Reset rewrite counter on new request1651-fix-reset-rewrite-count

We were spuriously throwing rewrite limit exceeded for non-looping
rewrites. This patch resets the count to zero at the start of a new
request and adds a test.

COUCHDB-1651

5 files changed, 31 insertions, 10 deletions

diff --git a/CHANGES b/CHANGES
index 3012e3deb..743b30a7d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -72,6 +72,8 @@ UUID Algorithms:
 URL Rewriter & Vhosts:
 
   * Database name is encoded during rewriting (allowing embedded /'s, etc)
+  * Reset rewrite counter on new request, avoiding unnecessary request
+    failures due to bogus rewrite limit reports
 
 Log System:
 
diff --git a/share/www/script/test/rewrite.js b/share/www/script/test/rewrite.js
index ed7d26cb0..e88803291 100644
--- a/share/www/script/test/rewrite.js
+++ b/share/www/script/test/rewrite.js
@@ -464,6 +464,7 @@ couchTests.rewrite = function(debug) {
     };
     db.save(ddoc_loop);
 
+    // Assert loop detection
     run_on_modified_server(
       [{section: "httpd",
         key: "rewrite_limit",
@@ -471,7 +472,23 @@ couchTests.rewrite = function(debug) {
       function(){
         var url = "/"+dbName+"/_design/loop/_rewrite/loop";
         var xhr = CouchDB.request("GET", url);
-        T(xhr.status = 400);
+        TEquals(400, xhr.status);
+      });
+
+    // Assert serial execution is not spuriously counted as loop
+    run_on_modified_server(
+      [{section: "httpd",
+        key: "rewrite_limit",
+        value: "2"},
+       {section: "httpd",
+        key: "secure_rewrites",
+        value: "false"}],
+      function(){
+        var url = "/"+dbName+"/_design/test/_rewrite/foo";
+        for (var i=0; i < 5; i++) {
+            var xhr = CouchDB.request("GET", url);
+            TEquals(200, xhr.status);
+        }
       });
   }
 }
diff --git a/src/couchdb/couch_db.hrl b/src/couchdb/couch_db.hrl
index 8d7d02095..40369344a 100644
--- a/src/couchdb/couch_db.hrl
+++ b/src/couchdb/couch_db.hrl
@@ -21,6 +21,8 @@
 % the lowest possible database sequence number
 -define(LOWEST_SEQ, 0).
 
+-define(REWRITE_COUNT, couch_rewrite_count).
+
 -define(JSON_ENCODE(V), ejson:encode(V)).
 -define(JSON_DECODE(V), ejson:decode(V)).
 
diff --git a/src/couchdb/couch_httpd.erl b/src/couchdb/couch_httpd.erl
index 3e3415bdd..66d28d2a2 100644
--- a/src/couchdb/couch_httpd.erl
+++ b/src/couchdb/couch_httpd.erl
@@ -226,6 +226,8 @@ make_fun_spec_strs(SpecStr) ->
 
 handle_request(MochiReq, DefaultFun, UrlHandlers, DbUrlHandlers,
     DesignUrlHandlers) ->
+    %% reset rewrite count for new request
+    erlang:put(?REWRITE_COUNT, 0),
 
     MochiReq1 = couch_httpd_vhost:dispatch_host(MochiReq),
 
diff --git a/src/couchdb/couch_httpd_rewrite.erl b/src/couchdb/couch_httpd_rewrite.erl
index 756cdefb2..232d2a362 100644
--- a/src/couchdb/couch_httpd_rewrite.erl
+++ b/src/couchdb/couch_httpd_rewrite.erl
@@ -119,15 +119,13 @@ handle_rewrite_req(#httpd{
     Prefix = <<"/", (?l2b(couch_util:url_encode(DbName)))/binary, "/", DesignId/binary>>,
     QueryList = lists:map(fun decode_query_value/1, couch_httpd:qs(Req)),
 
-    MaxRewritesList = couch_config:get("httpd", "rewrite_limit", "100"),
-    MaxRewrites = list_to_integer(MaxRewritesList),
-    case get(couch_rewrite_count) of
-        undefined ->
-            put(couch_rewrite_count, 1);
-        NumRewrites when NumRewrites < MaxRewrites ->
-            put(couch_rewrite_count, NumRewrites + 1);
-        _ ->
-            throw({bad_request, <<"Exceeded rewrite recursion limit">>})
+    RewritesSoFar = erlang:get(?REWRITE_COUNT),
+    MaxRewrites = list_to_integer(couch_config:get("httpd", "rewrite_limit", "100")),
+    case RewritesSoFar >= MaxRewrites of
+        true ->
+            throw({bad_request, <<"Exceeded rewrite recursion limit">>});
+        false ->
+            erlang:put(?REWRITE_COUNT, RewritesSoFar + 1)
     end,
 
     #doc{body={Props}} = DDoc,