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SCACHE(8)                                                            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, Post-
       fix 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  connection  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  end-
              point  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).

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 sta-
              tistics  with  connection  cache hit and miss rates
              for logical  destinations  and  for  physical  end-
              points.

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 the next  service  request
              before exiting.

       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 (postfix)
              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
       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)