risingwavelabs/risingwave · critical

failed to parse `RUST_LOG`

Error message

failed to parse `RUST_LOG`

What it means

init_risingwave_logger reads RUST_LOG and parses it with tracing_subscriber's `Targets` filter; `.expect("failed to parse `RUST_LOG`")` panics when the string is not a valid directive list. Valid syntax is comma-separated `target=level` pairs like `info,rw_stream=debug,tower=warn`.

Solutions

1. Fix RUST_LOG to valid directive syntax, e.g. RUST_LOG=info,risingwave_stream=debug.
2. Use only valid level names: error, warn, info, debug, trace (or plain module filter without level).
3. Unset RUST_LOG to fall back to the built-in default filter.
4. Test the filter in a small Rust snippet using Targets::from_str before deploying.

Example fix

// before (invalid directive)
RUST_LOG=verbose,rw_stream=debg
// after
RUST_LOG=info,rw_stream=debug

// Validate RUST_LOG syntax before launching
if let Ok(v) = std::env::var("RUST_LOG") {
    let valid_levels = ["error", "warn", "info", "debug", "trace"];
    for directive in v.split(',') {
        let level = directive.rsplit('=').next().unwrap_or(directive);
        assert!(
            directive.is_empty() || valid_levels.contains(&level) || !level.contains(|c: char| c.is_whitespace()),
            "invalid RUST_LOG directive: {directive}"
        );
    }
}

When it happens

Trigger: RUST_LOG set (and non-empty) with invalid directives — e.g. `RUST_LOG=trace,` malformed level names (`RUST_LOG=infos`), missing level (`rw=dd`), stray characters, or invalid target syntax.

Common situations: Typos in level names (verbose, warnning); pasting regex or log4j-style patterns; commas/semicolons mix-ups; invalid module paths; users attempting per-crate filters with unsupported syntax.

Understand the failure class

Background: "is not a valid" / "Invalid ... value" environment variable errors: how libraries validate env vars and what to do when they reject yours — this error's family across 48 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• failed to create directory
• Failed to parse RW_DEADLOCK_DETECTION
• {0}
• AZBLOB_ENDPOINT not found from environment variables
• Can't cast string to date (expected format is YYYY-MM-DD)

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/604f41247e6f9b37. Report an issue: GitHub.

Appendix: source

Thrown at src/utils/runtime/src/logger.rs:312

                    Level::DEBUG
                } else {
                    Level::INFO
                }
            }
        };
        filter = filter.with_default(default_level);

        // Overrides from settings.
        filter = filter.with_targets(settings.targets);
        if let Some(default_level) = settings.default_level {
            filter = filter.with_default(default_level);
        }

        // Overrides from env var.
        if let Ok(rust_log) = std::env::var(EnvFilter::DEFAULT_ENV)
            && !rust_log.is_empty()
        {
            let rust_log_targets: Targets = rust_log.parse().expect("failed to parse `RUST_LOG`");
            if let Some(default_level) = rust_log_targets.default_level() {
                filter = filter.with_default(default_level);
            }
            filter = filter.with_targets(rust_log_targets)
        };

        filter
    };

    let mut layers = vec![];

    // fmt layer (formatting and logging to `stdout` or `stderr`)
    {
        let fmt_layer = tracing_subscriber::fmt::layer()
            .with_thread_names(settings.with_thread_name)
            .with_timer(default_timer.clone())
            .with_ansi(settings.colorful)
            .with_writer(move || {

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