.cindex "queue" "routing"
.cindex "routing" "whole queue before delivery"
.cindex "first pass routing"
+.cindex "queue runner" "two phase"
An option starting with &%-qq%& requests a two-stage queue run. In the first
stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
every domain. Addresses are routed, local deliveries happen, but no remote
.new
Performance will be best if the &%queue_run_in_order%& option is false.
+If that is so and the &%queue_fast_ramp%& option is true then
+in the first phase of the run,
+once a threshold number of messages are routed for a given host,
+a delivery process is forked in parallel with the rest of the scan.
.wen
.cindex "hints database" "remembering routing"
or array; for the latter two a string-representation of the JSON
is returned.
For elements of type string, the returned value is de-quoted.
+
+
+.new
+.next
+.cindex LMDB
+.cindex lookup lmdb
+.cindex database lmdb
+&(lmdb)&: The given file is an LMDB database.
+LMDB is a memory-mapped key-value store,
+with API modeled loosely on that of BerkeleyDB.
+See &url(https://symas.com/products/lightning-memory-mapped-database/)
+for the feature set and operation modes.
+
+Exim provides read-only access via the LMDB C library.
+The library can be obtained from &url(https://github.com/LMDB/lmdb)
+or your operating system package repository.
+To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
+
+You will need to separately create the LMDB database file,
+possibly using the &"mdb_load"& utility.
+.wen
+
+
.next
.cindex "linear search"
.cindex "lookup" "lsearch"
.row &%hold_domains%& "hold delivery for these domains"
.row &%local_interfaces%& "for routing checks"
.row &%queue_domains%& "no immediate delivery for these"
+.row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
.row &%queue_only%& "no immediate delivery at all"
.row &%queue_only_file%& "no immediate delivery if file exists"
.row &%queue_only_load%& "no immediate delivery if load is high"
next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
+.new
+.option queue_fast_ramp main boolean false
+.cindex "queue runner" "two phase"
+.cindex "queue" "double scanning"
+If set to true, two-phase queue runs, initiated using &%-qq%& on the
+command line, may start parallel delivery processes during their first
+phase. This will be done when a threshold number of messages have been
+routed for a single host.
+.wen
+
+
.option queue_list_requires_admin main boolean true
.cindex "restricting access to features"
.oindex "&%-bp%&"
If the peer host matches the list after expansion then resumption
is offered and/or accepted.
-The &%tls_resumption_hosts% smtp transport option performs the
+The &%tls_resumption_hosts%& smtp transport option performs the
equivalent function for operation as a client.
If the peer host matches the list after expansion then resumption
is attempted (if a stored session is available) or the information