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[VCL Logging Abstraction] vcl abstraction around logging to make calls cleaner

View original Gist on GitHub

Tags: #tags: vcl, varnish, logging

1. 2019 approach.vcl

# log_it.vcl
sub log_it {
  log {"syslog <service_id> <service_name> :: "} req.http.X-MutableThing;
}

# vcl_recv
import "log_it"
set req.http.X-MutableThing = "foo"
call log_it;
set req.http.X-MutableThing = "bar"
call log_it;

logging-updated.vcl

declare local var.stage_id STRING;
declare local var.prod_id STRING;
declare local var.common STRING;
declare local var.debug_logs_active BOOL;
declare local var.defaults STRING;
declare local var.debug STRING;

# DO NOT add a space in front of "syslog"
# " syslog ..." will break the logging

set var.stage_id = "123";
set var.prod_id = "456";
set var.common = " :: " req.http.Fastly-Client-IP " '-' '-' " now " " req.request " " req.url " ";
set var.debug_logs_active = false;

if (req.service_id == var.stage_id) {
  set var.defaults = "syslog " var.stage_id " www-stage-fastly" var.common;
}
elsif (req.service_id == var.prod_id) {
  set var.defaults = "syslog " var.prod_id " fastly-www" var.common;
}
else {
  set var.defaults = ""; # no-op if an unidentified service
}
set var.debug = if (var.debug_logs_active, var.defaults, "");

logging.vcl

declare local var.logs_active BOOL;
declare local var.defaults STRING;

# Note: DO NOT add a space in front of "syslog"
#       e.g. " syslog ..." will break the logging

set var.logs_active = false;
set var.defaults = if (var.logs_active, "syslog <service_id> <endpoint> :: " req.http.Fastly-Client-IP " '-' '-' " now " " req.request " " req.url " ", "");

# some of the request variables used are specific to Fastly
# also the reference to <service_id> <endpoint> are specific to Fastly and Papertrail
# so your mileage may vary

main.vcl

sub vcl_recv {
#FASTLY recv
  include "logging"
  log var.defaults req.restarts " [main.vcl] X-FOO HEADER VALUE: " req.http.X-Foo;
}