idea for deadline observations

deadlines/src/main/java/com/palantir/deadlines/DeadlineExpirations.java

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+/*
+ * (c) Copyright 2025 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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 com.palantir.deadlines;
+
+import com.palantir.deadlines.DeadlineMetrics.Expired_Cause;
+import com.palantir.deadlines.DeadlineMetrics.Expired_Intent;
+import com.palantir.tritium.metrics.registry.SharedTaggedMetricRegistries;
+import org.jetbrains.annotations.VisibleForTesting;
+
+public final class DeadlineExpirations {
+    private final DeadlineMetrics metrics;
+
+    @VisibleForTesting
+    DeadlineExpirations(DeadlineMetrics metrics) {
+        this.metrics = metrics;
+    }
+
+    public DeadlineExpirations() {
+        this.metrics = DeadlineMetrics.of(SharedTaggedMetricRegistries.getSingleton());
+    }
+
+    public DeadlineExpirationValues get() {
+        long externalPropagate = getCountFor(Expired_Cause.EXTERNAL, Expired_Intent.PROPAGATE);
+        long externalPropagateAlreadyExpired =
+                getCountFor(Expired_Cause.EXTERNAL, Expired_Intent.PROPAGATE_ALREADY_EXPIRED);
+        long externalIgnore = getCountFor(Expired_Cause.EXTERNAL, Expired_Intent.IGNORE);
+        long internalPropagate = getCountFor(Expired_Cause.INTERNAL, Expired_Intent.PROPAGATE);
+        long internalPropagateAlreadyExpired =
+                getCountFor(Expired_Cause.INTERNAL, Expired_Intent.PROPAGATE_ALREADY_EXPIRED);
+        long internalIgnore = getCountFor(Expired_Cause.INTERNAL, Expired_Intent.IGNORE);
+
+        return new DeadlineExpirationValues(
+                new DeadlineExpirationValuesByIntent(
+                        externalPropagate, externalPropagateAlreadyExpired, externalIgnore),
+                new DeadlineExpirationValuesByIntent(
+                        internalPropagate, internalPropagateAlreadyExpired, internalIgnore));
+    }
+
+    private long getCountFor(Expired_Cause cause, Expired_Intent intent) {
+        return metrics.expired().cause(cause).intent(intent).build().getCount();
+    }
+
+    public record DeadlineExpirationValues(
+            DeadlineExpirationValuesByIntent externalExpirations,
+            DeadlineExpirationValuesByIntent internalExpirations) {
+
+        public DeadlineExpirationValues minus(DeadlineExpirationValues other) {
+            return new DeadlineExpirationValues(
+                    externalExpirations.minus(other.externalExpirations),
+                    internalExpirations.minus(other.internalExpirations));
+        }
+
+        public long totalExpirations() {
+            return externalExpirations.totalExpirations() + internalExpirations.totalExpirations();
+        }
+    }
+
+    public record DeadlineExpirationValuesByIntent(long propagate, long propagateAlreadyExpired, long ignore) {
+        DeadlineExpirationValuesByIntent minus(DeadlineExpirationValuesByIntent other) {
+            return new DeadlineExpirationValuesByIntent(
+                    propagate - other.propagate,
+                    propagateAlreadyExpired - other.propagateAlreadyExpired,
+                    ignore - other.ignore);
+        }
+
+        public long totalExpirations() {
+            return propagate + propagateAlreadyExpired + ignore;
+        }
+    }
+}

deadlines/src/test/java/com/palantir/deadlines/DeadlineExpirationsTest.java

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+/*
+ * (c) Copyright 2025 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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 com.palantir.deadlines;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.palantir.deadlines.DeadlineExpirations.DeadlineExpirationValues;
+import com.palantir.deadlines.DeadlineMetrics.Expired_Cause;
+import com.palantir.deadlines.DeadlineMetrics.Expired_Intent;
+import com.palantir.tritium.metrics.registry.DefaultTaggedMetricRegistry;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+final class DeadlineExpirationsTest {
+    DeadlineMetrics metrics;
+
+    @BeforeEach
+    public void before() {
+        metrics = DeadlineMetrics.of(new DefaultTaggedMetricRegistry());
+    }
+
+    @Test
+    public void test_observe_no_changes() {
+        DeadlineExpirations deadlineExpirations = new DeadlineExpirations(metrics);
+        DeadlineExpirationValues start = deadlineExpirations.get();
+        DeadlineExpirationValues obs = deadlineExpirations.get().minus(start);
+        assertThat(obs.totalExpirations()).isEqualTo(start.totalExpirations());
+    }
+
+    @Test
+    public void test_observe_change_external_propagate() {
+        DeadlineExpirations deadlineExpirations = new DeadlineExpirations(metrics);
+        DeadlineExpirationValues start = deadlineExpirations.get();
+
+        metrics.expired()
+                .cause(Expired_Cause.EXTERNAL)
+                .intent(Expired_Intent.PROPAGATE)
+                .build()
+                .mark();
+
+        DeadlineExpirationValues obs = deadlineExpirations.get().minus(start);
+
+        assertThat(obs.totalExpirations()).isEqualTo(1);
+        assertThat(obs.externalExpirations().propagate()).isEqualTo(1);
+    }
+
+    @Test
+    public void test_observe_change_multiple_observations() {
+        DeadlineExpirations deadlineExpirations = new DeadlineExpirations(metrics);
+        DeadlineExpirationValues start = deadlineExpirations.get();
+
+        metrics.expired()
+                .cause(Expired_Cause.EXTERNAL)
+                .intent(Expired_Intent.PROPAGATE)
+                .build()
+                .mark();
+
+        DeadlineExpirationValues obs1 = deadlineExpirations.get().minus(start);
+
+        assertThat(obs1.totalExpirations()).isEqualTo(1);
+        assertThat(obs1.externalExpirations().propagate()).isEqualTo(1);
+
+        metrics.expired()
+                .cause(Expired_Cause.INTERNAL)
+                .intent(Expired_Intent.IGNORE)
+                .build()
+                .mark();
+
+        DeadlineExpirationValues obs2 = deadlineExpirations.get().minus(obs1);
+
+        assertThat(obs2.totalExpirations()).isEqualTo(1);
+        assertThat(obs2.internalExpirations().ignore()).isEqualTo(1);
+    }
+}