absurdfarce commented on code in PR #1743:
URL:
https://github.com/apache/cassandra-java-driver/pull/1743#discussion_r1638440588
##########
core/src/main/java/com/datastax/oss/driver/internal/core/loadbalancing/DefaultLoadBalancingPolicy.java:
##########
@@ -96,14 +100,39 @@ public class DefaultLoadBalancingPolicy extends
BasicLoadBalancingPolicy impleme
private static final int MAX_IN_FLIGHT_THRESHOLD = 10;
private static final long RESPONSE_COUNT_RESET_INTERVAL_NANOS =
MILLISECONDS.toNanos(200);
- protected final Map<Node, AtomicLongArray> responseTimes = new
ConcurrentHashMap<>();
+ protected final LoadingCache<Node, NodeResponseRateSample> responseTimes;
protected final Map<Node, Long> upTimes = new ConcurrentHashMap<>();
private final boolean avoidSlowReplicas;
public DefaultLoadBalancingPolicy(@NonNull DriverContext context, @NonNull
String profileName) {
super(context, profileName);
this.avoidSlowReplicas =
profile.getBoolean(DefaultDriverOption.LOAD_BALANCING_POLICY_SLOW_AVOIDANCE,
true);
+ CacheLoader<Node, NodeResponseRateSample> cacheLoader =
+ new CacheLoader<Node, NodeResponseRateSample>() {
+ @Override
+ public NodeResponseRateSample load(Node key) {
+ NodeResponseRateSample sample = responseTimes.getIfPresent(key);
+ if (sample == null) {
+ sample = new NodeResponseRateSample();
+ } else {
+ sample.update();
+ }
+ return sample;
+ }
+ };
Review Comment:
To make this more concrete: I got the relevant test case
(DefaultLoadBalancingPolicyRequestTrackerTest) with the following changes:
```java
protected final ConcurrentMap<Node, NodeResponseRateSample> responseTimes;
protected final Map<Node, Long> upTimes = new ConcurrentHashMap<>();
private final boolean avoidSlowReplicas;
public DefaultLoadBalancingPolicy(@NonNull DriverContext context, @NonNull
String profileName) {
super(context, profileName);
this.avoidSlowReplicas =
profile.getBoolean(DefaultDriverOption.LOAD_BALANCING_POLICY_SLOW_AVOIDANCE,
true);
this.responseTimes =
new MapMaker().weakKeys().makeMap();
}
...
protected void updateResponseTimes(@NonNull Node node) {
this.responseTimes.compute(node, (k,v) -> v == null ? new
NodeResponseRateSample() : v.next());
}
...
// Exposed as protected for unit tests
protected class NodeResponseRateSample {
@VisibleForTesting
protected final long oldest;
@VisibleForTesting
protected final OptionalLong newest;
private NodeResponseRateSample() {
long now = nanoTime();
this.oldest = now;
this.newest = OptionalLong.empty();
}
private NodeResponseRateSample(long oldestSample) {
this(oldestSample, nanoTime());
}
private NodeResponseRateSample(long oldestSample, long newestSample) {
this.oldest = oldestSample;
this.newest = OptionalLong.of(newestSample);
}
@VisibleForTesting
protected NodeResponseRateSample(AtomicLongArray times) {
assert times.length() >= 1;
this.oldest = times.get(0);
this.newest = (times.length() > 1) ? OptionalLong.of(times.get(1)) :
OptionalLong.empty();
}
// Our newest sample becomes the oldest in the next generation
private NodeResponseRateSample next() {
return new NodeResponseRateSample(this.getNewestValidSample(),
nanoTime());
}
// If we have a pair of values return the newest, otherwise we have just
one value... so just return it
private long getNewestValidSample() { return
this.newest.orElse(this.oldest); }
// response rate is considered insufficient when less than 2 responses
were obtained in
// the past interval delimited by RESPONSE_COUNT_RESET_INTERVAL_NANOS.
private boolean hasSufficientResponses(long now) {
// If we only have one sample it's an automatic failure
if (!this.newest.isPresent())
return false;
long threshold = now - RESPONSE_COUNT_RESET_INTERVAL_NANOS;
return this.oldest - threshold >= 0;
}
}
```
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