NAME

scache - Postfix shared connection cache server

SYNOPSIS


ssccaacchhee [generic Postfix daemon options]

DESCRIPTION

The ssccaacchhee(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 endpoint may refer to zero or more connections.

The exact syntax of a logical destination or endpoint name is application dependent; the ssccaacchhee(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 ssccaacchhee(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 mmaaxx__iiddllee time units.

This server implements the following requests:

ssaavvee__eennddpp _t_t_l _e_n_d_p_o_i_n_t _e_n_d_p_o_i_n_t___p_r_o_p_e_r_t_i_e_s _f_i_l_e___d_e_s_c_r_i_p_t_o_r 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.
ffiinndd__eennddpp _e_n_d_p_o_i_n_t Look up cached properties and a cached file descriptor for the
specified endpoint.
ssaavvee__ddeesstt _t_t_l _d_e_s_t_i_n_a_t_i_o_n _d_e_s_t_i_n_a_t_i_o_n___p_r_o_p_e_r_t_i_e_s _e_n_d_p_o_i_n_t 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.
ffiinndd__ddeesstt _d_e_s_t_i_n_a_t_i_o_n Look up cached destination properties, cached endpoint properties,
and a cached file descriptor for the specified logical destination.

SECURITY



The ssccaacchhee(8) server is not security-sensitive. It does not
talk to the network, and it does not talk to local users.
The ssccaacchhee(8) server can run chrooted at fixed low privilege.
        

The ssccaacchhee(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 ssyyssllooggdd(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 mmaaiinn..ccff are picked up automatically as ssccaacchhee(8)
processes run for only a limited amount of time. Use the command
"ppoossttffiixx rreellooaadd" to speed up a change.
        

The text below provides only a parameter summary. See ppoossttccoonnff(5) for more details including examples.

RESOURCE CONTROLS



ccoonnnneeccttiioonn__ccaacchhee__ttttll__lliimmiitt ((22ss)) The maximal time-to-live value that the ssccaacchhee(8) connection
cache server allows.
ccoonnnneeccttiioonn__ccaacchhee__ssttaattuuss__uuppddaattee__ttiimmee ((660000ss)) How frequently the ssccaacchhee(8) server logs usage statistics with
connection cache hit and miss rates for logical destinations and for physical endpoints.

MISCELLANEOUS CONTROLS



ccoonnffiigg__ddiirreeccttoorryy ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt)) The default location of the Postfix main.cf and master.cf
configuration files.
ddaaeemmoonn__ttiimmeeoouutt ((1188000000ss)) How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer.
iippcc__ttiimmeeoouutt ((33660000ss)) The time limit for sending or receiving information over an internal
communication channel.
mmaaxx__iiddllee ((110000ss)) The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily.
pprroocceessss__iidd ((rreeaadd--oonnllyy)) The process ID of a Postfix command or daemon process.
pprroocceessss__nnaammee ((rreeaadd--oonnllyy)) The process name of a Postfix command or daemon process.
ssyysslloogg__ffaacciilliittyy ((mmaaiill)) The syslog facility of Postfix logging.
ssyysslloogg__nnaammee ((sseeee ''ppoossttccoonnff --dd'' oouuttppuutt)) 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 "ppoossttccoonnff rreeaaddmmee__ddiirreeccttoorryy" or
"ppoossttccoonnff hhttmmll__ddiirreeccttoorryy" 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