When links fail

In a distributed environment communications are always prone to failure. Here is how Beatrix helps us deal with failed links, and what our applications need to add to this:

• The ICommunicationServer interface allows connection failures to be handled, as already mentioned. This is server-side only.
• The default proxying access point netlet recognises a server failure and re-establishes communications with another.
• When we have an INetletHandle we can add a connection listener which gets called when our link to that netlet fails. INetletHandle is available client-side and server-side--see Figure .
• If a Beatrix netlet binds a service with a warrant and later the link fails, then Beatrix will try to rebind the warrant automatically.

However, even with this last feature there is usually more we need to do. In particular, Beatrix will not rebind any facets we have already bound as part of the service; using of any of these facets will result in an error thrown (org.jtrix.base.InternalError, a subclass of java.lang.Error). If we detect a connection failure then we might like to take some appropriate action with the unconnected facets.

As an example, a default access point netlet takes each service facet and wraps it. When it detects a link failure (via an INetletHandle listener) it binds a new facet. The client only accesses the wrapper and so does not detect any changes.