vmod_std

Varnish Standard Module

Manual section:

3

SYNOPSIS

import std [from "path"] ;

STRING toupper(STRING s)

STRING tolower(STRING s)

VOID set_ip_tos(INT tos)

REAL random(REAL lo, REAL hi)

VOID log(STRING s)

VOID syslog(INT priority, STRING s)

STRING fileread(STRING)

BOOL file_exists(STRING path)

VOID collect(HEADER hdr, STRING sep)

DURATION duration(STRING s, DURATION fallback)

INT integer(STRING s, INT fallback)

IP ip(STRING s, IP fallback, BOOL resolve)

REAL real(STRING s, REAL fallback)

INT real2integer(REAL r, INT fallback)

TIME real2time(REAL r, TIME fallback)

INT time2integer(TIME t, INT fallback)

REAL time2real(TIME t, REAL fallback)

BOOL healthy(BACKEND be)

INT port(IP ip)

VOID rollback(HTTP h)

VOID timestamp(STRING s)

STRING querysort(STRING)

BOOL cache_req_body(BYTES size)

STRING strstr(STRING s1, STRING s2)

TIME time(STRING s, TIME fallback)

STRING getenv(STRING name)

VOID late_100_continue(BOOL late)

BOOL syntax(REAL)

BOOL fnmatch(STRING pattern, STRING subject, BOOL pathname, BOOL noescape, BOOL period)

CONTENTS

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.

STRING toupper(STRING s)

Description

Converts the string s to uppercase.

Example

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

STRING tolower(STRING s)

Description

Converts the string s to lowercase.

Example

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

VOID set_ip_tos(INT tos)

Description

Sets the IP type-of-service (TOS) field for the current session to tos. Silently ignored if the listen address is a Unix domain socket. 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);
}

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);

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);

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.

Notice: Unlike VCL and other functions in the std vmod, this function will not fail VCL processing for workspace overflows: For an out of workspace condition, the syslog() function has no effect.

Example

std.syslog(9, “Something is wrong”);

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

STRING fileread(STRING)

Description

Reads a file and returns a string with the content. The result is cached indefinitely per filename.

Example

synthetic(“Response was served by “ + std.fileread(“/etc/hostname”));

Consider that the entire contents of the file appear in the string that is returned, including newlines that may result in invalid headers if std.fileread() is used to form a header. In that case, you may need to modify the string, for example with regsub():

set beresp.http.served-by = regsub(std.fileread("/etc/hostname"), "\R$", "");

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”));
}

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(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);

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(STRING s, IP fallback, BOOL resolve=1)

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.

If resolve is false, getaddrinfo() is called using AI_NUMERICHOST to avoid network lookups. This makes “pure” IP strings cheaper to convert.

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

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) {
…
}

INT real2integer(REAL r, INT fallback)

Description

Rounds the real r to the nearest integer, but round halfway cases away from zero (see round(3)). If conversion fails, fallback will be returned.

Example

set req.http.integer = std.real2integer(1140618699.00, 0); set req.http.posone = real2integer( 0.5, 0); # = 1.0 set req.http.negone = real2integer(-0.5, 0); # = -1.0

TIME real2time(REAL r, TIME fallback)

Description

Rounds the real r to the nearest integer (see func_real2integer) and returns the corresponding time when interpreted as a unix epoch. If conversion fails, fallback will be returned.

Example

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

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);

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);

BOOL healthy(BACKEND be)

Description

Returns true if the backend be is healthy.

INT port(IP ip)

Description

Returns the port number of the IP address ip. Always returns 0 for a *.ip variable whose value is 0.0.0.0 because the listen address is a Unix domain socket.

VOID rollback(HTTP h)

Description

Restores the h HTTP headers to their original state.

Example

std.rollback(bereq);

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”);

STRING querysort(STRING)

Description

Sorts the query string for cache normalization purposes.

Example

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

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)) {
…
}

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(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) {
…
}

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”);

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);
}
…
}

BOOL syntax(REAL)

Description

Returns the true if VCL version is at least REAL.

fnmatch(…)

BOOL fnmatch(
   STRING pattern,
   STRING subject,
   BOOL pathname=1,
   BOOL noescape=0,
   BOOL period=0
)
Description

Shell-style pattern matching; returns true if subject matches pattern, where pattern may contain wildcard characters such as * or ?.

The match is executed by the implementation of fnmatch(3) on your system. The rules for pattern matching on most systems include the following:

  • * matches any sequence of characters

  • ? matches a single character

  • a bracket expression such as [abc] or [!0-9] is interpreted as a character class according to the rules of basic regular expressions (not PCRE regexen), except that ! is used for character class negation instead of ^.

If pathname is true, then the forward slash character / is only matched literally, and never matches *, ? or a bracket expression. Otherwise, / may match one of those patterns. By default, pathname is true.

If noescape is true, then the backslash character \ is matched as an ordinary character. Otherwise, \ is an escape character, and matches the character that follows it in the pattern. For example, \\ matches \ when noescape is true, and \\ when false. By default, noescape is false.

If period is true, then a leading period character . only matches literally, and never matches *, ? or a bracket expression. A period is leading if it is the first character in subject; if pathname is also true, then a period that immediately follows a / is also leading (as in “/.”). By default, period is false.

fnmatch() invokes VCL failure and returns false if either of pattern or subject is NULL – for example, if an unset header is specified.

Examples
# Matches URLs such as /foo/bar and /foo/baz
if (std.fnmatch(“/foo/*”, req.url)) { … }

# Matches URLs such as /foo/bar/baz and /foo/baz/quux
if (std.fnmatch(“/foo/*/*”, bereq.url)) { … }

# Matches /foo/bar/quux, but not /foo/bar/baz/quux
if (std.fnmatch(“/foo/*/quux”, req.url)) { … }

# Matches /foo/bar/quux and /foo/bar/baz/quux
if (std.fnmatch(“/foo/*/quux”, req.url, pathname=false)) { … }

# Matches /foo/bar, /foo/car and /foo/far
if (std.fnmatch(“/foo/?ar”, req.url)) { … }

# Matches /foo/ followed by a non-digit
if (std.fnmatch(“/foo/[!0-9]”, req.url)) { … }

SEE ALSO