The inets httpd server docs say,
The following is to be put in the Erlang node application
configuration file to start an HTTP server at application startup:
[{inets, [{services, [{httpd, [{proplist_file,
"/var/tmp/server_root/conf/8888_props.conf"}]},
{httpd, [{proplist_file,
"/var/tmp/server_root/conf/8080_props.conf"}]}]}]}].
Where does that go in an app created by rebar3?
The OTP Application docs say,
7.8 Configuring an Application
An application can be configured using configuration parameters. These
are a list of {Par,Val} tuples specified by a key env in the .app
file:
{application, ch_app,
[{description, "Channel allocator"},
{vsn, "1"},
{modules, [ch_app, ch_sup, ch3]},
{registered, [ch3]},
{applications, [kernel, stdlib, sasl]},
{mod, {ch_app,[]}},
{env, [{file, "/usr/local/log"}]}
]}.
Par is to be an atom. Val is any term.
That seems to suggest that you create environment variables with {Name, Value} tuples. However, the required code specified in the httpd server docs does not seem to be in that format.
Just drop this into the sys.config file which is in config folder of your release. If you have anything there already, it will be in the format of:
[
{some_app, [{env_var, value},{...}]},
{another_app, [{env_var, value},{...}]},
% add here without outer[]...,
{kernel,
[{distributed, [{app_name, 5000,
['node#10.0.211.153', 'node_failover#10.8.222.15']}]},
{sync_nodes_mandatory, []},
{sync_nodes_optional, ['node_failover#10.8.222.15']},
{sync_nodes_timeout, 5000}]}
]
Related
How can I set configuration options for httpc's profiles when using rebar3?
Here is the only example being via erl -config inets.config that looks like this:
[{inets,
[{services,[{httpc,[{profile, server1}]},
{httpc, [{profile, server2}]}]}]
}].
I tried adopting it to my rebar3 project structure.
Code
Project was created with rebar3, with standard OTP layout:
rebar3 new release myapp
Here is my myapp/config/sys.config:
[
{ myapp, []},
{inets, [{services, [{httpc, [{profile, myapp}]}]}]}
].
rebar.config:
{erl_opts, [debug_info]}.
{deps, []}.
{relx, [{release, { myapp, "0.1.0" },
[myapp,
sasl]},
{sys_config, "./config/sys.config"},
{vm_args, "./config/vm.args"},
{dev_mode, true},
{include_erts, false},
{extended_start_script, true}]
}.
{profiles, [{prod, [{relx, [{dev_mode, false},
{include_erts, true}]}]
}]
}.
Here is my myapp.app.src file for completeness:
{application, myapp,
[{description, "An OTP application"},
{vsn, "0.1.0"},
{registered, []},
{mod, { myapp_app, []}},
{applications,
[kernel,
stdlib
]},
{env,[]},
{modules, []},
{maintainers, []},
{licenses, []},
{links, []}
]}.
Requests
Here is a request I'm trying to make from rebar`s shell:
$ ./rebar3 shell
1> ===> Booted myapp
1> ===> Booted sasl
...
1> httpc:request( "http://reddit.com", myapp).
** exception exit: {noproc,
{gen_server,call,
[httpc_myapp,
{request,
{request,undefined,<0.88.0>,0,http,
{"reddit.com",80},
"/",[],get,
{http_request_h,undefined,"keep-alive",undefined,
undefined,undefined,undefined,undefined,undefined,
undefined,...},
{[],[]},
{http_options,"HTTP/1.1",infinity,true,
{essl,[]},
undefined,false,infinity,...},
"http://reddit.com",[],none,[],1478280329839,
undefined,undefined,false}},
infinity]}}
in function gen_server:call/3 (gen_server.erl, line 212)
in call from httpc:handle_request/9 (httpc.erl, line 574)
Here is the request without a profile, to check that inets actually works:
2> httpc:request( "http://reddit.com").
=PROGRESS REPORT==== 4-Nov-2016::13:25:51 ===
supervisor: {local,inet_gethost_native_sup}
started: [{pid,<0.107.0>},{mfa,{inet_gethost_native,init,[[]]}}]
=PROGRESS REPORT==== 4-Nov-2016::13:25:51 ===
supervisor: {local,kernel_safe_sup}
started: [{pid,<0.106.0>},
{id,inet_gethost_native_sup},
{mfargs,{inet_gethost_native,start_link,[]}},
{restart_type,temporary},
{shutdown,1000},
{child_type,worker}]
{ok,{{"HTTP/1.1",200,"OK"},...
rebar3 itself use inets http clients so when It starts your application in shell, inets is already started and configured. One workaround would be stop inets before your application starts, as It's suggested by rebar3 developer (copied below). Another one would be boot your release in console mode:
./_build/default/rel/myapp/bin/myapp console
Beside that there is another problem with your project. You have not told you want inets being started for you. You should have this line in myapp.src:
{applications, [kernel, stdlib, inets]}
Or you can list inets in rebar.config release section, to tell relx this app should be included in release and started on boot.
{relx, [{release, { myapp, "0.1.0" }, [inets, myapp, sasl]} ]}
Stop Inets from Loading on rebar3 shell startup
Here is the copy of the full answer by Fred Hebert from the rebar3 mailing list:
We do need inets for package fetching and will likely not turn it off
automatically for all use cases as this could compromise general usage
of the rebar3 agent in case where the user application does not use
inets, but still asks to fetch packages in a subsequent run. The
workaround I would suggest would be to use a hook script for it. Hook
scripts run before we boot user applications and are regular escripts:
#!/usr/bin/env escript
main(_) -> application:stop(inets).
You can then hook the script in with:
{shell, [{script_file, "path/to/file"}]}
in rebar3.config, or with
rebar3 shell --script_file test/check_env.escript
I can't find anything in the documentation to suggest that rebar.config can contain the application configuration you want.
Instead, application configuration is often kept in a configuration directory in your application, and like the example you gave says, you must use the -config flag when launching erl to point to the configuration file.
If you use rebar3 for making release and start your service by script made with relx (from _build/default/rel/<release_name>/bin/<release_name> by default) the application configuration file is passed to erl for you. If config file exist in your application directory, by default in config/sys.config, It will be regarded as application configuration, otherwise an empty configuration will be made. You can customize Its path by relax' release option sys_config.
For our software, we typically had a single config/sys.config file. The structure is the same as the config sample you have provided. Note that the configuration file can contain settings for many different services. For example, mixing inets with one of ours:
[{inets, [
{services,[{httpc,[{profile, server1}]},
{httpc, [{profile, server2}]}]}
]},
{my_app, [
{my_setting, "my value"}
]}
].
We launch with erl -config config/sys.config.
This way if we need to set service configuration we can simply update our configuration file, which also houses the configuration specific to this application.
As far as I'm aware, this is the correct method to use. I have not been able to find documentation supporting any other way of doing this.
I am trying to start gproc as a dependency inside the app, but it fails with:
{error,{not_started,gproc}}
This is my app.src file which is used by Rebar3 when compiling:
{application, myapp,
[{description, "MyApp"},
{vsn, "0.1.0"},
{registered, []},
{mod, { my_app, []}},
{applications,
[kernel,
stdlib,
sasl,
gproc <--- Dependency, and is compiled with Rebar3
]},
{env,[]},
{modules, []},
{maintainers, []},
{licenses, []},
{links, []}
]}.
When starting from the shell with application:start(gproc). and then application:start(myapp). everything works beautifully. I don't understand why...
Maybe it is because of some sort of race condition?
The shell is started with:
erl -pa _build/default/lib/*/ebin -boot start_sasl -eval "application:start(myapp)"
Edit: When using rebar3 shell all works fine, what is the difference from the shell command I am using?
Use
application:ensure_all_started(myapp).
The plain start tries to start only the requested application, only verifying that the dependencies are already running.
Docs:
application:start/1:
Starts Application. If it is not loaded, the application controller first loads it using load/1. It ensures that any included applications are loaded, but does not start them. That is assumed to be taken care of in the code for Application.
application:ensure_all_started/1:
Equivalent to calling start/1,2 repeatedly on all dependencies that are not yet started for an application
I'm trying to use lager_syslog in my project but it seems like a driver is missing.
This is in my rebar.conf:
{deps, [
...
{lager_syslog, {git, "https://github.com/basho/lager_syslog.git", {branch, master}}}
]}.
My test handler:
{lager_syslog_backend, ["test", local1, info]},
The error:
19:29:09.981 [error] Lager failed to install handler {lager_syslog_backend,{"test",local1}} into lager_event, retrying later : {error,
{{shutdown,
{failed_to_start_child,
syslog,
"could not load driver syslog_drv: \"cannot open shared object file: No such file or directory\""}},
{syslog_app,
start,
[normal,
[]]}}}
Any suggestion?
thanks to Kenneth Lakin who answered my question in mailing list
IIRC, rebar3 moved the port compiler out to a rebar3 plugin, rather than
packing it in with the core project. From what I've seen, rebar2
projects that relied on it will fail to load their port drivers.
Add
{overrides,
[{override, syslog, [
{plugins, [pc]},
{artifacts, ["priv/syslog_drv.so"]},
{provider_hooks, [
{post,
[
{compile, {pc, compile}},
{clean, {pc, clean}}
]
}]
}
]}
]}.
to a rebar.conf in your project, clean, and rebuild. (The syslog project
is where lager_syslog's port driver lives.)
See also: https://github.com/blt/port_compiler#use-with-existing-dependency
My erlang application named "myapp1" builds fine using rebar as far as I do not include another erlang application "my_other_app" under its dependencies (deps). Once I add it to my dependencies, and specify it under rebar.config, its build fails in error as such:
> rebar compile
Uncaught error in rebar_core: {'EXIT',
{badarg,
[{re,run,[0.9,".*",[{capture,none}]],[]},
{rebar_deps,is_app_available,5,
[{file,"src/rebar_deps.erl"},{line,418}]},
{rebar_deps,find_dep_in_dir,3,
[{file,"src/rebar_deps.erl"},{line,380}]},
{rebar_deps,find_dep,3,
[{file,"src/rebar_deps.erl"},{line,362}]},
{rebar_deps,find_deps,4,
[{file,"src/rebar_deps.erl"},{line,345}]},
{rebar_deps,preprocess,2,
[{file,"src/rebar_deps.erl"},{line,63}]},
{rebar_core,acc_modules,5,
[{file,"src/rebar_core.erl"},{line,492}]},
{rebar_core,process_dir1,6,
[{file,"src/rebar_core.erl"},{line,195}]}]}}
The rebar.config is
%%-*- mode: erlang -*-
{deps, [
{webmachine, "1.10.*", {git, "git://github.com/basho/webmachine", "HEAD"}},
amqp_client,
rabbit_common,
my_other_app
]
}.
The tree structure is as such:
myapp1
-src/...
-ebin/...
-rebar.config
-deps/
-webmachine
-mochiweb
-my_other_app
-src/...
-ebin/...
-include/...
As far as I remove the my_other_app from the rebar.config, everything works (except that the application does not function given the fact I am excluding a required depdency, but at least it compiles after I comment the code that uses that dependency.
I am trying to understand what the "is_app_available" function does in rebar, as my my_other_app is indeed an OTP application, but it is not started at the time I compile with rebar (it will be started by the myapp1 itself once some services start.
It looks like the version for one of your applications might be an atom, 0.9, rather than the string, "0.9". The re module requires an iodata() for that argument. Try finding out which application that is and changing the atom to a string.
Found the issue...
The dependency application had a Vsn (version) to its my_other_app.app.src file that was not a string ( numeric value instead ). This caused rebar to error. Certainly rebar could have a more friendly capture/error message...
Therefore, make sure to verify the {vsn, "1.1"} tag, so it has a string rather than decimal/numeric.
{application, my_other_app, [
{description, "my other appapplication"},
{vsn, "1.1"},
{applications, [kernel, stdlib]},
{modules, [.........etc.etc.etc......]},
{registered, [my_other_app]},
{mod,{ my_other_app, {true} } }
]}.
What is the appropriate place for performing inets:start() ?
in `applicationname_app' module?
in applicationname_sup supervisor module?
in a child process hanging from the supervisor?\
someplace else?
(I am still struggling with inets:httpd)
Note: the answer cannot be to the tune " use a boot file " , please.
inets is a "stand-alone" Erlang application; inets:start() is just an alias to application:start(inets). I guess the answer pretty much depends on how you maintain your code.
If your code is packaged as an application, your .app file should list inets as required to be started before yours (see the applications tag). Starting your applicaion with application:start(my_app). will now ensure that inets is also started. Consequence: if you make a boot file, it will also start inets for you :-P
If you are keen on not using applications, I guess the choice depends on how your code works. If you will always need inets to be started, it is better started by any of your supervisors. If it is rarely needed, you can always make sure it is started with something like:
ensure_app_started(App) ->
case application:started(App) of
ok -> ok;
{error, already_started} -> ok;
Error -> Error
end.
In 2019, we use rebar3 to create an application and manage its dependencies. For dependencies that need to be downloaded, you add them to rebar.config, and rebar3 will download the dependencies. For example, if you add hackney (an http client) to rebar.config:
{erl_opts, [debug_info]}.
{deps, [
{hackney, ".*", {git, "git://github.com/benoitc/hackney.git", {branch, "master"}}}
]}.
{shell, [
% {config, "config/sys.config"},
{apps, [http_client]}
]}.
Then do:
../your_app_name$ rebar3 compile
rebar3 will download hackney and compile all the files in the application.
To make sure that all your dependencies get started before your app, you add the names of the dependencies to:
src/your_app_name.app.src
For instance,
{application, http_client,
[{description, "An OTP application"},
{vsn, "0.1.0"},
{registered, []},
{mod, {http_client_app, []}},
{applications,
[kernel,
stdlib,
hackney %%%<=========HERE
]},
{env,[]},
{modules, []},
{licenses, ["Apache 2.0"]},
{links, []}
]}.
The actual .app file gets created here:
_build/default/lib/your_app_name/ebin/your_app_name.app
To start your app in the shell along with all its dependencies, you do:
../your_app_name$ rebar3 shell
The inets application comes with erlang, so it doesn't need to be downloaded, so you don't specify inets as a dependency in rebar.config (you'll get an error when you $ rebar3 compile). You still need to specify inets as a dependency in your application in the file:
src/your_app_name.app.src
But rebar3 itself uses inets (to download your dependencies), so even if you didn't specify inets as a dependency in your application, inets would still get started before your app. You can test that by not specifying inets as a dependency in your application, then doing:
$ rebar3 shell
...
...
1> application:start(inets)
{error,{already_started,inets}}
But, don't rely on that and DO specify inets as a dependency in your application.
If your code is packaged as an application, list inets in the application resource file:
% Filename: ebin/flamingo.app
{application, flamingo,
[{vsn, "1.0.0"},
{modules, [flamingo_app,
flamingo_sup,
flamingo]},
{applications, [kernel,
stdlib,
inets]},
{mod, {flamingo_app, []}}
]}.
Then you can start the application using application:ensure_all_started(flamingo). This ensures that inets is started automatically for you (i.e. there is no need to explicitly call inets:start()).
For example (assuming the *.app file and *.beam files and are in ebin/):
$ erl -pa ebin/
Eshell V9.2 (abort with ^G)
1> application:ensure_all_started(flamingo).
{ok,[inets,flamingo]}