Item Gatherers

Item Gatherers

Syndicators in an IWWCM environment use Item Gatherers to group collections of related documents and keep an audit trail of how and when the collection has changed. When creating a Syndicator, it is necessary to select which Item Gatherer that the syndicator is to use. There are currently two Item Gatherers supported in an IWWCM environment:

All Items Gathers a collection of all deployable items.
The All Items gatherer should be used when replicating between two development environments, usually for the purposes of distributed editing.
All Live Items Gathers a collection of all deployable items that either do not use a Workflow or do have a Workflow and are published.
The All Live Items gatherer should be used when replicating between a development and production environment as this ensures that the production environment only contains items that can be accessed by end users. It also has the added benefit of reducing the amount of data that needs to be sent to the production server; hence reducing the impact replication has on performance.

There are certain items that are non syndicated:

All graphical Authoring Portlet related items
Administrator user
Administrators Group.
All Users group
Anonymous user
UI group
Item Gatherers
Syndicators
Subscribers
Indexes (updated automatically based on the data contained on the IWWCM server)

All IWWCM Subscribers do not have Item Gatherers, however they internally store an Item Cabinet that contains references to all documents that they believe are currently associated with the subscription. This Item Cabinet is used when a Rebuild action is performed or when a deletion notice for a document is received.

Item Formatters and Item Transformers

When IWWCM servers replicate, the Syndicator provides a URL for the Subscriber to retrieve the document from. This URL points to the Item Dispatcher business logic along with query parameters identifying the item required. The Item Dispatcher formats the document to the format as specified by the Syndicator. When the Subscriber receives the contents of the URL, it transforms the data back into a document. Syndicators and Subscribers must have compatible Item Formatters and Item Transformers otherwise the data transmitted will be incompatible.

When Syndication Occurs

Automatic Updates If an Item Gatherer has changed, then the recurring task mentioned above informs all Syndicators using the Item Gatherer that an update is outstanding for them. Once the system has settled down and no documents have changed for the duration between two consecutive runs of the ITEM recurring task, then the next time it runs, it sends update requests to the Syndication application for all Syndicators that are due to send updates to their Subscribers. Note that these updates are always partial.
Manual Updates and Rebuilds Users are able to manually force a partial update or a full rebuild of the Subscriber through either the Subscriber document or the associated Syndicator items. When the items are in read mode, the following buttons are available:

Rebuild Syndicator.

Clicking Rebuild Syndicator will send all documents that currently exist in the Syndicator's Item Gatherer to the Subscriber. The Subscriber will then store all documents that are sent, and if any documents remain in its Item Cabinet that were not sent through from the Syndicator, then they are removed. The rules for finding a winner still apply for Rebuilds like they do for Updates.
Occasionally, IWWCM indexes are required to be deleted by IWWCM administrators. A full syndicator rebuild should be performed prior to resuming authoring. Otherwise, some recent changes to IWWCM items may not be successfully syndicated.

Update Syndicator.

Clicking Update Syndicator will query the state of the Subscriber and then state of the Syndicator's Item Gatherer. It will then determine what documents need to be sent and deletion notices issued to update the Subscriber so that it is in the same state as the Syndicator's Item Gatherer. This is the exact same update that happens with the automatic updates are issued.

Partial Update Support The ICE standard allows for partial updates, and due to the amount of data that an IWWCM environment could potentially contain along with their size, this feature is extremely important. Whenever a document is added, updated, or deleted, a recurring task runs gathering the documents. It then notifies all the Item Gatherers to see if the changes have affected them, updating them as necessary.
Disable Replication Each Syndicator and Subscriber document has an Enabled flag. If this flag is false then all Update and Rebuild requests are disabled even if they are manually requested.

Success or Failure

When documents and delete notices are replicated, a formula must be used to determine if they are valid. If the replicated document does not already exist on the destination server, then the document is saved. If the replicated document does already exists on the destination server, then the last modified dates of the documents are compared, if the replicated document has a more recent modified date then it wins and is saved.
When a deletion notice is sent for a document, then the destination server checks to see if any other Subscribers contain the document that the deletion notice is for in their Item Cabinets. If none contain the document then the deletion notice is valid and the document is removed.
Parent topic: Syndication
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Automatic Updates	If an Item Gatherer has changed, then the recurring task mentioned above informs all Syndicators using the Item Gatherer that an update is outstanding for them. Once the system has settled down and no documents have changed for the duration between two consecutive runs of the ITEM recurring task, then the next time it runs, it sends update requests to the Syndication application for all Syndicators that are due to send updates to their Subscribers. Note that these updates are always partial.
Manual Updates and Rebuilds	Users are able to manually force a partial update or a full rebuild of the Subscriber through either the Subscriber document or the associated Syndicator items. When the items are in read mode, the following buttons are available: Rebuild Syndicator. Clicking Rebuild Syndicator will send all documents that currently exist in the Syndicator's Item Gatherer to the Subscriber. The Subscriber will then store all documents that are sent, and if any documents remain in its Item Cabinet that were not sent through from the Syndicator, then they are removed. The rules for finding a winner still apply for Rebuilds like they do for Updates. Occasionally, IWWCM indexes are required to be deleted by IWWCM administrators. A full syndicator rebuild should be performed prior to resuming authoring. Otherwise, some recent changes to IWWCM items may not be successfully syndicated. Update Syndicator. Clicking Update Syndicator will query the state of the Subscriber and then state of the Syndicator's Item Gatherer. It will then determine what documents need to be sent and deletion notices issued to update the Subscriber so that it is in the same state as the Syndicator's Item Gatherer. This is the exact same update that happens with the automatic updates are issued.
Partial Update Support	The ICE standard allows for partial updates, and due to the amount of data that an IWWCM environment could potentially contain along with their size, this feature is extremely important. Whenever a document is added, updated, or deleted, a recurring task runs gathering the documents. It then notifies all the Item Gatherers to see if the changes have affected them, updating them as necessary.
Disable Replication	Each Syndicator and Subscriber document has an Enabled flag. If this flag is false then all Update and Rebuild requests are disabled even if they are manually requested.