Make log format json escaping configurable

This will allow json logging in nginx ingress controllers which greatly
improves ease of log indexing and searching via elasticsearch.

After this change is made, users could set the following property in the
ingress configmap to enable json logging:

log-format-upstream: '{"proxy_protocol_addr": "$proxy_protocol_addr", "proxy_add_x_forwarded_for": "$proxy_add_x_forwarded_for", "remote_user": "$remote_user", "time_iso8601": "$time_iso8601", "request": "$request", "status": "$status", "body_bytes_sent": "$body_bytes_sent", "http_referer": "$http_referer", "http_user_agent": "$http_user_agent", "request_length": "$request_length", "request_time": "$request_time", "proxy_upstream_name": "$proxy_upstream_name", "upstream_addr": "$upstream_addr", "upstream_response_length": "$upstream_response_length", "upstream_response_time": "$upstream_response_time", "upstream_status": "$upstream_status"}'

controllers/nginx/pkg/config/config.go

@@ -175,6 +175,10 @@ type Configuration struct {
 	// Default: 4 8k
 	LargeClientHeaderBuffers string `json:"large-client-header-buffers"`
 
+	// Enable json escaping
+	// http://nginx.org/en/docs/http/ngx_http_log_module.html#log_format
+	LogFormatEscapeJson bool `json:"log-format-escape-json,omitempty"`
+
 	// Customize upstream log_format
 	// http://nginx.org/en/docs/http/ngx_http_log_module.html#log_format
 	LogFormatUpstream string `json:"log-format-upstream,omitempty"`
@@ -311,6 +315,7 @@ func NewDefault() Configuration {
 		KeepAlive:                75,
 		KeepAliveRequests:        100,
 		LargeClientHeaderBuffers: "4 8k",
+		LogFormatEscapeJson:      false,
 		LogFormatStream:          logFormatStream,
 		LogFormatUpstream:        logFormatUpstream,
 		MaxWorkerConnections:     16384,

controllers/nginx/rootfs/etc/nginx/template/nginx.tmpl

@@ -93,7 +93,7 @@ http {
     # disable warnings
     uninitialized_variable_warn off;
 
-    log_format upstreaminfo '{{ buildLogFormatUpstream $cfg }}';
+    log_format upstreaminfo {{ if $cfg.LogFormatEscapeJson }}escape=json {{ end }}'{{ buildLogFormatUpstream $cfg }}';
 
     {{/* map urls that should not appear in access.log */}}
     {{/* http://nginx.org/en/docs/http/ngx_http_log_module.html#access_log */}}