Unify behaviour and return value in private backends

Previous commit introduced badmatch, which I believe wasn't properly handled by the
layer above.

apps/ejabberd/src/mod_private_mnesia.erl

@@ -51,8 +51,10 @@ init(_Host, _Opts) ->
 
 multi_set_data(LUser, LServer, NS2XML) ->
     F = fun() -> multi_set_data_t(LUser, LServer, NS2XML) end,
-    {atomic, ok} = mnesia:transaction(F),
-    ok.
+    case mnesia:transaction(F) of
+        {atomic, ok} -> ok;
+        {aborted, Reason} -> {aborted, Reason}
+    end.
 
 multi_set_data_t(LUser, LServer, NS2XML) ->
     [set_data_t(LUser, LServer, NS, XML) || {NS, XML} <- NS2XML],

apps/ejabberd/src/mod_private_odbc.erl

@@ -44,8 +44,11 @@ init(_Host, _Opts) ->
 
 multi_set_data(LUser, LServer, NS2XML) ->
     F = fun() -> multi_set_data_t(LUser, LServer, NS2XML) end,
-    {atomic, ok} = odbc_queries:sql_transaction(LServer, F),
-    ok.
+    case odbc_queries:sql_transaction(LServer, F) of
+        {atomic, ok} -> ok;
+        {aborted, Reason} -> {aborted, Reason};
+        {error, Reason} -> {error, Reason}
+    end.
 
 multi_set_data_t(LUser, LServer, NS2XML) ->
     SLUser = ejabberd_odbc:escape(LUser),

apps/ejabberd/src/mod_private_riak.erl

@@ -33,8 +33,12 @@ init(_Host, _Opts) ->
 -spec multi_set_data(ejabberd:luser(), ejabberd:lserver(),
                     {binary(), ejabberd:xmlterm()}) -> ok.
 multi_set_data(LUser, LServer, NS2XML) ->
-    [set_private_data(LUser, LServer, NS, XML) || {NS, XML} <- NS2XML],
-    ok.
+    R = [set_private_data(LUser, LServer, NS, XML) || {NS, XML} <- NS2XML],
+    %% check if something returned with error msg
+    case lists:keyfind(error, 1, R) of
+        {error, Reason} -> {error, Reason};
+        false -> ok
+    end.
 
 -spec multi_get_data(ejabberd:luser(), ejabberd:lserver(),
                      {binary(), term()}) -> ok.
@@ -57,7 +61,7 @@ remove_user(LUser, LServer) ->
 
 set_private_data(LUser, LServer, NS, XML) ->
     Obj = riakc_obj:new(bucket_type(LServer), key(LUser, NS), xml:element_to_binary(XML)),
-    ok = mongoose_riak:put(Obj).
+    mongoose_riak:put(Obj).
 
 get_private_data(LUser, LServer, NS, Default) ->
     case mongoose_riak:get(bucket_type(LServer), key(LUser, NS)) of

doc/modules/mod_private.md

@@ -5,6 +5,10 @@ This module implements [XEP-0049 (Private XML Storage)](http://xmpp.org/extensio
 * **iqdisc**
 * **backend** (atom, default: `mnesia`) - Storage backend. Currently `mnesia`, `odbc`, `riak` and `mysql` are supported . `mysql` uses MySQL-specific queries so in some cases it is more efficient than generic `odbc`.
 
+**CAUTION:**  Riak backend doesn't support transactions(rollbacks), so please avoid inserting more
+than one value in one set request, otherwise you may end up with partially save data, backend returns
+first error.
+
 ### Example Configuration
 ```
 {mod_private, []}