Changes in Varnish 7.3¶
For information about updating your current Varnish deployment to the new version, see Upgrading to Varnish 7.3.
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¶
XXX changes in -p parameters
There is a new parameter transit_buffer disabled by default to limit the
amount of storage used for uncacheable responses. This is useful in situations
where slow clients may consume large but uncacheable objects, to prevent them
from filling up storage too fast at the expense of cacheable resources. When
transit buffer is enabled, a client request will effectively hold its backend
connection open until the client response delivery completes.
ESI processing changes¶
Response status codes other than 200 and 204 are now considered errors for ESI fragments.
Previously, any ESI:include object would be included, no matter what
the status of it were, 200, 503, didn’t matter.
From now on, by default, only objects with 200 and 204 status will be included and any other status code will fail the parent ESI request.
If objects with other status should be delivered, they should have
their status changed to 200 in VCL, for instance in sub
vcl_backend_error{}, vcl_synth{} or vcl_deliver{}.
If param.set feature +esi_include_onerror is used, and the
<esi:include …> tag has a onerror="continue" attribute, any
and all ESI:include objects will be delivered, no matter what their
status might be, and not even a partial delivery of them will fail the
parent ESI request. To be used with great caution.
Other changes in varnishd¶
In addition to classic Unix-domain sockets, Varnish now supports
abstract sockets. If the operating system supports them, as does any
fairly recent Linux kernel, abstract sockets can be specified using
the commonplace @ notation for accept sockets, e.g.:
varnishd -a @kandinsky
Weak Last-Modified headers whose timestamp lies within one second
of the corresponding Date header are no longer candidates for
revalidation. This means that a subsequent fetch will not, when a
stale object is available, include an If-Modified-Since header. A
weak Last-Modified header does not prevent Etag revalidation.
A cache hit on an object being streamed no longer prevents delivery of partial responses (status code 206) to range requests.
Changes to VCL¶
VCL variables¶
XXX new, deprecated or removed variables, or changed semantics
The variables req.xid, bereq.xid and sess.xid are now integers
instead of strings, but should remain usable without a VCL change in a string
context.
Transit buffer can be controlled per fetch with the beresp.transit_buffer
variable.
Other changes to VCL¶
Backends have a new .via attribute optionally referencing another backend:
backend detour {
.host = "...";
}
backend destination {
.host = "...";
.via = detour;
}
Attempting a connection for destination connects to detour with a
PROXYv2 protocol header targeting destination’s address. Optionally, the
destination backend could use the other new .authority attribute to
define an authority TLV in the PROXYv2 header.
Backends can connect to abstract sockets on linux:
backend miro {
.path = "@miro";
}
This is the same syntax as the varnishd -a command line option.
Probes have a new .expect_close attribute defaulting to true, matching
the current behavior. Setting it to false will defer final checks until
after the probe times out.
VMODs¶
XXX changes in the bundled VMODs
varnishlog¶
XXX changes concerning varnishlog(1) and/or vsl(7)
The in-memory and on-disk format of VSL records changed to allow 64bit VXID numbers. The new binary format is not compatible with previous versions, and log dumps performed with a previous Varnish release are no longer readable from now on. Consequently, unused log tags have been removed.
The VXID range is limited to VRT_INTEGER to fit in VCL the variables
req.xid, bereq.xid and sess.xid.
A ReqStart record is emitted for bad requests, allowing varnishncsa to
find the client IP address.
varnishadm¶
XXX changes concerning varnishadm(1) and/or varnish-cli(7)
The debug.xid command generally used by varnishtest now sets
up the next VXID directly.
varnishstat¶
XXX changes concerning varnishstat(1) and/or varnish-counters(7)
varnishtest¶
XXX changes concerning varnishtest(1) and/or vtc(7)
It is now possible to send special keys NPAGE, PPAGE, HOME and END to a process.
The -nolen option is implied for txreq and txresp when either
Content-Length or Transfer-Encoding headers are present.
A new stream.peer_window variable similar to stream.window is
available for HTTP/2 checks.