JS-rewritten post/put hangs or returns bad_request

[ermouth]

Expected Behavior

JS rewrite, returning {path:'whatever', method:'PUT', body:'body'} should send body to the rewritten endpoint.

Current Behavior

The body field of rewrite fn returned obj is in some cases dropped. If source request was POST/PUT, the rewritten requests hangs, or, if source request was GET-like, bad_request error is sent as response.

Steps to Reproduce

1. Create empty bucket named, say, zz
2. Put design doc with rewrites into the bucket. Below ddoc is intended to create new random doc on each request to _design/n/_rewrite endpoint:

{
  "_id": "_design/n",
  "rewrites": "function (r) {\n\tvar id = 'x'+(Date.now()+'').substr(-8);\n\treturn {\n\t\tpath:'../../'+id,\n\t\tmethod:'PUT',\n\t\theaders:{'content-type':'application/json',Accept:'application/json'},\n\t\tbody:JSON.stringify({_id:id,type:'test',val:Date.now().toString(36)})\n\t}\n}"
}

3. Call http:https://couchdb_ip/zz/_design/n/_rewrite.

Solution

The issue is caused by cleaning-up rewritten request prematurely here:
https://github.com/apache/couchdb/blob/master/src/chttpd/src/chttpd_rewrite.erl#L67.
It should only be cleaned if we have no body to send.

That line (L67) should be replaced with this code:

            Body = case couch_util:get_value(<<"body">>, Props) of
                undefined -> erlang:get(mochiweb_request_body);
                B -> B
            end,
            case Body of
                undefined -> NewMochiReq:cleanup();
                _ -> erlang:put(mochiweb_request_body, Body)
            end,

It seems to fix issue completely.

Your Environment

• Version used: 2.1.2, 2.2.0