#20365

Committed 27 Jul 2026 06:04AM UTC coverage: 89.199% (+0.07%) from 89.125%

Build # #20365

Build Type

push

github

Committed by

web-flow

Commit Message

core: Implement LB Delay Observability (Proposal A121) (#12807)

This PR implements **Attempt-Level RPC Delay Observability** across the core channel transport, built-in load balancers, xDS policies, and the OpenTelemetry telemetry plugin, aligned with [gRPC Proposal A121](https://github.com/grpc/proposal/pull/556).

Coverage Stats

38276 of 42911 relevant lines covered (89.2%)

0.89 hits per line

Source File
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81.36

/../xds/src/main/java/io/grpc/xds/WeightedRandomPicker.java

/*
 * Copyright 2019 The gRPC Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.grpc.xds;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.MoreObjects;
import com.google.common.primitives.UnsignedInteger;
import io.grpc.LoadBalancer.PickResult;
import io.grpc.LoadBalancer.PickSubchannelArgs;
import io.grpc.LoadBalancer.SubchannelPicker;
import java.util.Collections;
import java.util.List;
import java.util.Objects;

final class WeightedRandomPicker extends SubchannelPicker {

  @VisibleForTesting
  final List<WeightedChildPicker> weightedChildPickers;

  private final ThreadSafeRandom random;
  private final long totalWeight;

  static final class WeightedChildPicker {
    private final long weight;
    private final SubchannelPicker childPicker;

    WeightedChildPicker(long weight, SubchannelPicker childPicker) {
      checkArgument(weight >= 0, "weight is negative");
      checkArgument(weight <= UnsignedInteger.MAX_VALUE.longValue(), "weight is too large");
      checkNotNull(childPicker, "childPicker is null");

      this.weight = weight;
      this.childPicker = childPicker;
    }

    long getWeight() {
      return weight;
    }

    SubchannelPicker getPicker() {
      return childPicker;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      WeightedChildPicker that = (WeightedChildPicker) o;
      return weight == that.weight && Objects.equals(childPicker, that.childPicker);
    }

    @Override
    public int hashCode() {
      return Objects.hash(weight, childPicker);
    }

    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("weight", weight)
          .add("childPicker", childPicker)
          .toString();
    }
  }

  WeightedRandomPicker(List<WeightedChildPicker> weightedChildPickers) {
    this(weightedChildPickers, ThreadSafeRandom.ThreadSafeRandomImpl.instance);
  }

  @VisibleForTesting
  WeightedRandomPicker(List<WeightedChildPicker> weightedChildPickers, ThreadSafeRandom random) {
    checkNotNull(weightedChildPickers, "weightedChildPickers in null");
    checkArgument(!weightedChildPickers.isEmpty(), "weightedChildPickers is empty");

    this.weightedChildPickers = Collections.unmodifiableList(weightedChildPickers);

    long totalWeight = 0;
    for (WeightedChildPicker weightedChildPicker : weightedChildPickers) {
      long weight = weightedChildPicker.getWeight();
      checkArgument(weight >= 0, "weight is negative");
      checkNotNull(weightedChildPicker.getPicker(), "childPicker is null");
      totalWeight += weight;
    }
    this.totalWeight = totalWeight;
    checkArgument(totalWeight <= UnsignedInteger.MAX_VALUE.longValue(),
        "total weight greater than unsigned int can hold");

    this.random = random;
  }

  @Override
  public final PickResult pickSubchannel(PickSubchannelArgs args) {
    SubchannelPicker childPicker = null;

    if (totalWeight == 0) {
      childPicker =
          weightedChildPickers.get(random.nextInt(weightedChildPickers.size())).getPicker();
    } else {
      long rand = random.nextLong(totalWeight);

      // Find the first idx such that rand < accumulatedWeights[idx]
      // Not using Arrays.binarySearch for better readability.
      long accumulatedWeight = 0;
      for (WeightedChildPicker weightedChildPicker : weightedChildPickers) {
        accumulatedWeight += weightedChildPicker.getWeight();
        if (rand < accumulatedWeight) {
          childPicker = weightedChildPicker.getPicker();
          break;
        }
      }
      checkNotNull(childPicker, "childPicker not found");
    }

    PickResult res = childPicker.pickSubchannel(args);
    if (!res.hasResult() && res.getDelayType() != null) {
      return PickResult.withNoResult(res.getDelayType(),
          "weighted_target: " + (res.getDelayReason() != null ? res.getDelayReason() : ""));
    }
    return res;
  }

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("weightedChildPickers", weightedChildPickers)
        .add("totalWeight", totalWeight)
        .toString();
  }
}

1	/*
2	* Copyright 2019 The gRPC Authors
3	*
4	* Licensed under the Apache License, Version 2.0 (the "License");
5	* you may not use this file except in compliance with the License.
6	* You may obtain a copy of the License at
7	*
8	* http://www.apache.org/licenses/LICENSE-2.0
9	*
10	* Unless required by applicable law or agreed to in writing, software
11	* distributed under the License is distributed on an "AS IS" BASIS,
12	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13	* See the License for the specific language governing permissions and
14	* limitations under the License.
15	*/
16
17	package io.grpc.xds;
18
19	import static com.google.common.base.Preconditions.checkArgument;
20	import static com.google.common.base.Preconditions.checkNotNull;
21
22	import com.google.common.annotations.VisibleForTesting;
23	import com.google.common.base.MoreObjects;
24	import com.google.common.primitives.UnsignedInteger;
25	import io.grpc.LoadBalancer.PickResult;
26	import io.grpc.LoadBalancer.PickSubchannelArgs;
27	import io.grpc.LoadBalancer.SubchannelPicker;
28	import java.util.Collections;
29	import java.util.List;
30	import java.util.Objects;
31
32	final class WeightedRandomPicker extends SubchannelPicker {
33
34	@VisibleForTesting
35	final List<WeightedChildPicker> weightedChildPickers;
36
37	private final ThreadSafeRandom random;
38	private final long totalWeight;
39
40	static final class WeightedChildPicker {
41	private final long weight;
42	private final SubchannelPicker childPicker;
43
44	WeightedChildPicker(long weight, SubchannelPicker childPicker) {	1✔
45	checkArgument(weight >= 0, "weight is negative");	1✔
46	checkArgument(weight <= UnsignedInteger.MAX_VALUE.longValue(), "weight is too large");	1✔
47	checkNotNull(childPicker, "childPicker is null");	1✔
48
49	this.weight = weight;	1✔
50	this.childPicker = childPicker;	1✔
51	}	1✔
52
53	long getWeight() {
54	return weight;	1✔
55	}
56
57	SubchannelPicker getPicker() {
58	return childPicker;	1✔
59	}
60
61	@Override
62	public boolean equals(Object o) {
63	if (this == o) {	1✔
64	return true;	×
65	}
66	if (o == null \|\| getClass() != o.getClass()) {	1✔
67	return false;	×
68	}
69	WeightedChildPicker that = (WeightedChildPicker) o;	1✔
70	return weight == that.weight && Objects.equals(childPicker, that.childPicker);	1✔
71	}
72
73	@Override
74	public int hashCode() {
75	return Objects.hash(weight, childPicker);	×
76	}
77
78	@Override
79	public String toString() {
80	return MoreObjects.toStringHelper(this)	×
81	.add("weight", weight)	×
82	.add("childPicker", childPicker)	×
83	.toString();	×
84	}
85	}
86
87	WeightedRandomPicker(List<WeightedChildPicker> weightedChildPickers) {
88	this(weightedChildPickers, ThreadSafeRandom.ThreadSafeRandomImpl.instance);	1✔
89	}	1✔
90
91	@VisibleForTesting
92	WeightedRandomPicker(List<WeightedChildPicker> weightedChildPickers, ThreadSafeRandom random) {	1✔
93	checkNotNull(weightedChildPickers, "weightedChildPickers in null");	1✔
94	checkArgument(!weightedChildPickers.isEmpty(), "weightedChildPickers is empty");	1✔
95
96	this.weightedChildPickers = Collections.unmodifiableList(weightedChildPickers);	1✔
97
98	long totalWeight = 0;	1✔
99	for (WeightedChildPicker weightedChildPicker : weightedChildPickers) {	1✔
100	long weight = weightedChildPicker.getWeight();	1✔
101	checkArgument(weight >= 0, "weight is negative");	1✔
102	checkNotNull(weightedChildPicker.getPicker(), "childPicker is null");	1✔
103	totalWeight += weight;	1✔
104	}	1✔
105	this.totalWeight = totalWeight;	1✔
106	checkArgument(totalWeight <= UnsignedInteger.MAX_VALUE.longValue(),	1✔
107	"total weight greater than unsigned int can hold");
108
109	this.random = random;	1✔
110	}	1✔
111
112	@Override
113	public final PickResult pickSubchannel(PickSubchannelArgs args) {
114	SubchannelPicker childPicker = null;	1✔
115
116	if (totalWeight == 0) {	1✔
117	childPicker =	1✔
118	weightedChildPickers.get(random.nextInt(weightedChildPickers.size())).getPicker();	1✔
119	} else {
120	long rand = random.nextLong(totalWeight);	1✔
121
122	// Find the first idx such that rand < accumulatedWeights[idx]
123	// Not using Arrays.binarySearch for better readability.
124	long accumulatedWeight = 0;	1✔
125	for (WeightedChildPicker weightedChildPicker : weightedChildPickers) {	1✔
126	accumulatedWeight += weightedChildPicker.getWeight();	1✔
127	if (rand < accumulatedWeight) {	1✔
128	childPicker = weightedChildPicker.getPicker();	1✔
129	break;	1✔
130	}
131	}	1✔
132	checkNotNull(childPicker, "childPicker not found");	1✔
133	}
134
135	PickResult res = childPicker.pickSubchannel(args);	1✔
136	if (!res.hasResult() && res.getDelayType() != null) {	1✔
137	return PickResult.withNoResult(res.getDelayType(),	1✔
138	"weighted_target: " + (res.getDelayReason() != null ? res.getDelayReason() : ""));	1✔
139	}
140	return res;	1✔
141	}
142
143	@Override
144	public String toString() {
145	return MoreObjects.toStringHelper(this)	×
146	.add("weightedChildPickers", weightedChildPickers)	×
147	.add("totalWeight", totalWeight)	×
148	.toString();	×
149	}
150	}

grpc / grpc-java / #20365

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