✓ Request header ✓ Sent by client (~browser) ✓ Sent on every request ✓ Describes state ✓ Is not cached ✓ 3rd party tracking cookies vs own cookies About cookies Cookie: key=value;key2=value2
✓ Response header ✓ Sent by backend server ✓ Only when backend is called ✓ Changes state ✓ Is not cached ✓ Blacklisted for 120s (by default) About cookies Set-Cookie: key=another_value
$last_modified = $response->getLastModified(); if ($last_modified) { // See if the client has provided the required HTTP headers. $if_modified_since = $request->server->has('HTTP_IF_MODIFIED_SINCE') ? strtotime($request->server- >get('HTTP_IF_MODIFIED_SINCE')) : FALSE; $if_none_match = $request->server->has('HTTP_IF_NONE_MATCH') ? stripslashes($request->server- >get('HTTP_IF_NONE_MATCH')) : FALSE; if ($if_modified_since && $if_none_match // etag must match. && $if_none_match == $response->getEtag() // if-modified-since must match. && $if_modified_since == $last_modified->getTimestamp()) { $response->setStatusCode(304); $response->setContent(NULL); // In the case of a 304 response, certain headers must be sent, and the // remaining may not (see RFC 2616, section 10.3.5). foreach (array_keys($response->headers->all()) as $name) { if (!in_array($name, ['content-location', 'expires', 'cache-control', 'vary'])) { $response->headers->remove($name); } } } } Drupal\page_cache\StackMiddleware\PageCache
✓vcl_recv: receive request ✓vcl_hash: compose cache key ✓vcl_miss: not found in cache ✓vcl_hit: found in cache ✓vcl_pass: don’t store in cache ✓vcl_pipe: bypass cache ✓vcl_backend_fetch: connect to backend ✓vcl_backend_response: response from backend ✓vcl_backend_error: backend fetch failed
✓ req: incoming request object ✓ req_top: top level esi request ✓ bereq: request object to send to backend ✓ beresp: backend response ✓ resp: response to send back to client ✓ obj: cached object ✓ client: client information ✓ server: server information ✓ local: local TCP information ✓ remote: remote TCP information ✓ storage: storage information VCL Objects
sub vcl_purge { return (synth(200, "Purged")); } sub vcl_hit { if (obj.ttl >= 0s) { return (deliver); } if (obj.ttl + obj.grace > 0s) { return (deliver); } return (miss); } sub vcl_miss { return (fetch); } sub vcl_deliver { return (deliver); } Remove from cache Found in cache Not found in cache Return HTTP response to client
sub vcl_recv { set req.http.Surrogate-Capability = "key=ESI/1.0"; } sub vcl_backend_response { if (beresp.http.Surrogate-Control ~ "ESI/1.0") { unset beresp.http.Surrogate-Control; set beresp.do_esi = true; } } Edge Side Includes
header("Cache-Control: public,must-revalidate,s-maxage=10"); echo "Date in the ESI tag: ".date('Y-m-d H:i:s').' '; header("Cache-Control: no-store"); header(“Surrogate-Control: content='ESI/1.0'"); echo ''.PHP_EOL; echo "Date in the main page: ".date('Y-m-d H:i:s').' '; Main page ESI frame: esi.php Cached for 10 seconds Not cached
✓ Server-side ✓ Standardized ✓ Processed on the “edge”, no in the browser ✓ Generally faster Edge-Side Includes - Sequential - One fails, all fail - Limited implementation in Varnish - Not that common
Banning curl -XPURGE "http://example.com/products" curl -XPURGE -H "x-purge-regex:/products" "http://example.com" Add to ban list, remove on next request Remove patterns via “X-PURGE-REGEX”
Ban lurker Object User Varnish Server Sends HTTP response Response stored in object Sends BAN to Varnish Ban lurker thread Ban list Reads ban list Removes object ban req.http.host == localhost && req.url ~ /products
Ban lurker ban req.http.host == localhost && req.url ~ /products Lurker can’t match request info Lurker can only match what’s in the object Next visitor triggers cache remove
Lurker-friendly bans ban obj.http.x-host == localhost && obj.http.x-url ~ /products Lurker can match response info Ban lurker removes item from cache async
# Only allow BAN requests from IP addresses in the 'purge' ACL. if (req.method == "BAN") { # Same ACL check as above: if (!client.ip ~ purge) { return (synth(403, "Not allowed.")); } if (req.http.Purge-Cache-Tags) { ban("obj.http.Purge-Cache-Tags ~ " + req.http.Purge-Cache-Tags); } else { return (synth(403, "Purge-Cache-Tags header missing.")); } # Throw a synthetic page so the request won't go to the backend. return (synth(200, "Ban added.")); }
usage: varnishstat [-1lV] [-f field] [-t seconds|] [-n varnish_name] [-N filename] -1 # Print the statistics to stdout. -f field # Field inclusion glob # If it starts with '^' it is used as an exclusion list. -l # Lists the available fields to use with the -f option. -n varnish_name # The varnishd instance to get logs from. -N filename # Filename of a stale VSM instance. -t seconds| # Timeout before returning error on initial VSM connection. -V # Display the version number and exit. -x # Print statistics to stdout as XML. -j # Print statistics to stdout as JSON. Varnishstat usage
-- RFC 500 10 -1 1501598872 1501598869 1501598872 0 500 ✓ Don’t screw with the age header ✓ Only 497 second effective TTL ✓ Custom Age header (3 seconds off)
%s: %f %f %f | | | | | | | +- Time since last timestamp | | +---- Time since start of work unit | +------- Absolute time of event +----------- Event label Timestamp tag
✓ All response headers ✓ All tags that start with “Req” ✓ Exclude “x-“ response headers ✓ Include “response time” timestamp ✓ Exclude request protocol log lines, and the request accountancy log lines All-in-one
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