BUG?: Dsync over piped process (DSYNC_RUN_TYPE_CMD): EPIPE if X (done) is received in another write after F (finish)

[Timo Sirainen]

On 19 May 2016, at 03:54, J. Nick Koston <nick at cpanel.net> wrote:
> 
> Hi,
> 
> It appears that dsync closes the file handle once it gets the F (finish) response even if it hasn’t received the X (done) response. 
> If the X (done) response gets delivered in another write this will generate EPIPE in the connected process.
> 
> This is much easier to replicate over SSL, however the trace is provided without SSL since its easier to see whats going on.

Do you see this as causing some problem? I think this is intentional. The F(inish) tells the final response whether everything was OK or not, so all the work is done after that. The 'X' is described in code as:

		/* notify remote that we're closing. this is mainly to avoid
		   "read() failed: EOF" errors on failing dsyncs */
		o_stream_nsend_str(ibc->output,
			t_strdup_printf("%c\n", items[ITEM_DONE].chr));

and on the receiving side:

	if (line[0] == items[ITEM_DONE].chr) {
		/* remote cleanly closed the connection, possibly because of
		   some failure (which it should have logged). we don't want to
		   log any stream errors anyway after this. */
		dsync_ibc_stream_stop(ibc);
		return DSYNC_IBC_RECV_RET_TRYAGAIN;
	}

So I think it only matters in error handling.