Discard a payload on a delete attachment request

While including a payload within a DELETE request is not forbidden by RFC7231
its presence on a delete attachment request leaves a mochiweb acceptor
in a semi-opened state since mochiweb's using lazy load for the request bodies.
This makes a next immediate request to the same acceptor to hung
until previous request's receive timeout.

This PR adds a step to explicitly "drain" and discard an entity body on a
delete attachment request to prevent that.

src/chttpd/src/chttpd_db.erl

@@ -857,6 +857,9 @@ db_req(#httpd{path_parts=[_DbName, <<"_local">> | _Rest]}, _Db) ->
 db_req(#httpd{path_parts=[_, DocId]}=Req, Db) ->
     db_doc_req(Req, Db, DocId);
 
+db_req(#httpd{method='DELETE', path_parts=[_, DocId | FileNameParts]}=Req, Db) ->
+    chttpd:body(Req),
+    db_attachment_req(Req, Db, DocId, FileNameParts);
 db_req(#httpd{path_parts=[_, DocId | FileNameParts]}=Req, Db) ->
     db_attachment_req(Req, Db, DocId, FileNameParts).
 

test/elixir/test/attachments_test.exs

@@ -123,6 +123,21 @@ defmodule AttachmentsTest do
     assert resp.headers["location"] == nil
   end
 
+  @tag :with_db
+  test "delete attachment request with a payload should not block following requests", context do
+    db_name = context[:db_name]
+
+    resp = Couch.put("/#{db_name}/bin_doc", body: @bin_att_doc, query: %{w: 3})
+    assert resp.status_code in [201, 202]
+    rev = resp.body["rev"]
+
+    resp = Couch.delete("/#{db_name}/bin_doc/foo.txt", body: 'some payload', query: %{w: 3, rev: rev}, ibrowse: [{:max_sessions, 1}, {:max_pipeline_size, 1}])
+    assert resp.status_code == 200
+
+    resp = Couch.get("/", timeout: 1000, ibrowse: [{:max_sessions, 1}, {:max_pipeline_size, 1}])
+    assert resp.status_code == 200
+  end
+
   @tag :with_db
   test "saves binary", context do
     db_name = context[:db_name]