What causes "Invalid user_agent_patterns: {e}" in EpicGames/lore?

Validate each pattern with the same regex/pattern engine UserAgentFilter uses (e.g. test with `regex::Regex::new`)

Invalid user_agent_patterns

Error message

Invalid user_agent_patterns: {e}

What it means

async_main builds a UserAgentFilter from settings.server.user_agent.user_agent_patterns. UserAgentFilter::new compiles these patterns; any invalid pattern returns an error which is re-wrapped as this message, aborting server startup.

Solutions

Validate each pattern with the same regex/pattern engine UserAgentFilter uses (e.g. test with `regex::Regex::new`)
Fix or remove the offending pattern in [server.user_agent] user_agent_patterns
Add a config pre-check/lint step that compiles all patterns before deployment

Example fix

# before
[server.user_agent]
user_agent_patterns = ["^Mozilla.*[", "curl"]

# after
[server.user_agent]
user_agent_patterns = ["^Mozilla.*", "curl"]

Defensive patterns

Strategy: validation

Validate before calling

for pat in &settings.server.user_agent.user_agent_patterns {
    if let Err(e) = regex::Regex::new(pat) {
        return Err(format!("invalid user_agent_pattern '{pat}': {e}"));
    }
}

Type guard

fn valid_patterns(pats: &[String]) -> bool {
    pats.iter().all(|p| regex::Regex::new(p).is_ok())
}

Try / catch

let user_agent_filter = match UserAgentFilter::new(&ua.user_agent_patterns) {
    Ok(f) => Arc::new(f.with_unknown_sample_rate(ua.unknown_user_agent_sample_rate)),
    Err(e) => { eprintln!("Invalid user_agent_patterns: {e}"); std::process::exit(2); }
};

Prevention

Test every user-agent pattern against the regex engine before committing config
Add a config lint step that compiles all patterns in CI
Escape regex metacharacters when interpolating env vars into patterns

When it happens

Trigger: A user_agent_patterns entry in [server.user_agent] is not a valid pattern for the UserAgentFilter parser (malformed regex/wildcard syntax), so UserAgentFilter::new fails and the map_err produces this error.

Common situations: Hand-written regex with unbalanced brackets or invalid escapes in the TOML; copying patterns between filter implementations with different syntax; environment-variable overrides injecting unescaped special characters.

Related errors

AI-assisted analysis of EpicGames/lore@074eb0b0d1 (2026-09-13). Data as JSON: /api/errors/6341fbf37fd3052e. Report an issue: GitHub.

Appendix: source

Thrown at lore-server/src/server.rs:1677

            .inner
            .map(|provider| provider.detectors(runtime_handle.clone()))
            .unwrap_or_default();
        detectors.extend(self.registry.resource_detectors(runtime_handle));
        detectors
    }
}

async fn async_main(settings: (Settings, StringHash), config: ServerConfig) -> Result<()> {
    // Initialize metrics and tracing telemetry, returns a guard that will cleanup when it falls out
    // of scope
    let (settings, settings_hash) = settings;
    let runtime = runtime();
    let telemetry = settings.telemetry.clone().unwrap_or_default();
    let metrics_config = telemetry.metrics.clone().unwrap_or_default();
    let ua = &settings.server.user_agent;
    let user_agent_filter = Arc::new(
        UserAgentFilter::new(&ua.user_agent_patterns)
            .map_err(|e| anyhow::anyhow!("Invalid user_agent_patterns: {e}"))?
            .with_unknown_sample_rate(ua.unknown_user_agent_sample_rate),
    );

    // Initialize the plugin registry before telemetry: start with the
    // pre-populated registry from config, then register any build.rs-discovered
    // plugins. This must happen first so that every compiled-in plugin can
    // contribute OpenTelemetry resource detectors describing the deployment
    // environment it implies (e.g. AWS region, Nomad allocation).
    let mut plugin_registry = config.plugin_registry;
    plugins::register_all_plugins(&mut plugin_registry);

    let _guard = {
        let resource_detector_provider = PluginResourceDetectorProvider {
            inner: config.resource_detector_provider.as_deref(),
            registry: &plugin_registry,
        };
        TelemetryInitializer::from_config(
            &telemetry,

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