Introduces native Erlang query servers. Closes COUCHDB-377

Thanks Mark Hammond and Paul Davis for doing most of the work, and Michael McDaniel for the inspiration.

There is still room for improvement on the APIs exposed to the Erlang views, as well as likely a whole lot of work to be done to increase parallelism. But the important part now is that we have native Erlang views.


git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@803685 13f79535-47bb-0310-9956-ffa450edef68

11 files changed, 847 insertions, 151 deletions

diff --git a/share/www/script/couch.js b/share/www/script/couch.js
index af3bb8fb..eba60ad5 100644
--- a/share/www/script/couch.js
+++ b/share/www/script/couch.js
@@ -127,8 +127,8 @@ function CouchDB(name, httpHeaders) {
   }
 
   // Applies the map function to the contents of database and returns the results.
-  this.query = function(mapFun, reduceFun, options, keys) {
-    var body = {language: "javascript"};
+  this.query = function(mapFun, reduceFun, options, keys, language) {
+    var body = {language: language || "javascript"};
     if(keys) {
       body.keys = keys ;
     }
diff --git a/share/www/script/couch_tests.js b/share/www/script/couch_tests.js
index 3d415952..7ddfa312 100644
--- a/share/www/script/couch_tests.js
+++ b/share/www/script/couch_tests.js
@@ -81,6 +81,7 @@ loadScript("script/oauth.js");
 loadTest("oauth.js");
 loadTest("stats.js");
 loadTest("rev_stemming.js");
+loadTest("erlang_views.js");
 
 function makeDocs(start, end, templateDoc) {
   var templateDocSrc = templateDoc ? JSON.stringify(templateDoc) : "{}"
diff --git a/share/www/script/futon.browse.js b/share/www/script/futon.browse.js
index 29c0d86a..7fa880fd 100644
--- a/share/www/script/futon.browse.js
+++ b/share/www/script/futon.browse.js
@@ -206,32 +206,48 @@
 
       // Populate the languages dropdown, and listen to selection changes
       this.populateLanguagesMenu = function() {
+        var all_langs = {};
+        fill_language = function() {
+          var select = $("#language");
+          for (var language in all_langs) {
+            var option = $(document.createElement("option"))
+              .attr("value", language).text(language)
+              .appendTo(select);
+          }
+          if (select[0].options.length == 1) {
+            select[0].disabled = true;
+          } else {
+            select[0].disabled = false;
+            select.val(page.viewLanguage);
+            select.change(function() {
+              var language = $("#language").val();
+              if (language != page.viewLanguage) {
+                var mapFun = $("#viewcode_map").val();
+                if (mapFun == "" || mapFun == templates[page.viewLanguage]) {
+                  // no edits made, so change to the new default
+                  $("#viewcode_map").val(templates[language]);
+                }
+                page.viewLanguage = language;
+                $("#viewcode_map")[0].focus();
+              }
+              return false;
+            });
+          }
+        }
         $.couch.config({
           success: function(resp) {
-            var select = $("#language");
             for (var language in resp) {
-              var option = $(document.createElement("option"))
-                .attr("value", language).text(language)
-                .appendTo(select);
+              all_langs[language] = resp[language];
             }
-            if (select[0].options.length == 1) {
-              select[0].disabled = true;
-            } else {
-              select.val(page.viewLanguage);
-              select.change(function() {
-                var language = $("#language").val();
-                if (language != page.viewLanguage) {
-                  var mapFun = $("#viewcode_map").val();
-                  if (mapFun == "" || mapFun == templates[page.viewLanguage]) {
-                    // no edits made, so change to the new default
-                    $("#viewcode_map").val(templates[language]);
-                  }
-                  page.viewLanguage = language;
-                  $("#viewcode_map")[0].focus();
+
+            $.couch.config({
+              success: function(resp) {
+                for (var language in resp) {
+                  all_langs[language] = resp[language];
                 }
-                return false;
-              });
-            }
+                fill_language();
+              }
+            }, "native_query_servers");
           }
         }, "query_servers");
       }
diff --git a/share/www/script/test/changes.js b/share/www/script/test/changes.js
index d8abcc71..393ff034 100644
--- a/share/www/script/test/changes.js
+++ b/share/www/script/test/changes.js
@@ -161,13 +161,13 @@ couchTests.changes = function(debug) {
   var ddoc = {
     _id : "_design/changes_filter",
     "filters" : {
-      "bop" : "function(doc, req, userCtx) { return (doc.bop);}",
-      "dynamic" : stringFun(function(doc, req, userCtx) { 
+      "bop" : "function(doc, req) { return (doc.bop);}",
+      "dynamic" : stringFun(function(doc, req) { 
         var field = req.query.field;
         return doc[field];
       }),
-      "userCtx" : stringFun(function(doc, req, userCtx) {
-        return doc.user && (doc.user == userCtx.name);
+      "userCtx" : stringFun(function(doc, req) {
+        return doc.user && (doc.user == req.userCtx.name);
       })
     }
   }
diff --git a/share/www/script/test/erlang_views.js b/share/www/script/test/erlang_views.js
new file mode 100644
index 00000000..6a378690
--- /dev/null
+++ b/share/www/script/test/erlang_views.js
@@ -0,0 +1,82 @@
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+couchTests.erlang_views = function(debug) {
+  var db = new CouchDB("test_suite_db");
+  db.deleteDb();
+  db.createDb();
+  if (debug) debugger;
+
+
+
+  run_on_modified_server(
+    [{section: "native_query_servers",
+      key: "erlang",
+      value: "{couch_native_process, start_link, []}"}],
+    function() {
+      // Note we just do some basic 'smoke tests' here - the
+      // test/query_server_spec.rb tests have more comprehensive tests
+      var doc = {integer: 1, string: "str1", array: [1, 2, 3]};
+      T(db.save(doc).ok);
+
+      var mfun = 'fun({Doc}) -> ' +
+                 ' K = proplists:get_value(<<"integer">>, Doc, null), ' +
+                 ' V = proplists:get_value(<<"string">>, Doc, null), ' +
+                 ' Emit(K, V) ' +
+                 'end.';
+
+      // emitting a key value that is undefined should result in that row not
+      // being included in the view results
+      var results = db.query(mfun, null, null, null, "erlang");
+      T(results.total_rows == 1);
+      T(results.rows[0].key == 1);
+      T(results.rows[0].value == "str1");
+      // check simple reduction - another doc with same key.
+      var doc = {integer: 1, string: "str2"};
+      T(db.save(doc).ok);
+      rfun = "fun(Keys, Values, ReReduce) -> length(Values) end."
+      results = db.query(mfun, rfun, null, null, "erlang");
+      T(results.rows[0].value == 2);
+
+      // simple 'list' tests
+      var designDoc = {
+        _id:"_design/erlview",
+        language: "erlang",
+        lists: {
+          simple_list :
+            'fun(Head, {Req}) -> ' +
+            '  Send(<<"head">>), ' +
+            '  Fun = fun({Row}, _) -> ' +
+            '    Send(proplists:get_value(<<"value">>, Row, null)), ' +
+            '    {ok, nil} ' +
+            '  end, ' +
+            '  {ok, _} = FoldRows(Fun, nil), ' +
+            '  <<"tail">> ' +
+            'end. '
+        },
+        views: {
+          simple_view : {
+            map: mfun,
+            reduce: rfun
+          }
+        }
+      };
+      T(db.save(designDoc).ok);
+
+      // *sob* - show functions have problems :(
+      /***
+      var xhr = CouchDB.request("GET", "/test_suite_db/_design/erlview/_list/simple_list/simple_view");
+      T(xhr.status == 200, "standard get should be 200");
+      T(xhr.responseText == "head2tail");
+      ***/
+    });
+};
diff --git a/src/couchdb/Makefile.am b/src/couchdb/Makefile.am
index 6691dbba..7d7b1720 100644
--- a/src/couchdb/Makefile.am
+++ b/src/couchdb/Makefile.am
@@ -70,6 +70,7 @@ source_files = \
     couch_httpd_stats_handlers.erl \
     couch_key_tree.erl \
     couch_log.erl \
+    couch_native_process.erl \
     couch_os_process.erl \
     couch_query_servers.erl \
     couch_ref_counter.erl \
@@ -122,6 +123,7 @@ compiled_files = \
     couch_httpd_stats_handlers.beam \
     couch_key_tree.beam \
     couch_log.beam \
+    couch_native_process.beam \
     couch_os_process.beam \
     couch_query_servers.beam \
     couch_ref_counter.beam \
diff --git a/src/couchdb/couch_httpd_show.erl b/src/couchdb/couch_httpd_show.erl
index 294acbac..ed0b9ede 100644
--- a/src/couchdb/couch_httpd_show.erl
+++ b/src/couchdb/couch_httpd_show.erl
@@ -416,6 +416,7 @@ send_doc_update_response(Lang, UpdateSrc, DocId, Doc, Req, Db) ->
         end,
         NewDoc = couch_doc:from_json_obj({NewJsonDoc}),
         Code = 201,
+        % todo set location field
         {ok, _NewRev} = couch_db:update_doc(Db, NewDoc, Options);
     [<<"up">>, _Other, JsonResp] ->
         Code = 200,
diff --git a/src/couchdb/couch_native_process.erl b/src/couchdb/couch_native_process.erl
new file mode 100644
index 00000000..df879633
--- /dev/null
+++ b/src/couchdb/couch_native_process.erl
@@ -0,0 +1,347 @@
+% Licensed under the Apache License, Version 2.0 (the "License"); 
+% you may not use this file except in compliance with the License. 
+%
+% You may obtain a copy of the License at
+% http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, 
+% software distributed under the License is distributed on an 
+% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
+% either express or implied. 
+%
+% See the License for the specific language governing permissions
+% and limitations under the License. 
+%
+% This file drew much inspiration from erlview, which was written by and
+% copyright Michael McDaniel [http://autosys.us], and is also under APL 2.0
+%
+%
+% This module provides the smallest possible native view-server.
+% With this module in-place, you can add the following to your couch INI files:
+%  [native_query_servers]
+%  erlang={couch_native_process, start_link, []}
+%
+% Which will then allow following example map function to be used:
+%
+%  fun({Doc}) ->
+%    % Below, we emit a single record - the _id as key, null as value
+%    DocId = proplists:get_value(Doc, <<"_id">>, null),
+%    Emit(DocId, null)
+%  end.
+%
+% which should be roughly the same as the javascript:
+%    emit(doc._id, null);
+%
+% This module exposes enough functions such that a native erlang server can 
+% act as a fully-fleged view server, but no 'helper' functions specifically
+% for simplifying your erlang view code.  It is expected other third-party
+% extensions will evolve which offer useful layers on top of this view server
+% to help simplify your view code.
+-module(couch_native_process).
+
+-export([start_link/0]).
+-export([set_timeout/2, prompt/2, stop/1]).
+
+-define(STATE, native_proc_state).
+-record(evstate, {funs=[], query_config=[], list_pid=nil, timeout=5000}).
+
+-include("couch_db.hrl").
+
+start_link() ->
+    {ok, self()}.
+
+stop(_Pid) ->
+    ok.
+
+set_timeout(_Pid, TimeOut) ->
+    NewState = case get(?STATE) of
+    undefined ->
+        #evstate{timeout=TimeOut};
+    State ->
+        State#evstate{timeout=TimeOut}
+    end,
+    put(?STATE, NewState),
+    ok.
+
+prompt(Pid, Data) when is_pid(Pid), is_list(Data) ->
+    case get(?STATE) of
+    undefined ->
+        State = #evstate{},
+        put(?STATE, State);
+    State ->
+        State
+    end,
+    case is_pid(State#evstate.list_pid) of
+        true ->
+            case hd(Data) of
+                <<"list_row">> -> ok;
+                <<"list_end">> -> ok;
+                _ -> throw({error, query_server_error})
+            end;
+        _ ->
+            ok % Not listing
+    end,
+    {NewState, Resp} = run(State, Data),
+    put(?STATE, NewState),
+    case Resp of
+        {error, Reason} ->
+            Msg = io_lib:format("couch native server error: ~p", [Reason]),
+            {[{<<"error">>, list_to_binary(Msg)}]};
+        _ ->
+            Resp
+    end.
+
+run(_, [<<"reset">>]) ->
+    {#evstate{}, true};
+run(_, [<<"reset">>, QueryConfig]) ->
+    {#evstate{query_config=QueryConfig}, true};
+run(#evstate{funs=Funs}=State, [<<"add_fun">> , BinFunc]) ->
+    FunInfo = makefun(State, BinFunc),
+    {State#evstate{funs=Funs ++ [FunInfo]}, true};
+run(State, [<<"map_doc">> , Doc]) ->
+    Resp = lists:map(fun({Sig, Fun}) ->
+        erlang:put(Sig, []),
+        Fun(Doc),
+        lists:reverse(erlang:get(Sig))
+    end, State#evstate.funs),
+    {State, Resp};
+run(State, [<<"reduce">>, Funs, KVs]) ->
+    {Keys, Vals} =
+    lists:foldl(fun([K, V], {KAcc, VAcc}) ->
+        {[K | KAcc], [V | VAcc]}
+    end, {[], []}, KVs),
+    Keys2 = lists:reverse(Keys),
+    Vals2 = lists:reverse(Vals),
+    {State, catch reduce(State, Funs, Keys2, Vals2, false)};
+run(State, [<<"rereduce">>, Funs, Vals]) ->
+    {State, catch reduce(State, Funs, null, Vals, true)};
+run(State, [<<"validate">>, BFun, NDoc, ODoc, Ctx]) ->
+    {_Sig, Fun} = makefun(State, BFun),
+    {State, catch Fun(NDoc, ODoc, Ctx)};
+run(State, [<<"filter">>, Docs, Req]) ->
+    {_Sig, Fun} = hd(State#evstate.funs),
+    Resp = lists:map(fun(Doc) ->
+        case (catch Fun(Doc, Req)) of
+            true -> true;
+            _ -> false
+        end
+    end, Docs),
+    {State, [true, Resp]};
+run(State, [<<"show">>, BFun, Doc, Req]) ->
+    {_Sig, Fun} = makefun(State, BFun),
+    Resp = case (catch Fun(Doc, Req)) of
+        FunResp when is_list(FunResp) ->
+            FunResp;
+        FunResp when is_tuple(FunResp), size(FunResp) == 1 ->
+            [<<"resp">>, FunResp];
+        FunResp ->
+            FunResp
+    end,
+    {State, Resp};
+run(State, [<<"update">>, BFun, Doc, Req]) ->
+    {_Sig, Fun} = makefun(State, BFun),
+    Resp = case (catch Fun(Doc, Req)) of
+        [JsonDoc, JsonResp]  ->
+            [<<"up">>, JsonDoc, JsonResp]
+    end,
+    {State, Resp};
+run(State, [<<"list">>, Head, Req]) ->
+    {Sig, Fun} = hd(State#evstate.funs),
+    % This is kinda dirty
+    case is_function(Fun, 2) of
+        false -> throw({error, render_error});
+        true -> ok
+    end,
+    Self = self(),
+    SpawnFun = fun() ->
+        LastChunk = (catch Fun(Head, Req)),
+        case start_list_resp(Self, Sig) of
+            started ->
+                receive
+                    {Self, list_row, _Row} -> ignore;
+                    {Self, list_end} -> ignore
+                after State#evstate.timeout ->
+                    throw({timeout, list_cleanup_pid})
+                end;
+            _ ->
+                ok
+        end,
+        LastChunks =
+        case erlang:get(Sig) of
+            undefined -> [LastChunk];
+            OtherChunks -> [LastChunk | OtherChunks]
+        end,
+        Self ! {self(), list_end, lists:reverse(LastChunks)}
+    end,
+    erlang:put(do_trap, process_flag(trap_exit, true)),
+    Pid = spawn_link(SpawnFun),
+    Resp =
+    receive
+        {Pid, start, Chunks, JsonResp} ->
+            [<<"start">>, Chunks, JsonResp]
+    after State#evstate.timeout ->
+        throw({timeout, list_start})
+    end,
+    {State#evstate{list_pid=Pid}, Resp};
+run(#evstate{list_pid=Pid}=State, [<<"list_row">>, Row]) when is_pid(Pid) ->
+    Pid ! {self(), list_row, Row},
+    receive
+        {Pid, chunks, Data} ->
+            {State, [<<"chunks">>, Data]};
+        {Pid, list_end, Data} ->
+            receive
+                {'EXIT', Pid, normal} -> ok
+            after State#evstate.timeout ->
+                throw({timeout, list_cleanup})
+            end,
+            process_flag(trap_exit, erlang:get(do_trap)),
+            {State#evstate{list_pid=nil}, [<<"end">>, Data]}
+    after State#evstate.timeout ->
+        throw({timeout, list_row})
+    end;
+run(#evstate{list_pid=Pid}=State, [<<"list_end">>]) when is_pid(Pid) ->
+    Pid ! {self(), list_end},
+    Resp =
+    receive
+        {Pid, list_end, Data} ->
+            receive
+                {'EXIT', Pid, normal} -> ok
+            after State#evstate.timeout ->
+                throw({timeout, list_cleanup})
+            end,
+            [<<"end">>, Data]
+    after State#evstate.timeout ->
+        throw({timeout, list_end})
+    end,
+    process_flag(trap_exit, erlang:get(do_trap)),
+    {State#evstate{list_pid=nil}, Resp};
+run(_, Unknown) ->
+    ?LOG_ERROR("Native Process: Unknown command: ~p~n", [Unknown]),
+    throw({error, query_server_error}).
+
+bindings(State, Sig) ->
+    Self = self(),
+
+    Log = fun(Msg) ->
+        ?LOG_INFO(Msg, [])
+    end,
+
+    Emit = fun(Id, Value) ->
+        Curr = erlang:get(Sig),
+        erlang:put(Sig, [[Id, Value] | Curr])
+    end,
+
+    Start = fun(Headers) ->
+        erlang:put(list_headers, Headers)
+    end,
+
+    Send = fun(Chunk) ->
+        Curr =
+        case erlang:get(Sig) of
+            undefined -> [];
+            Else -> Else
+        end,
+        erlang:put(Sig, [Chunk | Curr])
+    end,
+
+    GetRow = fun() ->
+        case start_list_resp(Self, Sig) of
+            started ->
+                ok;
+            _ ->
+                Chunks =
+                case erlang:get(Sig) of
+                    undefined -> [];
+                    CurrChunks -> CurrChunks
+                end,
+                Self ! {self(), chunks, lists:reverse(Chunks)}
+        end,
+        erlang:put(Sig, []),
+        receive
+            {Self, list_row, Row} -> Row;
+            {Self, list_end} -> nil
+        after State#evstate.timeout ->
+            throw({timeout, list_pid_getrow})
+        end
+    end,
+   
+    FoldRows = fun(Fun, Acc) -> foldrows(GetRow, Fun, Acc) end,
+
+    [
+        {'Log', Log},
+        {'Emit', Emit},
+        {'Start', Start},
+        {'Send', Send},
+        {'GetRow', GetRow},
+        {'FoldRows', FoldRows}
+    ].
+
+% thanks to erlview, via:
+% http://erlang.org/pipermail/erlang-questions/2003-November/010544.html
+makefun(State, Source) ->
+    Sig = erlang:md5(Source),
+    BindFuns = bindings(State, Sig),
+    {Sig, makefun(State, Source, BindFuns)}.
+
+makefun(_State, Source, BindFuns) ->
+    FunStr = binary_to_list(Source),
+    {ok, Tokens, _} = erl_scan:string(FunStr),
+    Form = case (catch erl_parse:parse_exprs(Tokens)) of
+        {ok, [ParsedForm]} ->
+            ParsedForm;
+        {error, {LineNum, _Mod, [Mesg, Params]}}=Error ->
+            io:format(standard_error, "Syntax error on line: ~p~n", [LineNum]),
+            io:format(standard_error, "~s~p~n", [Mesg, Params]),
+            throw(Error)
+    end,
+    Bindings = lists:foldl(fun({Name, Fun}, Acc) ->
+        erl_eval:add_binding(Name, Fun, Acc)
+    end, erl_eval:new_bindings(), BindFuns),
+    {value, Fun, _} = erl_eval:expr(Form, Bindings),
+    Fun.
+
+reduce(State, BinFuns, Keys, Vals, ReReduce) ->
+    Funs = case is_list(BinFuns) of
+        true ->
+            lists:map(fun(BF) -> makefun(State, BF) end, BinFuns);
+        _ ->
+            [makefun(State, BinFuns)]
+    end,
+    Reds = lists:map(fun({_Sig, Fun}) ->
+        Fun(Keys, Vals, ReReduce)
+    end, Funs),
+    [true, Reds].
+
+foldrows(GetRow, ProcRow, Acc) ->
+    case GetRow() of
+        nil ->
+            {ok, Acc};
+        Row ->
+            case (catch ProcRow(Row, Acc)) of
+                {ok, Acc2} ->
+                    foldrows(GetRow, ProcRow, Acc2);
+                {stop, Acc2} ->
+                    {ok, Acc2}
+            end
+    end.
+
+start_list_resp(Self, Sig) ->
+    case erlang:get(list_started) of
+        undefined ->
+            Headers =
+            case erlang:get(list_headers) of
+                undefined -> {[{<<"headers">>, {[]}}]};
+                CurrHdrs -> CurrHdrs
+            end,
+            Chunks = 
+            case erlang:get(Sig) of
+                undefined -> [];
+                CurrChunks -> CurrChunks
+            end,
+            Self ! {self(), start, lists:reverse(Chunks), Headers},
+            erlang:put(list_started, true),
+            erlang:put(Sig, []),
+            started;
+        _ ->
+            ok
+    end.
diff --git a/src/couchdb/couch_query_servers.erl b/src/couchdb/couch_query_servers.erl
index fca7c85a..f94cc28b 100644
--- a/src/couchdb/couch_query_servers.erl
+++ b/src/couchdb/couch_query_servers.erl
@@ -25,6 +25,14 @@
 
 -include("couch_db.hrl").
 
+-record(proc, {
+    pid,
+    lang,
+    prompt_fun,
+    set_timeout_fun,
+    stop_fun
+}).
+
 start_link() ->
     gen_server:start_link({local, couch_query_servers}, couch_query_servers, [], []).
 
@@ -32,19 +40,19 @@ stop() ->
     exit(whereis(couch_query_servers), close).
 
 start_doc_map(Lang, Functions) ->
-    Pid = get_os_process(Lang),
+    Proc = get_os_process(Lang),
     lists:foreach(fun(FunctionSource) ->
-        true = couch_os_process:prompt(Pid, [<<"add_fun">>, FunctionSource])
+        true = proc_prompt(Proc, [<<"add_fun">>, FunctionSource])
     end, Functions),
-    {ok, {Lang, Pid}}.
+    {ok, Proc}.
 
-map_docs({_Lang, Pid}, Docs) ->
+map_docs(Proc, Docs) ->
     % send the documents
     Results = lists:map(
         fun(Doc) ->
             Json = couch_doc:to_json_obj(Doc, []),
 
-            FunsResults = couch_os_process:prompt(Pid, [<<"map_doc">>, Json]),
+            FunsResults = proc_prompt(Proc, [<<"map_doc">>, Json]),
             % the results are a json array of function map yields like this:
             % [FunResults1, FunResults2 ...]
             % where funresults is are json arrays of key value pairs:
@@ -63,8 +71,8 @@ map_docs({_Lang, Pid}, Docs) ->
 
 stop_doc_map(nil) ->
     ok;
-stop_doc_map({Lang, Pid}) ->
-    ok = ret_os_process(Lang, Pid).
+stop_doc_map(Proc) ->
+    ok = ret_os_process(Proc).
 
 group_reductions_results([]) ->
     [];
@@ -83,7 +91,7 @@ group_reductions_results(List) ->
 rereduce(_Lang, [], _ReducedValues) ->
     {ok, []};
 rereduce(Lang, RedSrcs, ReducedValues) ->
-    Pid = get_os_process(Lang),
+    Proc = get_os_process(Lang),
     Grouped = group_reductions_results(ReducedValues),
     Results = try lists:zipwith(
         fun
@@ -92,11 +100,11 @@ rereduce(Lang, RedSrcs, ReducedValues) ->
             Result;
         (FunSrc, Values) ->
             [true, [Result]] =
-                couch_os_process:prompt(Pid, [<<"rereduce">>, [FunSrc], Values]),
+                proc_prompt(Proc, [<<"rereduce">>, [FunSrc], Values]),
             Result
         end, RedSrcs, Grouped)
     after
-        ok = ret_os_process(Lang, Pid)
+        ok = ret_os_process(Proc)
     end,
     {ok, Results}.
 
@@ -121,12 +129,11 @@ recombine_reduce_results([_OsFun|RedSrcs], [OsR|OsResults], BuiltinResults, Acc)
 os_reduce(_Lang, [], _KVs) ->
     {ok, []};
 os_reduce(Lang, OsRedSrcs, KVs) ->
-    Pid = get_os_process(Lang),
-    OsResults = try couch_os_process:prompt(Pid,
-            [<<"reduce">>, OsRedSrcs, KVs]) of
+    Proc = get_os_process(Lang),
+    OsResults = try proc_prompt(Proc, [<<"reduce">>, OsRedSrcs, KVs]) of
         [true, Reductions] -> Reductions
     after
-        ok = ret_os_process(Lang, Pid)
+        ok = ret_os_process(Proc)
     end,
     {ok, OsResults}.
 
@@ -151,7 +158,7 @@ builtin_sum_rows(KVs) ->
     end, 0, KVs).
 
 validate_doc_update(Lang, FunSrc, EditDoc, DiskDoc, Ctx) ->
-    Pid = get_os_process(Lang),
+    Proc = get_os_process(Lang),
     JsonEditDoc = couch_doc:to_json_obj(EditDoc, [revs]),
     JsonDiskDoc =
     if DiskDoc == nil ->
@@ -159,7 +166,7 @@ validate_doc_update(Lang, FunSrc, EditDoc, DiskDoc, Ctx) ->
     true ->
         couch_doc:to_json_obj(DiskDoc, [revs])
     end,
-    try couch_os_process:prompt(Pid,
+    try proc_prompt(Proc,
             [<<"validate">>, FunSrc, JsonEditDoc, JsonDiskDoc, Ctx]) of
     1 ->
         ok;
@@ -168,14 +175,14 @@ validate_doc_update(Lang, FunSrc, EditDoc, DiskDoc, Ctx) ->
     {[{<<"unauthorized">>, Message}]} ->
         throw({unauthorized, Message})
     after
-        ok = ret_os_process(Lang, Pid)
+        ok = ret_os_process(Proc)
     end.
 % todo use json_apply_field
 append_docid(DocId, JsonReqIn) ->
     [{<<"docId">>, DocId} | JsonReqIn].
 
 render_doc_show(Lang, ShowSrc, DocId, Doc, Req, Db) ->
-    Pid = get_os_process(Lang),
+    Proc = get_os_process(Lang),
     {JsonReqIn} = couch_httpd_external:json_req_obj(Req, Db),
 
     {JsonReq, JsonDoc} = case {DocId, Doc} of
@@ -183,16 +190,16 @@ render_doc_show(Lang, ShowSrc, DocId, Doc, Req, Db) ->
         {DocId, nil} -> {{append_docid(DocId, JsonReqIn)}, null};
         _ -> {{append_docid(DocId, JsonReqIn)}, couch_doc:to_json_obj(Doc, [revs])}
     end,
-    try couch_os_process:prompt(Pid,
+    try proc_prompt(Proc,
         [<<"show">>, ShowSrc, JsonDoc, JsonReq]) of
     FormResp ->
         FormResp
     after
-        ok = ret_os_process(Lang, Pid)
+        ok = ret_os_process(Proc)
     end.
 
 render_doc_update(Lang, UpdateSrc, DocId, Doc, Req, Db) ->
-    Pid = get_os_process(Lang),
+    Proc = get_os_process(Lang),
     {JsonReqIn} = couch_httpd_external:json_req_obj(Req, Db),
 
     {JsonReq, JsonDoc} = case {DocId, Doc} of
@@ -200,51 +207,51 @@ render_doc_update(Lang, UpdateSrc, DocId, Doc, Req, Db) ->
         {DocId, nil} -> {{append_docid(DocId, JsonReqIn)}, null};
         _ -> {{append_docid(DocId, JsonReqIn)}, couch_doc:to_json_obj(Doc, [revs])}
     end,
-    try couch_os_process:prompt(Pid, 
+    try proc_prompt(Proc, 
         [<<"update">>, UpdateSrc, JsonDoc, JsonReq]) of
     FormResp ->
         FormResp
     after
-        ok = ret_os_process(Lang, Pid)
+        ok = ret_os_process(Proc)
     end.
 
 start_view_list(Lang, ListSrc) ->
-    Pid = get_os_process(Lang),
-    true = couch_os_process:prompt(Pid, [<<"add_fun">>, ListSrc]),
-    {ok, {Lang, Pid}}.
+    Proc = get_os_process(Lang),
+    proc_prompt(Proc, [<<"add_fun">>, ListSrc]),
+    {ok, Proc}.
 
-render_list_head({_Lang, Pid}, Req, Db, Head) ->
+render_list_head(Proc, Req, Db, Head) ->
     JsonReq = couch_httpd_external:json_req_obj(Req, Db),
-    couch_os_process:prompt(Pid, [<<"list">>, Head, JsonReq]).
+    proc_prompt(Proc, [<<"list">>, Head, JsonReq]).
 
-render_list_row({_Lang, Pid}, Db, {{Key, DocId}, Value}, IncludeDoc) ->
+render_list_row(Proc, Db, {{Key, DocId}, Value}, IncludeDoc) ->
     JsonRow = couch_httpd_view:view_row_obj(Db, {{Key, DocId}, Value}, IncludeDoc),
-    couch_os_process:prompt(Pid, [<<"list_row">>, JsonRow]);
+    proc_prompt(Proc, [<<"list_row">>, JsonRow]);
 
-render_list_row({_Lang, Pid}, _, {Key, Value}, _IncludeDoc) ->
+render_list_row(Proc, _, {Key, Value}, _IncludeDoc) ->
     JsonRow = {[{key, Key}, {value, Value}]},
-    couch_os_process:prompt(Pid, [<<"list_row">>, JsonRow]).
+    proc_prompt(Proc, [<<"list_row">>, JsonRow]).
 
-render_list_tail({Lang, Pid}) ->
-    JsonResp = couch_os_process:prompt(Pid, [<<"list_end">>]),
-    ok = ret_os_process(Lang, Pid),
+render_list_tail(Proc) ->
+    JsonResp = proc_prompt(Proc, [<<"list_end">>]),
+    ok = ret_os_process(Proc),
     JsonResp.
 
 start_filter(Lang, FilterSrc) ->
-    Pid = get_os_process(Lang),
-    true = couch_os_process:prompt(Pid, [<<"add_fun">>, FilterSrc]),
-    {ok, {Lang, Pid}}.
+    Proc = get_os_process(Lang),
+    true = proc_prompt(Proc, [<<"add_fun">>, FilterSrc]),
+    {ok, Proc}.
 
-filter_doc({_Lang, Pid}, Doc, Req, Db) ->
+filter_doc(Proc, Doc, Req, Db) ->
     JsonReq = couch_httpd_external:json_req_obj(Req, Db),
     JsonDoc = couch_doc:to_json_obj(Doc, [revs]),
     JsonCtx = couch_util:json_user_ctx(Db),
-    [true, [Pass]] = couch_os_process:prompt(Pid,
+    [true, [Pass]] = proc_prompt(Proc,
         [<<"filter">>, [JsonDoc], JsonReq, JsonCtx]),
     {ok, Pass}.
 
-end_filter({Lang, Pid}) ->
-    ok = ret_os_process(Lang, Pid).
+end_filter(Proc) ->
+    ok = ret_os_process(Proc).
     
 
 init([]) ->
@@ -258,58 +265,74 @@ init([]) ->
         fun("query_servers" ++ _, _) ->
             ?MODULE:stop()
         end),
+    ok = couch_config:register(
+        fun("native_query_servers" ++ _, _) ->
+            ?MODULE:stop()
+        end),
 
     Langs = ets:new(couch_query_server_langs, [set, private]),
-    PidLangs = ets:new(couch_query_server_pid_langs, [set, private]),
-    Pids = ets:new(couch_query_server_procs, [set, private]),
+    PidProcs = ets:new(couch_query_server_pid_langs, [set, private]),
+    LangProcs = ets:new(couch_query_server_procs, [set, private]),
     InUse = ets:new(couch_query_server_used, [set, private]),
+    % 'query_servers' specifies an OS command-line to execute.
     lists:foreach(fun({Lang, Command}) ->
-        true = ets:insert(Langs, {?l2b(Lang), Command})
+        true = ets:insert(Langs, {?l2b(Lang),
+                          couch_os_process, start_link, [Command]})
     end, couch_config:get("query_servers")),
+    % 'native_query_servers' specifies a {Module, Func, Arg} tuple.
+    lists:foreach(fun({Lang, SpecStr}) ->
+        {ok, {Mod, Fun, SpecArg}} = couch_util:parse_term(SpecStr),
+        true = ets:insert(Langs, {?l2b(Lang),
+                          Mod, Fun, SpecArg})
+    end, couch_config:get("native_query_servers")),
     process_flag(trap_exit, true),
-    {ok, {Langs, PidLangs, Pids, InUse}}.
+    {ok, {Langs, % Keyed by language name, value is {Mod,Func,Arg}
+          PidProcs, % Keyed by PID, valus is a #proc record.
+          LangProcs, % Keyed by language name, value is a #proc record
+          InUse % Keyed by PID, value is #proc record.
+          }}.
 
 terminate(_Reason, _Server) ->
     ok.
 
 
-handle_call({get_proc, Lang}, _From, {Langs, PidLangs, Pids, InUse}=Server) ->
+handle_call({get_proc, Lang}, _From, {Langs, PidProcs, LangProcs, InUse}=Server) ->
     % Note to future self. Add max process limit.
-    case ets:lookup(Pids, Lang) of
-    [{Lang, [Pid|_]}] ->
-        add_value(PidLangs, Pid, Lang),
-        rem_from_list(Pids, Lang, Pid),
-        add_to_list(InUse, Lang, Pid),
-        {reply, {recycled, Pid, get_query_server_config()}, Server};
+    case ets:lookup(LangProcs, Lang) of
+    [{Lang, [Proc|_]}] ->
+        add_value(PidProcs, Proc#proc.pid, Proc),
+        rem_from_list(LangProcs, Lang, Proc),
+        add_to_list(InUse, Lang, Proc),
+        {reply, {recycled, Proc, get_query_server_config()}, Server};
     _ ->
         case (catch new_process(Langs, Lang)) of
-        {ok, Pid} ->
-            add_to_list(InUse, Lang, Pid),
-            {reply, {new, Pid}, Server};
+        {ok, Proc} ->
+            add_to_list(InUse, Lang, Proc),
+            {reply, {new, Proc}, Server};
         Error ->
             {reply, Error, Server}
         end
     end;
-handle_call({ret_proc, Lang, Pid}, _From, {_, _, Pids, InUse}=Server) ->
+handle_call({ret_proc, Proc}, _From, {_, _, LangProcs, InUse}=Server) ->
     % Along with max process limit, here we should check
     % if we're over the limit and discard when we are.
-    add_to_list(Pids, Lang, Pid),
-    rem_from_list(InUse, Lang, Pid),
+    add_to_list(LangProcs, Proc#proc.lang, Proc),
+    rem_from_list(InUse, Proc#proc.lang, Proc),
     {reply, true, Server}.
 
 handle_cast(_Whatever, Server) ->
     {noreply, Server}.
 
-handle_info({'EXIT', Pid, Status}, {_, PidLangs, Pids, InUse}=Server) ->
-    case ets:lookup(PidLangs, Pid) of
-    [{Pid, Lang}] ->
+handle_info({'EXIT', Pid, Status}, {_, PidProcs, LangProcs, InUse}=Server) ->
+    case ets:lookup(PidProcs, Pid) of
+    [{Pid, Proc}] ->
         case Status of
         normal -> ok;
         _ -> ?LOG_DEBUG("Linked process died abnormally: ~p (reason: ~p)", [Pid, Status])
         end,
-        rem_value(PidLangs, Pid),
-        catch rem_from_list(Pids, Lang, Pid),
-        catch rem_from_list(InUse, Lang, Pid),
+        rem_value(PidProcs, Pid),
+        catch rem_from_list(LangProcs, Proc#proc.lang, Proc),
+        catch rem_from_list(InUse, Proc#proc.lang, Proc),
         {noreply, Server};
     [] ->
         ?LOG_DEBUG("Unknown linked process died: ~p (reason: ~p)", [Pid, Status]),
@@ -328,37 +351,55 @@ get_query_server_config() ->
 
 new_process(Langs, Lang) ->
     case ets:lookup(Langs, Lang) of
-    [{Lang, Command}] ->
-        couch_os_process:start_link(Command);
+    [{Lang, Mod, Func, Arg}] ->
+        {ok, Pid} = apply(Mod, Func, Arg),
+        {ok, #proc{lang=Lang,
+                   pid=Pid,
+                   % Called via proc_prompt, proc_set_timeout, and proc_stop
+                   prompt_fun={Mod, prompt},
+                   set_timeout_fun={Mod, set_timeout},
+                   stop_fun={Mod, stop}}};
     _ ->
         {unknown_query_language, Lang}
     end.
 
+proc_prompt(Proc, Args) ->
+    {Mod, Func} = Proc#proc.prompt_fun,
+    apply(Mod, Func, [Proc#proc.pid, Args]).
+
+proc_stop(Proc) ->
+    {Mod, Func} = Proc#proc.stop_fun,
+    apply(Mod, Func, [Proc#proc.pid]).
+
+proc_set_timeout(Proc, Timeout) ->
+    {Mod, Func} = Proc#proc.set_timeout_fun,
+    apply(Mod, Func, [Proc#proc.pid, Timeout]).
+
 get_os_process(Lang) ->
     case gen_server:call(couch_query_servers, {get_proc, Lang}) of
-    {new, Pid} ->
-        couch_os_process:set_timeout(Pid, list_to_integer(couch_config:get(
-                "couchdb", "os_process_timeout", "5000"))),
-        link(Pid),
-        Pid;
-    {recycled, Pid, QueryConfig} ->
-        case (catch couch_os_process:prompt(Pid, [<<"reset">>, QueryConfig])) of
+    {new, Proc} ->
+        proc_set_timeout(Proc, list_to_integer(couch_config:get(
+                            "couchdb", "os_process_timeout", "5000"))),
+        link(Proc#proc.pid),
+        Proc;
+    {recycled, Proc, QueryConfig} ->
+        case (catch proc_prompt(Proc, [<<"reset">>, QueryConfig])) of
         true ->
-            couch_os_process:set_timeout(Pid, list_to_integer(couch_config:get(
-                "couchdb", "os_process_timeout", "5000"))),
-            link(Pid),
-            Pid;
+            proc_set_timeout(Proc, list_to_integer(couch_config:get(
+                                "couchdb", "os_process_timeout", "5000"))),
+            link(Proc#proc.pid),
+            Proc;
         _ ->
-            catch couch_os_process:stop(Pid),
+            catch proc_stop(Proc),
             get_os_process(Lang)
         end;
     Error ->
         throw(Error)
     end.
 
-ret_os_process(Lang, Pid) ->
-    true = gen_server:call(couch_query_servers, {ret_proc, Lang, Pid}),
-    catch unlink(Pid),
+ret_os_process(Proc) ->
+    true = gen_server:call(couch_query_servers, {ret_proc, Proc}),
+    catch unlink(Proc#proc.pid),
     ok.
 
 add_value(Tid, Key, Value) ->
diff --git a/test/query_server_spec.rb b/test/query_server_spec.rb
index c9fb6942..42c7794c 100644
--- a/test/query_server_spec.rb
+++ b/test/query_server_spec.rb
@@ -14,36 +14,33 @@
 # spec test/query_server_spec.rb -f specdoc --color
 
 COUCH_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(COUCH_ROOT)
-LANGUAGE = "js"
+LANGUAGE = ENV["QS_LANG"] || "js"
+
+puts "Running query server specs for #{LANGUAGE} query server"
 
-require 'open3'
 require 'spec'
 require 'json'
 
 class OSProcessRunner
   def self.run
-    trace = false
+    trace = ENV["QS_TRACE"] || false
     puts "launching #{run_command}" if trace
     if block_given?
-      Open3.popen3(run_command) do |jsin, jsout, jserr|
-        js = QueryServerRunner.new(jsin, jsout, jserr, trace)
-        yield js
+      IO.popen(run_command, "r+") do |io|
+        qs = QueryServerRunner.new(io, trace)
+        yield qs
       end
     else
-      jsin, jsout, jserr = Open3.popen3(run_command)
-      QueryServerRunner.new(jsin, jsout, jserr, trace)
+      io = IO.popen(run_command, "r+")
+      QueryServerRunner.new(io, trace)
     end
   end
-  def initialize jsin, jsout, jserr, trace = false
-    @qsin = jsin
-    @qsout = jsout
-    @qserr = jserr
+  def initialize io, trace = false
+    @qsio = io
     @trace = trace
   end
   def close
-    @qsin.close
-    @qsout.close
-    @qserr.close
+    @qsio.close
   end
   def reset!
     run(["reset"])
@@ -63,10 +60,10 @@ class OSProcessRunner
   def rrun json
     line = json.to_json
     puts "run: #{line}" if @trace
-    @qsin.puts line
+    @qsio.puts line
   end
   def rgets
-    resp = @qsout.gets
+    resp = @qsio.gets
     puts "got: #{resp}"  if @trace
     resp
   end
@@ -75,7 +72,15 @@ class OSProcessRunner
     # err = @qserr.gets
     # puts "err: #{err}" if err
     if resp
-      rj = JSON.parse("[#{resp.chomp}]")[0]
+      begin
+        rj = JSON.parse("[#{resp.chomp}]")[0]
+      rescue JSON::ParserError
+        puts "JSON ERROR (dump under trace mode)"
+        # puts resp.chomp
+        while resp = rgets
+          # puts resp.chomp
+        end
+      end
       if rj.respond_to?(:[]) && rj.is_a?(Array)
         if rj[0] == "log"
           log = rj[1]
@@ -92,7 +97,10 @@ end
 
 class QueryServerRunner < OSProcessRunner
 
-  COMMANDS = {"js" => "#{COUCH_ROOT}/src/couchdb/couchjs #{COUCH_ROOT}/share/server/main.js" }
+  COMMANDS = {
+    "js" => "#{COUCH_ROOT}/src/couchdb/couchjs #{COUCH_ROOT}/share/server/main.js",
+    "erlang" => "#{COUCH_ROOT}/test/run_native_process.es"
+  }
 
   def self.run_command
     COMMANDS[LANGUAGE]
@@ -105,41 +113,90 @@ class ExternalRunner < OSProcessRunner
   end
 end
 
+
 functions = {
   "emit-twice" => {
-    "js" => %{function(doc){emit("foo",doc.a); emit("bar",doc.a)}}
+    "js" => %{function(doc){emit("foo",doc.a); emit("bar",doc.a)}},
+    "erlang" => <<-ERLANG
+      fun({Doc}) ->
+        A = proplists:get_value(<<"a">>, Doc, null),
+        Emit(<<"foo">>, A),
+        Emit(<<"bar">>, A)
+      end.
+    ERLANG
   },
   "emit-once" => {
-    "js" => %{function(doc){emit("baz",doc.a)}}
+    "js" => %{function(doc){emit("baz",doc.a)}},
+    "erlang" => <<-ERLANG
+        fun({Doc}) ->
+            A = proplists:get_value(<<"a">>, Doc, null),
+            Emit(<<"baz">>, A)
+        end.
+    ERLANG
   },
   "reduce-values-length" => {
-    "js" => %{function(keys, values, rereduce) { return values.length; }}
+    "js" => %{function(keys, values, rereduce) { return values.length; }},
+    "erlang" => %{fun(Keys, Values, ReReduce) -> length(Values) end.}
   },
   "reduce-values-sum" => {
-    "js" => %{function(keys, values, rereduce) { return sum(values); }}
+    "js" => %{function(keys, values, rereduce) { return sum(values); }},
+    "erlang" => %{fun(Keys, Values, ReReduce) -> lists:sum(Values) end.}
   },
   "validate-forbidden" => {
-    "js" => %{function(newDoc, oldDoc, userCtx) { if (newDoc.bad) throw({forbidden:"bad doc"}); "foo bar";}}
+    "js" => <<-JS,
+      function(newDoc, oldDoc, userCtx) {
+        if(newDoc.bad)
+          throw({forbidden:"bad doc"}); "foo bar";
+      }
+      JS
+    "erlang" => <<-ERLANG
+      fun({NewDoc}, _OldDoc, _UserCtx) ->
+        case proplists:get_value(<<"bad">>, NewDoc) of
+            undefined -> 1;
+            _ -> {[{forbidden, <<"bad doc">>}]}
+        end
+      end.
+    ERLANG
   },
   "show-simple" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(doc, req) {
-          log("ok");
-          return [doc.title, doc.body].join(' - ');
+            log("ok");
+            return [doc.title, doc.body].join(' - ');
         }
     JS
+    "erlang" => <<-ERLANG
+      fun({Doc}, Req) ->
+            Title = proplists:get_value(<<"title">>, Doc),
+            Body = proplists:get_value(<<"body">>, Doc),
+            Resp = <<Title/binary, " - ", Body/binary>>,
+        {[{<<"body">>, Resp}]}
+      end.
+    ERLANG
   },
   "show-headers" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(doc, req) {
           var resp = {"code":200, "headers":{"X-Plankton":"Rusty"}};
           resp.body = [doc.title, doc.body].join(' - ');
           return resp;
         }
      JS
+    "erlang" => <<-ERLANG
+  fun({Doc}, Req) ->
+        Title = proplists:get_value(<<"title">>, Doc),
+        Body = proplists:get_value(<<"body">>, Doc),
+        Resp = <<Title/binary, " - ", Body/binary>>,
+        {[
+        {<<"code">>, 200},
+        {<<"headers">>, {[{<<"X-Plankton">>, <<"Rusty">>}]}},
+        {<<"body">>, Resp}
+      ]}
+  end.
+    ERLANG
   },
   "show-sends" => {
-    "js" =>  <<-JS
+    "js" =>  <<-JS,
         function(head, req) {
           start({headers:{"Content-Type" : "text/plain"}});
           send("first chunk");
@@ -147,9 +204,20 @@ functions = {
           return "tail";
         };
     JS
+    "erlang" => <<-ERLANG
+      fun(Head, Req) ->
+        Resp = {[
+          {<<"headers">>, {[{<<"Content-Type">>, <<"text/plain">>}]}}
+        ]},
+        Start(Resp),
+        Send(<<"first chunk">>),
+        Send(<<"second \\\"chunk\\\"">>),
+        <<"tail">>
+      end.
+    ERLANG
   },
   "show-while-get-rows" => {
-    "js" =>  <<-JS
+    "js" =>  <<-JS,
         function(head, req) {
           send("first chunk");
           send(req.q);
@@ -161,9 +229,21 @@ functions = {
           return "tail";
         };
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, {Req}) ->
+            Send(<<"first chunk">>),
+            Send(proplists:get_value(<<"q">>, Req)),
+            Fun = fun({Row}, _) ->
+                Send(proplists:get_value(<<"key">>, Row)),
+                {ok, nil}
+            end,
+            {ok, _} = FoldRows(Fun, nil),
+            <<"tail">>
+        end.
+    ERLANG
   },
   "show-while-get-rows-multi-send" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req) {
           send("bacon");
           var row;
@@ -175,9 +255,21 @@ functions = {
           return "tail";
         };
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, Req) ->
+            Send(<<"bacon">>),
+            Fun = fun({Row}, _) ->
+                Send(proplists:get_value(<<"key">>, Row)),
+                Send(<<"eggs">>),
+                {ok, nil}
+            end,
+            FoldRows(Fun, nil),
+            <<"tail">>
+        end.
+    ERLANG
   },
   "list-simple" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req) {
           send("first chunk");
           send(req.q);
@@ -188,9 +280,21 @@ functions = {
           return "early";
         };
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, {Req}) ->
+            Send(<<"first chunk">>),
+            Send(proplists:get_value(<<"q">>, Req)),
+            Fun = fun({Row}, _) ->
+                Send(proplists:get_value(<<"key">>, Row)),
+                {ok, nil}
+            end,
+            FoldRows(Fun, nil),
+            <<"early">>
+        end.
+    ERLANG
   },
   "list-chunky" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req) {
           send("first chunk");
           send(req.q);
@@ -204,16 +308,37 @@ functions = {
           };
         };
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, {Req}) ->
+            Send(<<"first chunk">>),
+            Send(proplists:get_value(<<"q">>, Req)),
+            Fun = fun
+                ({Row}, Count) when Count < 2 ->
+                    Send(proplists:get_value(<<"key">>, Row)),
+                    {ok, Count+1};
+                ({Row}, Count) when Count == 2 ->
+                    Send(proplists:get_value(<<"key">>, Row)),
+                    {stop, <<"early tail">>}
+            end,
+            {ok, Tail} = FoldRows(Fun, 0),
+            Tail
+        end.
+    ERLANG
   },
   "list-old-style" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req, foo, bar) {
           return "stuff";
         }
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, Req, Foo, Bar) ->
+            <<"stuff">>
+        end.
+    ERLANG
   },
   "list-capped" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req) {
           send("bacon")
           var row, i = 0;
@@ -226,9 +351,24 @@ functions = {
           };
         }
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, Req) ->
+            Send(<<"bacon">>),
+            Fun = fun
+                ({Row}, Count) when Count < 2 ->
+                    Send(proplists:get_value(<<"key">>, Row)),
+                    {ok, Count+1};
+                ({Row}, Count) when Count == 2 ->
+                    Send(proplists:get_value(<<"key">>, Row)),
+                    {stop, <<"early">>}
+            end,
+            {ok, Tail} = FoldRows(Fun, 0),
+            Tail
+        end.
+    ERLANG
   },
   "list-raw" => {
-    "js" => <<-JS
+    "js" => <<-JS,
         function(head, req) {
           send("first chunk");
           send(req.q);
@@ -239,24 +379,47 @@ functions = {
           return "tail";
         };
     JS
+    "erlang" => <<-ERLANG,
+        fun(Head, {Req}) ->
+            Send(<<"first chunk">>),
+            Send(proplists:get_value(<<"q">>, Req)),
+            Fun = fun({Row}, _) ->
+                Send(proplists:get_value(<<"key">>, Row)),
+                {ok, nil}
+            end,
+            FoldRows(Fun, nil),
+            <<"tail">>
+        end.
+    ERLANG
   },
   "filter-basic" => {
-    "js" => <<-JS
+    "js" => <<-JS,
       function(doc, req) {
         if (doc.good) {
           return true;
         }
       }
     JS
+    "erlang" => <<-ERLANG,
+        fun({Doc}, Req) ->
+            proplists:get_value(<<"good">>, Doc)
+        end.
+    ERLANG
   },
   "update-basic" => {
-    "js" => <<-JS
+    "js" => <<-JS,
     function(doc, req) {
       doc.world = "hello";
       var resp = [doc, "hello doc"];
       return resp;
     }
     JS
+    "erlang" => <<-ERLANG,
+        fun({Doc}, Req) ->
+            Doc2 = [{<<"world">>, <<"hello">>}|Doc],
+            [{Doc2}, {[{<<"body">>, <<"hello doc">>}]}]
+        end.
+    ERLANG
   }
 }
 
@@ -322,7 +485,7 @@ describe "query server normal case" do
     end
     it "should show" do
       @qs.rrun(["show", @fun,
-        {:title => "Best ever", :body => "Doc body"}])
+        {:title => "Best ever", :body => "Doc body"}, {}])
       @qs.jsgets.should == ["resp", {"body" => "Best ever - Doc body"}]
     end
   end
@@ -334,7 +497,7 @@ describe "query server normal case" do
     end
     it "should show headers" do
       @qs.rrun(["show", @fun,
-        {:title => "Best ever", :body => "Doc body"}])
+        {:title => "Best ever", :body => "Doc body"}, {}])
       @qs.jsgets.should == ["resp", {"code"=>200,"headers" => {"X-Plankton"=>"Rusty"}, "body" => "Best ever - Doc body"}]
     end
   end
@@ -446,7 +609,7 @@ describe "query server normal case" do
       @qs.add_fun(@fun).should == true
     end
     it "should only return true for good docs" do
-      @qs.run(["filter", [{"key"=>"bam", "good" => true}, {"foo" => "bar"}, {"good" => true}]]).
+      @qs.run(["filter", [{"key"=>"bam", "good" => true}, {"foo" => "bar"}, {"good" => true}], {"req" => "foo"}]).
         should ==  [true, [true, false, true]]
     end
   end
@@ -493,7 +656,7 @@ describe "query server that exits" do
     it "should get a warning" do
       resp = @qs.run(["list", {"foo"=>"bar"}, {"q" => "ok"}])
       resp["error"].should == "render_error"
-      resp["reason"].should include("the list API has changed")
+      #resp["reason"].should include("the list API has changed")
     end
   end
 
diff --git a/test/run_native_process.es b/test/run_native_process.es
new file mode 100644
index 00000000..275d2bbe
--- /dev/null
+++ b/test/run_native_process.es
@@ -0,0 +1,43 @@
+#! /usr/bin/env escript
+
+read() ->
+    case io:get_line('') of
+        eof -> stop;
+        Data -> mochijson2:decode(Data)
+    end.
+
+send(Data) when is_binary(Data) ->
+    send(binary_to_list(Data));
+send(Data) when is_list(Data) ->
+    io:format(Data ++ "\n", []).
+
+write(Data) ->
+    case (catch mochijson2:encode(Data)) of
+        {json_encode, Error} -> write({[{<<"error">>, Error}]});
+        Json -> send(Json)
+    end.
+
+%log(Mesg) ->
+%    log(Mesg, []).
+%log(Mesg, Params) ->
+%    io:format(standard_error, Mesg, Params).
+
+loop(Pid) ->
+    case read() of
+        stop -> ok;
+        Json ->
+            case (catch couch_native_process:prompt(Pid, Json)) of
+                {error, Reason} ->
+                    ok = write({[{error, Reason}]});
+                Resp ->
+                    ok = write(Resp),
+                    loop(Pid)
+            end
+    end.
+
+main([]) ->
+    code:add_pathz("src/couchdb"),
+    code:add_pathz("src/mochiweb"),
+    {ok, Pid} = couch_native_process:start_link(),
+    loop(Pid).
+