Re: [HACKERS] replicator

On Mon, 3 Jan 2000, Philippe Marchesseault wrote:

> So it could become:
>
> SQL --IPC--> node-replicator
> | | |
> via TCP send statements to each node
> replicator (on local node)
> |
> via libpq send data to
> current (local) backend.
>
> > (not exist any master node, all nodes have connection to all nodes)
>
> Exactly, if the replicator dies only the node dies, everything else keeps
> working.

Hi,

I a little explore replication conception on Oracle and Sybase (in manuals).
(Know anyone some interesting links or publication about it?)

Firstly, I sure, untimely is write replication to PgSQL now, if we
haven't exactly conception for it. It need more suggestion from more
developers. We need firstly answers for next qestion:

1/ How replication concept choose for PG?
2/ How manage transaction for nodes? (and we need define any
replication protocol for this)
3/ How involve replication in current PG transaction code?

My idea (dream:-) is replication that allow you use full read-write on all
nodes and replication which use current transaction method in PG - not is
difference between more backends on one host or more backend on more hosts
- it makes "global transaction consistency".

Now is transaction manage via ICP (one host), my dream is alike manage
this transaction, but between more host via TCP. (And make optimalization
for this - transfer commited data/commands only.)

Any suggestion?

-------------------
Note:

(transaction oriented replication)

Sybase - I. model (only one node is read-write)

primary SQL data (READ-WRITE)
|
replication agent (transaction log monitoring)
|
primary distribution server (one or more repl. servers)
| / | \
| nodes (READ-ONLY)
|
secondary dist. server
/ | \
nodes (READ-ONLY)

If primary SQL is read-write and the other nodes *read-only*
=> system good work if connection is disable (data are save to
replication-log and if connection is available log is write
to node).

Sybase - II. model (all nodes read-write)

SQL data 1 --->--+ NODE I.
| |
^ |
| replication agent 1 (transaction log monitoring)
V |
| V
| |
replication server 1
|
^
V
|
replication server 2 NODE II.
| |
^ +-<-->--- SQL data 2
| |
replcation agent 2 -<--

Sorry, I not sure if I re-draw previous picture total good..

Karel