allow to include previous skynet stats (#562)

* allow to include previous skynet stats

* explain chunked response

docker-compose.yml

@@ -72,6 +72,7 @@ services:
       - ./docker/nginx/conf.d:/etc/nginx/conf.d:ro
       - ./docker/data/nginx/cache:/data/nginx/cache
       - ./docker/data/nginx/logs:/usr/local/openresty/nginx/logs
+      - ./docker/data/nginx/skynet:/data/nginx/skynet:ro
       - ./docker/data/sia/apipassword:/data/sia/apipassword:ro
       - webapp:/var/www/webportal:ro
     networks:

docker/nginx/conf.d/client.conf

@@ -105,6 +105,33 @@ server {
 	location /skynet/stats {
 		include /etc/nginx/conf.d/include/cors;
 
+		set $response_body ''; # we need a variable for full response body (not chuncked)
+
+		# modify the response to add numfiles and totalsize to account for node rotation
+		# example prevstats.lua: 'return { numfiles = 12345, totalsize = 123456789 }'
+		body_filter_by_lua_block {
+			local file_exists = io.open("/data/nginx/skynet/prevstats.lua")
+			if file_exists then
+				file_exists.close()
+				
+				-- because response data is chunked, we need to concat ngx.arg[1] until
+				-- last chunk is received (when ngx.arg[2] is set to true)
+				ngx.var.response_body = ngx.var.response_body .. ngx.arg[1]
+				
+				if ngx.arg[2] then
+					local json = require('cjson')
+					local prevstats = require('/data/nginx/skynet/prevstats')
+					local stats = json.decode(ngx.var.response_body)
+					stats.uploadstats.numfiles = stats.uploadstats.numfiles + prevstats.numfiles
+					stats.uploadstats.totalsize = stats.uploadstats.totalsize + prevstats.totalsize
+					ngx.arg[1] = json.encode(stats)
+				else
+					-- do not send any data in this chunk (wait for last chunk)
+					ngx.arg[1] = nil
+				end
+			end
+		}
+
 		proxy_cache skynet;
 		proxy_cache_valid any 10m; # cache stats for 10 minutes
 		proxy_set_header User-Agent: Sia-Agent;