Configuring Environment Variables

Overview

Environment variables allow you to pass dynamic parameters to a function without modifying code.

Scenario

Environment distinguishing: Configure different environment variables for the same function logic. For example, use environment variables to configure testing and development databases.
Configuration encryption: Configure encrypted environment variables to dynamically obtain authentication information (account, password, AK/SK) required to access other services.
Dynamic configuration: Configure environment variables for parameters that need to be dynamically adjusted, including query period and timeout, in function logic.

Procedure

You can configure encryption settings and environment variables to dynamically pass settings to your function code and libraries without changing your code.

Figure 1 Adding environment variables
Click to enlarge

For example, for Node.js, encryption settings and environment variable values can be obtained from getUserData(string key) in Context. For details, see Developing Functions in Node.js.

Environment variables and encryption settings are user-defined key-value pairs that store function settings. Keys can contain letters, digits, and underscores (_), and must start with a letter.
The total length of the key and value cannot exceed 4096 characters.
When you define environment variables, FunctionGraph displays all your input information in plain text. To ensure security, do not include sensitive information.
After encryption is enabled, key-value pairs are encrypted on the console and will remain encrypted during transmission.

Preset Parameters

The following lists preset parameters. Do not configure environment variables with the same names as any of these parameters.

**Table 1** Preset parameters and description
Environment Variable	Description	Obtaining Method and Default Value
RUNTIME_PROJECT_ID	Project ID	Obtain the value from a Context interface or a system environment variable.
RUNTIME_FUNC_NAME	Function name	Obtain the value from a Context interface or a system environment variable.
RUNTIME_FUNC_VERSION	Function version	Obtain the value from a Context interface or a system environment variable.
RUNTIME_HANDLER	Handler	Obtain the value from a system environment variable.
RUNTIME_TIMEOUT	Execution timeout allowed for a function.	Obtain the value from a system environment variable.
RUNTIME_USERDATA	Value passed through an environment variable	Obtain the value from a Context interface or a system environment variable.
RUNTIME_CPU	CPU usage of a function. The value is in proportion to MemorySize.	Obtain the value from a Context interface or a system environment variable.
RUNTIME_MEMORY	Memory size configured for a function	Obtain the value from a Context interface or a system environment variable. Unit: MB
RUNTIME_MAX_RESP_BODY_SIZE	Maximum size of a response body	Obtain the value from a system environment variable. Default value: 6,291,456 bytes
RUNTIME_INITIALIZER_HANDLER	Initializer	Obtain the value from a system environment variable.
RUNTIME_INITIALIZER_TIMEOUT	Initialization timeout of a function	Obtain the value from a system environment variable.
RUNTIME_ROOT	Runtime package path	Obtain the value from a system environment variable. Default value: /home/snuser/runtime
RUNTIME_CODE_ROOT	Path for storing code in a container	Obtain the value from a system environment variable. Default value: /opt/function/code
RUNTIME_LOG_DIR	Path for storing system logs in a container	Obtain the value from a system environment variable. Default value: /home/snuser/log

Example

You can use environment variables to configure which directory to install files in, where to store outputs, and how to store connection and logging settings. These settings are decoupled from the application logic, so you do not need to update your function code when you change the settings.

In the following code snippet, obs_output_bucket is the bucket used for storing processed images.

def handler(event, context):
    srcBucket, srcObjName = getObsObjInfo4OBSTrigger(event)
    obs_address = context.getUserData('obs_address')
    outputBucket = context.getUserData('obs_output_bucket')
    if obs_address is None:
        obs_address = '{obs_address_ip}'
    if outputBucket is None:
        outputBucket = 'casebucket-out'
            
    ak = context.getAccessKey()
    sk = context.getSecretKey()

    # download file uploaded by user from obs
    GetObject(obs_address, srcBucket, srcObjName, ak, sk)

    outFile = watermark_image(srcObjName)
    
    # Upload converted files to a new OBS bucket.
    PostObject (obs_address, outputBucket, outFile, ak, sk)

    return 'OK'

Using environment variable obs_output_bucket, you can flexibly set the OBS bucket used for storing output images.

Figure 2 Environment variables
Click to enlarge