lib: Add messaging_dgm

Messaging based on unix domain datagram sockets

This makes every process participating in messaging bind on a unix domain
datagram socket, similar to the source4 based messaging. The details are a bit
different though:

Retry after EWOULDBLOCK is done with a blocking thread, not by polling. This
was the only way I could in experiments avoid a thundering herd or high load
under Linux in extreme overload situations like many thousands of processes
sending to one blocked process. If there are better ideas to do this in a
simple way, I'm more than happy to remove the pthreadpool dependency again.

There is only one socket per process, not per task. I don't think that per-task
sockets are really necessary, we can do filtering in user space. The message
contains the destination server_id, which contains the destination task_id. I
think we can rebase the source4 based imessaging on top of this, allowing
multiple imessaging contexts on top of one messaging_context. I had planned to
do this conversion before this goes in, but Jeremy convinced me that this has
value in itself :-)

Per socket we also create a fcntl-based lockfile to allow race-free cleanup of
orphaned sockets. This lockfile contains the unique_id, which in the future
will make the server_id.tdb obsolete.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/source3/lib/messages.c b/source3/lib/messages.c
index 4ff933dc6e7..983fe699ed9 100644
--- a/source3/lib/messages.c
+++ b/source3/lib/messages.c
@@ -197,10 +197,10 @@ struct messaging_context *messaging_init(TALLOC_CTX *mem_ctx,
 	ctx->id = procid_self();
 	ctx->event_ctx = ev;
 
-	status = messaging_tdb_init(ctx, ctx, &ctx->local);
+	status = messaging_dgm_init(ctx, ctx, &ctx->local);
 
 	if (!NT_STATUS_IS_OK(status)) {
-		DEBUG(2, ("messaging_tdb_init failed: %s\n",
+		DEBUG(2, ("messaging_dgm_init failed: %s\n",
 			  nt_errstr(status)));
 		TALLOC_FREE(ctx);
 		return NULL;
@@ -245,9 +245,9 @@ NTSTATUS messaging_reinit(struct messaging_context *msg_ctx)
 
 	msg_ctx->id = procid_self();
 
-	status = messaging_tdb_init(msg_ctx, msg_ctx, &msg_ctx->local);
+	status = messaging_dgm_init(msg_ctx, msg_ctx, &msg_ctx->local);
 	if (!NT_STATUS_IS_OK(status)) {
-		DEBUG(0, ("messaging_tdb_init failed: %s\n",
+		DEBUG(0, ("messaging_dgm_init failed: %s\n",
 			  nt_errstr(status)));
 		return status;
 	}