[zeromq-dev] 12/CHP - Clustered Hashmap Protocol ...

[Marten Feldtmann]

Hey,

I'm trying to implement this protocol and have some question regarding 
to the protocol:

a) The client has a subscriber connection to the server. Should the 
"subtree specification" used in the state synchronization set as a 
filter in the subscriber connection - otherwise the client get all 
changes, though it initially mentioned to be interested only in a 
subtree of the overall hashmap ?

That would also indicate, that commands "KVPUB" and "KVSET" must follow 
this way ...

And to get the HUGZ command one must set at least two filter 
informations on the subscriber channel.

Without these filters the clients may get equally named keys from 
different subtrees and can not decide, what the correct one is.

b) A problematic situation arrises when switching from state 
synchronization to "normal subscriber message receiving". There is a 
possible gap, where a message (suitable for this client comes in) can 
get lost. The client may close the snapshot socket and opens the 
subscriber socket - but perhaps too late and it does not get the message 
mentioned above.

A solution might be, that the client subscribes to the server before it 
does a state synchronization - he may get additional messages but 
nothing gets lost.

c) KTHXBAI-Command: Would it better, if the server sends its actual 
sequence number and not the one he uses in KVSYNC commands. Then the 
client know, what he can throw away and it knows its server 
corresponding sequence number.

d) "HUGZ" command - should the "Frame 1" be better described as "8 bytes 
all filled with numeric value 0".


Any comments about these ideas ?