A metaspace is a virtual entity that contains spaces, which are containers that store the data used by applications.
Multiple metaspaces may exist at the same time, each one containing a completely independent set of spaces. This means, for example, that changes to a space called clients in a metaspace named
Dev have no impact on a space named
clients in a metaspace named
Prod. Since no single application can connect to two different metaspaces using the same metaspace name, metaspaces should always use different names.
An application can also join a space as a leech, without contributing any of its host's resources to the scalability of the space, and without experiencing any limitation in functionality or in its ability to use the space. A leech (as opposed to a seeder) is a peer of the space that is not considered by the distribution algorithm and therefore can join or leave the space without causing redistribution of the data.
The distribution role (Seeders or
Leeches) is a level of participation of a space member and does not indicate any limitation on use. Leeches have access to the same set of space operations as seeders. The choice of distribution role must be made on a per space basis: it may be that the best solution is to join some spaces as a seeder and others as a leech.
When the consumption mode of a destination is event listener, the destination behaves like a
subscriber in a publish-subscribe messaging system. When certain data changes or certain events occur, a callback function is invoked. You can choose the type of events to listen to: Put Event, Take Event, and Expire Event.
When the consumption mode is entry browser, the destination can monitor the space for data changes or certain events to occur, and can retrieve the tuple from the space using the
browser type - Get or Take.
A tuple is similar to a row in a database table: it is a container for data. Specifically, it is a sequence of named elements called fields (similar to the columns in a database table) which contain values of a specific type. Each tuple in a space represents a set of related data.
Table 23 shows the operators that are supported in the ActiveSpaces filters:
Table 24 shows the formats for values used in filters.