DNS Propagation Latency Benchmark

DNS propagation latency is the amount of time required for a DNS change to be 
pushed to the authoritative DNS servers for a zone. This benchmark repository
measures DNS latency using any number of compute resources. To do so, the 
compute resources query authoritative DNS servers for a runtime defined zone
update. Once the zone update is detected, the runtime will be captured and 
returned as the propagation latency. For accurate metrics, this benchmark 
should be scheduled to execute precisely when the DNS changes will be submitted
to the provider. This benchmark requires dig and php be installed on compute 
resources where it is installed.

RUNTIME PARAMETERS:
* answer:    (REQUIRED) Expected response to the question (e.g. answer=4.5.6.7)
* debug:     (1|0) - whether or not to enable debug statements in the iteration
             output logs (default is off)
* multiple:  (1|0) - whether to require a valid answer from all DNS servers or
             a single server. Default behavior is multiple=0, meaning latency 
             will be captured for the first server that responds correctly.
             If multiple=1, multiple latency measurements will be captured, 
             for each server - and test execution will continue until all 
             servers have responded
* options    other dig query options (e.g. -p "options=+notcp +time=10")
* question:  (REQUIRED) DNS record to query (e.g. question=www) - do not
             include the zone in the question
* servers:   Comma separated list of DNS servers that should be queried... if 
             not specified, the authoritative servers for 'zone' will be
						 assumed
* spacing:   The amount of time to wait in seconds between each query iteration
             (default spacing is 1 second)
* zone:      (REQUIRED) The DNS zone (domain name) being tested

METRIC:
* latency:   DNS propagation latency metric(s) - multiple metrics may be 
             returned if multiple=1 and multiple authoritative servers are
             assigned to the zone (or explicitly specified using the 'servers'
             runtime parameter). Latency is measured in seconds with 4 decimal
             places
* [server]:  latency metrics for individual servers. If multiple=1, multiple
             metrics will be returned, one for each server, otherwise, only 1 
             such metric will be returned associated with the server that first 
             responded with a correct answer


The output of this benchmark varies depending on the 'multiple' parameter value:

EXAMPLE [multiple=0]:
latency=31.4529
ns=ns-1607.awsdns-08.co.uk

EXAMPLE [multiple=1]:
latency1=31.4529
ns1=ns-1607.awsdns-08.co.uk
latency2=36.4397
ns2=ns-266.awsdns-33.com
latency3=23.8576
ns3=ns-1195.awsdns-21.org