max_parallel transport option

[users/jgh/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 8b8a531b9dcdfedf2626b344448897e0dfb49f4b..f9a8efa982615c95177757c94e00bddb6b9f4507 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -1575,7 +1575,7 @@ If a host is unreachable for a period of time, a number of messages may be
 waiting for it by the time it recovers, and sending them in a single SMTP
 connection is clearly beneficial. Whenever a delivery to a remote host is
 deferred,
 waiting for it by the time it recovers, and sending them in a single SMTP
 connection is clearly beneficial. Whenever a delivery to a remote host is
 deferred,

-.cindex "hints database"
+.cindex "hints database" "deferred deliveries"

 Exim makes a note in its hints database, and whenever a successful
 SMTP delivery has happened, it looks to see if any other messages are waiting
 for the same host. If any are found, they are sent over the same SMTP
 Exim makes a note in its hints database, and whenever a successful
 SMTP delivery has happened, it looks to see if any other messages are waiting
 for the same host. If any are found, they are sent over the same SMTP


@@ -6993,6 +6993,15 @@ Retries for the dnsdb lookup can be controlled by a retry modifier.
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 

+.new
+.cindex cacheing "of dns lookup"
+.cindex TTL "of dns lookup"
+.cindex DNS TTL
+Dnsdb lookup results are cached within a single process (and its children).
+The cache entry lifetime is limited to the smallest time-to-live (TTL)
+value of the set of returned DNS records.
+.wen
+

 
 .section "Pseudo dnsdb record types" "SECID66"
 .cindex "MX record" "in &(dnsdb)& lookup"
 
 .section "Pseudo dnsdb record types" "SECID66"
 .cindex "MX record" "in &(dnsdb)& lookup"


@@ -9390,7 +9399,7 @@ yields &"42"&, and
 .code
 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
 .endd
 .code
 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
 .endd

-yields &"result: 99"&.
+yields &"result: 42"&.

 
 If {<&'string3'&>} is omitted, an empty string is used for string3.
 If {<&'string2'&>} is also omitted, the value that was
 
 If {<&'string3'&>} is omitted, an empty string is used for string3.
 If {<&'string2'&>} is also omitted, the value that was


@@ -11319,9 +11328,10 @@ not the same as the user id of the originator of a message (see
 &$originator_uid$&). If Exim re-execs itself, this variable in the new
 incarnation normally contains the Exim uid.
 
 &$originator_uid$&). If Exim re-execs itself, this variable in the new
 incarnation normally contains the Exim uid.
 

-.vitem &$compile_date$&
-.vindex "&$compile_date$&"
-The date on which the Exim binary was compiled.
+.vitem &$callout_address$&
+.vindex "&$callout_address$&"
+After a callout for verification, spamd or malware daemon service, the
+address that was connected to.

 
 .vitem &$compile_number$&
 .vindex "&$compile_number$&"
 
 .vitem &$compile_number$&
 .vindex "&$compile_number$&"


@@ -14467,7 +14477,7 @@ routing, but which are not used for listening by the daemon. See section
 . Allow this long option name to split; give it unsplit as a fifth argument
 . for the automatic .oindex that is generated by .option.
 
 . Allow this long option name to split; give it unsplit as a fifth argument
 . for the automatic .oindex that is generated by .option.
 

-.option "extract_addresses_remove_ &~&~arguments" main boolean true &&&
+.option "extract_addresses_remove_arguments" main boolean true &&&

          extract_addresses_remove_arguments
 .oindex "&%-t%&"
 .cindex "command line" "addresses with &%-t%&"
          extract_addresses_remove_arguments
 .oindex "&%-t%&"
 .cindex "command line" "addresses with &%-t%&"


@@ -20529,6 +20539,32 @@ transport, the &[initgroups()]& function is called when running the transport
 to ensure that any additional groups associated with the uid are set up.
 
 
 to ensure that any additional groups associated with the uid are set up.
 
 

+.new
+.option max_parallel transports integer&!! unset
+.cindex limit "transport parallelism"
+.cindex transport "parallel processes"
+.cindex transport "concurrency limit"
+.cindex "delivery" "parallelism for transport"
+If this option is set and expands to an integer greater than zero
+it limits the number of concurrent runs of the transport.
+The control does not apply to shadow transports.
+
+.cindex "hints database" "transport concurrency control"
+Exim implements this control by means of a hints database in which a record is
+incremented whenever a transport process is beaing created. The record
+is decremented and possibly removed when the process terminates.
+Obviously there is scope for
+records to get left lying around if there is a system or program crash. To
+guard against this, Exim ignores any records that are more than six hours old.
+
+If you use this option, you should also arrange to delete the
+relevant hints database whenever your system reboots. The names of the files
+start with &_misc_& and they are kept in the &_spool/db_& directory. There
+may be one or two files, depending on the type of DBM in use. The same files
+are used for ETRN and smtp transport serialization.
+.wen
+
+

 .option message_size_limit transports string&!! 0
 .cindex "limit" "message size per transport"
 .cindex "size" "of message, limit"
 .option message_size_limit transports string&!! 0
 .cindex "limit" "message size per transport"
 .cindex "size" "of message, limit"


@@ -22426,6 +22462,10 @@ If two messages arrive at almost the same time, and both are routed to a pipe
 delivery, the two pipe transports may be run concurrently. You must ensure that
 any pipe commands you set up are robust against this happening. If the commands
 write to a file, the &%exim_lock%& utility might be of use.
 delivery, the two pipe transports may be run concurrently. You must ensure that
 any pipe commands you set up are robust against this happening. If the commands
 write to a file, the &%exim_lock%& utility might be of use.

+.new
+Alternatively the &%max_parallel%& option could be used with a value
+of "1" to enforce serialization.
+.wen

 
 
 
 
 
 


@@ -23608,6 +23648,10 @@ start with &_misc_& and they are kept in the &_spool/db_& directory. There
 may be one or two files, depending on the type of DBM in use. The same files
 are used for ETRN serialization.
 
 may be one or two files, depending on the type of DBM in use. The same files
 are used for ETRN serialization.
 

+.new
+See also the &%max_parallel%& generic transport option.
+.wen
+

 
 .option size_addition smtp integer 1024
 .cindex "SMTP" "SIZE"
 
 .option size_addition smtp integer 1024
 .cindex "SMTP" "SIZE"


@@ -29207,9 +29251,15 @@ deny  dnslists = blackholes.mail-abuse.org
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd

-DNS list lookups are cached by Exim for the duration of the SMTP session,
+.cindex cacheing "of dns lookup"
+.cindex DNS TTL
+DNS list lookups are cached by Exim for the duration of the SMTP session
+.new
+(but limited by the DNS return TTL value),
+.wen

 so a lookup based on the IP address is done at most once for any incoming
 so a lookup based on the IP address is done at most once for any incoming

-connection. Exim does not share information between multiple incoming
+connection (assuming long-enough TTL).
+Exim does not share information between multiple incoming

 connections (but your local name server cache should be active).
 
 
 connections (but your local name server cache should be active).
 
 


@@ -30962,6 +31012,10 @@ malware = * / defer_ok / tmo=10s
 .endd
 A timeout causes the ACL to defer.
 
 .endd
 A timeout causes the ACL to defer.
 

+.vindex "&$callout_address$&"
+When a connection is made to the scanner the expansion variable &$callout_address$&
+is set to record the actual address used.
+

 .vindex "&$malware_name$&"
 When a virus is found, the condition sets up an expansion variable called
 &$malware_name$& that contains the name of the virus. You can use it in a
 .vindex "&$malware_name$&"
 When a virus is found, the condition sets up an expansion variable called
 &$malware_name$& that contains the name of the virus. You can use it in a


@@ -31112,6 +31166,10 @@ a dollar sign. In this case, the expansion may return a string that is
 used as the list so that multiple spamd servers can be the result of an
 expansion.
 
 used as the list so that multiple spamd servers can be the result of an
 expansion.
 

+.vindex "&$callout_address$&"
+When a connection is made to the server the expansion variable &$callout_address$&
+is set to record the actual address used.
+

 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
 .code
 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
 .code


@@ -36241,6 +36299,9 @@ Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
 .next
 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
 &(smtp)& transport)
 .next
 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
 &(smtp)& transport)

+.next
+Limiting the concurrency of specific transports (when &%max_parallel%& is set
+in a transport)

 .endlist
 
 
 .endlist