SCACHE(8postfix)                                                                 SCACHE(8postfix)



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 end‐
       point 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 pas‐
              sivated 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 destina‐
              tion name, together with destination specific connection properties.  The  destina‐
              tion  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 destination.

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  privi‐
       lege.

       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 lim‐
       ited 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 includ‐
       ing 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  incom‐
              ing 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(8postfix)