Allow distribution config customization

core/src/main/java/com/linecorp/armeria/client/metric/AbstractMetricCollectingClient.java

@@ -31,6 +31,7 @@
 import com.linecorp.armeria.internal.common.metric.RequestMetricSupport;
 
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.netty.util.AttributeKey;
 
 /**
@@ -46,20 +47,25 @@ abstract class AbstractMetricCollectingClient<I extends Request, O extends Respo
     private final MeterIdPrefixFunction meterIdPrefixFunction;
     @Nullable
     private final BiPredicate<? super RequestContext, ? super RequestLog> successFunction;
+    private final DistributionStatisticConfig distributionStatisticConfig;
 
     AbstractMetricCollectingClient(
             Client<I, O> delegate, MeterIdPrefixFunction meterIdPrefixFunction,
-            @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction) {
+            @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction,
+            DistributionStatisticConfig distributionStatisticConfig) {
         super(delegate);
         this.meterIdPrefixFunction = requireNonNull(meterIdPrefixFunction, "meterIdPrefixFunction");
         this.successFunction = successFunction;
+        this.distributionStatisticConfig =
+                requireNonNull(distributionStatisticConfig, "distributionStatisticConfig");
     }
 
     @Override
     public final O execute(ClientRequestContext ctx, I req) throws Exception {
         RequestMetricSupport.setup(ctx, REQUEST_METRICS_SET, meterIdPrefixFunction, false,
                                    successFunction != null ? successFunction::test
-                                                           : ctx.options().successFunction());
+                                                           : ctx.options().successFunction(),
+                                   distributionStatisticConfig);
         return unwrap().execute(ctx, req);
     }
 }

core/src/main/java/com/linecorp/armeria/client/metric/MetricCollectingClient.java

@@ -29,6 +29,7 @@
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 
 /**
  * Decorates an {@link HttpClient} to collect metrics into {@link MeterRegistry}.
@@ -65,7 +66,8 @@ public static MetricCollectingClientBuilder builder(MeterIdPrefixFunction meterI
     }
 
     MetricCollectingClient(HttpClient delegate, MeterIdPrefixFunction meterIdPrefixFunction,
-                           @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction) {
-        super(delegate, meterIdPrefixFunction, successFunction);
+                           @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction,
+                           DistributionStatisticConfig distributionStatisticConfig) {
+        super(delegate, meterIdPrefixFunction, successFunction, distributionStatisticConfig);
     }
 }

core/src/main/java/com/linecorp/armeria/client/metric/MetricCollectingClientBuilder.java

@@ -26,6 +26,8 @@
 import com.linecorp.armeria.common.metric.AbstractMetricCollectingBuilder;
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
+
 /**
  * Builds a {@link MetricCollectingClient} instance.
  */
@@ -41,13 +43,20 @@
         return (MetricCollectingClientBuilder) super.successFunction(successFunction);
     }
 
+    @Override
+    public MetricCollectingClientBuilder distributionStatisticConfig(
+            DistributionStatisticConfig distributionStatisticConfig) {
+        return (MetricCollectingClientBuilder) super.distributionStatisticConfig(distributionStatisticConfig);
+    }
+
     /**
      * Returns a newly-created {@link MetricCollectingClient} decorating {@link HttpClient} based
      * on the properties of this builder.
      */
     public MetricCollectingClient build(HttpClient delegate) {
         requireNonNull(delegate, "delegate");
-        return new MetricCollectingClient(delegate, meterIdPrefixFunction(), successFunction());
+        return new MetricCollectingClient(delegate, meterIdPrefixFunction(), successFunction(),
+                                          distributionStatisticConfig());
     }
 
     /**

core/src/main/java/com/linecorp/armeria/client/metric/MetricCollectingRpcClient.java

@@ -29,6 +29,7 @@
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 
 import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 
 /**
  * Decorates an {@link RpcClient} to collect metrics into {@link MeterRegistry}.
@@ -65,7 +66,8 @@ public static MetricCollectingRpcClientBuilder builder(MeterIdPrefixFunction met
 
     MetricCollectingRpcClient(
             RpcClient delegate, MeterIdPrefixFunction meterIdPrefixFunction,
-            @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction) {
-        super(delegate, meterIdPrefixFunction, successFunction);
+            @Nullable BiPredicate<? super RequestContext, ? super RequestLog> successFunction,
+            DistributionStatisticConfig distributionStatisticConfig) {
+        super(delegate, meterIdPrefixFunction, successFunction, distributionStatisticConfig);
     }
 }

core/src/main/java/com/linecorp/armeria/client/metric/MetricCollectingRpcClientBuilder.java

@@ -26,6 +26,8 @@
 import com.linecorp.armeria.common.metric.AbstractMetricCollectingBuilder;
 import com.linecorp.armeria.common.metric.MeterIdPrefixFunction;
 
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
+
 /**
  * Builds a {@link MetricCollectingRpcClient} instance.
  */
@@ -41,13 +43,21 @@
         return (MetricCollectingRpcClientBuilder) super.successFunction(successFunction);
     }
 
+    @Override
+    public MetricCollectingRpcClientBuilder distributionStatisticConfig(
+            DistributionStatisticConfig distributionStatisticConfig) {
+        return (MetricCollectingRpcClientBuilder)
+                super.distributionStatisticConfig(distributionStatisticConfig);
+    }
+
     /**
      * Returns a newly-created {@link MetricCollectingRpcClient} decorating {@link RpcClient} based
      * on the properties of this builder.
      */
     public MetricCollectingRpcClient build(RpcClient delegate) {
         requireNonNull(delegate, "delegate");
-        return new MetricCollectingRpcClient(delegate, meterIdPrefixFunction(), successFunction());
+        return new MetricCollectingRpcClient(delegate, meterIdPrefixFunction(), successFunction(),
+                                             distributionStatisticConfig());
     }
 
     /**

core/src/main/java/com/linecorp/armeria/common/DefaultFlagsProvider.java

@@ -32,6 +32,7 @@
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 
 /**
  * Implementation of {@link FlagsProvider} which provides default values to {@link Flags}.
@@ -467,4 +468,9 @@ public MeterRegistry meterRegistry() {
     public Long defaultUnhandledExceptionsReportIntervalMillis() {
         return DEFAULT_UNHANDLED_EXCEPTIONS_REPORT_INTERVAL_MILLIS;
     }
+
+    @Override
+    public DistributionStatisticConfig distributionStatisticConfig() {
+        return DistributionStatisticConfigUtil.DEFAULT_DIST_STAT_CFG;
+    }
 }

core/src/main/java/com/linecorp/armeria/common/DistributionStatisticConfigUtil.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2024 LINE Corporation
+ *
+ * LINE Corporation licenses this file to you 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:
+ *
+ *   https://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 com.linecorp.armeria.common;
+
+import java.time.Duration;
+
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
+
+final class DistributionStatisticConfigUtil {
+    static final DistributionStatisticConfig DEFAULT_DIST_STAT_CFG =
+            DistributionStatisticConfig.builder()
+                                       .percentilesHistogram(false)
+                                       .serviceLevelObjectives()
+                                       .percentiles(0, 0.5, 0.75, 0.9, 0.95, 0.98, 0.99, 0.999, 1.0)
+                                       .percentilePrecision(2)
+                                       .minimumExpectedValue(1.0)
+                                       .maximumExpectedValue(Double.MAX_VALUE)
+                                       .expiry(Duration.ofMinutes(3))
+                                       .bufferLength(3)
+                                       .build();
+
+    private DistributionStatisticConfigUtil() {}
+}

core/src/main/java/com/linecorp/armeria/common/Flags.java

@@ -71,8 +71,11 @@
 import com.linecorp.armeria.server.file.HttpFile;
 import com.linecorp.armeria.server.logging.LoggingService;
 
+import io.micrometer.core.instrument.DistributionSummary;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.Timer;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.netty.buffer.ByteBufAllocator;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.EventLoopGroup;
@@ -405,6 +408,9 @@ private static boolean validateTransportType(TransportType transportType, String
             getValue(FlagsProvider::defaultUnhandledExceptionsReportIntervalMillis,
                      "defaultUnhandledExceptionsReportIntervalMillis", value -> value >= 0);
 
+    private static final DistributionStatisticConfig DISTRIBUTION_STATISTIC_CONFIG =
+            getValue(FlagsProvider::distributionStatisticConfig, "distributionStatisticConfig");
+
     /**
      * Returns the specification of the {@link Sampler} that determines whether to retain the stack
      * trace of the exceptions that are thrown frequently by Armeria. A sampled exception will have the stack
@@ -1475,6 +1481,30 @@ public static long defaultUnhandledExceptionsReportIntervalMillis() {
         return DEFAULT_UNHANDLED_EXCEPTIONS_REPORT_INTERVAL_MILLIS;
     }
 
+    /**
+     * Returns the default {@link DistributionStatisticConfig} of the {@link Timer}s and
+     * {@link DistributionSummary}s created by Armeria.
+     *
+     * <p>The default value of this flag is as follows:
+     * <pre>{@code
+     * DistributionStatisticConfig.builder()
+     *     .percentilesHistogram(false)
+     *     .serviceLevelObjectives()
+     *     .percentiles(
+     *          0, 0.5, 0.75, 0.9, 0.95, 0.98, 0.99, 0.999, 1.0)
+     *     .percentilePrecision(2)
+     *     .minimumExpectedValue(1.0)
+     *     .maximumExpectedValue(Double.MAX_VALUE)
+     *     .expiry(Duration.ofMinutes(3))
+     *     .bufferLength(3)
+     *     .build();
+     * }</pre>
+     */
+    @UnstableApi
+    public static DistributionStatisticConfig distributionStatisticConfig() {
+        return DISTRIBUTION_STATISTIC_CONFIG;
+    }
+
     @Nullable
     private static String nullableCaffeineSpec(Function<FlagsProvider, String> method, String flagName) {
         return caffeineSpec(method, flagName, true);

core/src/main/java/com/linecorp/armeria/common/FlagsProvider.java

@@ -56,6 +56,7 @@
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.EventLoopGroup;
 import io.netty.handler.codec.http2.Http2Exception;
@@ -1118,4 +1119,28 @@ default MeterRegistry meterRegistry() {
     default Long defaultUnhandledExceptionsReportIntervalMillis() {
         return null;
     }
+
+    /**
+     * Returns the {@link DistributionStatisticConfig} where armeria utilizes.
+     *
+     * <p>The default value of this flag is as follows:
+     * <pre>{@code
+     * DistributionStatisticConfig.builder()
+     *     .percentilesHistogram(false)
+     *     .serviceLevelObjectives()
+     *     .percentiles(
+     *          0, 0.5, 0.75, 0.9, 0.95, 0.98, 0.99, 0.999, 1.0)
+     *     .percentilePrecision(2)
+     *     .minimumExpectedValue(1.0)
+     *     .maximumExpectedValue(Double.MAX_VALUE)
+     *     .expiry(Duration.ofMinutes(3))
+     *     .bufferLength(3)
+     *     .build();
+     * }</pre>
+     */
+    @Nullable
+    @UnstableApi
+    default DistributionStatisticConfig distributionStatisticConfig() {
+        return null;
+    }
 }

core/src/main/java/com/linecorp/armeria/common/metric/AbstractMetricCollectingBuilder.java

@@ -26,6 +26,8 @@
 import com.linecorp.armeria.common.logging.RequestLog;
 import com.linecorp.armeria.server.ServerBuilder;
 
+import io.micrometer.core.instrument.distribution.DistributionStatisticConfig;
+
 /**
  * Builds an implementing class of {@link AbstractMetricCollectingBuilder} instance.
  */
@@ -36,6 +38,8 @@ public abstract class AbstractMetricCollectingBuilder {
     @Nullable
     private BiPredicate<? super RequestContext, ? super RequestLog> successFunction;
 
+    private DistributionStatisticConfig distributionStatisticConfig = MoreMeters.distributionStatisticConfig();
+
     /**
      * Creates a new instance with the specified {@link MeterIdPrefixFunction}.
      */
@@ -83,4 +87,21 @@ public AbstractMetricCollectingBuilder successFunction(
         this.successFunction = requireNonNull(successFunction, "successFunction");
         return this;
     }
+
+    /**
+     * Returns the {@code distributionStatisticConfig}.
+     */
+    protected final DistributionStatisticConfig distributionStatisticConfig() {
+        return distributionStatisticConfig;
+    }
+
+    /**
+     * Defines a custom {@link DistributionStatisticConfig} to use for the distribution config.
+     */
+    public AbstractMetricCollectingBuilder distributionStatisticConfig(
+            DistributionStatisticConfig distributionStatisticConfig) {
+        this.distributionStatisticConfig = requireNonNull(distributionStatisticConfig,
+                                                          "distributionStatisticConfig");
+        return this;
+    }
 }