Ubuntu Manpage: VCL - Varnish Configuration Language

Provided by: varnish_6.2.1-2ubuntu0.2_amd64

NAME

       VCL - Varnish Configuration Language

DESCRIPTION

The VCL language is a small domain-specific language designed to be used to describe
request handling and document caching policies for Varnish Cache.

When a new configuration is loaded, the varnishd management process translates the VCL
code to C and compiles it to a shared object which is then loaded into the server process.

This document focuses on the syntax of the VCL language. For a full description of syntax
and semantics, with ample examples, please see the online documentation at
https://www.varnish-cache.org/docs/ .

Starting with Varnish 4.0, each VCL file must start by declaring its version with vcl
<major>.<minor>; marker at the top of the file. See more about this under Versioning
below.

Operators
The following operators are available in VCL:

= Assignment operator.

== Comparison.

~ Match. Can either be used with regular expressions or ACLs.

! Negation.

&& Logical and.

|| Logical or.

Conditionals
VCL has if and else statements. Nested logic can be implemented with the elseif statement
(elsif/elif/else if are equivalent).

Note that there are no loops or iterators of any kind in VCL.

Strings, booleans, time, duration, integers and real numbers
These are the data types in Varnish. You can set or unset these.

Example:

set req.http.User-Agent = "unknown";
unset req.http.Range;

Strings
Basic strings are enclosed in double quotes "...", and may not contain newlines. Long
strings are enclosed in {"..."}. They may contain any character including single double
quotes ", newline and other control characters except for the NUL (0x00) character.

Booleans
Booleans can be either true or false. In addition, in a boolean context some data types
will evaluate to true or false depending on their value.

String types will evaluate to false if they are unset. This allows checks of the type if
(req.http.opthdr) {} to test if a header exists, even if it is empty, whereas if
(req.http.opthdr == "") {} does not distinguish if the header does not exist or if it is
empty.

Backend types will evaluate to false if they don't have a backend assigned; integer types
will evaluate to false if their value is zero; duration types will evaluate to false if
their value is equal or less than zero.

Time
VCL has time. A duration can be added to a time to make another time. In string context
they return a formatted string in RFC1123 format, e.g. Sun, 06 Nov 1994 08:49:37 GMT.

The keyword now returns a notion of the current time, which is kept consistent during vcl
subroutine invocations, so during the execution of a vcl subroutine callback (vcl_* {}),
including all user-defined subroutines being called, now always returns the same value.

Durations
Durations are defined by a number followed by a unit. The number can include a fractional
part, e.g. 1.5s. The supported units are:

ms milliseconds

s seconds

m minutes

h hours

d days

w weeks

y years

In string context they return a string with their value rounded to 3 decimal places and
excluding the unit, e.g. 1.500.

Integers
Certain fields are integers, used as expected. In string context they return a string,
e.g. 1234.

Real numbers
VCL understands real numbers. In string context they return a string with their value
rounded to 3 decimal places, e.g. 3.142.

Regular Expressions
Varnish uses Perl-compatible regular expressions (PCRE). For a complete description please
see the pcre(3) man page.

To send flags to the PCRE engine, such as to do case insensitive matching, add the flag
within parens following a question mark, like this:

# If host is NOT example dot com..
if (req.http.host !~ "(?i)example\.com$") {
...
}

Include statement
To include a VCL file in another file use the include keyword:

include "foo.vcl";

Import statement
The import statement is used to load Varnish Modules (VMODs.)

Example:

import std;
sub vcl_recv {
std.log("foo");
}

Comments
Single lines of VCL can be commented out using // or #. Multi-line blocks can be commented
out with /*block*/.

Example:

sub vcl_recv {
// Single line of out-commented VCL.
# Another way of commenting out a single line.
/*
Multi-line block of commented-out VCL.
*/
}

Backend definition
A backend declaration creates and initialises a named backend object. A declaration start
with the keyword backend followed by the name of the backend. The actual declaration is in
curly brackets, in a key/value fashion.:

backend name {
.attribute = "value";
}

One of the attributes .host or .path is mandatory (but not both). The attributes will
inherit their defaults from the global parameters. The following attributes are available:

.host The host to be used. IP address or a hostname that resolves to a single IP
address. This attribute is mandatory, unless .path is declared.

.path (VCL >= 4.1)
The absolute path of a Unix domain socket at which a backend is listening. If the
file at that path does not exist or is not accessible to Varnish at VCL load time,
then the VCL compiler issues a warning, but does not fail. This makes it possible
to start the UDS-listening peer, or set the socket file's permissions, after
starting Varnish or loading VCL with a UDS backend. But the socket file must exist
and have necessary permissions before the first connection is attempted, otherwise
fetches will fail. If the file does exist and is accessible, then it must be a
socket; otherwise the VCL load fails. One of .path or .host must be declared (but
not both). .path may only be used in VCL since version 4.1.

.port The port on the backend that Varnish should connect to. Ignored if a Unix domain
socket is declared in .path.

.host_header
A host header to add to probes and regular backend requests if they have no such
header.

.connect_timeout
Timeout for connections.

Default: connect_timeout parameter, see varnishd(1)

.first_byte_timeout
Timeout for first byte.

Default: first_byte_timeout parameter, see varnishd(1)

.between_bytes_timeout
Timeout between bytes.

Default: between_bytes_timeout parameter, see varnishd(1)

.probe Attach a probe to the backend. See Probes

.proxy_header
The PROXY protocol version Varnish should use when connecting to this backend.
Allowed values are 1 and 2.

Notice this setting will lead to backend connections being used for a single
request only (subject to future improvements). Thus, extra care should be taken
to avoid running into failing backend connections with EADDRNOTAVAIL due to no
local ports being available. Possible options are:

• Use additional backend connections to extra IP addresses or TCP ports

• Increase the number of available ports (Linux sysctl
net.ipv4.ip_local_port_range)

• Reuse backend connection ports early (Linux sysctl net.ipv4.tcp_tw_reuse)

.max_connections
Maximum number of open connections towards this backend. If Varnish reaches the
maximum Varnish it will start failing connections.

Backends can be used with directors. Please see the vmod_directors(3) man page for more
information.

Probes
Probes will query the backend for status on a regular basis and mark the backend as down
it they fail. A probe is defined as this:

probe name {
.attribute = "value";
}

The probe named default is special and will be used for all backends which do not
explicitly reference a probe.

There are no mandatory options. These are the options you can set:

.url The URL to query. Defaults to /. Mutually exclusive with .request

.request
Specify a full HTTP request using multiple strings. .request will have \r\n
automatically inserted after every string. Mutually exclusive with .url.

Note that probes require the backend to complete sending the response and close
the connection within the specified timeout, so .request will, for HTTP/1.1,
most likely need to contain a "Connection: close" string.

.expected_response
The expected HTTP response code. Defaults to 200.

.timeout
The timeout for the probe. Default is 2s.

.interval
How often the probe is run. Default is 5s.

.initial
How many of the polls in .window are considered good when Varnish starts.
Defaults to the value of .threshold - 1. In this case, the backend starts as
sick and requires one single poll to be considered healthy.

.window
How many of the latest polls we examine to determine backend health. Defaults
to 8.

.threshold
How many of the polls in .window must have succeeded to consider the backend to
be healthy. Defaults to 3.

Access Control List (ACL)
An Access Control List (ACL) declaration creates and initialises a named access control
list which can later be used to match client addresses:

acl localnetwork {
"localhost"; # myself
"192.0.2.0"/24; # and everyone on the local network
! "192.0.2.23"; # except for the dial-in router
}

If an ACL entry specifies a host name which Varnish is unable to resolve, it will match
any address it is compared to. Consequently, if it is preceded by a negation mark, it will
reject any address it is compared to, which may not be what you intended. If the entry is
enclosed in parentheses, however, it will simply be ignored.

To match an IP address against an ACL, simply use the match operator:

if (client.ip ~ localnetwork) {
return (pipe);
}

VCL objects
A VCL object can be instantiated with the new keyword:

sub vcl_init {
new b = directors.round_robin()
b.add_backend(node1);
}

This is only available in vcl_init.

Subroutines
A subroutine is used to group code for legibility or reusability:

sub pipe_if_local {
if (client.ip ~ localnetwork) {
return (pipe);
}
}

Subroutines in VCL do not take arguments, nor do they return values. The built in
subroutines all have names beginning with vcl_, which is reserved.

To call a subroutine, use the call keyword followed by the subroutine's name:

sub vcl_recv {
call pipe_if_local;
}

Return statements
The ongoing vcl_* subroutine execution ends when a return(<action>) statement is made.

The <action> specifies how execution should proceed. The context defines which actions are
available.

Multiple subroutines
If multiple subroutines with the name of one of the built-in ones are defined, they are
concatenated in the order in which they appear in the source.

The built-in VCL distributed with Varnish will be implicitly concatenated when the VCL is
compiled.

VCL Variables
Variables provide read, write and delete access to almost all aspects of the work at hand.

Reading a variable is done simply by using its name in VCL:

if (client.ip ~ bad_guys) {
return (synth(400));
}

Writing a variable, where this is possible, is done with a set statement:

set resp.http.never = "Let You Down";

Similarly, deleting a variable, for the few variables where this is possible, is done with
a unset statement:

unset req.http.cookie;

Which operations are possible on each variable is described below, often with the
shorthand "backend" which covers the vcl_backend_* methods and "client" which covers the
rest, except vcl_init and vcl_fini.

When setting a variable, the right hand side of the equal sign must have the variables
type, you cannot assign a STRING to a variable of type NUMBER, even if the string is "42".
(Explicit conversion functions can be found in vmod_std(3)).

local, server, remote and client
These variables describe the network connection between the client and varnishd.

Without PROXY protocol:

client server
remote local
v v
CLIENT ------------ VARNISHD

With PROXY protocol:

client server remote local
v v v v
CLIENT ------------ PROXY ------------ VARNISHD

local.ip
Type: IP

Readable from: client, backend

The IP address (and port number) of the local end of the TCP connection, for instance
192.168.1.1:81

If the connection is a UNIX domain socket, the value will be 0.0.0.0:0

local.endpoint VCL >= 4.1
Type: STRING

Readable from: client, backend

The address of the '-a' socket the session was accepted on.

If the argument was -a foo=:81 this would be ":81"

local.socket VCL >= 4.1
Type: STRING

Readable from: client, backend

The name of the '-a' socket the session was accepted on.

If the argument was -a foo=:81 this would be "foo".

Note that all '-a' gets a default name on the form a%d if no name is provided.

remote.ip
Type: IP

Readable from: client, backend

The IP address of the other end of the TCP connection. This can either be the clients
IP, or the outgoing IP of a proxy server.

If the connection is a UNIX domain socket, the value will be 0.0.0.0:0

client.ip
Type: IP

Readable from: client, backend

The client's IP address, either the same as local.ip or what the PROXY protocol told
us.

client.identity
Type: STRING

Readable from: client

Writable from: client

Identification of the client, used to load balance in the client director. Defaults to
client.ip

This variable can be overwritten with more precise information, for instance extracted
from a Cookie: header.

server.ip
Type: IP

Readable from: client, backend

The IP address of the socket on which the client connection was received, either the
same as server.ip or what the PROXY protocol told us.

server.hostname
Type: STRING

Readable from: all

The host name of the server, as returned by the gethostname(3) system function.

server.identity
Type: STRING

Readable from: all

The identity of the server, as set by the -i parameter.

If an -i parameter is not passed to varnishd, the return value from gethostname(3)
system function will be used.

req and req_top
These variables describe the present request, and when ESI:include requests are being
processed, req_top points to the request received from the client.

req
Type: HTTP

Readable from: client

The entire request HTTP data structure. Mostly useful for passing to VMODs.

req.method
Type: STRING

Readable from: client

Writable from: client

The request method (e.g. "GET", "HEAD", ...)

req.hash
Type: BLOB

Readable from: vcl_hit, vcl_miss, vcl_pass, vcl_purge, vcl_deliver

The hash key of this request. Mostly useful for passing to VMODs, but can also be
useful for debugging hit/miss status.

req.url
Type: STRING

Readable from: client

Writable from: client

The requested URL, for instance "/robots.txt".

req.proto VCL <= 4.0
Type: STRING

Readable from: client

Writable from: client

The HTTP protocol version used by the client, usually "HTTP/1.1" or "HTTP/2.0".

req.proto VCL >= 4.1
Type: STRING

Readable from: client

The HTTP protocol version used by the client, usually "HTTP/1.1" or "HTTP/2.0".

req.http.*
Type: HEADER

Readable from: client

Writable from: client

Unsetable from: client

The headers of request, things like req.http.date.

The RFCs allow multiple headers with the same name, and both set and unset will remove
all headers with the name given.

req.restarts
Type: INT

Readable from: client

A count of how many times this request has been restarted.

req.storage
Type: STEVEDORE

Readable from: client

Writable from: client

The storage backend to use to save this request body.

req.esi_level
Type: INT

Readable from: client

A count of how many levels of ESI requests we're currently at.

req.ttl
Type: DURATION

Readable from: client

Writable from: client

Upper limit on the object age for cache lookups to return hit.

req.grace
Type: DURATION

Readable from: client

Writable from: client

Upper limit on the object grace.

During lookup the minimum of req.grace and the object's stored grace value will be used
as the object's grace.

req.xid
Type: STRING

Readable from: client

Unique ID of this request.

req.esi VCL <= 4.0
Type: BOOL

Readable from: client

Writable from: client

Set to false to disable ESI processing regardless of any value in beresp.do_esi.
Defaults to true. This variable is replaced by resp.do_esi in VCL 4.1.

req.can_gzip
Type: BOOL

Readable from: client

True if the client provided gzip or x-gzip in the Accept-Encoding header.

req.backend_hint
Type: BACKEND

Readable from: client

Writable from: client

Set bereq.backend to this if we attempt to fetch. When set to a director, reading this
variable returns an actual backend if the director has resolved immediately, or the
director otherwise. When used in string context, returns the name of the director or
backend, respectively.

req.hash_ignore_busy
Type: BOOL

Readable from: client

Writable from: client

Default: false

Ignore any busy object during cache lookup.

You only want to do this when you have two server looking up content sideways from each
other to avoid deadlocks.

req.hash_always_miss
Type: BOOL

Readable from: client

Writable from: client

Default: false

Force a cache miss for this request, even if perfectly good matching objects are in the
cache.

This is useful to force-update the cache without invalidating existing entries in case
the fetch fails.

req.is_hitmiss
Type: BOOL

Readable from: client

If this request resulted in a hitmiss

req.is_hitpass
Type: BOOL

Readable from: client

If this request resulted in a hitpass

req_top.method
Type: STRING

Readable from: client

The request method of the top-level request in a tree of ESI requests. (e.g. "GET",
"HEAD"). Identical to req.method in non-ESI requests.

req_top.url
Type: STRING

Readable from: client

The requested URL of the top-level request in a tree of ESI requests. Identical to
req.url in non-ESI requests.

req_top.http.*
Type: HEADER

Readable from: client

HTTP headers of the top-level request in a tree of ESI requests. Identical to
req.http. in non-ESI requests.

req_top.proto
Type: STRING

Readable from: client

HTTP protocol version of the top-level request in a tree of ESI requests. Identical to
req.proto in non-ESI requests.

bereq
This is the request we send to the backend, it is built from the clients req.* fields by
filtering out "per-hop" fields which should not be passed along (Connection:, Range: and
similar).

Slightly more fields are allowed through for pass fetches than for miss fetches, for
instance Range.

bereq
Type: HTTP

Readable from: backend

The entire backend request HTTP data structure. Mostly useful as argument to VMODs.

bereq.xid
Type: STRING

Readable from: backend

Unique ID of this request.

bereq.retries
Type: INT

Readable from: backend

A count of how many times this request has been retried.

bereq.backend
Type: BACKEND

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

This is the backend or director we attempt to fetch from. When set to a director,
reading this variable returns an actual backend if the director has resolved
immediately, or the director otherwise. When used in string context, returns the name
of the director or backend, respectively.

bereq.body
Type: BODY

Unsetable from: vcl_backend_fetch

The request body.

Unset will also remove bereq.http.Content-Length.

bereq.hash
Type: BLOB

Readable from: vcl_pipe, backend

The hash key of this request, a copy of req.hash.

bereq.method
Type: STRING

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

The request type (e.g. "GET", "HEAD").

Regular (non-pipe, non-pass) fetches are always "GET"

bereq.url
Type: STRING

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

The requested URL, copied from req.url

bereq.proto VCL <= 4.0
Type: STRING

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

The HTTP protocol version, "HTTP/1.1" unless a pass or pipe request has "HTTP/1.0" in
req.proto

bereq.proto VCL >= 4.1
Type: STRING

Readable from: vcl_pipe, backend

The HTTP protocol version, "HTTP/1.1" unless a pass or pipe request has "HTTP/1.0" in
req.proto

bereq.http.*
Type: HEADER

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

Unsetable from: vcl_pipe, backend

The headers to be sent to the backend.

bereq.uncacheable
Type: BOOL

Readable from: backend

Indicates whether this request is uncacheable due to a pass in the client side or a hit
on an hit-for-pass object.

bereq.connect_timeout
Type: DURATION

Readable from: vcl_pipe, backend

Writable from: vcl_pipe, backend

Default: .connect_timeout attribute from the backend_definition, which defaults to the
connect_timeout parameter, see varnishd(1)

The time in seconds to wait for a backend connection to be established.

bereq.first_byte_timeout
Type: DURATION

Readable from: backend

Writable from: backend

Default: .first_byte_timeout attribute from the backend_definition, which defaults to
the first_byte_timeout parameter, see varnishd(1)

The time in seconds to wait getting the first byte back from the backend. Not
available in pipe mode.

bereq.between_bytes_timeout
Type: DURATION

Readable from: backend

Writable from: backend

Default: .between_bytes_timeout attribute from the backend_definition, which defaults
to the between_bytes_timeout parameter, see varnishd(1)

The time in seconds to wait between each received byte from the backend. Not available
in pipe mode.

bereq.is_bgfetch
Type: BOOL

Readable from: backend

True for fetches where the client got a hit on an object in grace, and this fetch was
kicked of in the background to get a fresh copy.

beresp
The response received from the backend, one cache misses, the store object is built from
beresp.

beresp
Type: HTTP

Readable from: vcl_backend_response, vcl_backend_error

The entire backend response HTTP data structure, useful as argument to VMOD functions.

beresp.body
Type: BODY

Writable from: vcl_backend_error

For producing a synthetic body.

beresp.proto VCL <= 4.0
Type: STRING

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

The HTTP protocol version the backend replied with.

beresp.proto VCL >= 4.1
Type: STRING

Readable from: vcl_backend_response, vcl_backend_error

The HTTP protocol version the backend replied with.

beresp.status
Type: INT

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

The HTTP status code returned by the server.

Status codes on the form XXYZZ can be set where XXYZZ is less than 65536 and Y is
[1...9]. Only YZZ will be sent back to clients.

XX can be therefore be used to pass information around inside VCL, for instance
return(synth(22404)) from vcl_recv{} to vcl_synth{}

beresp.reason
Type: STRING

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

The HTTP status message returned by the server.

beresp.http.*
Type: HEADER

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Unsetable from: vcl_backend_response, vcl_backend_error

The HTTP headers returned from the server.

beresp.do_esi
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Default: false

Set it to true to parse the object for ESI directives. Will only be honored if req.esi
is true.

beresp.do_stream
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Default: true

Deliver the object to the client while fetching the whole object into varnish.

For uncacheable objects, storage for parts of the body which have been sent to the
client may get freed early, depending on the storage engine used.

This variable has no effect if do_esi is true or when the response body is empty.

beresp.do_gzip
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Default: false

Set to true to gzip the object while storing it.

If http_gzip_support is disabled, setting this variable has no effect.

beresp.do_gunzip
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Default: false

Set to true to gunzip the object while storing it in the cache.

If http_gzip_support is disabled, setting this variable has no effect.

beresp.was_304
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

When true this indicates that we got a 304 response to our conditional fetch from the
backend and turned that into beresp.status = 200

beresp.uncacheable
Type: BOOL

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Inherited from bereq.uncacheable, see there.

Setting this variable makes the object uncacheable.

This may may produce a hit-for-miss object in the cache.

Clearing the variable has no effect and will log the warning "Ignoring attempt to reset
beresp.uncacheable".

beresp.ttl
Type: DURATION

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

The object's remaining time to live, in seconds.

beresp.age
Type: DURATION

Readable from: vcl_backend_response, vcl_backend_error

The age of the object.

beresp.grace
Type: DURATION

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Set to a period to enable grace.

beresp.keep
Type: DURATION

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Set to a period to enable conditional backend requests.

The keep time is cache lifetime in addition to the ttl.

Objects with ttl expired but with keep time left may be used to issue conditional
(If-Modified-Since / If-None-Match) requests to the backend to refresh them.

beresp.backend
Type: BACKEND

Readable from: vcl_backend_response, vcl_backend_error

This is the backend we fetched from. If bereq.backend was set to a director, this will
be the backend selected by the director. When used in string context, returns its
name.

beresp.backend.name
Type: STRING

Readable from: vcl_backend_response, vcl_backend_error

Name of the backend this response was fetched from. Same as beresp.backend.

beresp.backend.ip VCL <= 4.0
Type: IP

Readable from: vcl_backend_response

IP of the backend this response was fetched from.

beresp.storage
Type: STEVEDORE

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

The storage backend to use to save this object.

beresp.storage_hint VCL <= 4.0
Type: STRING

Readable from: vcl_backend_response, vcl_backend_error

Writable from: vcl_backend_response, vcl_backend_error

Deprecated since varnish 5.1 and discontinued since VCL 4.1 (varnish 6.0). Use
beresp.storage instead.

Hint to Varnish that you want to save this object to a particular storage backend.

beresp.filters
Type: STRING

Readable from: vcl_backend_response

Writable from: vcl_backend_response

List of Varnish Fetch Processor (VFP) filters the beresp.body will be pulled through.

VFP Filters change the body before going into the cache and/or being handed to the
client side, where it may get processed again by resp.filters.

The following VFP filters exist in varnish-cache:

• gzip: compress a body using gzip

• testgunzip: Test if a body is valid gzip and refuse it otherwise

• gunzip: Uncompress gzip content

• esi: ESI-process plain text content

• esi_gzip: Save gzipped snippets for efficient ESI-processing

This filter enables stitching together ESI from individually gzipped fragments,
saving processing power for re-compression on the client side at the expense of some
compression efficiency.

Additional VFP filters are available from VMODs.

By default, beresp.filters is constructed as follows:

• gunzip gets added for gzipped content if beresp.do_gunzip or beresp.do_esi are true.

• esi_gzip gets added if beresp.do_esi is true together with beresp.do_gzip or content
is already compressed.

• esi gets added if beresp.do_esi is true

• gzip gets added for uncompressed content if beresp.do_gzip is true

• testgunzip gets added for compressed content if beresp.do_gunzip is false.

obj
This is the object we found in cache. It cannot be modified.

obj.proto
Type: STRING

Readable from: vcl_hit

The HTTP protocol version stored in the object.

obj.status
Type: INT

Readable from: vcl_hit

The HTTP status code stored in the object.

obj.reason
Type: STRING

Readable from: vcl_hit

The HTTP reason phrase stored in the object.

obj.hits
Type: INT

Readable from: vcl_hit, vcl_deliver

The count of cache-hits on this object.

In vcl_deliver a value of 0 indicates a cache miss.

obj.http.*
Type: HEADER

Readable from: vcl_hit

The HTTP headers stored in the object.

obj.ttl
Type: DURATION

Readable from: vcl_hit, vcl_deliver

The object's remaining time to live, in seconds.

obj.age
Type: DURATION

Readable from: vcl_hit, vcl_deliver

The age of the object.

obj.grace
Type: DURATION

Readable from: vcl_hit, vcl_deliver

The object's grace period in seconds.

obj.keep
Type: DURATION

Readable from: vcl_hit, vcl_deliver

The object's keep period in seconds.

obj.uncacheable
Type: BOOL

Readable from: vcl_deliver

Whether the object is uncacheable (pass, hit-for-pass or hit-for-miss).

obj.storage
Type: STEVEDORE

Readable from: vcl_hit, vcl_deliver

The storage backend where this object is stored.

resp
This is the response we send to the client, it is built from either beresp (pass/miss),
obj (hits) or created from whole cloth (synth).

With the exception of resp.body all resp.* variables available in both vcl_deliver{} and
vcl_synth{} as a matter of symmetry.

resp
Type: HTTP

Readable from: vcl_deliver, vcl_synth

The entire response HTTP data structure, useful as argument to VMODs.

resp.body
Type: BODY

Writable from: vcl_synth

To produce a synthetic response body, for instance for errors.

resp.proto VCL <= 4.0
Type: STRING

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

The HTTP protocol version to use for the response.

resp.proto VCL >= 4.1
Type: STRING

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

The HTTP protocol version to use for the response.

resp.status
Type: INT

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

The HTTP status code that will be returned.

Assigning a HTTP standardized code to resp.status will also set resp.reason to the
corresponding status message.

resp.status 200 will get changed into 304 by core code after a return(deliver) from
vcl_deliver for conditional requests to cached content if validation succeeds.

resp.reason
Type: STRING

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

The HTTP status message that will be returned.

resp.http.*
Type: HEADER

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

Unsetable from: vcl_deliver, vcl_synth

The HTTP headers that will be returned.

resp.do_esi VCL >= 4.1
Type: BOOL

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

Default: Set if ESI parsing has happened.

This can be used to selectively disable ESI processing, even though ESI parsing
happened during fetch. This is useful when Varnish caches peer with each other.

resp.is_streaming
Type: BOOL

Readable from: vcl_deliver, vcl_synth

Returns true when the response will be streamed while being fetched from the backend.

resp.filters
Type: STRING

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

List of VDP filters the resp.body will be pushed through.

Special variables
now
Type: TIME

Readable from: all

The current time, in seconds since the UNIX epoch.

When converted to STRING in expressions it returns a formatted timestamp like Tue, 20
Feb 2018 09:30:31 GMT

sess
A session corresponds to the "conversation" that Varnish has with a single client
connection, over which one or more request/response transactions may take place. It may
comprise the traffic over an HTTP/1 keep-alive connection, or the multiplexed traffic over
an HTTP/2 connection.

sess.xid VCL >= 4.1
Type: STRING

Readable from: client, backend

Unique ID of this session.

storage
storage.<name>.free_space
Type: BYTES

Readable from: client, backend

Free space available in the named stevedore. Only available for the malloc stevedore.

storage.<name>.used_space
Type: BYTES

Readable from: client, backend

Used space in the named stevedore. Only available for the malloc stevedore.

storage.<name>.happy
Type: BOOL

Readable from: client, backend

Health status for the named stevedore. Not available in any of the current stevedores.

Functions
The following built-in functions are available:

ban(STRING)
Invalidates all objects in cache that match the given expression with the ban
mechanism.

The format of STRING is:

<field> <operator> <arg> [&& <field> <oper> <arg> ...]

• <field>:

• string fields:

• req.url: The request url

• req.http.*: Any request header

• obj.status: The cache object status

• obj.http.*: Any cache object header

obj.status is treated as a string despite the fact that it is actually an integer.

• duration fields:

• obj.ttl: Remaining ttl at the time the ban is issued

• obj.age: Object age at the time the ban is issued

• obj.grace: The grace time of the object

• obj.keep: The keep time of the object

• <operator>:

• for all fields:

• ==: <field> and <arg> are equal

• !=: <field> and <arg> are unequal

strings are compared case sensitively

• for string fields:

• ~: <field> matches the regular expression <arg>

• !~:<field> does not match the regular expression <arg>

• for duration fields:

• >: <field> is greater than <arg>

• >=: <field> is greater than or equal to <arg>

• <: <field> is less than <arg>

• <=: <field> is less than or equal to <arg>

• <arg>:

• for string fields:

Either a literal string or a regular expression. Note that <arg> does not use any
of the string delimiters like " or {"..."} used elsewhere in varnish. To match
against strings containing whitespace, regular expressions containing \s can be
used.

• for duration fields:

A VCL duration like 10s, 5m or 1h, see Durations

Expressions can be chained using the and operator &&. For or semantics, use several
bans.

The unset <field> is not equal to any string, such that, for a non-existing header, the
operators == and ~ always evaluate as false, while the operators != and !~ always
evaluate as true, respectively, for any value of <arg>.

hash_data(input)
Adds an input to the hash input. In the built-in VCL hash_data() is called on the host
and URL of the request. Available in vcl_hash.

synthetic(STRING)
Prepare a synthetic response body containing the STRING. Available in vcl_synth and
vcl_backend_error.

Identical to set resp.body / set beresp.body.

regsub(str, regex, sub)
Returns a copy of str with the first occurrence of the regular expression regex
replaced with sub. Within sub, \0 (which can also be spelled \&) is replaced with the
entire matched string, and \n is replaced with the contents of subgroup n in the
matched string.

regsuball(str, regex, sub)
As regsub(), but this replaces all occurrences.

For converting or casting VCL values between data types use the functions available in the
std VMOD.

VERSIONING

       Multiple versions of the VCL syntax can coexist within certain constraints.

       The VCL syntax version at the start of VCL file specified with -f sets the hard limit that
       cannot be exceeded anywhere, and it selects the appropriate version of the builtin VCL.

       That means that you can never include vcl 9.1; from vcl 8.7;,  but  the  opposite  may  be
       possible, to the extent the compiler supports it.

       Files pulled in via include do not need to have a vcl X.Y; but it may be a good idea to do
       it anyway, to not have surprises in the future.  The syntax version  set  in  an  included
       file  only applies to that file and any files it includes - unless these set their own VCL
       syntax version.

       The version of Varnish this file belongs to supports syntax 4.0 only.

EXAMPLES

       For examples, please see the online documentation.

HISTORY

       VCL was developed by Poul-Henning Kamp in cooperation with Verdens Gang AS, Redpill Linpro
       and  Varnish Software.  This manual page is written by Per Buer, Poul-Henning Kamp, Martin
       Blix Grydeland, Kristian Lyngstøl, Lasse Karstensen and possibly others.

COPYRIGHT

       This document is licensed under the same  license  as  Varnish  itself.  See  LICENSE  for
       details.

       • Copyright (c) 2006 Verdens Gang AS

       • Copyright (c) 2006-2015 Varnish Software AS

                                                                                           VCL(7)

NAME

DESCRIPTION

VERSIONING

EXAMPLES

SEE ALSO

HISTORY

COPYRIGHT