On Jan 24, 2007, at 12:25 PM, Jeff Genender wrote:
Need to bounce some ideas here...
A while back I put a URL array in the ServerMetaData so the client
could
failover. I now need to get that list to the client.
So here is an idea...
1) The server has knowledge of the list of EJB servers in the cluster.
It computes a hash on this list.
2) The client, on initial contact with the JNDIRequestHandler, will
get
the server list in the payload response.
3) The client computes a hash of this list and keeps it somewhere on
it's side.
4) With each interaction or method call (or other EJB lookup), the
client sends this hash (4 bytes?) along with it's request payload
to the
server.
5) The server gets the EJB request and compares the hash against it's
own computed version (see step 1).
6) If the hash equals the client's version, the server sends the
normal
payload response. Goto step 4.
7) If the server's cluster list changes, it has a different computed
hash, and notices the client's hash is different. It sends a normal
payload, but also adds a new cluster list for the client to use
appended
to the payload.
8) Client has new cluster list and computes a new hash. Goto step 4.
Thoughts on this?
First quick thoughts. You likely don't need the client to create
the hash, no reason the server can't send the hash it has at the time
it sends the URIs. For that matter, it doesn't have to be a hash, it
could simply be a version number. I.e. instead of the server
creating a hash for the current URI set, it could simply give them a
version number (one byte) which it will increment on every change to
the URI set. Then using the same logic you mention, if the server
sees the client has a different number it will send the URIs +
version number back to the client with the other data.
Thoughts?
-David
