add pattern for cloudfront access log

Fixes logstash-plugins#167

patterns/aws

@@ -9,3 +9,6 @@ ELB_URI %{URIPROTO:proto}://(?:%{USER}(?::[^@]*)?@)?(?:%{URIHOST:urihost})?(?:%{
 ELB_REQUEST_LINE (?:%{WORD:verb} %{ELB_URI:request}(?: HTTP/%{NUMBER:httpversion})?|%{DATA:rawrequest})
 
 ELB_ACCESS_LOG %{TIMESTAMP_ISO8601:timestamp} %{NOTSPACE:elb} %{IP:clientip}:%{INT:clientport:int} (?:(%{IP:backendip}:?:%{INT:backendport:int})|-) %{NUMBER:request_processing_time:float} %{NUMBER:backend_processing_time:float} %{NUMBER:response_processing_time:float} %{INT:response:int} %{INT:backend_response:int} %{INT:received_bytes:int} %{INT:bytes:int} "%{ELB_REQUEST_LINE}"
+
+CLOUDFRONT_ACCESS_LOG (?<timestamp>%{YEAR}-%{MONTHNUM}-%{MONTHDAY}\t%{TIME})\t%{WORD:x_edge_location}\t(?:%{NUMBER:sc_bytes:int}|-)\t%{IPORHOST:clientip}\t%{WORD:cs_method}\t%{HOSTNAME:cs_host}\t%{NOTSPACE:cs_uri_stem}\t%{NUMBER:sc_status:int}\t%{GREEDYDATA:referrer}\t%{GREEDYDATA:agent}\t%{GREEDYDATA:cs_uri_stem}\t%{GREEDYDATA:cookies}\t%{WORD:x_edge_result_type}\t%{NOTSPACE:x_edge_request_id}\t%{HOSTNAME:x_host_header}\t%{URIPROTO:cs_protocol}\t%{INT:cs_bytes:int}\t%{GREEDYDATA:time_taken:float}\t%{GREEDYDATA:x_forwarded_for}\t%{GREEDYDATA:ssl_protocol}\t%{GREEDYDATA:ssl_cipher}\t%{GREEDYDATA:x_edge_response_result_type}
+