View Source nova_plugin behaviour (nova v0.9.4)

Plugins can be run at two different times; either in the beginning or at the end of a request. They can modify both the actual request or the nova-state. A plugin is implemented with the nova_plugin behaviour and needs to implement three different functions: pre_request/2, post_request/2 and plugin_info/0.

A plugin can return either {ok, NewState}, {break, NewState}, {stop, NewState}, {error, Reason}.

{ok, NewState} will continue the normal execution with the NewState.

{break, NewState} breaks the execution of the current plugin-chain. This means that if a pre_request-plugin returns the break-statement the rest of the plugins in that chain will be skipped.

{stop, NewState} stops the execution. The plugin is responsible in this case for returning a proper response to the client.

{error, Reason} will stop the execution and call the nova_error plugin, resulting in a 500 response back to the user. If debug mode is enabled the reason will be returned in the 500-response.

Link to this section Summary

Link to this section Types

-type request_type() :: pre_request | post_request.

Link to this section Callbacks

-callback plugin_info() ->
               {Title :: binary(),
                Version :: binary(),
                Author :: binary(),
                Description :: binary(),
                Options :: [{Key :: atom(), OptionDescription :: binary()}]}.
Link to this callback

post_request/2

View Source (optional)
-callback post_request(State :: nova:state(), Options :: map()) ->
                {ok, State0 :: nova:state()} |
                {break, State0 :: nova:state()} |
                {stop, State0 :: nova:state()} |
                {error, Reason :: term()}.
Link to this callback

pre_request/2

View Source (optional)
-callback pre_request(State :: nova:state(), Options :: map()) ->
               {ok, State0 :: nova:state()} |
               {break, State0 :: nova:state()} |
               {stop, State0 :: nova:state()} |
               {error, Reason :: term()}.