Hi, We were previously receiving Error 503 in Varnish and then it has fixed after the fresh reinstall. But we are getting the same error again. I have observed that this appears when Ajax requests increase.
*http://.com/wp-admin/admin-ajax.php Failed to load resource: the server responded with a status of 503 (Backend fetch failed)* Is there an error in Default.vcl file? /* SET THE HOST AND PORT OF WORDPRESS * *********************************************************/ vcl 4.0; import std; backend default { .host = "******"; .port = "8080"; } # SET THE ALLOWED IP OF PURGE REQUESTS # ########################################################## acl purge { "localhost"; "127.0.0.1"; "******"; } #THE RECV FUNCTION # ########################################################## sub vcl_recv { if (req.http.Host == "***.com/forum" || req.url ~ "forum") { return (pass); } # set realIP by trimming CloudFlare IP which will be used for various checks set req.http.X-Actual-IP = regsub(req.http.X-Forwarded-For, "[, ].*$", ""); # FORWARD THE IP OF THE REQUEST if (req.restarts == 0) { if (req.http.x-forwarded-for) { set req.http.X-Forwarded-For = req.http.X-Forwarded-For + ", " + client.ip; } else { set req.http.X-Forwarded-For = client.ip; } } # Purge request check sections for hash_always_miss, purge and ban # BLOCK IF NOT IP is not in purge acl # ########################################################## # Enable smart refreshing using hash_always_miss if (req.http.Cache-Control ~ "no-cache") { if (client.ip ~ purge || !std.ip(req.http.X-Actual-IP, "1.2.3.4") ~ purge) { set req.hash_always_miss = true; } } if (req.method == "PURGE") { if (!client.ip ~ purge || !std.ip(req.http.X-Actual-IP, "1.2.3.4") ~ purge) { return(synth(405,"Not allowed.")); } return (purge); } if (req.method == "BAN") { # Same ACL check as above: if (!client.ip ~ purge || !std.ip(req.http.X-Actual-IP, "1.2.3.4") ~ purge) { return(synth(403, "Not allowed.")); } ban("req.http.host == " + req.http.host + " && req.url == " + req.url); # Throw a synthetic page so the # request won't go to the backend. return(synth(200, "Ban added")); } # Unset cloudflare cookies # Remove has_js and CloudFlare/Google Analytics __* cookies. set req.http.Cookie = regsuball(req.http.Cookie, "(^|;\s*)(_[_a-z]+|has_js)=[^;]*", ""); # Remove a ";" prefix, if present. set req.http.Cookie = regsub(req.http.Cookie, "^;\s*", ""); # For Testing: If you want to test with Varnish passing (not caching) uncomment # return( pass ); # DO NOT CACHE RSS FEED if (req.url ~ "/feed(/)?") { return ( pass ); } ## Do not cache search results, comment these 3 lines if you do want to cache them if (req.url ~ "/\?s\=") { return ( pass ); } # CLEAN UP THE ENCODING HEADER. # SET TO GZIP, DEFLATE, OR REMOVE ENTIRELY. WITH VARY ACCEPT-ENCODING # VARNISH WILL CREATE SEPARATE CACHES FOR EACH # DO NOT ACCEPT-ENCODING IMAGES, ZIPPED FILES, AUDIO, ETC. # ########################################################## if (req.http.Accept-Encoding) { if (req.url ~ "\.(jpg|png|gif|gz|tgz|bz2|tbz|mp3|ogg)$") { # No point in compressing these unset req.http.Accept-Encoding; } elsif (req.http.Accept-Encoding ~ "gzip") { set req.http.Accept-Encoding = "gzip"; } elsif (req.http.Accept-Encoding ~ "deflate") { set req.http.Accept-Encoding = "deflate"; } else { # unknown algorithm unset req.http.Accept-Encoding; } } # PIPE ALL NON-STANDARD REQUESTS # ########################################################## if (req.method != "GET" && req.method != "HEAD" && req.method != "PUT" && req.method != "POST" && req.method != "TRACE" && req.method != "OPTIONS" && req.method != "DELETE") { return (pipe); } # ONLY CACHE GET AND HEAD REQUESTS # ########################################################## if (req.method != "GET" && req.method != "HEAD") { return (pass); } # OPTIONAL: DO NOT CACHE LOGGED IN USERS (THIS OCCURS IN FETCH TOO, EITHER # COMMENT OR UNCOMMENT BOTH # ########################################################## if ( req.http.cookie ~ "wordpress_logged_in" ) { return( pass ); } # IF THE REQUEST IS NOT FOR A PREVIEW, WP-ADMIN OR WP-LOGIN # THEN UNSET THE COOKIES # ########################################################## if (!(req.url ~ "wp-(login|admin)") && !(req.url ~ "&preview=true" ) ){ unset req.http.cookie; } # IF BASIC AUTH IS ON THEN DO NOT CACHE # ########################################################## if (req.http.Authorization || req.http.Cookie) { return (pass); } # IF YOU GET HERE THEN THIS REQUEST SHOULD BE CACHED # ########################################################## return (hash); # This is for phpmyadmin if (req.http.Host == "ki1.org") { return (pass); } if (req.http.Host == "mysql.ki1.org") { return (pass); } } # HIT FUNCTION # ########################################################## sub vcl_hit { # IF THIS IS A PURGE REQUEST THEN DO THE PURGE # ########################################################## if (req.method == "PURGE") { # # This is now handled in vcl_recv. # # purge; return (synth(200, "Purged.")); } return (deliver); } # MISS FUNCTION # ########################################################## sub vcl_miss { if (req.method == "PURGE") { # # This is now handled in vcl_recv. # # purge; return (synth(200, "Purged.")); } return (fetch); } # FETCH FUNCTION # ########################################################## sub vcl_backend_response { # I SET THE VARY TO ACCEPT-ENCODING, THIS OVERRIDES W3TC # TENDANCY TO SET VARY USER-AGENT. YOU MAY OR MAY NOT WANT # TO DO THIS # ########################################################## set beresp.http.Vary = "Accept-Encoding"; # IF NOT WP-ADMIN THEN UNSET COOKIES AND SET THE AMOUNT OF # TIME THIS PAGE WILL STAY CACHED (TTL) # ########################################################## if (!(bereq.url ~ "wp-(login|admin)|forum") && !bereq.http.cookie ~ "wordpress_logged_in" && !bereq.http.host == "***.com/forum" ) { unset beresp.http.set-cookie; set beresp.ttl = 52w; # set beresp.grace =1w; } if (beresp.ttl <= 0s || beresp.http.Set-Cookie || beresp.http.Vary == "*") { set beresp.ttl = 120 s; # set beresp.ttl = 120s; set beresp.uncacheable = true; return (deliver); } return (deliver); } # DELIVER FUNCTION # ########################################################## sub vcl_deliver { # IF THIS PAGE IS ALREADY CACHED THEN RETURN A 'HIT' TEXT # IN THE HEADER (GREAT FOR DEBUGGING) # ########################################################## if (obj.hits > 0) { set resp.http.X-Cache = "HIT"; # IF THIS IS A MISS RETURN THAT IN THE HEADER # ########################################################## } else { set resp.http.X-Cache = "MISS"; } }
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