Merge branch 'fm/apt-rate-limit' into 'main'

http: use Retry-After HTTP header to optimize retries

See merge request apt-team/apt!383

2 files changed, 29 insertions, 1 deletions

diff --git a/methods/basehttp.cc b/methods/basehttp.cc
index 26b633cba..d335e6fa0 100644
--- a/methods/basehttp.cc
+++ b/methods/basehttp.cc
@@ -263,6 +263,21 @@ bool RequestState::HeaderLine(string const &Line)			/*{{{*/
       return true;
    }
 
+   if (stringcasecmp(Tag, "Retry-After:") == 0)
+   {
+      unsigned long _retry_after_s;
+      if (RFC1123StrToTime(Val, RetryAfter))
+      {
+	 return true;
+      }
+      if (StrToNum(Val.c_str(), _retry_after_s, 4, 10) == 1)
+      {
+	 RetryAfter = time(nullptr) + _retry_after_s;
+	 return true;
+      }
+      return _error->Error(_("Unknown date format"));
+   }
+
    if (Server->RangesAllowed && stringcasecmp(Tag, "Via:") == 0)
    {
       auto const parts = VectorizeString(Val, ' ');
@@ -884,7 +899,19 @@ int BaseHttpMethod::Loop()
 	       599, // Network Connect Timeout Error
 	    };
 	    if (std::find(std::begin(TransientCodes), std::end(TransientCodes), Req.Result) != std::end(TransientCodes))
-	       Fail(true);
+	    {
+	       if (Req.RetryAfter)
+	       {
+		  std::unordered_map<std::string, std::string> fields;
+		  fields["Retry-After"] = std::to_string(Req.RetryAfter);
+		  SetFailReason("TooManyRequests");
+		  FailWithContext(std::string("TooManyRequests"), true, fields);
+	       }
+	       else
+	       {
+		  Fail(true);
+	       }
+	    }
 	    else
 	       Fail();
 	    break;
diff --git a/methods/basehttp.h b/methods/basehttp.h
index 080ea527e..c077ea384 100644
--- a/methods/basehttp.h
+++ b/methods/basehttp.h
@@ -57,6 +57,7 @@ struct RequestState
    enum {Chunked,Stream,Closes} Encoding = Closes;
    enum {Header, Data} State = Header;
    std::string Location;
+   time_t RetryAfter = 0;
 
    FileFd File;