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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package ai.vespa.feed.client.impl;
import ai.vespa.feed.client.FeedClient;
import ai.vespa.feed.client.HttpResponse;
import java.time.Duration;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.LongSupplier;
import java.util.logging.Logger;
import static java.util.Objects.requireNonNull;
import static java.util.logging.Level.INFO;
import static java.util.logging.Level.WARNING;
/**
* Breaks the circuit when no successes have been recorded for a specified time.
*
* @author jonmv
*/
public class GracePeriodCircuitBreaker implements FeedClient.CircuitBreaker {
private static final Logger log = Logger.getLogger(GracePeriodCircuitBreaker.class.getName());
private final AtomicBoolean halfOpen = new AtomicBoolean(false);
private final AtomicBoolean open = new AtomicBoolean(false);
private final LongSupplier nanoClock;
private final long never;
private final AtomicLong failingSinceNanos;
private final AtomicReference<String> detail = new AtomicReference<>();
private final long graceNanos;
private final long doomNanos;
/**
* Creates a new circuit breaker with the given grace periods.
* @param grace the period of consecutive failures before state changes to half-open.
*/
public GracePeriodCircuitBreaker(Duration grace) {
this(System::nanoTime, grace, null);
}
/**
* Creates a new circuit breaker with the given grace periods.
* @param grace the period of consecutive failures before state changes to half-open.
* @param doom the period of consecutive failures before shutting down.
*/
public GracePeriodCircuitBreaker(Duration grace, Duration doom) {
this(System::nanoTime, grace, doom);
if (doom.isNegative())
throw new IllegalArgumentException("Doom delay must be non-negative");
}
GracePeriodCircuitBreaker(LongSupplier nanoClock, Duration grace, Duration doom) {
if (grace.isNegative())
throw new IllegalArgumentException("Grace delay must be non-negative");
this.nanoClock = requireNonNull(nanoClock);
this.never = nanoClock.getAsLong() + (1L << 60);
this.graceNanos = grace.toNanos();
this.doomNanos = doom == null ? -1 : doom.toNanos();
this.failingSinceNanos = new AtomicLong(never);
}
@Override
public void success() {
failingSinceNanos.set(never);
if ( ! open.get() && halfOpen.compareAndSet(true, false))
log.log(INFO, "Circuit breaker is now closed, after a request was successful");
}
@Override
public void failure(HttpResponse response) {
failure(response.toString());
}
@Override
public void failure(Throwable cause) {
failure(cause.toString());
}
private void failure(String detail) {
if (failingSinceNanos.compareAndSet(never, nanoClock.getAsLong()))
this.detail.set(detail);
}
@Override
public State state() {
long failingNanos = nanoClock.getAsLong() - failingSinceNanos.get();
if (failingNanos > graceNanos && halfOpen.compareAndSet(false, true))
log.log(INFO, "Circuit breaker is now half-open, as no requests have succeeded for the " +
"last " + failingNanos / 1_000_000 + "ms. The server will be pinged to see if it recovers" +
(doomNanos >= 0 ? ", but this client will give up if no successes are observed within " + doomNanos / 1_000_000 + "ms" : "") +
". First failure was '" + detail.get() + "'.");
if (doomNanos >= 0 && failingNanos > doomNanos && open.compareAndSet(false, true))
log.log(WARNING, "Circuit breaker is now open, after " + doomNanos / 1_000_000 + "ms of failing request, " +
"and this client will give up and abort its remaining feed operations.");
return open.get() ? State.OPEN : halfOpen.get() ? State.HALF_OPEN : State.CLOSED;
}
}
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