As for the log format, a specific and relatively compact JSON format is required. The following config can be made available globally in the http {} block:
log_format postgres_bridge_json escape=json '{'
'"hostname":"$hostname",'
'"ts":"$msec",'
'"server":{'
'"name":"$server_name",'
'"port":"$server_port"'
'},"client":{'
'"addr":"$remote_addr",'
'"forwarded_for":"$http_x_forwarded_for",'
'"referer":"$http_referer",'
'"ua":"$http_user_agent"'
'},"req":{'
'"host":"$host",'
'"length":"$request_length",'
'"method":"$request_method",'
'"proto":"$server_protocol",'
'"scheme":"$scheme",'
'"uri":"$request_uri"'
'},"res":{'
'"body_length":"$body_bytes_sent",'
'"duration":"$request_time",'
'"length":"$bytes_sent",'
'"status":"$status"'
'},"upstream":{'
'"addr":"$upstream_addr",'
'"bytes_received":"$upstream_bytes_received",'
'"bytes_sent":"$upstream_bytes_sent",'
'"cache_status":"$upstream_cache_status",'
'"connect_time":"$upstream_connect_time",'
'"host":"$proxy_host",'
'"response_length":"$upstream_response_length",'
'"response_time":"$upstream_response_time",'
'"status":"$upstream_status"'
'}'
'}';
To send access log entries, set the following, either globally in http {} or for a specific server {} block:
access_log syslog:server=nginx-syslog-bridge.example.com:514,nohostname postgres_bridge_json;