macintux

%% Useful in Erlang shell. These assume an already-defined handle named "Riak"

Get = fun(X, Y) -> helpers:get(Riak, X, Y) end.
RawGet = fun(X, Y) -> helpers:raw_get(Riak, X, Y) end.
Put = fun(X) -> helpers:put(Riak, X) end.
Update = fun(X, Y, Z) -> helpers:update(Riak, X, Y, Z) end.
Resolve = fun(X, Y) -> helpers:update(Riak, X, Y) end.
New = fun(X, Y, Z) -> helpers:new(X, Y, Z) end.

%% Add an object to Riak and retrieve it:

macintux

Assuming you've created a text file named "ordered" with the PDFs in the sequence you'd like to create:

$ cp /System/Library/Automator/Combine\ PDF\ Pages.action/Contents/Resources/join.py /usr/local/bin/join-pdfs

$ perl -e '$first = <STDIN>; chomp $first; while(<STDIN>) { $index++; $intmdt = "foo$index.pdf"; chomp; system("join-pdfs -o $intmdt $first $_"); $first = $intmdt; }' < ordered

Now you'll have a host of foo.pdf files; the last one is the one you want to rename to something useful, then rm foo*.pdf.

macintux

Put

API

• Starting: https://github.com/basho/riak_kv/blob/1.4.2/src/riak_kv_wm_object.erl#L619
• We create a new riak_object and populate the various fields with the headers, metadata supplied by the client.
• Big suprise, we eventually call riak_client:put: https://github.com/basho/riak_kv/blob/1.4.2/src/riak_client.erl#L143
• If/when the client returns any errors these are handled in handle_common_errors and it is nice to return human readable errors to client :)

Riak_client

macintux

I started working on some missing documentation in the Erlang stdlib, and found one particularly confusing rabbit hole.

gen_server.xml

In the documentation for gen_server, I found debug options for start_link which lacked type information:

    Dbg = trace | log | statistics | {logfile,FileName} | {install,{Func,FuncState}}</v>
        SOpts = [term()]

FileName isn't defined, Func and FuncState aren't defined, so I decided to dig into the source to document their types.

macintux

Doc: http://www.erlang.org/doc/reference_manual/typespec.html

-type square() :: tuple(pos_integer(), pos_integer()).
-type side() :: 'white'|'black'.
-type movefun() :: fun((square(), square(), side()) -> tuple(square(), list(square()))).
-type movedef() :: tuple(atom(), movefun()).

-record(move, { piece,
 start,

macintux

curl -XPOST http://localhost:8098/mapred
  -H"Content-Type: application/json"
  -d  '{"inputs":"notifications","query":[{"map":{"language":"erlang","source":"fun(O,_,_) when element(1,O) == r_object -> S=byte_size(term_to_binary(riak_object:get_values(O))), if (S>1048576) -> {ok,C}=riak:local_client(),C:delete(riak_object:bucket(O),riak_object:key(O)),[riak_object:key(O)]; true -> [] end;(_,_,_) -> [] end."}}]}'

macintux

This is not intended to be comprehensive or authoritative, just free online resources I've found valuable while learning more about Erlang.

Similar lists

• 0xAX's list of Erlang bookmarks
• Federico Carrone, Erlang Spawned Shelter
• Ivan Uemlianin's list of resources on various BEAM languages
• David Robakowski's curated list of awesome Erlang libraries, resources and shiny things
• Julius Beckmann's curated list of amazingly awesome Elixir and Erlang libraries, resources and shiny things

Instruction

macintux

#!/usr/local/bin/python

import riak

Riak = riak.RiakClient(pb_port=10017, protocol='pbc')
TweetsBucket = Riak.bucket('tweets')

results = TweetsBucket.get_index("hashtags_bin", "android",
                                 "androie", return_terms=False)

macintux

#!/usr/local/bin/python

import riak

Riak = riak.RiakClient(pb_port=10017, protocol='pbc')
TweetsBucket = Riak.bucket('tweets')

results = TweetsBucket.get_index("hashtags_bin", "android",
                                 "androie", return_terms=True)

macintux

• https://ferd.ca/a-distributed-systems-reading-list.html
• http://the-paper-trail.org/blog/distributed-systems-theory-for-the-distributed-systems-engineer/
• https://github.com/palvaro/CMPS290S-Winter16/blob/master/readings.md
• http://muratbuffalo.blogspot.com/2015/12/my-distributed-systems-seminars-reading.html
• http://christophermeiklejohn.com/distributed/systems/2013/07/12/readings-in-distributed-systems.html
• http://michaelrbernste.in/2013/11/06/distributed-systems-archaeology-works-cited.html
• http://rxin.github.io/db-readings/
• http://research.microsoft.com/en-us/um/people/lamport/pubs/pubs.html
• http://pdos.csail.mit.edu/dsrg/papers/
• http://scalingsystems.com/2011/09/07/reading-list-for-distributed-systems/