Implement support for HTTP 429 Too Many Requests (#7760)

* Implement support for HTTP 429 Too Many Requests
Will obey the corresponding HTTP `Retry-After` header at domain level.

* Implement 503 Service Unavailable

* Sanitize Retry-After

* Reduce default value when Retry-After is absent
And make configuration parameter

* Retry-After also for favicons

1 files changed, 6 insertions, 2 deletions

diff --git a/config.default.php b/config.default.php
index 0707b9f87..f42fdc215 100644
--- a/config.default.php
+++ b/config.default.php
@@ -103,10 +103,14 @@ return [
 		# Especially important for multi-user setups.
 		# Might be overridden by HTTP response headers.
 		'cache_duration' => 800,
-		# Minimal cache duration (in seconds), overriding HTTP response headers `Cache-Control` and `Expires`,
+		# Minimal cache duration (in seconds), overriding HTTP response headers `Cache-Control` and `Expires`.
 		'cache_duration_min' => 60,
-		# Maximal cache duration (in seconds), overriding HTTP response headers `Cache-Control` and `Expires`,
+		# Maximal cache duration (in seconds), overriding HTTP response headers `Cache-Control` and `Expires`.
 		'cache_duration_max' => 86400,
+		# Default rate limit duration (in seconds), when HTTP response header `Retry-After` is absent.
+		'retry_after_default' => 1500,
+		# Maximal rate limit duration (in seconds), overriding HTTP response header `Retry-After`.
+		'retry_after_max' => 172800,
 
 		# SimplePie HTTP request timeout in seconds.
 		'timeout' => 20,