clock

Overview

This demo shows how to use IceStorm.

To run the demo, start the IceStorm service:

icebox --Ice.Config=config.icebox

This configuration assumes there is a subdirectory named db in the current working directory.

In a separate window:

./Build/subscriber

In another window:

./Build/publisher

While the publisher continues to run, "tick" messages should be displayed in the subscriber window.

Options

Both the subscriber and publisher take an optional topic name as a final argument. The default value for this topic is "time".

Through the use of command-line options, both the subscriber and publisher can use different QoS for sending and receiving messages.

Subscriber Options

./Build/subscriber --oneway

The subscriber receives events as oneway messages. This is the default.

./Build/subscriber --datagram

The subscriber receives events as datagrams.

./Build/subscriber --twoway

The subscriber receives events as twoway messages.

./Build/subscriber --ordered

The subscriber receives events as twoway messages with guaranteed ordering.

./Build/subscriber --batch

This is an additional flag that forwards datagram and oneway events to the subscriber in batches.

./Build/subscriber --id <id>

This option specifies a unique identity for this subscriber. When you use this option, you should also run the subscriber on a fixed port by setting the Clock.Subscriber.Endpoints property. For example:

./Build/subscriber --Clock.Subscriber.Endpoints="tcp -p <port> -h <host>"

Replace "tcp" with "udp" when using the --datagram option.

./Build/subscriber --retryCount <count>

This option sets the retry count for a subscriber. This option should be used in conjunction with the --id option. Setting retryCount changes the default subscriber QoS to twoway.

Publisher Options

./Build/publisher --oneway

The publisher sends events as oneway messages. This is the default.

./Build/publisher --datagram

The publisher sends events as datagrams.

./Build/publisher --twoway

The publisher sends events as twoway messages.

Running the demo on several hosts

You must modify several configuration files in order to run the publisher, subscriber, and IceStorm service on separate hosts. For the sake of discussion, let us assume that the processes are running on the following hosts:

• Host <P>: publisher
• Host <S>: subscriber
• Host <I>: IceStorm

Replace <P>, <S>, and <I> with the appropriate host names or IP addresses in the steps below:

1. Edit the subscriber's configuration file, config.sub, and change the TopicManager.Proxy property to

   TopicManager.Proxy=DemoIceStorm/TopicManager:default -h <I> -p 10000
   

2. Edit the publisher's configuration file, Publisher/config.pub, and change the TopicManager.Proxy property to

   TopicManager.Proxy=DemoIceStorm/TopicManager:default -h <I> -p 10000
   

3. Since the default configurations for the subscriber and IceStorm endpoints listen only to localhost, you must also modify the Endpoints properties to explicitly include the host machine's name or IP address.

   In Subscriber/config.sub:

   Clock.Subscriber.Endpoints=tcp -h <S>:udp -h <S>
   

   In config.service:

   IceStorm.TopicManager.Endpoints=default -h <I> -p 10000
   IceStorm.Publish.Endpoints=tcp -h <I> -p 10001:udp -h <I> -p 10001
   

If you experience any network delays or errors, edit all of the configuration files and enable the Ice.Trace.Network property. Running the processes with this property enabled displays a log of Ice's network activity and may help you to identify the problem more quickly.