varnish-cli - Man Page

The Varnish CLI is similar to another command line interface, the Bourne Shell. Commands are usually terminated with a newline, and they may take arguments. The command and its arguments are tokenized before parsing, and as such arguments containing spaces must be enclosed in double quotes.

It means that command parsing of

help banner

is equivalent to

"help" banner

because the double quotes only indicate the boundaries of the help token.

Within double quotes you can escape characters with \ (backslash). The \n, \r, and \t get translated to newlines, carriage returns, an tabs.  Double quotes and backslashes themselves can be escaped with \" and \\ respectively.

To enter characters in octals use the \nnn syntax. Hexadecimals can be entered with the \xnn syntax.

Commands may not end with a newline when a shell-style here document (here-document or heredoc) is used. The format of a here document is:

<< word
     here document
word

word can be any continuous string chosen to make sure it doesn't appear naturally in the following here document. Traditionally EOF or END is used.

Integrating with the Varnish CLI can be sometimes surprising when quoting is involved. For instance in Bourne Shell the delimiter used with here documents may or may not be separated by spaces from the << token:

cat <<EOF
hello
world
EOF
hello
world

With the Varnish CLI, the << and EOF tokens must be separated by at least one blank:

vcl.inline boot <<EOF
106 258
Message from VCC-compiler:
VCL version declaration missing
Update your VCL to Version 4 syntax, and add
        vcl 4.0;
on the first line of the VCL files.
('<vcl.inline>' Line 1 Pos 1)
<<EOF
##---

Running VCC-compiler failed, exited with 2
VCL compilation failed

With the missing space, the here document can be added and the actual VCL can be loaded:

vcl.inline test << EOF
vcl 4.0;

backend be {
        .host = "localhost";
}
EOF
200 14
VCL compiled.

A big difference with a shell here document is the handling of the << token. Just like command names can be quoted, the here document token keeps its meaning, even quoted:

vcl.inline test "<<" EOF
vcl 4.0;

backend be {
        .host = "localhost";
}
EOF
200 14
VCL compiled.

When using a front-end to the Varnish-CLI like varnishadm, one must take into account the double expansion happening.  First in the shell launching the varnishadm command and then in the Varnish CLI itself. When a command's parameter require spaces, you need to ensure that the Varnish CLI will see the double quotes:

varnishadm param.set cc_command '"my alternate cc command"'

Change will take effect when VCL script is reloaded

Otherwise if you don't quote the quotes, you may get a seemingly unrelated error message:

varnishadm param.set cc_command "my alternate cc command"
Unknown request.
Type 'help' for more info.
Too many parameters

Command failed with error code 105

If you are quoting with a here document, you must wrap it inside a shell multi-line argument:

varnishadm vcl.inline test '<< EOF
vcl 4.0;

backend be {
        .host = "localhost";
}
EOF'
VCL compiled.

Another difference with a shell here document is that only one here document can be used on a single command line. For example, it is possible to do this in a shell script:

#!/bin/sh

cat << EOF1 ; cat << EOF2
hello
EOF1
world
EOF2

The expected output is:

hello
world

With the Varnish CLI, only the last parameter may use the here document form, which greatly restricts the number of commands that can effectively use them. Trying to use multiple here documents only takes the last one into account.

For example:

command argument << EOF1 << EOF2
heredoc1
EOF1
heredoc2
EOF2

This conceptually results in the following command line:

• "command"
• "argument"
• "<<"
• "EOF1"
• "heredoc1\nEOF1\nheredoc2\n"

Other pitfalls include variable expansion of the shell invoking varnishadm but this is not directly related to the Varnish CLI. If you get the quoting right you should be fine even with complex commands.

A number of commands with informational responses support a -j parameter for JSON output, as specified below. The top-level structure of the JSON response is an array with these first three elements:

• A version number for the JSON format (integer)
• An array of strings that comprise the CLI command just received
• The time at which the response was generated, as a Unix epoch time in seconds with millisecond precision (floating point)

The remaining elements of the array form the data that are specific to the CLI command, and their structure and content depend on the command.

For example, the response to status -j just contains a string in the top-level array indicating the state of the child process ("running", "stopped" and so forth):

[ 2, ["status", "-j"], 1538031732.632, "running"
]

The JSON responses to other commands may have longer lists of elements, which may have simple data types or form structured objects.

JSON output is only returned if command execution was successful. The output for an error response is always the same as it would have been for the command without the -j parameter.

A backend pattern can be a backend name or a combination of a VCL name and backend name in "VCL.backend" format.  If the VCL name is omitted, the active VCL is assumed.  Partial matching on the backend and VCL names is supported using shell-style wildcards, e.g. asterisk (*).

Examples:

backend.list def*
backend.list b*.def*
backend.set_health default sick
backend.set_health def* healthy
backend.set_health * auto

A ban expression consists of one or more conditions.  A condition consists of a field, an operator, and an argument.  Conditions can be ANDed together with "&&".

A field can be any of the variables from VCL, for instance req.url, req.http.host or obj.http.set-cookie.

Operators are "==" for direct comparison, "~" for a regular expression match, and ">" or "<" for size comparisons.  Prepending an operator with "!" negates the expression.

The argument could be a quoted string, a regexp, or an integer. Integers can have "KB", "MB", "GB" or "TB" appended for size related fields.

A VCL program goes through several states related to the different commands: it can be loaded, used, and later discarded. You can load several VCL programs and switch at any time from one to another. There is only one active VCL, but the previous active VCL will be maintained active until all its transactions are over.

Over time, if you often refresh your VCL and keep the previous versions around, resource consumption will increase, you can't escape that. However, most of the time you want to pay the price only for the active VCL and keep older VCLs in case you'd need to rollback to a previous version.

The VCL temperature allows you to minimize the footprint of inactive VCLs. Once a VCL becomes cold, Varnish will release all the resources that can be be later reacquired. You can manually set the temperature of a VCL or let varnish automatically handle it.