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configuration.md

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Configuration

Basics

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Sanic holds the configuration in the config attribute of the application object. The configuration object is merely an object that can be modified either using dot-notation or like a dictionary. :--:1

app = Sanic("myapp")
app.config.DB_NAME = "appdb"
app.config["DB_USER"] = "appuser"

:---

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You can also use the update() method like on regular dictionaries. :--:1

db_settings = {
    'DB_HOST': 'localhost',
    'DB_NAME': 'appdb',
    'DB_USER': 'appuser'
}
app.config.update(db_settings)

:---

::: tip It is standard practice in Sanic to name your config values in uppercase letters. Indeed, you may experience weird behaviors if you start mixing uppercase and lowercase names. :::

Loading

Environment variables

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Any environment variables defined with the SANIC_ prefix will be applied to the Sanic config. For example, setting SANIC_REQUEST_TIMEOUT will be loaded by the application automatically and fed into the REQUEST_TIMEOUT config variable. :--:1

$ export SANIC_REQUEST_TIMEOUT=10
>>> print(app.config.REQUEST_TIMEOUT)
10

:---

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You can change the prefix that Sanic is expecting at startup. :--:1

$ export MYAPP_REQUEST_TIMEOUT=10
>>> app = Sanic(__name__, load_env='MYAPP_')
>>> print(app.config.REQUEST_TIMEOUT)
10

:---

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You can also disable environment variable loading completely. :--:1

app = Sanic(__name__, load_env=False)

:---

Using Sanic.update_config

The Sanic instance has a very versatile method for loading config: app.update_config. You can feed it a path to a file, a dictionary, a class, or just about any other sort of object.

From a file

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Let's say you have my_config.py file that looks like this. :--:1

# my_config.py
A = 1
B = 2

:---

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You can load this as config values by passing its path to app.update_config. :--:1

>>> app.update_config("/path/to/my_config.py")
>>> print(app.config.A)
1

:---

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This path also accepts bash style environment variables. :--:1

$ export my_path="/path/to"
app.update_config("${my_path}/my_config.py")

:---

::: tip Just remember that you have to provide environment variables in the format ${environment_variable} and that $environment_variable is not expanded (is treated as "plain" text). :::

From a dict

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The app.update_config method also works on plain dictionaries. :--:1

app.update_config({"A": 1, "B": 2})

:---

From a class or object

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You can define your own config class, and pass it to app.update_config :--:1

class MyConfig:
    A = 1
    B = 2

app.update_config(MyConfig)

:---

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It even could be instantiated. :--:1

app.update_config(MyConfig())

:---

Builtin values

Variable Default Description
ACCESS_LOG True Disable or enable access log
FALLBACK_ERROR_FORMAT html Format of error response if an exception is not caught and handled
FORWARDED_FOR_HEADER X-Forwarded-For The name of "X-Forwarded-For" HTTP header that contains client and proxy ip
FORWARDED_SECRET None Used to securely identify a specific proxy server (see below)
GRACEFUL_SHUTDOWN_TIMEOUT 15.0 How long to wait to force close non-idle connection (sec)
KEEP_ALIVE True Disables keep-alive when False
KEEP_ALIVE_TIMEOUT 5 How long to hold a TCP connection open (sec)
PROXIES_COUNT None The number of proxy servers in front of the app (e.g. nginx; see below)
REAL_IP_HEADER None The name of "X-Real-IP" HTTP header that contains real client ip
REGISTER True Whether the app registry should be enabled
REQUEST_BUFFER_QUEUE_SIZE 100 Request streaming buffer queue size
REQUEST_BUFFER_SIZE 65536 Request buffer size before request is paused, default is 64 Kib
REQUEST_ID_HEADER X-Request-ID The name of "X-Request-ID" HTTP header that contains request/correlation ID
REQUEST_MAX_SIZE 100000000 How big a request may be (bytes), default is 100 megabytes
REQUEST_TIMEOUT 60 How long a request can take to arrive (sec)
RESPONSE_TIMEOUT 60 How long a response can take to process (sec)
USE_UVLOOP True (except Windows) Whether to override the loop policy to use uvloop. Supported only with app.run.
WEBSOCKET_MAX_QUEUE 32 Maximum length of the queue that holds incoming messages
WEBSOCKET_MAX_SIZE 2^20 Maximum size for incoming messages (bytes)
WEBSOCKET_PING_INTERVAL 20 A Ping frame is sent every ping_interval seconds.
WEBSOCKET_PING_TIMEOUT 20 Connection is closed when Pong is not received after ping_timeout seconds
WEBSOCKET_READ_LIMIT 2^16 High-water limit of the buffer for incoming bytes
WEBSOCKET_WRITE_LIMIT 2^16 High-water limit of the buffer for outgoing bytes

::: tip FYI The USE_UVLOOP value will be ignored if running with Gunicorn. :::

::: tip FYI The WEBSOCKET_ values will be ignored if in ASGI mode. :::

Timeouts

REQUEST_TIMEOUT

A request timeout measures the duration of time between the instant when a new open TCP connection is passed to the Sanic backend server, and the instant when the whole HTTP request is received. If the time taken exceeds the REQUEST_TIMEOUT value (in seconds), this is considered a Client Error so Sanic generates an HTTP 408 response and sends that to the client. Set this parameter's value higher if your clients routinely pass very large request payloads or upload requests very slowly.

RESPONSE_TIMEOUT

A response timeout measures the duration of time between the instant the Sanic server passes the HTTP request to the Sanic App, and the instant a HTTP response is sent to the client. If the time taken exceeds the RESPONSE_TIMEOUT value (in seconds), this is considered a Server Error so Sanic generates an HTTP 503 response and sends that to the client. Set this parameter's value higher if your application is likely to have long-running process that delay the generation of a response.

KEEP_ALIVE_TIMEOUT

What is Keep Alive? And what does the Keep Alive Timeout value do?

Keep-Alive is a HTTP feature introduced in HTTP 1.1. When sending a HTTP request, the client (usually a web browser application) can set a Keep-Alive header to indicate the http server (Sanic) to not close the TCP connection after it has send the response. This allows the client to reuse the existing TCP connection to send subsequent HTTP requests, and ensures more efficient network traffic for both the client and the server.

The KEEP_ALIVE config variable is set to True in Sanic by default. If you don't need this feature in your application, set it to False to cause all client connections to close immediately after a response is sent, regardless of the Keep-Alive header on the request.

The amount of time the server holds the TCP connection open is decided by the server itself. In Sanic, that value is configured using the KEEP_ALIVE_TIMEOUT value. By default, it is set to 5 seconds. This is the same default setting as the Apache HTTP server and is a good balance between allowing enough time for the client to send a new request, and not holding open too many connections at once. Do not exceed 75 seconds unless you know your clients are using a browser which supports TCP connections held open for that long.

For reference:

  • Apache httpd server default keepalive timeout = 5 seconds
  • Nginx server default keepalive timeout = 75 seconds
  • Nginx performance tuning guidelines uses keepalive = 15 seconds
  • IE (5-9) client hard keepalive limit = 60 seconds
  • Firefox client hard keepalive limit = 115 seconds
  • Opera 11 client hard keepalive limit = 120 seconds
  • Chrome 13+ client keepalive limit > 300+ seconds

Proxy configuration

See proxy configuration section