What causes "balancer.check_interval must be > 0" in shadowsocks/shadowsocks-rust?

Set check_interval to a positive duration, e.g. check_interval = "10s".

balancer.check_interval must be > 0

Error message

balancer.check_interval must be > 0

What it means

During configuration validation, balancer.check_interval (the periodic health-check interval for the server balancer) must be a duration greater than zero. A zero-second interval would cause a busy health-check loop, so Config::check rejects it with ErrorKind::Invalid.

Source

Thrown at crates/shadowsocks-service/src/config.rs:2876

                return Err(err);
            }

            for local_config in &self.local {
                local_config.config.check_integrity()?;
            }

            // Balancer related checks
            if let Some(rtt) = self.balancer.max_server_rtt
                && rtt.as_secs() == 0
            {
                let err = Error::new(ErrorKind::Invalid, "balancer.max_server_rtt must be > 0", None);
                return Err(err);
            }

            if let Some(intv) = self.balancer.check_interval
                && intv.as_secs() == 0
            {
                let err = Error::new(ErrorKind::Invalid, "balancer.check_interval must be > 0", None);
                return Err(err);
            }
        }

        if self.config_type.is_server() && self.server.is_empty() {
            let err = Error::new(
                ErrorKind::MissingField,
                "missing any valid servers in configuration",
                None,
            );
            return Err(err);
        }

        #[cfg(feature = "local-online-config")]
        if self.config_type.is_online_config() && self.server.is_empty() {
            let err = Error::new(
                ErrorKind::MissingField,
                "missing any valid servers in configuration",

View on GitHub (pinned to 8eb0f0a65b)

Solutions

Set check_interval to a positive duration, e.g. check_interval = "10s".
To disable periodic checking, remove the check_interval key instead of setting it to 0.
Validate durations before loading by parsing them yourself and asserting as_secs() > 0.

Example fix

// before (config.toml)
[balancer]
check_interval = 0

// after
[balancer]
check_interval = "10s"

Defensive patterns

Strategy: validation

Validate before calling

// Rust: before loading config
if let Some(intv) = balancer_check_interval {
    assert!(intv.as_secs() > 0 || intv.subsec_nanos() > 0, "check_interval must be > 0");
}

Prevention

Use omission (not 0) to disable health checks.
Pick sane defaults (e.g. 10s) in config templates instead of 0 placeholders.
Validate durations with a typed parser (std::time::Duration::from_str) before writing config files.

When it happens

Trigger: Building/loading a local-mode Config where the balancer.check_interval field is Some but its value is 0 seconds (e.g. check_interval = 0 or "0s"), then calling check/validation as part of Config::from_*/load.

Common situations: Hand-written configs where the author set check_interval = 0 to try to disable health checks; templated configs with unfilled 0 placeholders; mistyped duration units so the value collapses to zero seconds.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of shadowsocks/shadowsocks-rust@8eb0f0a65b (2026-09-09). Data as JSON: /api/errors/dedece5b967fada1. Report an issue: GitHub.