[Spread-users] Message metadata visible to clients

[Pierce, J. Will]

Hi all,

 

I ran across some interesting behavior in a spread client...  It looks
like there's a lot of

extra information available to a client, on a per-message basis, from
the spread

message headers.  I wonder if this extra information is intentionally
shared with

clients, or is accidental (and might be removed).

 

The specific are:

*	A client receives the full list of groups a message is destined
for
*	The sender's SELF_DISCARD flag is preserved in the receiver's
copy

 

To illustrate:

Client "A" joins group G1, and G2

Client "B" joins G1

"A" sends a single message to both [G1, G2] groups, with the
SELF_DISCARD flag set.

Client "B" receives the message, and gets extra information,

- it sees that the message was sent to G2 also, and that the sender
specified SELF_DISCARD.

 

At first, it seems like there's information leakage, when client "B"
learns of the existence of

"G2" when it sees messages delivered on "G1" that are also sent to "G2".
I kind of like this,

since it keeps open the option that a smart client may take the
grouplist into consideration

when processing a message.  So, you could conceivably send a message to
both a single

client (unicast to private name) and also to a group with multiple
listeners, and get some

very interesting behaviors on top.

 

The SELF_DISCARD flag is less interesting, I guess, but I do wonder if
it's intentional or accidental

that a client can determine the sender's choice for a message...

 

I'm still very new to spread, so please forgive and correct any mistakes
or assumptions I've made...

 

- Will

 

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