View Source nova_plugin behaviour (nova v0.10.4)

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.

Summary

Types

request_type/0

Callbacks

plugin_info/0
post_request/2
pre_request/2

Types

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request_type/0

View Source 
-type request_type() :: pre_request | post_request.

Callbacks

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plugin_info/0

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