Answering my own e-mail:
The function has to be executed on a Riak node. The script should call
rpc:call(Host, riak_kv_mrc_pipe, mapred, [Inputs, Phases])
instead of
riak_kv_mrc_pipe:mapred(Inputs, Phases).
Miro
On Tue, Feb 26, 2013 at 10:39 PM, Miroslav Urbanek
<miroslav.urba...@gmail.com> wrote:
> Dear Riak users,
>
> I have an Erlang script for counting the number of objects in a Riak bucket:
>
> ...
> Inputs = <<"buckets">>,
> Phases = [{reduce,{modfun,riak_kv_mapreduce,reduce_count_inputs},none,true}],
> ...
> {ok, Client} = riak:client_connect(Host)
> Client:mapred(Inputs, Phases)
> ...
>
> After the update to 1.3, this no longer works. In the mailing list
> archive I found an alternative method:
>
> riak_kv_mrc_pipe:mapred(Inputs, Phases)
>
> However, I'm getting the following error:
>
> escript: exception exit: {noproc,{gen_server,call,
> [riak_kv_mrc_sink_sup,
> {start_child,[<0.2.0>,[]]},
> infinity]}}
> in function gen_server:call/3 (gen_server.erl, line 188)
> in call from riak_kv_mrc_pipe:mapred_stream_sink/3
> (src/riak_kv_mrc_pipe.erl, line 266)
> in call from riak_kv_mrc_pipe:mapred/3 (src/riak_kv_mrc_pipe.erl, line 219)
>
> What does it mean? What's the optimal way to count number of keys in a
> bucket in Riak 1.3 anyway?
>
> Here's the complete script:
>
> #!/usr/bin/env escript
>
> main(_) ->
>
> Host = 'riak@domain',
> Inputs = <<"bucket">>,
> Phases =
> [{reduce,{modfun,riak_kv_mapreduce,reduce_count_inputs},none,true}],
>
> ok = application:start(inets),
> {ok, _} = net_kernel:start([count]),
> true = auth:set_cookie('riak'),
> true = net_kernel:connect_node(Host),
>
> case riak_kv_mrc_pipe:mapred(Inputs, Phases) of
> {ok, Result} -> io:format("OK: ~p~n", Result);
> {error, Reason} -> io:format("Error: ~p~n", Reason)
> end.
>
> Thanks,
> Miro
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