1SCACHE(8) System Manager's Manual SCACHE(8)
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6 scache - Postfix shared connection cache server
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9 scache [generic Postfix daemon options]
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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.
15 The connection cache is organized into logical destination names, phys‐
17 ical endpoint names, and connections.
18 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.
23 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.
28 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.
35 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.
39 This server implements the following requests:
41 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.
47 find_endp endpoint
49 Look up cached properties and a cached file descriptor for the
50 specified endpoint.
51 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.
57 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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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.
67 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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72 Problems and transactions are logged to syslogd(8).
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75 The session cache cannot be shared among multiple machines.
76 When a connection expires from the cache, it is closed without the
78 appropriate protocol specific handshake.
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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.
84 The text below provides only a parameter summary. See postconf(5) for
86 more details including examples.
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89 connection_cache_ttl_limit (2s)
90 The maximal time-to-live value that the scache(8) connection
91 cache server allows.
92 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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99 config_directory (see 'postconf -d' output)
100 The default location of the Postfix main.cf and master.cf con‐
101 figuration files.
102 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.
106 ipc_timeout (3600s)
108 The time limit for sending or receiving information over an
109 internal communication channel.
110 max_idle (100s)
112 The maximum amount of time that an idle Postfix daemon process
113 waits for an incoming connection before terminating voluntarily.
114 process_id (read-only)
116 The process ID of a Postfix command or daemon process.
117 process_name (read-only)
119 The process name of a Postfix command or daemon process.
120 syslog_facility (mail)
122 The syslog facility of Postfix logging.
123 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".
127 Available in Postfix 3.3 and later:
129 service_name (read-only)
131 The master.cf service name of a Postfix daemon process.
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134 smtp(8), SMTP client
135 postconf(5), configuration parameters
136 master(8), process manager
137 syslogd(8), system logging
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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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145 The Secure Mailer license must be distributed with this software.
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148 This service was introduced with Postfix version 2.2.
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151 Wietse Venema
152 IBM T.J. Watson Research
153 P.O. Box 704
154 Yorktown Heights, NY 10598, USA
155 Wietse Venema
157 Google, Inc.
158 111 8th Avenue
159 New York, NY 10011, USA
160 SCACHE(8)