webMethods Broker

Broker:  webMethods Broker component is a messaging backbone in integration where messages or documents can be exchanged between integration servers or with in an integration server. This component facilitates asynchronous message based integration using publish & subscribe model.

Basic function of the broker is to store the documents that are published by the integration server and keeps in its local memory to get subscribed by elements on same integration server or different integration server(s).

If I write step by step then,

Step 1: IS publishes the documents to the Broker

Step 2: Broker stores the documents

Step 3: IS subscribes documents from broker & processes documents. 

Let me explore these 3 steps more in detail  using publish & subscribe model.

Publish & Subscribe Model:

This model is used to publish the documents to the broker from one integration server & these documents get subscribed by one or more integration servers.

Publishing documents to broker can be happened in following two ways.

1. Publish documents when broker is available

2. Publish documents when broker is not available

1. Publish documents when broker is available:

Before publishing documents to the broker, make sure that the document is publishable type. This can be done using properties of the document(Select publishable type to 'True').

• A service hosted on integration server publishes the document to the broker.
• Dispatcher on IS will get a connection from the connection pool to establish a connection to the broker.
• Document will be received by the broker through the connection that has been established.
• Broker validates the storage type of the document on each receive. 
• Documents will be sent to memory directly if the storage type of the document is 'Volatile'.
• Documents will be sent to memory and to disk if the storage type of the document is 'Guaranteed'.

2. Publish documents when broker is not available:

Before publishing documents to the broker, make sure that the document is publishable type. This can be done using properties of the document(Select publishable type to 'True').

• A service hosted on integration server publishes the document to the broker.
• Dispatcher on IS will get a connection from the connection pool to establish a connection to the broker.
• If the broker is down or unable to establish a connection, then dispatcher validates the document against its storage type.
• Dispatcher discards the document if the storage type is volatile.
• Dispatcher routes the document to the OutBoundDocStore(ClientSide CSQ), if the document type is guarenteed & if  CSQ is configured. These documents will be sent to broker on FIFO basis later on the availability of the broker.
• Dispatcher throws ISRuntime exception if the document storage type is 'Guaranteed' and no CSQ is configured.