627 lines
20 KiB
Rust
627 lines
20 KiB
Rust
use std::{
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sync::atomic::{AtomicU32, AtomicU64, AtomicU8, Ordering},
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time::{Duration, Instant},
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};
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use tracing::info;
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use crate::observability::metrics::Metrics;
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/// Circuit breaker configuration
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#[derive(Debug, Clone)]
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pub struct CircuitBreakerConfig {
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/// Number of consecutive failures to open the circuit
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pub failure_threshold: u32,
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/// Success threshold to close circuit from half-open
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pub success_threshold: u32,
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/// Duration to wait before attempting half-open
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pub timeout_duration: Duration,
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/// Time window for failure counting
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pub window_duration: Duration,
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}
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impl Default for CircuitBreakerConfig {
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fn default() -> Self {
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Self {
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failure_threshold: 5,
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success_threshold: 2,
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timeout_duration: Duration::from_secs(30),
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window_duration: Duration::from_secs(60),
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}
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}
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}
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/// Circuit breaker state constants for atomic storage
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const STATE_CLOSED: u8 = 0;
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const STATE_OPEN: u8 = 1;
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const STATE_HALF_OPEN: u8 = 2;
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/// Circuit breaker state
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub enum CircuitState {
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/// Normal operation - requests are allowed
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Closed,
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/// Circuit is open - requests are rejected
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Open,
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/// Testing if service has recovered - limited requests allowed
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HalfOpen,
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}
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impl std::fmt::Display for CircuitState {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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CircuitState::Closed => write!(f, "Closed"),
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CircuitState::Open => write!(f, "Open"),
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CircuitState::HalfOpen => write!(f, "HalfOpen"),
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}
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}
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}
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impl CircuitState {
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pub fn as_str(&self) -> &'static str {
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match self {
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CircuitState::Closed => "closed",
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CircuitState::Open => "open",
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CircuitState::HalfOpen => "half_open",
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}
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}
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pub fn to_int(&self) -> u8 {
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match self {
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CircuitState::Closed => STATE_CLOSED,
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CircuitState::Open => STATE_OPEN,
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CircuitState::HalfOpen => STATE_HALF_OPEN,
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}
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}
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fn from_int(v: u8) -> Self {
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match v {
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STATE_CLOSED => CircuitState::Closed,
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STATE_OPEN => CircuitState::Open,
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STATE_HALF_OPEN => CircuitState::HalfOpen,
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_ => CircuitState::Closed, // Default to closed for safety
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}
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}
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}
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/// Get current time as milliseconds since an arbitrary epoch.
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/// Uses Instant for monotonic time, converting to ms for atomic storage.
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#[inline]
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fn now_ms() -> u64 {
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// Use a static reference point for consistent timing
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static START: std::sync::OnceLock<Instant> = std::sync::OnceLock::new();
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let start = START.get_or_init(Instant::now);
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start.elapsed().as_millis() as u64
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}
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/// Circuit breaker implementation using lock-free atomics for hot paths.
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///
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/// This implementation avoids RwLock contention by using atomic operations
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/// for state checks (the most common operation). Only state transitions
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/// use compare-and-swap which is still lock-free.
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#[derive(Debug)]
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pub struct CircuitBreaker {
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/// Circuit state stored as atomic u8 (0=Closed, 1=Open, 2=HalfOpen)
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state: AtomicU8,
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consecutive_failures: AtomicU32,
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consecutive_successes: AtomicU32,
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total_failures: AtomicU64,
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total_successes: AtomicU64,
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/// Last failure time in milliseconds (from now_ms())
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last_failure_time_ms: AtomicU64,
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/// Last state change time in milliseconds (from now_ms())
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last_state_change_ms: AtomicU64,
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config: CircuitBreakerConfig,
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metric_label: String,
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}
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impl CircuitBreaker {
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/// Create a new circuit breaker with default configuration
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pub fn new() -> Self {
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Self::with_config_and_label(CircuitBreakerConfig::default(), String::new())
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}
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/// Create a new circuit breaker with custom configuration and metric label
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pub fn with_config_and_label(config: CircuitBreakerConfig, metric_label: String) -> Self {
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let init_state = CircuitState::Closed;
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Metrics::set_worker_cb_state(&metric_label, init_state.to_int());
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Self {
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state: AtomicU8::new(STATE_CLOSED),
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consecutive_failures: AtomicU32::new(0),
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consecutive_successes: AtomicU32::new(0),
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total_failures: AtomicU64::new(0),
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total_successes: AtomicU64::new(0),
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last_failure_time_ms: AtomicU64::new(0),
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last_state_change_ms: AtomicU64::new(now_ms()),
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config,
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metric_label,
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}
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}
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/// Get the metric label
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pub fn metric_label(&self) -> &str {
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&self.metric_label
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}
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/// Check if a request can be executed (lock-free hot path)
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#[inline]
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pub fn can_execute(&self) -> bool {
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let state = self.state();
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match state {
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CircuitState::Closed => true,
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CircuitState::Open => false,
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CircuitState::HalfOpen => true,
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}
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}
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/// Get the current state (lock-free)
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#[inline]
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pub fn state(&self) -> CircuitState {
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self.check_and_update_state_returning()
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}
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/// Check and update state, returning the current state (lock-free)
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#[inline]
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fn check_and_update_state_returning(&self) -> CircuitState {
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let current_state_int = self.state.load(Ordering::Acquire);
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let current_state = CircuitState::from_int(current_state_int);
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if current_state == CircuitState::Open {
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let last_change_ms = self.last_state_change_ms.load(Ordering::Acquire);
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let elapsed_ms = now_ms().saturating_sub(last_change_ms);
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let timeout_ms = self.config.timeout_duration.as_millis() as u64;
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if elapsed_ms >= timeout_ms {
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// Try to transition to HalfOpen using CAS
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if self
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.state
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.compare_exchange(
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STATE_OPEN,
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STATE_HALF_OPEN,
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Ordering::AcqRel,
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Ordering::Acquire,
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)
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.is_ok()
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{
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self.last_state_change_ms.store(now_ms(), Ordering::Release);
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self.consecutive_failures.store(0, Ordering::Release);
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self.consecutive_successes.store(0, Ordering::Release);
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info!("Circuit breaker state transition: open -> half_open");
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Metrics::record_worker_cb_transition(&self.metric_label, "open", "half_open");
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Metrics::set_worker_cb_state(&self.metric_label, STATE_HALF_OPEN);
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self.publish_gauge_metrics();
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return CircuitState::HalfOpen;
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}
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// Another thread already transitioned, re-read the state
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return CircuitState::from_int(self.state.load(Ordering::Acquire));
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}
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}
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current_state
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}
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/// Record the outcome of a request
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pub fn record_outcome(&self, success: bool) {
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if success {
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self.record_success();
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} else {
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self.record_failure();
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}
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let outcome_str = if success { "success" } else { "failure" };
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Metrics::record_worker_cb_outcome(&self.metric_label, outcome_str);
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self.publish_gauge_metrics();
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}
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/// Record a successful request
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pub fn record_success(&self) {
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self.total_successes.fetch_add(1, Ordering::Relaxed);
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self.consecutive_failures.store(0, Ordering::Release);
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let successes = self.consecutive_successes.fetch_add(1, Ordering::AcqRel) + 1;
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let current_state = CircuitState::from_int(self.state.load(Ordering::Acquire));
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match current_state {
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CircuitState::HalfOpen => {
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if successes >= self.config.success_threshold {
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self.transition_to(CircuitState::Closed);
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}
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}
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CircuitState::Closed => {}
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CircuitState::Open => {
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tracing::warn!("Success recorded while circuit is open");
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}
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}
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}
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/// Record a failed request
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pub fn record_failure(&self) {
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self.total_failures.fetch_add(1, Ordering::Relaxed);
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self.consecutive_successes.store(0, Ordering::Release);
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let failures = self.consecutive_failures.fetch_add(1, Ordering::AcqRel) + 1;
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// Update last failure time atomically
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self.last_failure_time_ms.store(now_ms(), Ordering::Release);
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let current_state = CircuitState::from_int(self.state.load(Ordering::Acquire));
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match current_state {
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CircuitState::Closed => {
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if failures >= self.config.failure_threshold {
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self.transition_to(CircuitState::Open);
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}
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}
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CircuitState::HalfOpen => {
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self.transition_to(CircuitState::Open);
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}
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CircuitState::Open => {}
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}
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}
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/// Transition to a new state (uses CAS for lock-free operation)
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fn transition_to(&self, new_state: CircuitState) {
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let new_state_int = new_state.to_int();
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let old_state_int = self.state.swap(new_state_int, Ordering::AcqRel);
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let old_state = CircuitState::from_int(old_state_int);
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if old_state != new_state {
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self.last_state_change_ms.store(now_ms(), Ordering::Release);
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match new_state {
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CircuitState::Closed => {
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self.consecutive_failures.store(0, Ordering::Release);
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self.consecutive_successes.store(0, Ordering::Release);
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}
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CircuitState::Open => {
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self.consecutive_successes.store(0, Ordering::Release);
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}
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CircuitState::HalfOpen => {
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self.consecutive_failures.store(0, Ordering::Release);
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self.consecutive_successes.store(0, Ordering::Release);
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}
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}
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let from = old_state.as_str();
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let to = new_state.as_str();
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info!("Circuit breaker state transition: {} -> {}", from, to);
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Metrics::record_worker_cb_transition(&self.metric_label, from, to);
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Metrics::set_worker_cb_state(&self.metric_label, new_state.to_int());
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self.publish_gauge_metrics();
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}
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}
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/// Get the number of consecutive failures
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pub fn consecutive_failures(&self) -> u32 {
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self.consecutive_failures.load(Ordering::Acquire)
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}
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/// Get the number of consecutive successes
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pub fn consecutive_successes(&self) -> u32 {
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self.consecutive_successes.load(Ordering::Acquire)
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}
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/// Get total failures
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pub fn total_failures(&self) -> u64 {
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self.total_failures.load(Ordering::Relaxed)
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}
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/// Get total successes
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pub fn total_successes(&self) -> u64 {
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self.total_successes.load(Ordering::Relaxed)
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}
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/// Get time since last failure
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pub fn time_since_last_failure(&self) -> Option<Duration> {
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let last_ms = self.last_failure_time_ms.load(Ordering::Acquire);
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if last_ms == 0 {
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None
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} else {
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let elapsed_ms = now_ms().saturating_sub(last_ms);
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Some(Duration::from_millis(elapsed_ms))
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}
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}
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/// Get time since last state change
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pub fn time_since_last_state_change(&self) -> Duration {
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let last_ms = self.last_state_change_ms.load(Ordering::Acquire);
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let elapsed_ms = now_ms().saturating_sub(last_ms);
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Duration::from_millis(elapsed_ms)
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}
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/// Check if the circuit is in a half-open state
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pub fn is_half_open(&self) -> bool {
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self.state() == CircuitState::HalfOpen
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}
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/// Record a test success (for health check probing)
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pub fn record_test_success(&self) {
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if self.is_half_open() {
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self.record_success();
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}
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}
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/// Record a test failure (for health check probing)
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pub fn record_test_failure(&self) {
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if self.is_half_open() {
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self.record_failure();
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}
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}
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/// Reset the circuit breaker to closed state
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pub fn reset(&self) {
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self.transition_to(CircuitState::Closed);
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self.consecutive_failures.store(0, Ordering::Release);
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self.consecutive_successes.store(0, Ordering::Release);
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self.publish_gauge_metrics();
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}
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/// Force the circuit to open (for manual intervention)
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pub fn force_open(&self) {
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self.transition_to(CircuitState::Open);
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}
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/// Get circuit breaker statistics
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pub fn stats(&self) -> CircuitBreakerStats {
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CircuitBreakerStats {
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state: self.state(),
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consecutive_failures: self.consecutive_failures(),
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consecutive_successes: self.consecutive_successes(),
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total_failures: self.total_failures(),
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total_successes: self.total_successes(),
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time_since_last_failure: self.time_since_last_failure(),
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time_since_last_state_change: self.time_since_last_state_change(),
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}
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}
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fn publish_gauge_metrics(&self) {
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Metrics::set_worker_cb_consecutive_failures(
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&self.metric_label,
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self.consecutive_failures(),
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);
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Metrics::set_worker_cb_consecutive_successes(
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&self.metric_label,
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self.consecutive_successes(),
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);
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}
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}
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impl Clone for CircuitBreaker {
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fn clone(&self) -> Self {
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Self {
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state: AtomicU8::new(self.state.load(Ordering::Acquire)),
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consecutive_failures: AtomicU32::new(self.consecutive_failures.load(Ordering::Acquire)),
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consecutive_successes: AtomicU32::new(
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self.consecutive_successes.load(Ordering::Acquire),
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),
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total_failures: AtomicU64::new(self.total_failures.load(Ordering::Relaxed)),
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total_successes: AtomicU64::new(self.total_successes.load(Ordering::Relaxed)),
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last_failure_time_ms: AtomicU64::new(self.last_failure_time_ms.load(Ordering::Acquire)),
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last_state_change_ms: AtomicU64::new(self.last_state_change_ms.load(Ordering::Acquire)),
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config: self.config.clone(),
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metric_label: self.metric_label.clone(),
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}
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}
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}
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impl Default for CircuitBreaker {
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fn default() -> Self {
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Self::new()
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}
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}
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/// Circuit breaker statistics
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#[derive(Debug, Clone)]
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pub struct CircuitBreakerStats {
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pub state: CircuitState,
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pub consecutive_failures: u32,
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pub consecutive_successes: u32,
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pub total_failures: u64,
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pub total_successes: u64,
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pub time_since_last_failure: Option<Duration>,
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pub time_since_last_state_change: Duration,
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}
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#[cfg(test)]
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mod tests {
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use std::thread;
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use super::*;
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#[test]
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fn test_circuit_breaker_initial_state() {
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let cb = CircuitBreaker::new();
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assert_eq!(cb.state(), CircuitState::Closed);
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assert!(cb.can_execute());
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assert_eq!(cb.consecutive_failures(), 0);
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assert_eq!(cb.consecutive_successes(), 0);
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}
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#[test]
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fn test_circuit_opens_on_threshold() {
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let config = CircuitBreakerConfig {
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failure_threshold: 3,
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..Default::default()
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};
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let cb = CircuitBreaker::with_config_and_label(config, String::new());
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assert_eq!(cb.state(), CircuitState::Closed);
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Closed);
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Closed);
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Open);
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assert!(!cb.can_execute());
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assert_eq!(cb.consecutive_failures(), 3);
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}
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#[test]
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fn test_circuit_half_open_after_timeout() {
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let config = CircuitBreakerConfig {
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failure_threshold: 1,
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timeout_duration: Duration::from_millis(100),
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..Default::default()
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};
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let cb = CircuitBreaker::with_config_and_label(config, String::new());
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Open);
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thread::sleep(Duration::from_millis(150));
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assert_eq!(cb.state(), CircuitState::HalfOpen);
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assert!(cb.can_execute());
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}
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#[test]
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fn test_circuit_closes_on_success_threshold() {
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let config = CircuitBreakerConfig {
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failure_threshold: 1,
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success_threshold: 2,
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timeout_duration: Duration::from_millis(50),
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..Default::default()
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};
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let cb = CircuitBreaker::with_config_and_label(config, String::new());
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Open);
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thread::sleep(Duration::from_millis(100));
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assert_eq!(cb.state(), CircuitState::HalfOpen);
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cb.record_success();
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assert_eq!(cb.state(), CircuitState::HalfOpen);
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cb.record_success();
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assert_eq!(cb.state(), CircuitState::Closed);
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assert!(cb.can_execute());
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}
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#[test]
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fn test_circuit_reopens_on_half_open_failure() {
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let config = CircuitBreakerConfig {
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failure_threshold: 1,
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timeout_duration: Duration::from_millis(50),
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..Default::default()
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};
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let cb = CircuitBreaker::with_config_and_label(config, String::new());
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Open);
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thread::sleep(Duration::from_millis(100));
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assert_eq!(cb.state(), CircuitState::HalfOpen);
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cb.record_failure();
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assert_eq!(cb.state(), CircuitState::Open);
|
|
assert!(!cb.can_execute());
|
|
}
|
|
|
|
#[test]
|
|
fn test_success_resets_failure_count() {
|
|
let config = CircuitBreakerConfig {
|
|
failure_threshold: 3,
|
|
..Default::default()
|
|
};
|
|
let cb = CircuitBreaker::with_config_and_label(config, String::new());
|
|
|
|
cb.record_failure();
|
|
cb.record_failure();
|
|
assert_eq!(cb.consecutive_failures(), 2);
|
|
|
|
cb.record_success();
|
|
assert_eq!(cb.consecutive_failures(), 0);
|
|
assert_eq!(cb.consecutive_successes(), 1);
|
|
|
|
cb.record_failure();
|
|
cb.record_failure();
|
|
assert_eq!(cb.state(), CircuitState::Closed);
|
|
}
|
|
|
|
#[test]
|
|
fn test_manual_reset() {
|
|
let config = CircuitBreakerConfig {
|
|
failure_threshold: 1,
|
|
..Default::default()
|
|
};
|
|
let cb = CircuitBreaker::with_config_and_label(config, String::new());
|
|
|
|
cb.record_failure();
|
|
assert_eq!(cb.state(), CircuitState::Open);
|
|
|
|
cb.reset();
|
|
assert_eq!(cb.state(), CircuitState::Closed);
|
|
assert_eq!(cb.consecutive_failures(), 0);
|
|
assert_eq!(cb.consecutive_successes(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn test_force_open() {
|
|
let cb = CircuitBreaker::new();
|
|
assert_eq!(cb.state(), CircuitState::Closed);
|
|
|
|
cb.force_open();
|
|
assert_eq!(cb.state(), CircuitState::Open);
|
|
assert!(!cb.can_execute());
|
|
}
|
|
|
|
#[test]
|
|
fn test_stats() {
|
|
let config = CircuitBreakerConfig {
|
|
failure_threshold: 2,
|
|
..Default::default()
|
|
};
|
|
let cb = CircuitBreaker::with_config_and_label(config, String::new());
|
|
|
|
cb.record_success();
|
|
cb.record_failure();
|
|
cb.record_failure();
|
|
|
|
let stats = cb.stats();
|
|
assert_eq!(stats.state, CircuitState::Open);
|
|
assert_eq!(stats.consecutive_failures, 2);
|
|
assert_eq!(stats.consecutive_successes, 0);
|
|
assert_eq!(stats.total_failures, 2);
|
|
assert_eq!(stats.total_successes, 1);
|
|
}
|
|
|
|
#[test]
|
|
fn test_clone() {
|
|
let cb1 = CircuitBreaker::new();
|
|
cb1.record_failure();
|
|
|
|
let cb2 = cb1.clone();
|
|
assert_eq!(cb2.consecutive_failures(), 1);
|
|
|
|
cb1.record_failure();
|
|
assert_eq!(cb1.consecutive_failures(), 2);
|
|
assert_eq!(cb2.consecutive_failures(), 1); // cb2 is unchanged
|
|
}
|
|
|
|
#[test]
|
|
fn test_thread_safety() {
|
|
use std::sync::Arc;
|
|
|
|
let cb = Arc::new(CircuitBreaker::new());
|
|
let mut handles = vec![];
|
|
|
|
for _ in 0..10 {
|
|
let cb_clone = Arc::clone(&cb);
|
|
let handle = thread::spawn(move || {
|
|
for _ in 0..100 {
|
|
cb_clone.record_failure();
|
|
}
|
|
});
|
|
handles.push(handle);
|
|
}
|
|
|
|
for handle in handles {
|
|
handle.join().unwrap();
|
|
}
|
|
|
|
assert_eq!(cb.total_failures(), 1000);
|
|
}
|
|
}
|