vmod_purge(3)

Name
vmod_purge - Vinyl Cache Purge Module

SYNOPSIS

    import purge [as name] [from "path"]
    INT hard()
    INT soft(DURATION ttl, DURATION grace, DURATION keep)

DESCRIPTION

vmod_purge contains functions that offer a finer-grained control than return(purge) from vcl_recv{}. The functions can only be called from vcl_hit{} or vcl_miss{} and they should in general be used in both to ensure that all variants of a same object are taken care of.

EXAMPLE

    sub vcl_recv {
        if (req.method == "PURGE") {
            if (client.ip !~ purge_acl) {
                return (synth(405));
            }
            return (hash);
        }
    }
    sub my_purge {
        set req.http.purged = purge.hard();
        if (req.http.purged == "0") {
            return (synth(404));
        }
        else {
            return (synth(200));
        }
    }
    sub vcl_hit {
        if (req.method == "PURGE") {
            call my_purge;
        }
    }
    sub vcl_miss {
        if (req.method == "PURGE") {
            call my_purge;
        }
    }
    sub vcl_synth {
        if (req.method == "PURGE") {
            if (req.http.purged) {
                set resp.http.purged = req.http.purged;
            }
            return (deliver);
        }
    }

  INT hard()

This is equivalent to return(purge) but explicitly called from vcl_hit{} and vcl_miss{}. It returns the number of purged objects.

Example:

    set req.http.purged = purge.hard();

Restricted to: vcl_hit, vcl_miss.

  INT soft(DURATION ttl, DURATION grace, DURATION keep)

    INT soft(DURATION ttl=0, DURATION grace=-1, DURATION keep=-1)

Sets the ttl, grace and keep. By default, ttl is set to 0 with grace and keep periods left untouched. Setting grace or keep to a negative value or to something higher than the objects current value leaves them untouched. Setting all three parameters to 0 is equivalent to a hard purge. Returns the number of soft-purged objects.

A soft-purge can only decrease the lifetime of an object. Let's consider an object in cache created with ttl, grace, and keep of 60 seconds each:

purge.soft(ttl = 0s, grace = -1s, keep = -1s);

•   If the object is fresh, the ttl is reduced to 0 seconds and the object expires after 120 seconds.

•   If the object is stale, the expiry time is not changed.

    purge.soft(ttl = 0s, grace = 10s, keep = 10s);

•   If the object is fresh, the ttl is reduced to 0 seconds, grace and keep are reduced to 10 seconds. The object expires after 20 seconds.

•   If the object has been stale for 5 seconds, grace is reduced to 5 seconds and keep is reduced to 10 seconds. The object expires after 15 seconds.

•   If the object has been stale for 15 seconds, grace is reduced to 0 seconds and keep is reduced to 5 seconds. The object expires after 5 seconds.

•   If the object has been stale for 20 seconds or more, the object immediately expires.

    purge.soft(ttl = 10s, grace = -1s, keep = -1s);

•   If the object has been fresh for 5 seconds, the ttl is reduced to 10 seconds. The object expires after 130 seconds.

•   If the object has been fresh for 55 seconds, the ttl is not changed. The object expires after 125 seconds.

•   If the object is stale, the expiry time is not changed.

    When the expiry time of an object is reduced due to a softpurge, an EXP_Reduce entry is logged under the ExpKill VSL tag. If a softpurge does not reduce the expiry time of an object, an EXP_Unchanged entry is logged instead.

    Restricted to: vcl_hit, vcl_miss.

SEE ALSO

•   vcl(7)

COPYRIGHT

    Copyright (c) 2017 Varnish Software AS
    All rights reserved.
    Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
    SPDX-License-Identifier: BSD-2-Clause
    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:
    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.
    THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
    ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.