Merged revision 1043524 from trunk

    Calculate and verify MD5 digests outside of a couch_file server
    
    This has a significant positive impact on the performance, both for readers and writers,
    when there are several requests in parallel acessing the same database or view index file.
    
    $ node tests/compare_write_and_read.js --wclients 100 --rclients 200 \
      -name1 md5_out -name2 trunk \
      -url1 http://localhost:5984/ -url2 http://localhost:5985/ \
      --duration 120
    
    
    run 1) http://graphs.mikeal.couchone.com/#/graph/5c859b3e7d1b9bd0488cfe271105130c
    
    run 2) http://graphs.mikeal.couchone.com/#/graph/5c859b3e7d1b9bd0488cfe2711051bba
    
    Closes COUCHDB-980



git-svn-id: https://svn.apache.org/repos/asf/couchdb/branches/1.1.x@1044283 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 15 insertions, 8 deletions

diff --git a/src/couchdb/couch_file.erl b/src/couchdb/couch_file.erl
index 9d2c42ca..56ebc4f2 100644
--- a/src/couchdb/couch_file.erl
+++ b/src/couchdb/couch_file.erl
@@ -120,7 +120,19 @@ pread_binary(Fd, Pos) ->
 
 
 pread_iolist(Fd, Pos) ->
-    gen_server:call(Fd, {pread_iolist, Pos}, infinity).
+    case gen_server:call(Fd, {pread_iolist, Pos}, infinity) of
+    {ok, IoList, <<>>} ->
+        {ok, IoList};
+    {ok, IoList, Md5} ->
+        case couch_util:md5(IoList) of
+        Md5 ->
+            {ok, IoList};
+        _ ->
+            exit({file_corruption, <<"file corruption">>})
+        end;
+    Error ->
+        Error
+    end.
 
 %%----------------------------------------------------------------------
 %% Purpose: The length of a file, in bytes.
@@ -296,15 +308,10 @@ handle_call({pread_iolist, Pos}, _From, File) ->
     1 ->
         {Md5, IoList} = extract_md5(
             maybe_read_more_iolist(RestRawData, 16 + Len, NextPos, File)),
-        case couch_util:md5(IoList) of
-        Md5 ->
-            {reply, {ok, IoList}, File};
-        _ ->
-            {stop, file_corruption, {error,file_corruption}, File}
-        end;
+        {reply, {ok, IoList, Md5}, File};
     0 ->
         IoList = maybe_read_more_iolist(RestRawData, Len, NextPos, File),
-        {reply, {ok, IoList}, File}
+        {reply, {ok, IoList, <<>>}, File}
     end;
 handle_call({pread, Pos, Bytes}, _From, #file{fd=Fd,tail_append_begin=TailAppendBegin}=File) ->
     {ok, Bin} = file:pread(Fd, Pos, Bytes),