fix: do not integer overflow when attempt gets too high (#16)

* fix: do not integer overflow when attempt gets too high * Update ExponentialBackoffTest.java
grafana · Feb 15, 2022 · f59bcd6 · f59bcd6
1 parent 66cc8f7
commit f59bcd6
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Showing 2 changed files with 8 additions and 5 deletions.
diff --git a/agent/src/main/java/io/pyroscope/javaagent/ExponentialBackoff.java b/agent/src/main/java/io/pyroscope/javaagent/ExponentialBackoff.java
@@ -22,9 +22,11 @@ final class ExponentialBackoff {
 
     final int error() {
         attempt += 1;
-        final int multiplier = (int) Math.pow(2, attempt);
-        final int upper = Math.min(cap, base * multiplier);
-        return random.nextInt(upper);
+        int multiplier = cap / base;
+        if ((multiplier >> attempt) > 0) {
+            multiplier = 1 << attempt;
+        }
+        return random.nextInt(base * multiplier);
     }
 
     final void reset() {

diff --git a/agent/src/test/java/io/pyroscope/javaagent/ExponentialBackoffTest.java b/agent/src/test/java/io/pyroscope/javaagent/ExponentialBackoffTest.java
@@ -32,7 +32,8 @@ void test() {
         assertEquals(4_000, exponentialBackoff.error());
         assertEquals(8_000, exponentialBackoff.error());
         assertEquals(16_000, exponentialBackoff.error());
-        assertEquals(30_000, exponentialBackoff.error());
-        assertEquals(30_000, exponentialBackoff.error());
+        for (int i = 0; i < 100; i++) {
+            assertEquals(30_000, exponentialBackoff.error());
+        }
     }
 }