1 files changed, 65 insertions, 0 deletions
diff --git a/vespajlib/src/main/java/com/yahoo/time/TimeBudget.java b/vespajlib/src/main/java/com/yahoo/time/TimeBudget.java
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index 00000000000..fa18cb5e467
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+++ b/vespajlib/src/main/java/com/yahoo/time/TimeBudget.java
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+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.time;
+
+import com.google.common.util.concurrent.UncheckedTimeoutException;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+
+/**
+ * A TimeBudget can be used to track the time of an ongoing operation with a timeout.
+ *
+ * @author hakon
+ */
+public class TimeBudget {
+    private final Clock clock;
+    private final Instant start;
+    private final Duration timeout;
+
+    /** Returns a TimeBudget with a start time of now, and with the given timeout. */
+    public static TimeBudget fromNow(Clock clock, Duration timeout) {
+        return new TimeBudget(clock, clock.instant(), timeout);
+    }
+
+    private TimeBudget(Clock clock, Instant start, Duration timeout) {
+        this.clock = clock;
+        this.start = start;
+        this.timeout = makeNonNegative(timeout);
+    }
+
+    /** Returns time since start. */
+    public Duration timePassed() {
+        return nonNegativeBetween(start, clock.instant());
+    }
+
+    /** Returns the original timeout. */
+    public Duration originalTimeout() {
+        return timeout;
+    }
+
+    /**
+     * Returns the time until deadline.
+     *
+     * @return time until deadline. It's toMillis() is guaranteed to be positive.
+     * @throws UncheckedTimeoutException if the deadline has been reached or passed.
+     */
+    public Duration timeLeftOrThrow() {
+        Instant now = clock.instant();
+        Duration left = Duration.between(now, start.plus(timeout));
+        if (left.toMillis() <= 0) {
+            throw new UncheckedTimeoutException("Time since start " + nonNegativeBetween(start, now) +
+                    " exceeds timeout " + timeout);
+        }
+
+        return left;
+    }
+
+    private static Duration nonNegativeBetween(Instant start, Instant end) {
+        return makeNonNegative(Duration.between(start, end));
+    }
+
+    private static Duration makeNonNegative(Duration duration) {
+        return duration.isNegative() ? Duration.ZERO : duration;
+    }
+}