phpman > man > scache(8postfix)

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 phys‐
       ical 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 ter‐
       minates 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  passi‐
              vated 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 connection properties. The destination  prop‐
              erties 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 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) or postlogd(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  spe‐
       cific 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  ter‐
              minated 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)
              A  prefix  that is prepended to the process name in syslog records, so that, for exam‐
              ple, "smtpd" becomes "prefix/smtpd".

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

SEE ALSO
       smtp(8), SMTP client
       postconf(5), configuration parameters
       master(8), process manager
       postlogd(8), Postfix logging
       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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA



                                                                                    SCACHE(8postfix)