1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
// Copyright Yahoo. 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.FINE;
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 static final long NEVER = 1L << 60;
private final AtomicLong failingSinceMillis = new AtomicLong(NEVER);
private final AtomicBoolean halfOpen = new AtomicBoolean(false);
private final AtomicBoolean open = new AtomicBoolean(false);
private final LongSupplier clock;
private final AtomicReference<String> detail = new AtomicReference<>();
private final long graceMillis;
private final long doomMillis;
/**
* 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::currentTimeMillis, 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::currentTimeMillis, grace, doom);
if (doom.isNegative())
throw new IllegalArgumentException("Doom delay must be non-negative");
}
GracePeriodCircuitBreaker(LongSupplier clock, Duration grace, Duration doom) {
if (grace.isNegative())
throw new IllegalArgumentException("Grace delay must be non-negative");
this.clock = requireNonNull(clock);
this.graceMillis = grace.toMillis();
this.doomMillis = doom == null ? -1 : doom.toMillis();
}
@Override
public void success() {
failingSinceMillis.set(NEVER);
if ( ! open.get() && halfOpen.compareAndSet(true, false))
log.log(FINE, "Circuit breaker is now closed");
}
@Override
public void failure(HttpResponse response) {
failure(response.toString());
}
@Override
public void failure(Throwable cause) {
failure(cause.toString());
}
private void failure(String detail) {
if (failingSinceMillis.compareAndSet(NEVER, clock.getAsLong()))
this.detail.set(detail);
}
@Override
public State state() {
long failingMillis = clock.getAsLong() - failingSinceMillis.get();
if (failingMillis > graceMillis && halfOpen.compareAndSet(false, true))
log.log(INFO, "Circuit breaker is now half-open, as no requests have succeeded for the " +
"last " + failingMillis + "ms. The server will be pinged to see if it recovers" +
(doomMillis >= 0 ? ", but this client will give up if no successes are observed within " + doomMillis + "ms" : "") +
". First failure was '" + detail.get() + "'.");
if (doomMillis >= 0 && failingMillis > doomMillis && open.compareAndSet(false, true))
log.log(WARNING, "Circuit breaker is now open, after " + doomMillis + "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;
}
}
|
