivery modes available in EMS?

Persistent
When a producer sends a PERSISTENT message, the producer must wait for the server to reply with a confirmation. The message is persisted on disk by the server. This delivery mode ensures delivery of messages to the destination on the server in almost all circumstances. However, the cost is that this delivery mode incurs two-way network traffic for each message or committed transaction of a group of messages

Non-Persistent
Sending a NON_PERSISTENT message omits the overhead of persisting the message on disk to improve performance.
If authorization is disabled on the server, the server does not send a confirmation to the message producer.
If authorization is enabled on the server, the default condition is for the producer to wait for the server to reply with a confirmation in the same manner as when using PERSISTENT mode.
Regardless of whether authorization is enabled or disabled, you can use the npsend_check_mode parameter in the tibemsd.conf file to specify the conditions under which the server is to send confirmation of NON_PERSISTENT messages to the producer

Reliable
EMS extends the JMS delivery modes to include reliable delivery. Sending a RELIABLE_DELIVERY message omits the server confirmation to improve performance regardless of the authorization setting.
When using RELIABLE_DELIVERY mode, the server never sends the producer a receipt confirmation or access denial and the producer does not wait for it. Reliable mode decreases the volume of message traffic, allowing higher message rates, which is useful for messages containing time-dependent data, such as stock price quotations.

If a persistent message is published on to a TOPIC, Does these messages will store on disk if topic doesn’t have durable subscriber or subscriber with a fault-tolerant connection?
No. Persistent messages published to a topic are written to disk only if that topic has at least one durable subscriber or one subscriber with a fault-tolerant connection to the EMS server. In the absence of a durable subscriber or subscriber with a fault-tolerant connection, there are no subscribers that need messages resent in the event of a server failure. In this case, the server does not needlessly save persistent messages. This improves performance by eliminating the unnecessary disk I/O to persist the messages

What are the different types of acknowledgement modes in EMS message delivery?
• Auto
• Client
• Dups_ok
• No_ack
• Explciit
• Explicit_client_dups_ok
• Transitional
• Local transitional.

What are the different types of messages that can be used in EMS
• Text
• Simple
• Bytes
• Map
• XML test
• Object
• Object ref
• Stream

Tell me about bridges. Why do we use them, Syntax to create bridges, use of message selector?
• Some applications require the same message to be sent to more than one destination possibly of different types. So we use bridges in that scenario.
• create bridge source=type:dest_name target=type:dest_name [selector=selector]

What is the purpose for stores.conf

This file defines the locations either store files or a database, where the EMS server will store messages or metadata. Each store configured is either a file-based or a database store.

How many modes are the messages written to store file.
• Two Modes: Synchronous and Asynchronous
• Default is asynchronous

What is tibemsd.conf
• It is the main configuration file that controls the characteristics of the EMS server

Name destination properties and explain them.
• Global, secure, maxmsgs, maxbytes, flowcontrol, sender_name, sender_name_enforced, trace,maxRedelivery

What are the different modes of installation in Ems?
• GUI mode
• Console mode
• Silent mode

What are the messaging models supported by JMS
• Point-to-point
• Publish-subscribe
• Multicast
What is the use of routes? What kind of destinations can be used in routes?
• Topics and queues m-hops

What happens if the message expires/exceeded the value specified by maxredelivery property on queue?
• If the jms_preserve_undelivered property is set to true, then it moves he message to undelivered message queue, if set to false, the message is deleted by the server.

In how many ways can a destination be created?
• Static-created by server
• Dynamic-created by client
• Temporary destinations.

What are the wild cards that we use in ems? how do they work for queues and topics
• *,> you can subscribe to wildcard topics but can’t publish to them. Where as in case of queues we can’t either send /receive.

Is bridges are transitive?
• NO

What Are flow control on destinations
• Some times the producer may send messages faster than the consumers can receive them. So, the message capacity on the server will be exhausted. So we use flow control. Flow control can be specified on destinations.

What Are flow control on bridges and routes
• Flow control has to be specified on both sides of bridges where as on routes it operates differently on sender side and receiver side.

What are the permissions that you can grant to users to access queues
• Receive
• Send
• Browse
What are the permissions that you can grant to users to access topics
• Subscribe
• Publish
• Durable
• Use_durable

Tell me about multicasting in EMS
• Multicast is a messaging model that broadcasts messages to many consumers at once rather than sending messages individually to each consumer. EMS uses Pragmatic general multicast to broadcast messages published to multicast enabled topics.
• Each multicast enabled topic is associated with a channel.

What are the advantages and disadvantages of multicasting?
• Advantages: as the message broadcasts only once thereby reducing the amount of bandwidth used in publish and subscribe model. Reduces the network traffic.
• Disadvantages: Offers only last-hop delivery. So can’t be used to send messages between servers.

On what destinations can you use multicast?
• Topics

Suppose, you got an error while accessing a queue, that you don’t have necessary permissions to access the queue. What might be the solution/reason?
• The user that is assigned to the queue and the user used while creating

How does the secondary server know that the primary server is failed?
• Based on heartbeat intervals

What is JMS queue requestor?
• The JMS Queue Requestor activity is used to send a request to a JMS queue name and receive a response back from the JMS client

What is JMS topic requestor?
• The JMS Topic Requestor activity is used to communicate with a JMS application’s request-response service. This service invokes an operation with input and output. The request is sent to a JMS topic and the JMS application returns the response to the request.

How do you add ems server to administrator?
• Using domain utility

How do you remove individual messages from destinations?
• Use Purge Command.

What are the messaging models does EMS support?
• Point-to-Point (Queue)
• Publish and Subscribe (Topic)
• Multicast (Topic)

What are the limitations of the Durable Subscriber?
• As long as the durable subscriber exists
• Expiration time of the message
• Storage limit of that Topic

What are the EMS Destination features?
• Secure Property
• Trace Property
• Store Property
• Redelivery policy
• Flow control
• Exclusive property for queues

What are the extra features are available in EMS apart from JMS?
• The JMS standard specifies two delivery modes for messages, PERSISTENT and NON_PERSISTENT. EMS also includes a RELIABLE_DELIVERY mode that eliminates some of the overhead associated with the other delivery modes.
For consumer sessions, you can specify a NO_ACKNOWLEDGE mode so that consumers do not need to acknowledge receipt of messages, if desired. EMS also provides an EXPLICIT_CLIENT_ACKNOWLEDGE and EXPLICIT_CLIENT_DUPS_OK_ACKNOWLEDGE mode that restricts the acknowledgement to single messages
• EMS extends the MapMessage and StreamMessage body types. These extensions allow EMS to exchange messages with TIBCO Rendezvous and ActiveEnterprise formats that have certain features not available within the JMS MapMessage and StreamMessage

What is structure of JMS Message?
• Header(Required)
• Properties(optional)
• Body(optional)

Where does the undelivered messages will be stored?
• If a message expires or has exceeded the value specified by the maxRedelivery property on a queue, the server checks the message’s JMS_TIBCO_PRESERVE_UNDELIVERED property. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to true, the server moves the message to the undelivered message queue, $sys.undelivered. This undelivered message queue is a system queue that is always present and cannot be deleted. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to false, the message will be deleted by the server
• You can only set the undelivered property on individual messages, there is no way to set the undelivered message queue as an option at the per-topic or per-queue level

What is the Maximum message size is supported by EMS?
• EMS supports messages up to a maximum size of 512MB. However, we recommend that application programs use smaller messages, since messages approaching this maximum size will strain the performance limits of most current hardware and operating system platforms

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