.. _whatsnew_changes_7.4:

%%%%%%%%%%%%%%%%%%%%%% Changes in Varnish 7.4 %%%%%%%%%%%%%%%%%%%%%%

For information about updating your current Varnish deployment to the new version, see :ref:whatsnew_upgrading_7.4.

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_.

.. _change log: https://github.com/varnishcache/varnish-cache/blob/master/doc/changes.rst

varnishd

HTTP/2 header field validation is now more strict with respect to allowed characters.

The :ref:vcl-step(7) manual page has been added to document the VCL state machines.

VCL Tracing


VCL tracing now needs to be explicitly activated by setting the
``req.trace`` or ``bereq.trace`` VCL variables, which are initialized
from the ``feature +trace`` flag. Only if the trace variables are set
will ``VCL_trace`` log records be generated.

Consequently, ``VCL_trace`` has been removed from the default
``vsl_mask``, so any trace records will be emitted by
default. ``vsl_mask`` can still be used to filter ``VCL_trace``
records.

To trace ``vcl_init {}`` and ``vcl_fini {}``, set the ``feature
+trace`` flag while the vcl is loaded/discarded.

Parameters
~~~~~~~~~~

The ``startup_timeout`` parameter now specifically replaces
``cli_timeout`` for the initial startup only.

Changes to VCL
==============

The ``Content-Length`` and ``Transfer-Encoding`` headers are now
protected. For the common use case of ``unset
(be)req.http.Content-Length`` to dismiss a body, ``unset
(be)req.body`` should be used.

varnishlog
==========

Object creation failures by the selected storage engine are now logged
under the ``Error`` tag as ``Failed to create object from %s
%s``.

varnishadm
==========

Tabulation of the ``vcl.list`` CLI output has been modified slightly.

varnishstat
===========

The counter ``MAIN.http1_iovs_flush`` has been added to track the
number of premature ``writev()`` calls due to an insufficient number
of IO vectors. This number is configured through the ``http1_iovs``
parameter for client connections and implicitly defined by the amount
of free workspace for backend connections.

varnishtest
===========

The basename of the test directory is now available as the ``vtcid``
macro to serve as a unique string across concurrently running tests.

The ``varnishd_args_prepend`` and ``varnishd_args_append`` macros have
been added to allow addition of arguments to ``varnishd`` invocations
before and after those added by ``varnishtest`` by default.

``User-Agent`` request and ``Server`` response headers are now created
by default, containing the respective client and server name. The
``txreq -nouseragent`` and ``txresp -noserver`` options disable
addition of these headers.

Changes for developers and VMOD authors
=======================================

Call sites of VMOD functions and methods can now be restricted to
built-in subroutines using the ``$Restrict`` stanza in the VCC file.

``.vcc`` files of VMODs are now installed to
``/usr/share/varnish/vcc`` (or equivalent) to enable re-use by other
tools like code editors.

API Changes

The varnishapi version has been increased to 3.1 and the VSHA256_*, VENC_Encode_Base64() and VENC_Decode_Base64() functions are now exposed.

In struct vsmwseg and struct vsm_fantom, the class member has been renamed to category.

The VSB_quote_pfx() (and, consequently, VSB_quote()) function no longer produces \v for a vertical tab. This improves compatibility with JSON.

Additions to varnish C header files


The ``PTOK()`` macro has been added to ``vas.h`` to simplify error
checking of ``pthread_*`` POSIX functions.

The ``v_cold`` macro has been added to add ``__attribute__((cold))``
on compilers supporting it. It is used for ``VRT_fail()`` to mark
failure code paths as cold.

The utility macros ``ALLOC_OBJ_EXTRA()`` and ``ALLOC_FLEX_OBJ()`` have
been added to ``miniobj.h`` to simplify allocation of objects larger
than a struct and such with a flexible array.

*eof*