I've been playing with using postcommit hooks in some code. I
couldn't find an example, so looking at the source, I think the right
way to set one up is something like:
PHook = {struct, [ {<<"mod">>, <<?MODULE_STRING>>}, {<<"fun">>,
<<"notify_change">>}]},
RiakClient:set_bucket(<<?MY_KEY>>, [{postcommit, [PHook]}]),
Is there a better way?
Also, in debugging my hook, I found that wrapping the hook so I could
see exceptions made it much easier. I made the following patch that I
think might be useful to others, as well:
diff -r e836ea266eca apps/riak_kv/src/riak_kv_put_fsm.erl
--- a/apps/riak_kv/src/riak_kv_put_fsm.erl Thu May 13 17:28:01 2010 -0400
+++ b/apps/riak_kv/src/riak_kv_put_fsm.erl Thu May 13 14:50:07 2010 -0700
@@ -314,7 +314,7 @@
invoke_hook(precommit, Mod0, Fun0, undefined, RObj) ->
Mod = binary_to_atom(Mod0, utf8),
Fun = binary_to_atom(Fun0, utf8),
- Mod:Fun(RObj);
+ wrap_hook(Mod, Fun, RObj);
invoke_hook(precommit, undefined, undefined, JSName, RObj) ->
case riak_kv_js_manager:blocking_dispatch({{jsfun, JSName}, RObj}) of
{ok, <<"fail">>} ->
@@ -331,13 +331,22 @@
invoke_hook(postcommit, Mod0, Fun0, undefined, Obj) ->
Mod = binary_to_atom(Mod0, utf8),
Fun = binary_to_atom(Fun0, utf8),
- proc_lib:spawn(fun() -> Mod:Fun(Obj) end);
+ proc_lib:spawn(fun() -> wrap_hook(Mod,Fun,Obj) end);
invoke_hook(postcommit, undefined, undefined, _JSName, _Obj) ->
error_logger:warning_msg("Javascript post-commit hooks aren't
implemented");
%% NOP to handle all other cases
invoke_hook(_, _, _, _, RObj) ->
RObj.
+wrap_hook(Mod, Fun, Obj)->
+ try Mod:Fun(Obj)
+ catch
+ EType:X ->
+ error_logger:error_msg("problem invoking hook ~p:~p ->
~p:~p~n~p~n",
+ [Mod, Fun, EType, X,
erlang:get_stacktrace()]),
+ fail
+ end.
+
merge_robjs(RObjs0,AllowMult) ->
RObjs1 = [X || X <- [riak_kv_util:obj_not_deleted(O) ||
O <- RObjs0], X /= undefined],
Bruce
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