Re: Streaming Replication patch for CommitFest 2009-09

Hi,

On Thu, Sep 17, 2009 at 5:08 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> I'm thinking that walreceiver should be a stand-alone program that the
> startup process launches, similar to how it invokes restore_command in
> PITR recovery. Instead of using system(), though, it would use
> fork+exec, and a pipe to communicate.

This approach is OK if the stand-alone walreceiver is treated steadily
by the startup process like a child process under postmaster:

* Handling of some interrupts: SIGHUP, SIGTERM?, SIGINT, SIGQUIT...
For example, the startup process would need to rethrow walreceiver
the interrupt from postmaster.

* Communication with other child processes: stats collector? syslogger?...
For example, the log message generated by walreceiver should also
be collected by syslogger if requested.

For now, I think that pipe is enough for communication between the
startup process and walreceiver. Though there was the idea to pass
XLOG to the startup process via wal_buffers, in which pipe is not
suitable, I think that is overkill.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center