1SCACHE(8)                   System Manager's Manual                  SCACHE(8)
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NAME

6       scache - Postfix shared connection cache server
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SYNOPSIS

9       scache [generic Postfix daemon options]
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DESCRIPTION

12       The  scache(8)  server  maintains a shared multi-connection cache. This
13       information can be used by, for example, Postfix SMTP clients or  other
14       Postfix delivery agents.
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16       The connection cache is organized into logical destination names, phys‐
17       ical endpoint names, and connections.
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19       As a specific example, logical SMTP  destinations  specify  (transport,
20       domain,  port),  and  physical  SMTP  endpoints  specify (transport, IP
21       address, port).  An SMTP connection may be  saved  after  a  successful
22       mail transaction.
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24       In  the general case, one logical destination may refer to zero or more
25       physical endpoints, one physical endpoint may be referenced by zero  or
26       more  logical  destinations, and one endpoint may refer to zero or more
27       connections.
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29       The exact syntax of a logical destination or endpoint name is  applica‐
30       tion  dependent;  the  scache(8) server does not care.  A connection is
31       stored as a file descriptor together with application-dependent  infor‐
32       mation  that  is  needed to re-activate a connection object. Again, the
33       scache(8) server is completely unaware of the details of that  informa‐
34       tion.
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36       All  information  is stored with a finite time to live (ttl).  The con‐
37       nection cache  daemon  terminates  when  no  client  is  connected  for
38       max_idle time units.
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40       This server implements the following requests:
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42       save_endp ttl endpoint endpoint_properties file_descriptor
43              Save  the specified file descriptor and connection property data
44              under the specified endpoint name. The endpoint  properties  are
45              used  by  the  client  to  re-activate  a  passivated connection
46              object.
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48       find_endp endpoint
49              Look up cached properties and a cached file descriptor  for  the
50              specified endpoint.
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52       save_dest ttl destination destination_properties endpoint
53              Save  the  binding between a logical destination and an endpoint
54              under the destination name, together with  destination  specific
55              connection  properties.  The  destination properties are used by
56              the client to re-activate a passivated connection object.
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58       find_dest destination
59              Look up cached destination properties, cached  endpoint  proper‐
60              ties,  and  a  cached  file descriptor for the specified logical
61              destination.
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SECURITY

64       The scache(8) server is not security-sensitive. It does not talk to the
65       network, and it does not talk to local users.  The scache(8) server can
66       run chrooted at fixed low privilege.
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68       The scache(8) server is not a trusted process. It must not be  used  to
69       store information that is security sensitive.
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DIAGNOSTICS

72       Problems and transactions are logged to syslogd(8).
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BUGS

75       The session cache cannot be shared among multiple machines.
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77       When  a  connection  expires  from  the cache, it is closed without the
78       appropriate protocol specific handshake.
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CONFIGURATION PARAMETERS

81       Changes to main.cf are picked up automatically as  scache(8)  processes
82       run for only a limited amount of time. Use the command "postfix reload"
83       to speed up a change.
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85       The text below provides only a parameter summary. See  postconf(5)  for
86       more details including examples.
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RESOURCE CONTROLS

89       connection_cache_ttl_limit (2s)
90              The  maximal  time-to-live  value  that the scache(8) connection
91              cache server allows.
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93       connection_cache_status_update_time (600s)
94              How frequently the scache(8) server logs usage  statistics  with
95              connection cache hit and miss rates for logical destinations and
96              for physical endpoints.
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MISCELLANEOUS CONTROLS

99       config_directory (see 'postconf -d' output)
100              The default location of the Postfix main.cf and  master.cf  con‐
101              figuration files.
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103       daemon_timeout (18000s)
104              How  much  time  a  Postfix  daemon process may take to handle a
105              request before it is terminated by a built-in watchdog timer.
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107       ipc_timeout (3600s)
108              The time limit for sending  or  receiving  information  over  an
109              internal communication channel.
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111       max_idle (100s)
112              The  maximum  amount of time that an idle Postfix daemon process
113              waits for an incoming connection before terminating voluntarily.
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115       process_id (read-only)
116              The process ID of a Postfix command or daemon process.
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118       process_name (read-only)
119              The process name of a Postfix command or daemon process.
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121       syslog_facility (mail)
122              The syslog facility of Postfix logging.
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124       syslog_name (see 'postconf -d' output)
125              A prefix that  is  prepended  to  the  process  name  in  syslog
126              records, so that, for example, "smtpd" becomes "prefix/smtpd".
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128       Available in Postfix 3.3 and later:
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130       service_name (read-only)
131              The master.cf service name of a Postfix daemon process.
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SEE ALSO

134       smtp(8), SMTP client
135       postconf(5), configuration parameters
136       master(8), process manager
137       syslogd(8), system logging
138

README FILES

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

145       The Secure Mailer license must be distributed with this software.
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HISTORY

148       This service was introduced with Postfix version 2.2.
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AUTHOR(S)

151       Wietse Venema
152       IBM T.J. Watson Research
153       P.O. Box 704
154       Yorktown Heights, NY 10598, USA
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156       Wietse Venema
157       Google, Inc.
158       111 8th Avenue
159       New York, NY 10011, USA
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