gistfile1.txt

1. What's the best way to declare dependencies for erlang? I would have thought using rebar's transitive dependency management would be the way to go... put external dependencies in rebar.config, run 'rebar get-deps && rebar compile' and you're off to the races. But this thread indicates that this could break apps with shared dependencies. If both apps A and B depend on C, and C hoarks, then both apps A and B die, too.

http://stackoverflow.com/questions/11141198/when-to-use-erlang-applicationstart-or-included-applications-and-a-supervisor


2. Assuming that this thread was incorrect, and that rebar dependencies are the way to go, I'm having a teensy problem. I was following Dizzy's 2011 presentation (http://vimeo.com/22700527) and thought, sweet, I'll create a sample app and have it depend on ibrowse (very cool app).

REPRO:

1. make basic app

$ mkdir foo
$ cd foo
$ rebar create-app appid=foo
$ find .
.
./src
./src/foo_sup.erl
./src/foo.app.src
./src/foo_app.erl

2. verify compiles

$ rebar compile
==> foo (compile)
Compiled src/foo_app.erl
Compiled src/foo_sup.erl

3. add dependency

create rebar.config:

{deps, [
        {ibrowse, ".*", {git, "git://github.com/cmullaparthi/ibrowse.git", {tag, "v4.0.1"}}}
    ]
}.

4. get deps

$ rebar get-deps
==> foo (get-deps)
Pulling ibrowse from {git,"git://github.com/cmullaparthi/ibrowse.git",
                          {tag,"v4.0.1"}}
Cloning into 'ibrowse'...
==> ibrowse (get-deps)

5. verify compiles

[todd@quebec-01 foo]$ rebar compile
==> ibrowse (compile)
Compiled src/ibrowse_lib.erl
Compiled src/ibrowse_lb.erl
Compiled src/ibrowse_app.erl
Compiled src/ibrowse_test.erl
Compiled src/ibrowse_sup.erl
Compiled src/ibrowse.erl
/home/todd/projects/erlang/foo/deps/ibrowse/src/ibrowse_http_client.erl:999: Warning: variable 'State' is unused
Compiled src/ibrowse_http_client.erl
==> foo (compile)

******************************************
Ok, now here is the part where I'm confused,
how is one supposed to declare the
******************************************

6. Add the dependency, 'ibrowse' to my foo application's list of dependencies...(http://www.erlang.org/doc/man/app.html)...

deps/ibrowse/ebin/ibrowse.app shows:

        Application = ibrowse

Ok, so I'll update my src/foo.app.src from:

{application, foo,
 [
  {description, ""},
  {vsn, "1"},
  {registered, []},
  {applications, [
                  kernel,
                  stdlib
                 ]},
  {mod, { foo_app, []}},
  {env, []}
 ]}.


to

{application, foo,
 [
  {description, ""},
  {vsn, "1"},
  {registered, []},
  {applications, [
                  kernel,
                  stdlib,
<<< added >>>     ibrowse
                 ]},
  {mod, { foo_app, []}},
  {env, []}
 ]}.

7. compile

$ rebar compile

8. verify compiles ok, and that the ebin/foo.app has been updated to include the ibrowse dependency...

{application,foo,
             [{description,[]},
              {vsn,"1"},
              {registered,[]},
              {applications,[kernel,stdlib,ibrowse]},
              {mod,{foo_app,[]}},
              {env,[]},
              {modules,[foo_app,foo_sup]}]}.

Ok, looks good.

9. start the app, foo

$ erl -pa ebin/ -pa deps/ibrowse/ebin/
Erlang R15B02 (erts-5.9.2) [source] [64-bit] [smp:6:6] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.9.2  (abort with ^G)

1> application:start(foo).
{error,{not_started,ibrowse}}

Ok, that didn't work...

10. try starting ibrowse first, then foo

$ erl -pa ebin/ -pa deps/ibrowse/ebin/
Erlang R15B02 (erts-5.9.2) [source] [64-bit] [smp:6:6] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.9.2  (abort with ^G)
1> ibrowse:start().
{ok,<0.34.0>}
2> application:start(foo).
{error,{not_started,ibrowse}}


Ok, that's it. Any ideas what I'm doing wrong, or how I should go about debugging this app as it fails to startup?