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VMOD dyncounters - Varnish dynamic counters module

Author: Emmanuel Hocdet
Date: 2020-04-17
Version: 0.1
Support Varnish Version:6.2.x 6.3.x 6.4.x

DESCRIPTION

vmod_dyncounters enables custom counters in a dynamic manner. Dynamic counters can persist between VCL loads. This module is designed to support many dynamic counters: you must take care of cardinality and VSM memory.

vcl sample:

import dyncounters;

sub vcl_init {
    new TEST = dyncounters.head();
}
sub vcl_recv {
    TEST.incr(req.method, "suffix", 1);
}

varnishstat -1 -f "TEST*":

TEST.GET.suffix              1         0.00
TEST.HEAD.suffix             2         0.00

vcl sample:

import dyncounters;
import proxy;

sub vcl_init {
    new SSL = dyncounters.head();
    SSL.doc("req", format=integer, type=counter, level=info, oneliner="requests");
}
sub vcl_recv {
    if (proxy.is_ssl()) {
       SSL.incr(proxy.ssl_version() + ":" + proxy.ssl_cipher() + ":" + req.proto, "req", 1);
    }
}

varnishstat -1 -f "SSL*":

SSL.TLSv1.2:ECDHE-ECDSA-AES256-GCM-SHA384:HTTP/1.1.req            7         0.00 requests
SSL.TLSv1.2:ECDHE-ECDSA-AES128-GCM-SHA256:HTTP/1.1.req            1         0.00 requests
SSL.TLSv1.3:TLS_AES_128_GCM_SHA256:HTTP/1.1.req                   6         0.00 requests

new xhead = dyncounters.head()

Description
Create a head of dynamic counters. The object name is the prefix of all counter names attached to the head. It appears as such in varnishstat, at the same level as MGT, MAIN, VBE, ... The head and its counters persist between VCLs as long as a VCL has vcl_init the object.
Example
new DYNC = dyncounters.head();

VOID xhead.doc(STRING suffix, ENUM format, ENUM type, ENUM level, STRING oneliner)

VOID xhead.doc(
      STRING suffix,
      ENUM {bitmap, bytes, duration, integer} format=integer,
      ENUM {bitmap, counter, gauge} type=counter,
      ENUM {info, debug, diag} level=info,
      STRING oneliner=""
)
Description

Create a documentation for all counters with suffix suffix attached to the object head. This documentation is unique and persist with object head: any re-declaration of suffix will be ignored.

suffix Counter suffix.

format Counter format.

type Counter type.

level Counter level.

oneliner Counter description.

Example
DYNC.doc("req", format=integer, type=counter, level=info, oneliner="requests");

VOID xhead.incr(STRING radical, STRING suffix, INT d)

Description
Increment value of counter "<head name>.<radical>.<suffix>" The counter is created on the fly if it does not exist. Documentation for "suffix" is created on the fly if it does not exist (with default values). Negative values are ignored.
Example
DYNC.incr(req.method, "req", 1);

VOID xhead.decr(STRING radical, STRING suffix, INT d)

Description
Decrement value of counter "<head name>.<radical>.<suffix>" The counter is created on the fly if it does not exist. Documentation for "suffix" is created on the fly if it does not exist (with default values). Negative values are ignored.
Example
DYNC.decr(req.method, "req", 1);

VOID xhead.set(STRING radical, STRING suffix, INT d)

Description
Set value of counter "<head name>.<radical>.<suffix>" The counter is created on the fly if it does not exist. Documentation for "suffix" is created on the fly if it does not exist (with default values). Negative values are ignored.
Example
DYNC.set(req.method, "req", 1);

Compilation

For other platforms you would use compilation.

The source tree is based on autotools to configure the building, and does also have the necessary bits in place to do functional unit tests using the varnishtest tool.

Building requires the Varnish header files and uses pkg-config to find the necessary paths.

Usage:

./autogen.sh
./configure

If you have installed Varnish to a non-standard directory, call autogen.sh and configure with PKG_CONFIG_PATH pointing to the appropriate path. For instance, when varnishd configure was called with --prefix=$PREFIX, use

export PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
export ACLOCAL_PATH=${PREFIX}/share/aclocal

The module will inherit its prefix from Varnish, unless you specify a different --prefix when running the configure script for this module.

Make targets:

  • make - builds the vmod.
  • make install - installs your vmod.
  • make check - runs the unit tests in src/tests/*.vtc.
  • make distcheck - run check and prepare a tarball of the vmod.

If you build a dist tarball, you don't need any of the autotools or pkg-config. You can build the module simply by running:

./configure
make

Installation directories

By default, the vmod configure script installs the built vmod in the directory relevant to the prefix. The vmod installation directory can be overridden by passing the vmoddir variable to make install.

COMMON PROBLEMS

  • configure: error: Need varnish.m4 -- see README.rst

    Check whether PKG_CONFIG_PATH and ACLOCAL_PATH were set correctly before calling autogen.sh and configure

  • Incompatibilities with different Varnish Cache versions

    Make sure you build this vmod against its correspondent Varnish Cache version. For instance, to build against Varnish Cache 4.1, this vmod must be built from branch 4.1.

  • Require GCC

    This vmod using GCC Atomic builtins.

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