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# 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_hit` counts the number of times an existing connection pool was

    found while creating a backend.

- `VCP.ref_miss` counts the number of times an existing connection pool was

    not 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.

## Changes for developers and VMOD authors

hdr_t type is now a structured type but keeps the same memory layout as before.

`VRT_VSC_Alloc()` was renamed to `VRT_VSC_Allocv()` and a new version of `VRT_VSC_Alloc()` that takes a `va_list` argument was reintroduced. This makes it consistent with our naming conventions.

vmod authors can now specify C names for function/method arguments like follows:

> [BOOL bool:boolean]

This is useful to avoid name clashes with keywords reserved by the language.

`struct strands` and `struct vrt_blob` have become mini objects.

The `vcountof()` utility macro has been added to `vdef.h`

eof