Go function runtime logging

Cloud Functions automatically captures a Go application's standard output streams and sends them to the centralized logging system available in Yandex Cloud. In addition to the application run history, the system logs request execution events.

Additional messages are logged using standard language constructs:

1. fmt.Print / Println: Outputs a message to the standard output stream, stdout.
2. print / println: Outputs a message to the standard error stream, stderr.
3. time.Now + time.Since: Returns the action duration.

For more information about string formatting, see the relevant section of the documentation. Learn about the print and println built-in functions here and about the time package and its functionality here.

System messagesSystem messages

When processing each function call, the system also logs START, END, and REPORT system messages:

START RequestID: <request_ID> Version: <function_version_ID>
END RequestID: <request_ID>
REPORT RequestID: <request_ID>
    Duration: 236.606 ms
    Billed Duration: 300 ms
    Memory Size: 128 MB
    Max Memory Used: 22 MB
    Queuing Duration: 0.027 ms
    Function Init Duration: 225.298 ms

All lines contain the ID of the request (RequestID), which is generated automatically when the function is invoked.

The REPORT line provides a report on the function run. It contains additional information about the resources consumed:

• Duration: Time spent invoking the function. It includes the Queuing Duration and Function Init Duration parameters.
• Billed Duration: Time billed based on the pricing policy.
• Memory Size: Amount of memory specified at version creation, MB.
• Max Memory Used: Memory used when the request starts running.
• Queuing Duration: Time spent by the request in the internal queue. If this time increases, it may indicate a lack of function instances. The maximum number of instances is determined by the quotas.
• Function Init Duration: Time spent initializing the runtime and loading the function code.