Upgrading to Varnish 7.1


Varnish now has an infrastructure in place to rename parameters or VCL variables while keeping a deprecated alias for compatibility.


There are plans to rename certain arguments. When this happens, aliases will not be listed by param.show [-j|-l] commands, but they will be displayed by param.show [-j] <param>. Systems operating on top of varnishadm or the Varnish CLI can be updated to anticipate this change with the help of the deprecated_dummy parameter added for testing purposes.

The deprecated vsm_space parameter was removed. It was ignored and having no effect since Varnish 6.0.0 and should have disappeared with the 7.0.0 release. The sub-argument of the -l command line option that was used as a shorthand for vsm_space is also no longer accepted.

Command line options

A common pattern when a CLI script is used during startup is to combine the -I and -f '' options to prevent an automatic startup of the cache process. In this case a start command is usually present in the CLI script, most likely as the last command. This enables loading VCLs and potentially VCL labels which require a specific order if the active VCL is supposed to switch execution to labels.

To support this pattern, a VCL loaded through the CLI script is no longer implicitly used if there is no active VCL yet. If no VCL was loaded through the -b or -f options it means that an explicit vcl.use command is needed before the start command.

In the scenario described above, that would already be the case since the desired active VCL would likely need to be loaded last, not eligible for an implicit vcl.use since dependencies were loaded first. This change should not affect existing -I scripts, but if it does, simply add the missing vcl.use command.

Other changes in varnishd

The ESI parser now recognizes the onerror="continue" attribute of the <esi:include/> XML tag.

The +esi_include_onerror feature flag controls if the attribute is honored: If enabled, failure of an include stops ESI processing unless the onerror="continue" attribute was set for it.

The feature flag is off by default, preserving the existing behavior to continue ESI processing despite include failures.

Users of persistent storage engines be advised that objects created before the introduction of this change can not carry the onerror="continue" attribute and, consequently, will be handled as if it was not present if the +esi_include_onerror feature flag is enabled.

Also, as this change is not backwards compatible, downgrades with persisted storage are not supported across this release.


The deprecated err_shell command was removed, use shell -err instead.

Changes for developers and VMOD authors


Backends have reference counters now to avoid the uncertainty of a task holding onto a dynamic backend for a long time, for example in the waiting list, with the risk of the backend going away during the transaction.

Assignments should be replaced as such:

-lvalue = expr;
+VRT_Assign_Backend(&lvalue, expr);

For backends which are guaranteed at least VCL lifetime, the respective VMOD can opt out of reference counting with VRT_StaticDirector() to avoid the reference counting overhead.


Two new functions VRT_AddFilter() and VRT_RemoveFilter() manage filters as VDP/VFP pairs. When used as pairs, the filters must have the same name, otherwise operating with only one fetch or delivery filter is fine.

Unlike its deprecated predecessors VRT_AddVFP() and VRT_AddVDP(), the new VRT_AddFilter() returns an error string. The VRT_RemoveVFP() and VRT_RemoveVDP() functions are also deprecated and kept for now as wrappers of VRT_RemoveFilter() without error handling.

VMOD deprecated aliases

A VMOD author can from now on rename a function or object method without immediately breaking compatibility by declaring the old name as an alias.

In the VMOD descriptor, it is possible to add the following stanza:

$Alias deprecated_function original_function


$Alias .deprecated_method objec.original_method

This is a good occasion to revisit unfortunate name choices in existing VMODs.

Platform Support


To make the selection of the main process deterministic for the kill mode, a PID file is now expected by default in the varnish service. In a setup where the service command for ExecStart is overridden, a -P option matching the PIDFile setting is needed.