Varnish vmod for creating a uuid
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Latest commit f303842 Jul 16, 2015 @mbroome mbroome Merge branch 'varnish-4.x'

README.rst

vmod_uuid

Varnish UUID Module

Author: Mitchell Broome, Geoff Simmons
Date: 2014-12-11
Version: 1.0
Manual section:3

SYNOPSIS

import uuid;

DESCRIPTION

UUID Varnish vmod used to generate a uuid, including versions 1, 3, 4 and 5 as specified in RFC 4122. See the RFC for details about the various versions.

FUNCTIONS

uuid

Prototype
uuid()
Return value
STRING
Description
Returns a uuid version 1 (based on MAC address and the current time)
UUID
set req.http.X-Flow-ID = "cache-" + uuid.uuid();

uuid_v1

Prototype
uuid_v1()
Return value
STRING
Description
Returns a uuid version 1. The functions uuid() and uuid_v1() are aliases for one another.
Example
set req.http.X-Flow-ID = "cache-" + uuid.uuid_v1();

uuid_v3

Prototype
uuid_v3(STRING namespace, STRING name)
Return value
STRING
Description
Returns a uuid version 3, based on an MD5 hash formed from namespace and name. The namespace argument MUST be one of the following:
  • "nil" (for the "nil UUID")
  • "ns:DNS" (for the domain name system)
  • "ns:URL" (for the URL namespace)
  • "ns:OID" (for the ISO object identifier namespace)
  • "ns:X500" (for X.500 distinguished names)
  • a valid 36-character representation of a UUID, i.e. a string of the form "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", where all of the x's are hex digits, with appropriate restrictions on UUID formats (cf. the RFC)

If these conditions are not met, then uuid_v3() fails; it returns a null string (typically, the header specified in VCL will not be set), and an error message is emitted to the Varnish log with the tag VCL_error.

The name argument can be any string.

Example
set req.http.X-DNS-ID = uuid.uuid_v3("ns:DNS", "www.widgets.com");
set req.http.X-MyNS-ID = uuid.uuid_v3("6ba7b810-9dad-11d1-80b4-00c04fd430c8", "www.widgets.com");

uuid_v4

Prototype
uuid_v4()
Return value
STRING
Description
Returns a uuid version 4, based on random numbers.
Example
set req.http.X-Rand-ID = uuid.uuid_v4();

uuid_v5

Prototype
uuid_v5(STRING namespace, STRING name)
Return value
STRING
Description
Returns a uuid version 5, based on a SHA1 hash formed from namespace and name. The same restrictions and failure conditions regarding the namespace argument hold as for uuid_v3() above. The name argument can be any string.
Example
set req.http.X-DNS-ID = uuid.uuid_v5("ns:DNS", "www.widgets.com");
set req.http.X-MyNS-ID = uuid.uuid_v5("6ba7b810-9dad-11d1-80b4-00c04fd430c8", "www.widgets.com");

DEPENDENCIES

Libvmod-uuid requires the OSSP uuid library to generate uuids. It is available at http://www.ossp.org/pkg/lib/uuid/ or possibly as a prepackaged library from your linux distribution.

In the case of Redhat/Fedora/CentOS, the rpm is named uuid. Ensure you install the rpms with the following command:

yum install -y uuid uuid-devel

INSTALLATION

The installation process is standard for a Varnish 4 VMOD -- build the VMOD on a system where an instance of Varnish 4 is installed, and the auto-tools will attempt to locate the Varnish instance, and then pull in libraries and other support files from there.

Quick start

This sequence should be enough in typical setups:

  1. ./autogen.sh (for git-installation)
  2. ./configure
  3. make
  4. make check (regression tests)
  5. make install (may require root: sudo make install)

In your VCL you could then use this vmod along the following lines:

import uuid;

sub vcl_recv {
        # This sets req.http.X-Flow-ID to "cache-uuid"
        set req.http.X-Flow-ID = "cache-" + uuid.uuid();
}

Alternative configs

As with Varnish itself, you can set additional flags and macros in the configure step, and/or define environment variables to affect the build config.

For example, if you are building the VMOD against a Varnish instance with a non-standard installation prefix, then set these env variables before running configure:

  • PREFIX=/path/to/varnish/install/prefix
  • export PKG_CONFIG_PATH=$PREFIX/lib/pkgconfig
  • export ACLOCAL_PATH=$PREFIX/share/aclocal
  • export PATH=$PREFIX/bin:$PREFIX/sbin:$PATH

configure must locate the varnishtest and varnishd binaries so that make check can be run. Usually it should be able to find them, but if necessary you can set the variables VARNISHTEST and/or VARNISHD with the full paths.

For developers

As with Varnish, you can use these configure options for stricter compiling:

  • --enable-developer-warnings
  • --enable-extra-developer-warnings (for GCC 4)
  • --enable-werror

The VMOD must always build successfully with these options enabled.

Also as with Varnish, you can add --enable-debugging-symbols, so that the VMOD's symbols are available to debuggers, in core dumps and so forth.

HISTORY

COPYRIGHT

This document is licensed under the same license as the libvmod-uuid project. See LICENSE for details.