From e9e8ce2add2b7c020daa02228e506e7c02828c15 Mon Sep 17 00:00:00 2001
From: Guilhem Moulin <guilhem@fripost.org>
Date: Thu, 17 Apr 2014 04:56:43 +0200
Subject: Decongestion potential bottlenecks on trivial_rewrite(8).

Which might be caused by slow LDAP lookups in transport_maps.  Instead,
we alias each addresses for which we want a custom transport to a
dedicated "dummy" domain, and use a static (CDB) transport_maps to map
said domains to their transport;  the receiver can then use canonical(8)
to restore the original envelope recipient.  Since the alias resolution
is performed by cleanup(8), which can run in parallel with other
instances, it should decongestion bottlenecks under heavy loads.

So far only the MX:es have been decongestioned.  The list manager and
the MDA should be treated as well.
---
 roles/MX/templates/etc/postfix/main.cf.j2 | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

(limited to 'roles/MX/templates/etc/postfix/main.cf.j2')

diff --git a/roles/MX/templates/etc/postfix/main.cf.j2 b/roles/MX/templates/etc/postfix/main.cf.j2
index 6c2004a..8bed701 100644
--- a/roles/MX/templates/etc/postfix/main.cf.j2
+++ b/roles/MX/templates/etc/postfix/main.cf.j2
@@ -51,25 +51,22 @@ relayhost     = [{{ MTA_out.host }}]:{{ MTA_out.port }}
 relay_domains =
 
 # Virtual transport
-{% if 'LDA' in group_names %}
-virtual_transport = smtpl:[127.0.0.1]:{{ LDA.port }}
-{% else %}
-virtual_transport = smtps:[{{ LDA.host }}]:{{ LDA.port }}
-{% endif %}
-
+# We use a dedicated "virtual" domain to decongestion potential
+# bottlenecks on trivial_rewrite(8) due to slow LDAP lookups in
+# tranport_maps.
+virtual_transport = error:5.1.1 Virtual transport unavailable
 virtual_mailbox_domains = ldap:$config_directory/virtual/mailbox_domains.cf
 virtual_alias_maps      = pcre:$config_directory/virtual/reserved_alias.pcre
+                          # first we do the alias resolution...
                           ldap:$config_directory/virtual/alias.cf
-                          # stop the alias resolution (by making finding
-                          # an A -> A alias) before searching for
-                          # catch-alls and domain aliases
-                          $virtual_mailbox_maps
+                          # ...and unless there is matching mailbox/list...
+                          ldap:$config_directory/virtual/mailbox.cf
+                          ldap:$config_directory/virtual/list.cf
+                          # ...we resolve alias domains and catch alls
                           ldap:$config_directory/virtual/alias_domains.cf
                           ldap:$config_directory/virtual/catchall.cf
-virtual_mailbox_maps    = ldap:$config_directory/virtual/mailbox.cf
-                          ldap:$config_directory/virtual/list.cf
-transport_maps          = cdb:$config_directory/virtual/transport_reserved_alias
-                          ldap:$config_directory/virtual/transport_list.cf
+virtual_mailbox_maps    =
+transport_maps          = cdb:$config_directory/virtual/transport
 
 # Don't rewrite remote headers
 local_header_rewrite_clients     =
@@ -77,6 +74,7 @@ local_header_rewrite_clients     =
 smtp_send_xforward_command       = yes
 # Avoid splitting the envelope and scanning messages multiple times
 smtp_destination_recipient_limit = 1000
+reserved-alias_recipient_limit   = 1
 # Tolerate occasional high latency
 smtp_data_done_timeout           = 1200s
 
-- 
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