OSF DCE Application Development Guide--Introduction and Style Guide

OSF DCE Application Development Guide—Introduction and Style Guide

1.6.3.1 The Possibility of Binding Failure

Perhaps the most important thing to mention about this step is that it may not at ﬁrst

succeed. Remember that the client imported a partial binding to the server. Completion

of the binding, and therefore of the remote call, depends on the endpoint mapper’s being

able to successfully complete the incoming binding with a good endpoint for either the

speciﬁed server (if one is speciﬁed) or for one of its own choosing. This in turn depends

on the up-to-dateness of the host’s endpoint database, and that depends on such things as

other servers’ being conscientious about unregistering themselves when terminating, and

so on. Even the target host speciﬁed may not be valid when the call is made because of

any one of the various network problems that can occur.

In other words, the client should regard an unused binding not as a ﬁrm promise that

comes directly from the server, but rather as a well-meant expression of intent passed on

by the name service and based on circumstances not entirely under anyone’s control.

This is the reason for the series of binding import calls described earlier. The prudent

thing for a client to do after importing a binding is, therefore, to assume that it will have

to perform one or more times a series of steps something like the contents of the

following loop:

1. Annotate the binding handle for security.

2. Try it out: attempt a remote call with it.

3. If the call succeeds, discard the binding import context and proceed to step 5 in

this loop.

4. Otherwise, if the call fails, import the next binding and return to step 1 in this loop.

5. Proceed with remote operations until ﬁnished.

If all imported bindings happen to fail, this could be because the client’s cache of

bindings has become stale. The client could then try calling

rpc_ns_mgmt_handle_set_exp_age( ) with a low timeout value, and then retry the

previous loop. A last resort could be to allow the user to type in a string binding.

Note that if you are using the auto-binding method and the binding becomes unusable for

some reason, the RPC runtime will rebind under most conditions.

1.6.3.2 The Result of Successful Binding

If my_rpc_op( ) or its equivalent does succeed, the binding will as a result be complete

(even if it was partial before), and the information in it can be regarded with much more

assurance from then on. Subsequent remote procedure calls by the client to the same

server will go straight to the bound-to server.

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