IceStorm Interfaces

This page provides a brief introduction to the Slice interfaces comprising the IceStorm service. See the online Slice API Reference XREF for the Slice documentation.

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The TopicManager Interface

The TopicManager is a singleton object that acts as a factory and repository of Topic objects. Its interface and related types are shown below:

Slice
module IceStorm
{
    dictionary<string, Topic*> TopicDict;

    exception TopicExists
    {
        string name;
    }

    exception NoSuchTopic
    {
        string name;
    }
 
    exception InvalidTopic
    {
        string reason;
    }

    interface TopicManager
    {
        Topic* create(string name) throws TopicExists, InvalidTopic;
        idempotent Topic* retrieve(string name) throws NoSuchTopic;
        idempotent TopicDict retrieveAll();
        idempotent Ice::SliceChecksumDict getSliceChecksums();
    }
}

The create operation is used to create a new topic, which must have a unique name. The retrieve operation allows a client to obtain a proxy for an existing topic, and retrieveAll supplies a dictionary of all existing topics. The getSliceChecksums operation returns Slice checksums for the IceStorm definitions.

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The Topic Interface

The Topic interface represents a topic and provides several administrative operations for configuring links and managing subscribers.

Slice
module IceStorm
{
    struct LinkInfo
    {
        Topic* theTopic;
        string name;
        int cost;
    }
    sequence<LinkInfo> LinkInfoSeq;

    dictionary<string, string> QoS;

    exception LinkExists
    {
        string name;
    }

    exception NoSuchLink
    {
        string name;
    }

    exception AlreadySubscribed {}

    exception BadQoS
    {
        string reason;
    }

    interface Topic
    {
        idempotent string getName();
        idempotent Object* getPublisher();
        idempotent Object* getNonReplicatedPublisher();
        Object* subscribeAndGetPublisher(QoS theQoS, Object* subscriber)
            throws AlreadySubscribed, BadQoS;
        idempotent void unsubscribe(Object* subscriber);
        idempotent void link(Topic* linkTo, int cost)
            throws LinkExists;
        idempotent void unlink(Topic* linkTo) throws NoSuchLink;
        idempotent LinkInfoSeq getLinkInfoSeq();
        void destroy();
    }
}

The getName operation returns the name assigned to the topic, while the getPublisher and getNonReplicatedPublisher operations return proxies for the topic's publisher object.

The subscribeAndGetPublisher operation adds a subscriber's proxy to the topic; if another subscriber proxy already exists with the same object identity, the operation throws AlreadySubscribed. The operation returns a proxy for a subscriber-specific publisher object.

The unsubscribe operation removes the subscriber from the topic.

A link to another topic is created using the link operation; if a link already exists to the given topic, the LinkExists exception is raised. Links are destroyed using the unlink operation.

Finally, the destroy operation permanently destroys the topic.

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See Also