Struct CircuitBreaker

pub struct CircuitBreaker { /* private fields */ }

A `CircuitBreaker`` throttler rejects retry attempts if the success rate is too low.

This struct implements the gRPC throttler algorithm. The throttler works by tracking the number of available “tokens” for a retry attempt. If this number goes below a threshold all retry attempts are throttled.

Retry failures decrement the number of tokens by a given cost. Completed requests (successfully or not) increase the tokens by 1.

Note: the number of tokens may go below the throttling threshold as multiple concurrent requests may fail and decrease the token count.

Note: throttling only applies to retry attempts, the initial requests is never throttled. This may increases the token count even if all retry attempts are throttled.

Implementations

impl CircuitBreaker

pub fn new(tokens: u64, min_tokens: u64, error_cost: u64) -> Result<Self>

Creates a new instance.

Parameters

• tokens - the initial number of tokens. This is decreased by error_cost on each retry failure, and increased by 1 when a request succeeds.
• min_tokens - stops accepting retry attempts when the number of tokens is at or below this value.
• error_cost - decrease the token count by this value on failed request attempts.

Example

fn configure_throttler() -> Result<http_client::ClientConfig> {
    let throttler = CircuitBreaker::new(1000, 250, 10)?;
    Ok(http_client::ClientConfig::default().set_retry_throttler(throttler))
}

pub fn clamp(tokens: u64, min_tokens: u64, error_cost: u64) -> Self

Creates a new instance, adjusting min_tokens if needed.`

Parameters

• tokens - the initial number of tokens. This is decreased by error_cost on each retry failure, and increased by 1 when a request succeeds.
• min_tokens - stops accepting retry attempts when the number of tokens is at or below this value. Clamped to be <= tokens.
• error_cost - decrease the token count by this value on failed request attempts.

Example

fn configure_throttler() -> http_client::ClientConfig {
    let throttler = CircuitBreaker::clamp(1000, 250, 10);
    http_client::ClientConfig::default().set_retry_throttler(throttler)
}

Trait Implementations

impl Clone for CircuitBreaker

fn clone(&self) -> CircuitBreaker

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CircuitBreaker

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CircuitBreaker

fn default() -> Self

Initialize a CircuitBreaker configured with recommended values.

Example

fn configure_throttler() -> http_client::ClientConfig {
    let throttler = CircuitBreaker::default();
    http_client::ClientConfig::default().set_retry_throttler(throttler)
}

impl RetryThrottler for CircuitBreaker

fn throttle_retry_attempt(&self) -> bool

Called by the retry loop before issuing a retry attempt. Returns true if the request should be throttled.

fn on_retry_failure(&mut self, flow: &RetryFlow)

Called by the retry loop after a retry failure.

fn on_success(&mut self)

Called by the retry loop when a RPC succeeds.