SCACHE(8)						      System Manager's Manual							 SCACHE(8)

NAME

       scache - Postfix shared connection cache server

SYNOPSIS

       scache [generic Postfix daemon options]

DESCRIPTION

       The scache(8) server maintains a shared multi-connection cache. This information can be used by, for example, Postfix SMTP clients or other
       Postfix delivery agents.

       The connection cache is organized into logical destination names, physical endpoint names, and connections.

       As a specific example, logical SMTP destinations specify (transport, domain, port), and physical  SMTP  endpoints  specify  (transport,	IP
       address, port).	An SMTP connection may be saved after a successful mail transaction.

       In  the general case, one logical destination may refer to zero or more physical endpoints, one physical endpoint may be referenced by zero
       or more logical destinations, and one endpoint may refer to zero or more connections.

       The exact syntax of a logical destination or endpoint name is application dependent; the scache(8) server does not care.  A  connection	is
       stored  as  a file descriptor together with application-dependent information that is needed to re-activate a connection object. Again, the
       scache(8) server is completely unaware of the details of that information.

       All information is stored with a finite time to live (ttl).  The connection cache  daemon  terminates  when  no	client	is  connected  for
       max_idle time units.

       This server implements the following requests:

       save_endp ttl endpoint endpoint_properties file_descriptor
	      Save  the specified file descriptor and connection property data under the specified endpoint name. The endpoint properties are used
	      by the client to re-activate a passivated connection object.

       find_endp endpoint
	      Look up cached properties and a cached file descriptor for the specified endpoint.

       save_dest ttl destination destination_properties endpoint
	      Save the binding between a logical destination and an endpoint under the destination name, together with destination  specific  con-
	      nection properties. The destination properties are used by the client to re-activate a passivated connection object.

       find_dest destination
	      Look  up	cached destination properties, cached endpoint properties, and a cached file descriptor for the specified logical destina-
	      tion.

SECURITY

       The scache(8) server is not security-sensitive. It does not talk to the network, and it does not talk to local users.  The scache(8) server
       can run chrooted at fixed low privilege.

       The scache(8) server is not a trusted process. It must not be used to store information that is security sensitive.

DIAGNOSTICS

       Problems and transactions are logged to syslogd(8).

BUGS

       The session cache cannot be shared among multiple machines.

       When a connection expires from the cache, it is closed without the appropriate protocol specific handshake.

CONFIGURATION PARAMETERS

       Changes	to  main.cf  are  picked  up  automatically as scache(8) processes run for only a limited amount of time. Use the command "postfix
       reload" to speed up a change.

       The text below provides only a parameter summary. See postconf(5) for more details including examples.

RESOURCE CONTROLS

       connection_cache_ttl_limit (2s)
	      The maximal time-to-live value that the scache(8) connection cache server allows.

       connection_cache_status_update_time (600s)
	      How frequently the scache(8) server logs usage statistics with connection cache hit and miss rates for logical destinations and  for
	      physical endpoints.

MISCELLANEOUS CONTROLS

       config_directory (see 'postconf -d' output)
	      The default location of the Postfix main.cf and master.cf configuration files.

       daemon_timeout (18000s)
	      How much time a Postfix daemon process may take to handle a request before it is terminated by a built-in watchdog timer.

       ipc_timeout (3600s)
	      The time limit for sending or receiving information over an internal communication channel.

       max_idle (100s)
	      The maximum amount of time that an idle Postfix daemon process waits for an incoming connection before terminating voluntarily.

       process_id (read-only)
	      The process ID of a Postfix command or daemon process.

       process_name (read-only)
	      The process name of a Postfix command or daemon process.

       syslog_facility (mail)
	      The syslog facility of Postfix logging.

       syslog_name (see 'postconf -d' output)
	      The mail system name that is prepended to the process name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd".

SEE ALSO

       smtp(8), SMTP client
       postconf(5), configuration parameters
       master(8), process manager
       syslogd(8), system logging

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       CONNECTION_CACHE_README, Postfix connection cache

LICENSE

       The Secure Mailer license must be distributed with this software.

HISTORY

       This service was introduced with Postfix version 2.2.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

																	 SCACHE(8)