I'm trying to create two instances of webmachine in one erlang application. Each instance is to run on a different port and has its own specific configuration. Following the webmachine doc here, I have added the following processes to be started in my supervisor spec (application_sup.erl):
{
webmachine_instance_1,
{ webmachine_mochiweb, start,
[
[
{ ip, "0.0.0.0"},
{ port, 8000},
{ dispatch, [ {["*"], file_resource, []} ] }
]
]
},
permanent,
5000,
worker,
dynamic
},
{
webmachine_instance_2,
{ webmachine_mochiweb, start,
[
[
{ ip, "0.0.0.0"},
{ port, 8080},
{ dispatch, [ {["*"], file_resource, []} ] }
]
]
},
permanent,
5000,
worker,
dynamic
}
When I include both instances, I get a start error and cannot start my erlang application. After just trying to run the application with a single instance of webmachine (webmachine_instance_1 OR webmachine_instance_2), my application starts up fine.
Here is the specific error:
=PROGRESS REPORT==== 11-Mar-2014::17:00:31 ===
supervisor: {local, application_sup}
started: [{pid,<0.230.0>},
{name,webmachine_instance_1},
{mfargs,
{webmachine_mochiweb,start,
[[{ip,"0.0.0.0"},
{port,8000},
{dispatch, [{['*'],
file_resource,
[]
}]}]
]
}
},
{restart_type,permanent},
{shutdown,5000},
{child_type,worker}]
=SUPERVISOR REPORT==== 11-Mar-2014::17:00:31 ===
Supervisor: {local, application_sup}
Context: start_error
Reason: {'EXIT',
{undef,
[{webmachine_mochiweb,start,
[{ip,"0.0.0.0"},
{port,8080},
{dispatch,[{["*"],file_resource,[]}]}],
[]},
{supervisor,do_start_child,2,
[{file,"supervisor.erl"},{line,303}]},
{supervisor,start_children,3,
[{file,"supervisor.erl"},{line,287}]},
{supervisor,init_children,2,
[{file,"supervisor.erl"},{line,253}]},
{gen_server,init_it,6,
[{file,"gen_server.erl"},{line,304}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,227}]}]}}
Offender: [{pid,undefined},
{name,webmachine_instance_2},
{mfargs,
{webmachine_mochiweb,start,
[{ip,"0.0.0.0"},
{port,8080},
{dispatch,[{["*"],file_resource,[]}]}]}},
{restart_type,permanent},
{shutdown,5000},
{child_type,worker}]
I am fairly new to erlang and might not quite understand the underlying issues here - according to the webmachine doc we should be able to start two instances of the same application but with different configurations in an erlang app.
Thanks for any help/discussion on this issue!
Your child process config should have the following form:
{Name,
{webmachine_mochiweb, start, [WebConfig]},
permanent, 5000, worker, [mochiweb_socket_server]}
where Name
and WebConfig
must be unique to your webmachine instance. The WebConfig
part should include name
and dispatch_group
properties. For example:
WebConfig = [{name,instance1},
{dispatch_group,instance1},
{ip, Ip},
{port, Port},
{log_dir, "priv/log"},
{dispatch, Dispatch}],
So, for multiple instances you might have something like this for your supervisor spec:
WebConfig1 = [{name,instance1},
{dispatch_group,instance1},
{ip, Ip},
{port, Port},
{log_dir, "priv/log"},
{dispatch, Dispatch}],
WebConfig2 = [{name,instance2},
{dispatch_group,instance2},
{ip, Ip},
{port, Port+1},
{log_dir, "priv/log"},
{dispatch, Dispatch}],
Web1 = {instance1,
{webmachine_mochiweb, start, [WebConfig1]},
permanent, 5000, worker, [mochiweb_socket_server]},
Web2 = {instance2,
{webmachine_mochiweb, start, [WebConfig2]},
permanent, 5000, worker, [mochiweb_socket_server]},
Processes = [Web1, Web2],
{ok, { {one_for_one, 10, 10}, Processes} }.
One other thing: judging from the name application_sup
appearing in your question, you may have run the webmachine ./scripts/new_webmachine.sh
and specified the application name as application
. If so, don't do this, since application
is the name of a key Erlang OTP module, and your code will clash with it and cause all kinds of problems.