macintux

-module(thunk).
-compile(export_all).

%% > thunk:take(3, thunk:forever_zero()).
%% [0,0,0]
%% > thunk:take(3, thunk:fib()).
%% [1,1,2]
%% > thunk:take(18, thunk:fib()).
%% [1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,1597,2584]

macintux

For many developers, the thought of learning functional programming is intimidating. Parentheses, lambda calculus, type theory, and you can't even modify a variable!

In this talk we'll look at code that does useful work without requiring a Ph.D. in greybeard. Talk to software on another computer without opening a socket. Iterate over your data without setting up an iterator class hierarchy. Disassemble a network protocol header with this one cool line of code!

We'll talk about ideas that are being adopted by languages you probably already use. No functional programming experience required, just a willingness to see what can happen when you think outside the OO box.

macintux

%% Date formats in Erlang are a bit tricky to keep straight,
%% especially since the `calendar' library leverages Gregorian seconds
%% (seconds since year 0) rather than the more traditional UNIX epoch
%% seconds.
%%
%% This module illustrates the structures and conversions.

-module(erlang_dates).

-compile(export_all).

macintux

• Peter Frisch, 2016: The Year of the Zettabyte
• Eric Elliott, The Dao of Immutability
• Chris Okasaki, Purely Functional Data Structures (PDF)
• Pat Helland, Immutability Changes Everything (Video) / Whitepaper (PDF)
• Rich Hickey, Persistent Data Structures and Managed References (Video)
• Rich Hickey, Deconstructing the Database (Video)
• Jay Kreps, The Log: What every software engineer should know about real-time data's unifying abstraction

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

Whitepapers

• BBN, RFC 677
• Lamport, Time, Clocks, and the Ordering of Events in a Distributed System
• Version vectors, Detection of Mutual Inconsistency in Distributed Systems
• Vector clocks, Timestamps in Message-Passing Systems That Preserve the Partial Ordering
• Hybrid clocks, Logical Physical Clocks and Consistent Snapshots in Globally Distributed Databases
• Interval tree clocks, Interval Tree Clocks: A Logical Clock for Dynamic Systems

Other resources

• Jon Moore, Strange Loop 2015, How to Have your Causality and Wall Clocks, Too

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

%% 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

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

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