There's a lot of parameters that can be configured in Nova. This document will try to explain them all.
Cowboy configuration
Nova uses Cowboy as the webserver. Cowboy is a very flexible webserver and Nova tries to expose as much of this flexibility as possible. This means that you can configure Cowboy in a lot of different ways. The configuration is done in the nova-application under cowboy_configuration-key in your sys.config.
| Key | Description | Value | Default |
|---|---|---|---|
stream_handlers |
Stream handlers are used to handle streaming requests. You can configure multiple stream handlers. Read more in the subsection Stream handlers | list() |
[nova_stream_h, cowboy_compress_h, cowboy_stream_h] |
middleware_handlers |
Middleware handlers are used to handle middleware requests. You can configure multiple middleware handlers. Read more in the subsection Middleware handlers | list() |
[nova_router, nova_plugin_handler, nova_security_handler, nova_handler, nova_plugin_handler] |
options |
Cowboy options. Read more in the subsection Cowboy options | map() |
#{compress => true} |
ip |
IP to bind to | tuple |
{0, 0, 0, 0} |
port |
Port to bind to | integer() |
8080 |
use_ssl |
If SSL should be used | boolean() |
false |
ssl_options |
Transport options for SSL. Nova uses ranch_ssl module so read about available options on their page. | ranch_ssl:opts() |
#{cert => "/path/to/fullchain.pem", key => "/path/to/privkey.pem"} |
ssl_port |
Port to bind to when using SSL | integer() |
8443 |
ca_cert |
Path to CA-cert Deprecated since 0.10.3 - Read with ssl_options |
string() |
undefined |
cert |
Path to cert Deprecated since 0.10.3 - Replaced with ssl_options |
string() |
undefined |
Nova specific configurations
Following parameters should be defined under the nova-key in your sys.config.
| Key | Description | Value | Default |
|---|---|---|---|
use_persistent_term |
Use persistent_term module to store routing tree |
boolean() |
true |
use_stacktrace |
If Nova should include stacktrace in error-pages | boolean() |
false |
render_error_pages |
If Nova should render error-pages for HTML-request | boolean() |
true |
use_sessions |
Turn off/on support for sessions | boolean() |
true |
session_manager |
Specifify a module to use as the session manager. Defaults to nova_session_ets |
atom() |
nova_session_ets |
use_strict_routing |
If the routing module should work under the strict mode. Using strict mode will cause errors if non-deterministic paths are detected. This is a beta-function so use with caution. | boolean() |
false |
bootstrap_application |
Define which application to bootstrap with Nova. This should be the name of your application. | atom() |
Will crash if not defined |
cowboy_configuration |
If you need some additional configuration done to Cowboy this is the place. Check nova_sup module to learn which keys that can be defined. |
map() |
#{} |
shutdown_delay |
Milliseconds to wait before suspending the listener during shutdown. Useful for letting load balancers drain traffic. See the Graceful shutdown guide. | integer() |
0 |
shutdown_drain_timeout |
Maximum milliseconds to wait for active connections to finish during shutdown. See the Graceful shutdown guide. | integer() |
15000 |
Application parameters
These parameters can be specified in your main application (Eg the one you've specified in the bootstrap-section).
| Key | Description | Value |
|---|---|---|
json_lib |
JSON lib to use. Read more in the subsection Configure json lib | atom() |
watchers |
Watchers are external programs that will run together with Nova. Watchers are defined as list of tuples where the tuples is in format {Command, ArgumentList} (Like [{my_app, "npm", ["run", "watch"], #{workdir => "priv/assets/js/my-app"}}]) |
[{string(), string()}] | [{atom(), string(), map()}] | [{atom(), string(), list(), map()}] |
router_module |
Module that contains the routes/1 callback |
atom() |
Configure json_lib
One can configure which json library to use for encoding/decoding json structures. The module defined for this should expose two different functions:
encode(Structure) -> binary() | iolist()
decode(JsonString) -> {ok, Structure}
Handling errors in Nova
Nova will by default render a error page if an error occurs. This page will be rendered using the nova_error-template. This template can be overridden by defining a template with the same name in your application.
By defauly Nova outputs a lot of information, including the stacktrace. This might not be a good approach in production. To turn off stacktraces in production you can add the following to your sys.config:
{nova, [{render_error_pages, false}]}
This will exclude stacktrace from the error page.
Note Nova is aware about which accept-headers the request is sent with and will respond with the correct content-type. If the request is sent with application/json Nova will respond with a JSON-structure instead of a HTML-page.