r"
^(?P<timestamp>\d{4}/\d{2}/\d{2}\ \d{2}:\d{2}:\d{2})
\ \[(?P<severity>emerg|alert|crit|error|warn|notice|info)\]
\ (?P<process_id>\d+)
\#(?P<thread_id>\d+):
\ \*(?P<connection_id>\d+)
\ (?P<error>.+?)
(?:\ while\ (?P<context>.+?))?
,\ client:\ (?P<client_ip>\d+\.\d+\.\d+\.\d+)
,\ server:\ (?P<server>.+?)
(?:,\ request:\ \"(?P<request_method>[A-Z]+?)
\ (?P<request_path>\/.+?)
\ (?P<request_protocol>.+?)\")?
(?:,\ upstream:\ \"(?P<upstream>.+?)\")?
(?:,\ host:\ \"(?P<host>.+?)\")?
(?:,\ referrer:\ \"(?P<referrer>.+?)\")?
$
"
xs