emqx/apps/emqx_resource/README.md

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# emqx_resource
The `emqx_resource` is a behavior that manages configuration specs and runtime states
for resources like mysql or redis backends.
It is intended to be used by the emqx_bridges and all other resources that need CRUD operations
to their configs, and need to initialize the states when creating.
There can be foreign references between resource instances via resource-id.
So they may find each other via this Id.
The main idea of the emqx resource is to put all the `general` code in a common lib, including
the config operations (like config validation, config dump back to files), and the state management.
And we put all the `specific` codes to the callback modules.
## Try it out
$ ./demo.sh
Eshell V11.1.8 (abort with ^G)
1> == the demo log tracer <<"log_tracer_clientid_shawn">> started.
config: #{<<"config">> =>
#{<<"bulk">> => <<"10KB">>,<<"cache_log_dir">> => <<"/tmp">>,
<<"condition">> => #{<<"clientid">> => <<"abc">>},
<<"level">> => <<"debug">>},
<<"id">> => <<"log_tracer_clientid_shawn">>,
<<"resource_type">> => <<"log_tracer">>}
1> emqx_resource_instance:health_check(<<"log_tracer_clientid_shawn">>).
== the demo log tracer <<"log_tracer_clientid_shawn">> is working well
state: #{health_checked => 1,logger_handler_id => abc}
ok
2> emqx_resource_instance:health_check(<<"log_tracer_clientid_shawn">>).
== the demo log tracer <<"log_tracer_clientid_shawn">> is working well
state: #{health_checked => 2,logger_handler_id => abc}
ok
3> emqx_resource_instance:query(<<"log_tracer_clientid_shawn">>, get_log).
== the demo log tracer <<"log_tracer_clientid_shawn">> received request: get_log
state: #{health_checked => 2,logger_handler_id => abc}
"this is a demo log messages..."
4> emqx_resource_instance:remove(<<"log_tracer_clientid_shawn">>).
== the demo log tracer <<"log_tracer_clientid_shawn">> stopped.
state: #{health_checked => 0,logger_handler_id => abc}
ok
5> emqx_resource_instance:query(<<"log_tracer_clientid_shawn">>, get_log).
** exception error: {get_instance,{<<"log_tracer_clientid_shawn">>,not_found}}