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Logging

Availability: Linux and embedded runtimes

A cell logs what happened while it ran. Each line goes to the node's logger.

Operations​

  • Log a message at one of five levels: trace, debug, info, warn, error.

Example​

use myrmic_sdk::{LogLevel, Metadata};

#[myrmic_sdk::cmd]
fn log_everything(md: Metadata) -> myrmic_sdk::Result {
    myrmic_sdk::trace!("a trace message")?;
    myrmic_sdk::debug!("a debug message")?;
    myrmic_sdk::info!("an info message")?;
    myrmic_sdk::warn!("a warning message")?;
    myrmic_sdk::error!("an error message")?;

    // The same as info!, with the level chosen in code.
    myrmic_sdk::log(&myrmic_sdk::format!("logged by {}", md.id), LogLevel::Info)?;

    Ok(())
}

Behavior​

Normal​

A log is not part of the handler's transaction. A handler that fails and is rolled back still leaves its lines in the log.

The runtime's log config decides what happens to a log line: which levels get through, how it is printed, and whether it is exported or stored.

Errors​

Logging fails when the runtime cannot be reached, and when the message is not a valid UTF-8 string.

Limits​

A log message is readable outside the cell, so keep secrets and sensitive data out of it.

API documentation​

For the level macros, see trace!, debug!, info!, warn! and error!. For logging without a macro, see log, LogLevel and format!.

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