macintux

Riak

• http://docs.basho.com/
• http://littleriakbook.com/

General NoSQL

• http://highlyscalable.wordpress.com/2012/09/18/distributed-algorithms-in-nosql-databases/
• http://highlyscalable.wordpress.com/2012/03/01/nosql-data-modeling-techniques/
• http://architects.dzone.com/articles/relational-databases-vs-nosql

Consistency challenges

macintux

Name your parameters

Erlang atoms are awesome. Use them.

Counter-example:

    Existing = get_bucket_type(BucketType, undefined, false),

What do undefined and false mean on the other end? Who knows?

macintux

%% Replace the item at `Index' in `List' with `Element'.
%% Zero-based indexing. Deal with it.
-spec replace_list_element(non_neg_integer(), term(), list()).
replace_list_element(Index, Element, List) ->
    {Prefix, Suffix} = lists:split(Index, List),
    Prefix ++ [Element] ++ tl(Suffix).

macintux

=ERROR REPORT==== 4-Aug-2015::09:01:01 ===
** gen_event handler lager_stderr_backend crashed.
** Was installed in lager_event
** Last event was: {log,{lager_msg,[],
                                   [{application,cuttlefish},
                                    {module,cuttlefish_conf},
                                    {function,generate_element},
                                    {line,122},
                                    {pid,"<0.719.0>"},
                                    {node,nonode@nohost}],

macintux

%%% @author John Daily <jd@epep.us>
%%% @copyright (C) 2012, John Daily
%%% @doc
%%%   Assignment from programmingpraxis.com
%%%
%%% @reference See <a href="http://programmingpraxis.com/2009/02/19/rpn-calculator/">RPN Calculator</a>.
%%% @end

-module(rpncalc).
-export([rpn/0]).

macintux

%%% @author John Daily <jd@epep.us>
%%% @copyright (C) 2012, John Daily
%%% @doc
%%%   The httpc module in inets does not appear to offer any way to
%%%   determine the "real" URL if it follows a series of redirects
%%%   during its request. This code addresses that gap.
%%%
%%%   The code does not interpret any HTML-based redirect, such as a
%%%   meta refresh.

macintux

#!/usr/bin/env escript
% -*- mode: erlang -*-

main([BeamFile]) ->
    {ok,{_,[{abstract_code,{_,AC}}]}} = beam_lib:chunks(BeamFile,[abstract_code]),
    io:fwrite("~s~n", [erl_prettypr:format(erl_syntax:form_list(AC))]).

macintux

Riak's MapReduce functionality cannot survive a node failure. If a vnode involved with a query fails while actively processing the request, the entire query will have to be re-run. The failed query should be automatically terminated, but you'll have to re-run the query yourself.

If you create queries using Riak Pipe (the technology layer beneath MapReduce), it is possible to create queries that can survive a vnode failure, but that is not a trivial exercise.

Regarding the empty result set you're seeing: one possibility is that a vnode has failed recently and has come back online without data. MapReduce will not currently trigger a read repair, but that problem should be resolved with the forthcoming Riak 1.3 release.

macintux

124> <<T7/utf8, Excess/binary>> = hd(Blob).
<<77,195,131,194,188,110,99,104,101,110>>
125> Excess.
<<195,131,194,188,110,99,104,101,110>>
126> T7.
77

macintux

Content no longer valid

You're free to view the older revisions of this gist, but much of this content has been rewritten and will appear on the [Basho blog] (http://basho.com/blog) in the very near future.

Update: First part of the series is now at http://basho.com/understanding-riaks-configurable-behaviors-part-1/