Logs

Writing and viewing logs is a crucial tool for debugging and monitoring your code. Serverless Functions offer you the option to utilize loggers to report status effectively.

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Native Logging

The Internet Computer provides a native, simple logging system where logs are persisted within the blockchain up to a maximum size of 4 KiB.

note

If new logs exceed the 4 KiB limit, the oldest entries will be removed. Logs persist across Satellite upgrades.

These logs are the preferred method for writing and viewing logs, as they are more efficient and cost-effective compared to the custom solution below. They also persist regardless of whether the update call succeeds or fails.

However, native logs do not yet support log levels, that's why all entries will appear as "Error" in the Juno Console.

Any printed or trapped messages using the ic_cdk crate are automatically collected as logs.

Example Usage

fn log() {
    ic_cdk::print("This is a log entry.");

    ic_cdk::trap("There was an error.");
}

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Custom Logging

Custom logging provides a flexible way to track and debug function executions within your Satellite if the native logging does not answer your needs.

How does it work?

Logs are stored in stable memory, accommodating up to 100 entries. Once this limit is reached, the oldest entry is discarded. It's important to note that since logs are saved in memory, your hooks should return a success—meaning they should not trap—otherwise, the information cannot be preserved.

Available loggers

Logger	Level	Description
log	Info	Logs a message.
log_with_data	Info	Logs a message with additional serialized data.
info	Info	Logs an informational message.
info_with_data	Info	Logs an informational message with additional serialized data.
debug	Debug	Logs an debug-level message.
debug_with_data	Debug	Logs a debug-level message with additional serialized data.
warn	Warning	Logs a warning message.
warn_with_data	Warning	Logs a warning message with additional serialized data.
error	Error	Logs an error message.
error_with_data	Error	Logs an error message with additional serialized data.