Ubuntu Manpage: VCL-Variables - The complete album

NAME

       VCL-Variables - The complete album

DESCRIPTION

This is a list of all variables in the VCL language.

Variable names take the form scope.variable[.index], for instance:

req.url
beresp.http.date
client.ip

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

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 remote.ip or what the PROXY protocol told
us.

client.identity
Type: STRING

Readable from: client, backend

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.

The header name * is a VCL symbol and as such cannot, for example, start with a
numeral. Custom VMODs exist for handling of such header names.

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.

See req.http.* for general notes.

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: vcl_pipe, 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.

See req.http.* for general notes.

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.

bereq.is_hitmiss
Type: BOOL

Readable from: backend

If this backend request was caused by a hitmiss.

bereq.is_hitpass
Type: BOOL

Readable from: backend

If this backend request was caused by a hitpass.

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.

More information in the HTTP response status section.

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.

See req.http.* for general notes.

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.

It is a VCL error to use beresp.do_esi after setting beresp.filters.

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.

It is a VCL error to use beresp.do_gzip after setting beresp.filters.

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.

It is a VCL error to use beresp.do_gunzip after setting beresp.filters.

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

Default: Cache-Control s-maxage or max-age directives, or a value computed from the
Expires header's deadline, or the default_ttl parameter.

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

beresp.age
Type: DURATION

Readable from: vcl_backend_response, vcl_backend_error

Default: Age header, or zero.

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

Default: Cache-Control stale-while-revalidate directive, or default_grace parameter.

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

Default: default_keep parameter.

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.
The order left to right signifies processing from backend to cache, iow the leftmost
filter is run first on the body as received from the backend after decoding of any
transfer encodings.

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.

After beresp.filters is set, using any of the beforementioned beresp.do_* switches is a
VCL error.

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.

More information in the HTTP response status section.

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.

See req.http.* for general notes.

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.

obj.can_esi
Type: BOOL

Readable from: vcl_hit, vcl_deliver

If the object can be ESI processed, that is if setting resp.do_esi or adding esi to
resp.filters in vcl_deliver {} would cause the response body to be ESI processed.

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

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.

More information in the HTTP response status section.

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.

For the validation, first req.http.If-None-Match is compared against resp.http.Etag. If
they compare equal according to the rules for weak validation (see RFC7232), a 304 is
sent.

Secondly, req.http.If-Modified-Since is compared against resp.http.Last-Modified or, if
it is unset, against the point in time when the object was last modified based on the
Date and Age headers received with the backend response which created the object. If
the object has not been modified based on that comparison, a 304 is sent.

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.

See req.http.* for general notes.

resp.do_esi VCL >= 4.1
Type: BOOL

Readable from: vcl_deliver, vcl_synth

Writable from: vcl_deliver, vcl_synth

Default: obj.can_esi

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.

It is a VCL error to use resp.do_esi after setting resp.filters.

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.

Before resp.filters is set, the value read will be the default filter list as
determined by varnish based on resp.do_esi and request headers.

After resp.filters is set, changing any of the conditions which otherwise determine the
filter selection will have no effiect. Using resp.do_esi is an error once resp.filters
is set.

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.

sess.timeout_idle
Type: DURATION

Readable from: client

Writable from: client

Idle timeout for this session, defaults to the timeout_idle parameter, see varnishd(1)

sess.timeout_linger
Type: DURATION

Readable from: client

Writable from: client

Linger timeout for this session, defaults to the timeout_linger parameter, see
varnishd(1)

sess.send_timeout
Type: DURATION

Readable from: client

Writable from: client

Total timeout for ordinary HTTP1 responses, defaults to the send_timeout parameter, see
varnishd(1)

sess.idle_send_timeout
Type: DURATION

Readable from: client

Writable from: client

Send timeout for individual pieces of data on client connections, defaults to the
idle_send_timeout parameter, see varnishd(1)

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.

HTTP response status
A HTTP status code has 3 digits XYZ where X must be between 1 and 5 included. Since it is
not uncommon to see HTTP clients or servers relying on non-standard or even invalid status
codes, Varnish can work with any status between 100 and 999.

Within VCL code it is even possible to use status codes in the form VWXYZ as long as the
overall value is lower than 65536, but only the XYZ part will be sent to the client, by
which time the X must also have become non-zero.

The VWXYZ form of status codes can be communicate extra information in resp.status and
beresp.status to return(synth(...)) and return(error(...)), to indicate which synthetic
content to produce:

sub vcl_recv {
if ([...]) {
return synth(12404);
}
}

sub vcl_synth {
if (resp.status == 12404) {
[...] // this specific 404
} else if (resp.status % 1000 == 404) {
[...] // all other 404's
}
}

The obj.status variable will inherit the VWXYZ form, but in a ban expresion only the XYZ
part will be available. The VWXYZ form is strictly limited to VCL execution.

Assigning an HTTP standardized code to resp.status or beresp.status will also set
resp.reason or beresp.reason to the corresponding status message.

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 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) 2006-2021 Varnish Software AS

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