Changes in Varnish-Cache 8.0¶
For information about updating your current Varnish deployment to the new version, see Upgrading to Varnish-Cache 8.0.
A more detailed and technical account of changes in Varnish, with links to issues that have been fixed and pull requests that have been merged, may be found in the change log.
varnishd¶
Parameters¶
Read only parameter can no longer be set through an alias.
Deprecated aliases for parameters can no longer be set read only, it should instead be done directly on the parameters they point to.
A new parameter uncacheable_ttl defines the TTL of objects marked as
uncacheable (or hit-for-miss) by the built-in VCL. It is accessible in VCL as
the param.uncacheable_ttl variable.
The http_req_overflow_status parameter can now also be set to 500.
The default value for ban_any_variant is now 0. This means that during a
lookup, only the matching variants of an object will be evaluated against the
ban list.
As a side effect, variants that are rarely requested may never get a chance to
be tested against req based bans, which can lead to an accumulation of bans
over time. In such cases, it is recommended to set ban_any_variant to a
higher value.
Other changes in varnishd¶
The Content-Length response header is now also sent in response to all
HEAD requests.
builtin.vcl has been updated to return a synthetic 501 response and close
the connection when receiving requests with an unknown/unsupported http method
instead of piping them.
Handling of request coalescing using the waitinglist mechanism has been changed fundamentally in order to allow for all requests waiting in parallel to handle a newly arriving cache entry object as successfully revalidated - in other words, cases where a response with a ttl and grace value of 0 seconds still serves multiple client requests.
A stop command to the varnishd process now explicitly waits for all VCL
references to be returned, which is the same as waiting for all ongoing
transactions to complete. There is currently no timeout. If this new behavior is
unwanted, the worker process can still be terminated externally.
Request body read failures now result in a 400 response status.
Changes to VCL¶
VCL variables¶
Some runtime parameters can now be accessed from VCL as param.<param_name>.
See VCL-VARIABLES(7) for the list of available parameters.
Other changes to VCL¶
VCL control has been added over the logic to handle 304 Not Modified
responses to backend requests. The subroutine vcl_backend_refresh is now
getting called with 304 response objects as beresp and the stale object
to potentially re-use as obj_stale. From this subroutine, return(merge)
will invoke the header merging and re-use of the stale object body which so far
was the only option. But besides the usual options to fail, abandon, retry or
return an error, it now also offers the options to return the stale object as-is
(return(obj_stale)) or to return whatever headers are received or created in
beresp.http using return(beresp). The latter option allows for almost
full control over the response headers to use with the stale object, with the
exception of the Content-Length, Content-Encoding, Etag and
Last-Modified headers, which are copied from the stale object for
correctness.
VMODs¶
The VMOD functions std.real2integer(), std.real2time(),
std.time2integer() and std.time2real() have been removed. They had
been marked deprecated since Varnish Cache release 6.2.0 (2019-03-15).
The plug-in replacements for these functions are:
std.real2integer():std.integer(real=std.round(...), fallback=...)
std.real2time():std.time(real=std.round(...), fallback=...)
std.time2integer():std.integer(time=..., fallback=...)
std.time2real():std.real(time=..., fallback=...)
The already deprecated VMOD function cookie.format_rfc1123() is now removed.
It had been renamed to cookie.format_date().
VUTs¶
VUTs now print backtraces to syslog after a crash.
varnishlog¶
The format of logs emitted under the ESI_xmlerror tag has been changed
slightly with a colon added after the ERR and WARN prefixes. This allows
use of prefix-matching with vsl clients, for example using
%{VSL:ESI_xmlerror:WARN}x.
varnishadm¶
The new ban expression variable obj.last_hit allows to remove objects from cache which have not been accessed for a given amount of time. This is particularly useful to get rid of request bans by removing all objects which have not been touched since the request ban.
varnishstat¶
New VSC counters for connection pools have been added:
VCP.ref_hitcounts the number of times an existing connection pool wasfound while creating a backend.
VCP.ref_misscounts the number of times an existing connection pool wasnot found while creating a backend.
New counters transit_stored and transit_buffered have been added. The
former is the number of bytes stored in cache for uncachable body data, and the
latter is the number of bytes of body data for which the transit_buffer
limitation has been used.
varnishstat will automatically switch to -1 output if stdout isn’t a
terminal (allowing varnishstat | grep MAIN). A new -c switch has been
added to force curses (interactive terminal) mode.
varnishtest¶
varnishtest now prints a backtrace to stderr after a crash.
The bundled varnishtest sources have now been replaced with the separate VTest2 repository.
varnishncsa¶
varnishncsa regained the ability to log headers set from VCL through the
%{X[:first|last]}i and %{X[:first|last]}o formats. :first means
that the value of the header when it is first seen in a VSL transaction is
logged, while :last means that the final one is logged.
The default behavior is unchanged when neither :first nor :last is
specified.