Configuration

Any reasonably complex application will need configuration that is not baked into the actual code. Settings might be different for different environments or installations.

Basics

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:

app = Sanic('myapp')
app.config.DB_NAME = 'appdb'
app.config.DB_USER = 'appuser'

Since the config object actually is a dictionary, you can use its update method in order to set several values at once:

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

In general the convention is to only have UPPERCASE configuration parameters. The methods described below for loading configuration only look for such uppercase parameters.

Loading Configuration

There are several ways how to load configuration.

From Environment Variables

Any 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. You can pass a different prefix to Sanic:

app = Sanic(__name__, load_env='MYAPP_')

Then the above variable would be MYAPP_REQUEST_TIMEOUT. If you want to disable loading from environment variables you can set it to False instead:

app = Sanic(__name__, load_env=False)

From an Object

If there are a lot of configuration values and they have sensible defaults it might be helpful to put them into a module:

import myapp.default_settings

app = Sanic('myapp')
app.config.from_object(myapp.default_settings)

or also by path to config:

app = Sanic('myapp')
app.config.from_object('config.path.config.Class')

You could use a class or any other object as well.

From a File

Usually you will want to load configuration from a file that is not part of the distributed application. You can load configuration from a file using from_pyfile(/path/to/config_file). However, that requires the program to know the path to the config file. So instead you can specify the location of the config file in an environment variable and tell Sanic to use that to find the config file:

app = Sanic('myapp')
app.config.from_envvar('MYAPP_SETTINGS')

Then you can run your application with the MYAPP_SETTINGS environment variable set:

#$ MYAPP_SETTINGS=/path/to/config_file python3 myapp.py
#INFO: Goin' Fast @ http://0.0.0.0:8000

The config files are regular Python files which are executed in order to load them. This allows you to use arbitrary logic for constructing the right configuration. Only uppercase variables are added to the configuration. Most commonly the configuration consists of simple key value pairs:

# config_file
DB_HOST = 'localhost'
DB_NAME = 'appdb'
DB_USER = 'appuser'

Builtin Configuration Values

Out of the box there are just a few predefined values which can be overwritten when creating the application. Note that websocket configuration values will have no impact if running in ASGI mode.

Variable

Default

Description

REQUEST_MAX_SIZE

100000000

How big a request may be (bytes)

REQUEST_BUFFER_QUEUE_SIZE

100

Request streaming buffer queue size

REQUEST_TIMEOUT

60

How long a request can take to arrive (sec)

RESPONSE_TIMEOUT

60

How long a response can take to process (sec)

KEEP_ALIVE

True

Disables keep-alive when False

KEEP_ALIVE_TIMEOUT

5

How long to hold a TCP connection open (sec)

WEBSOCKET_MAX_SIZE

2^20

Maximum size for incoming messages (bytes)

WEBSOCKET_MAX_QUEUE

32

Maximum length of the queue that holds incoming messages

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

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

GRACEFUL_SHUTDOWN_TIMEOUT

15.0

How long to wait to force close non-idle connection (sec)

ACCESS_LOG

True

Disable or enable access log

FORWARDED_SECRET

None

Used to securely identify a specific proxy server (see below)

PROXIES_COUNT

None

The number of proxy servers in front of the app (e.g. nginx; see below)

FORWARDED_FOR_HEADER

“X-Forwarded-For”

The name of “X-Forwarded-For” HTTP header that contains client and proxy ip

REAL_IP_HEADER

None

The name of “X-Real-IP” HTTP header that contains real client ip

The different Timeout variables:

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

When you use a reverse proxy server (e.g. nginx), the value of request.ip will contain ip of a proxy, typically 127.0.0.1. Sanic may be configured to use proxy headers for determining the true client IP, available as request.remote_addr. The full external URL is also constructed from header fields if available.

Without proper precautions, a malicious client may use proxy headers to spoof its own IP. To avoid such issues, Sanic does not use any proxy headers unless explicitly enabled.

Services behind reverse proxies must configure FORWARDED_SECRET, REAL_IP_HEADER and/or PROXIES_COUNT.

Forwarded header

  • Set FORWARDED_SECRET to an identifier used by the proxy of interest.

The secret is used to securely identify a specific proxy server. Given the above header, secret Pr0xy would use the information on the first line and secret _1234proxy would use the second line. The secret must exactly match the value of secret or by. A secret in by must begin with an underscore and use only characters specified in RFC 7239 section 6.3, while secret has no such restrictions.

Sanic ignores any elements without the secret key, and will not even parse the header if no secret is set.

All other proxy headers are ignored once a trusted forwarded element is found, as it already carries complete information about the client.

Traditional proxy headers

  • Set REAL_IP_HEADER to x-real-ip, true-client-ip, cf-connecting-ip or other name of such header.

  • Set PROXIES_COUNT to the number of entries expected in x-forwarded-for (name configurable via FORWARDED_FOR_HEADER).

If client IP is found by one of these methods, Sanic uses the following headers for URL parts:

  • x-forwarded-proto, x-forwarded-host, x-forwarded-port, x-forwarded-path and if necessary, x-scheme.

Proxy config if using …

  • a proxy that supports forwarded: set FORWARDED_SECRET to the value that the proxy inserts in the header
    • Apache Traffic Server: CONFIG proxy.config.http.insert_forwarded STRING for|proto|host|by=_secret

    • NGHTTPX: nghttpx –add-forwarded=for,proto,host,by –forwarded-for=ip –forwarded-by=_secret

    • NGINX: Nginx Deployment.

  • a custom header with client IP: set REAL_IP_HEADER to the name of that header

  • x-forwarded-for: set PROXIES_COUNT to 1 for a single proxy, or a greater number to allow Sanic to select the correct IP

  • no proxies: no configuration required!

Changes in Sanic 19.9

Earlier Sanic versions had unsafe default settings. From 19.9 onwards proxy settings must be set manually, and support for negative PROXIES_COUNT has been removed.