vmod_std

Varnish Standard Module

Manual section

3

SYNOPSIS

import std [from “path”] ;

DESCRIPTION

vmod_std contains basic functions which are part and parcel of Varnish, but which for reasons of architecture fit better in a VMOD.

One particular class of functions in vmod_std is the conversions functions which all have the form:

TYPE type(STRING, TYPE)

These functions attempt to convert STRING to the TYPE, and if that fails, they return the second argument, which must have the given TYPE.

toupper

STRING toupper(STRING s)
Description

Converts the string s to uppercase.

Example

set beresp.http.scream = std.toupper(“yes!”);

tolower

STRING tolower(STRING s)
Description

Converts the string s to lowercase.

Example

set beresp.http.nice = std.tolower(“VerY”);

set_ip_tos

VOID set_ip_tos(INT tos)
Description

Sets the IP type-of-service (TOS) field for the current session to tos. Please note that the TOS field is not removed by the end of the request so probably want to set it on every request should you utilize it.

Example
if (req.url ~ “^/slow/”) {
std.set_ip_tos(0);
}

random

REAL random(REAL lo, REAL hi)
Description

Returns a random real number between lo and hi. This function uses the “testable” random generator in varnishd which enables determinstic tests to be run (See m00002.vtc). This function should not be used for cryptographic applications.

Example

set beresp.http.random-number = std.random(1, 100);

log

VOID log(STRING s)
Description

Logs the string s to the shared memory log, using VSL tag SLT_VCL_Log.

Example

std.log(“Something fishy is going on with the vhost ” + req.http.host);

syslog

VOID syslog(INT priority, STRING s)
Description

Logs the string s to syslog tagged with priority. priority is formed by ORing the facility and level values. See your system’s syslog.h file for possible values.

Example

std.syslog(9, “Something is wrong”);

This will send a message to syslog using LOG_USER | LOG_ALERT.

fileread

STRING fileread(PRIV_CALL, STRING)
Description

Reads a file and returns a string with the content. Please note that it is not recommended to send variables to this function the caching in the function doesn’t take this into account. Also, files are not re-read.

Example

set beresp.http.served-by = std.fileread(“/etc/hostname”);

file_exists

BOOL file_exists(STRING path)
Description

Returns true if path or the file pointed to by path exists, false otherwise.

Example
if (std.file_exists(“/etc/return_503”)) {
return (synth(503, “Varnish is in maintenance”));
}

collect

VOID collect(HEADER hdr, STRING sep=", ")
Description

Collapses multiple hdr headers into one long header. The default separator sep is the standard comma separator to use when collapsing headers, with an additional whitespace for pretty printing.

Care should be taken when collapsing headers. In particular collapsing Set-Cookie will lead to unexpected results on the browser side.

Examples
std.collect(req.http.accept);
std.collect(req.http.cookie, “; “);

duration

DURATION duration(STRING s, DURATION fallback)
Description

Converts the string s to seconds. s must be quantified with ms (milliseconds), s (seconds), m (minutes), h (hours), d (days), w (weeks) or y (years) units. If conversion fails, fallback will be returned.

Example

set beresp.ttl = std.duration(“1w”, 3600s);

integer

INT integer(STRING s, INT fallback)
Description

Converts the string s to an integer. If conversion fails, fallback will be returned.

Example
if (std.integer(req.http.foo, 0) > 5) {
…
}

ip

IP ip(STRING s, IP fallback)
Description

Converts the string s to the first IP number returned by the system library function getaddrinfo(3). If conversion fails, fallback will be returned.

Example
if (std.ip(req.http.X-forwarded-for, “0.0.0.0”) ~ my_acl) {
…
}

real

REAL real(STRING s, REAL fallback)
Description

Converts the string s to a real. If conversion fails, fallback will be returned.

Example
if (std.real(req.http.foo, 0.0) > 5.5) {
…
}

real2integer

INT real2integer(REAL r, INT fallback)
Description

Converts the real r to an integer. If conversion fails, fallback will be returned.

Example

set req.http.integer = std.real2integer(1140618699.00, 0);

real2time

TIME real2time(REAL r, TIME fallback)
Description

Converts the real r to a time. If conversion fails, fallback will be returned.

Example

set req.http.time = std.real2time(1140618699.00, now);

time2integer

INT time2integer(TIME t, INT fallback)
Description

Converts the time t to a integer. If conversion fails, fallback will be returned.

Example

set req.http.int = std.time2integer(now, 0);

time2real

REAL time2real(TIME t, REAL fallback)
Description

Converts the time t to a real. If conversion fails, fallback will be returned.

Example

set req.http.real = std.time2real(now, 1.0);

healthy

BOOL healthy(BACKEND be)
Description

Returns true if the backend be is healthy.

port

INT port(IP ip)
Description

Returns the port number of the IP address ip.

rollback

VOID rollback(HTTP h)
Description

Restores the h HTTP headers to their original state.

Example

std.rollback(bereq);

timestamp

VOID timestamp(STRING s)
Description

Introduces a timestamp in the log with the current time, using the string s as the label. This is useful to time the execution of lengthy VCL procedures, and makes the timestamps inserted automatically by Varnish more accurate.

Example

std.timestamp(“curl-request”);

querysort

STRING querysort(STRING)
Description

Sorts the query string for cache normalization purposes.

Example

set req.url = std.querysort(req.url);

cache_req_body

BOOL cache_req_body(BYTES size)
Description

Caches the request body if it is smaller than size. Returns true if the body was cached, false otherwise.

Normally the request body is not available after sending it to the backend. By caching it is possible to retry pass operations, e.g. POST and PUT.

Example
if (std.cache_req_body(1KB)) {
…
}

strstr

STRING strstr(STRING s1, STRING s2)
Description

Returns a string beginning at the first occurrence of the string s2 in the string s1, or an empty string if s2 is not found.

Note that the comparison is case sensitive.

Example
if (std.strstr(req.url, req.http.restrict)) {
…
}

This will check if the content of req.http.restrict occurs anywhere in req.url.

time

TIME time(STRING s, TIME fallback)
Description

Converts the string s to a time. If conversion fails, fallback will be returned.

Supported formats:

“Sun, 06 Nov 1994 08:49:37 GMT”
“Sunday, 06-Nov-94 08:49:37 GMT”
“Sun Nov 6 08:49:37 1994”
“1994-11-06T08:49:37”
“784111777.00”
“784111777”
Example
if (std.time(resp.http.last-modified, now) < now - 1w) {
…
}

getenv

STRING getenv(STRING name)
Description

Return environment variable name or the empty string.

See getenv(3)

Example
set req.http.My-Env = std.getenv(“MY_ENV”);

late_100_continue

VOID late_100_continue(BOOL late)
Description

Controls when varnish reacts to an Expect: 100-continue client request header.

Varnish always generates a 100 Continue response if requested by the client trough the Expect: 100-continue header when waiting for request body data.

But, by default, the 100 Continue response is already generated immediately after vcl_recv returns to reduce latencies under the assumption that the request body will be read eventually.

Calling std.late_100_continue(true) in vcl_recv will cause the 100 Continue response to only be sent when needed. This may cause additional latencies for processing request bodies, but is the correct behavior by strict interpretation of RFC7231.

This function has no effect outside vcl_recv and after calling std.cache_req_body() or any other function consuming the request body.

Example
vcl_recv {
std.late_100_continue(true);

if (req.method == “POST”) {
std.late_100_continue(false);
return (pass);
}
…
}

SEE ALSO