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Posted to pr@cassandra.apache.org by "nivykani (via GitHub)" <gi...@apache.org> on 2026/01/07 18:18:45 UTC
[PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
nivykani opened a new pull request, #4549:
URL: https://github.com/apache/cassandra/pull/4549
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The [Cassandra Jira](https://issues.apache.org/jira/browse/CASSANDRA-21102)
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "dcapwell (via GitHub)" <gi...@apache.org>.
dcapwell commented on PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#issuecomment-3731134081
```
commit 386183fce11707f176b736d92e50cb75ad0680b8
Author: Nivy Kani <ni...@apple.com>
Date: Thu Jan 8 14:27:36 2026 -0800
Fix off-by-one bug in exponential backoff for repair retry config
patch by Nivy Kani; reviewed by David Capwell, Jyothsna Konisa for CASSANDRA-21102
```
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "nivykani (via GitHub)" <gi...@apache.org>.
nivykani commented on code in PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#discussion_r2670315876
##########
test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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
+ *
+ * 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 org.apache.cassandra.service;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+public class TimeoutStrategyTest {
+
+ @Test
+ public void testParseLatencyModifierExponential() {
Review Comment:
Great catch with the overflows; Integer.MIN_VALUE would break this logic so I added a max(a, 0). For Integer.MAX_VALUE, the maximum number of retries has to be specified in the input string. Also added a case for fractional bases.
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "dcapwell (via GitHub)" <gi...@apache.org>.
dcapwell commented on code in PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#discussion_r2674064326
##########
test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java:
##########
@@ -0,0 +1,72 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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
+ *
+ * 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 org.apache.cassandra.service;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+public class TimeoutStrategyTest {
Review Comment:
style: `{` are always on a new line
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "dcapwell (via GitHub)" <gi...@apache.org>.
dcapwell commented on code in PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#discussion_r2674061499
##########
src/java/org/apache/cassandra/service/TimeoutStrategy.java:
##########
@@ -97,7 +97,8 @@ interface LatencyModifierFactory
default LatencyModifier identity() { return (l, a) -> l; }
default LatencyModifier multiply(double constant) { return (l, a) -> saturatedCast(l * constant); }
default LatencyModifier multiplyByAttempts(double multiply) { return (l, a) -> saturatedCast(l * multiply * a); }
- default LatencyModifier multiplyByAttemptsExp(double base) { return (l, a) -> saturatedCast(l * pow(base, a)); }
+ // Ensure attempts is non-negative before subtracting 1.
+ default LatencyModifier multiplyByAttemptsExp(double base) { return (l, a) -> saturatedCast(l * pow(base, max(0, (max(a, 0) - 1)))); }
Review Comment:
this looks safe
```
$ rg '\^attempts' src
src/java/org/apache/cassandra/config/RetrySpec.java
164: return RetryStrategy.parse(spec.baseSleepTime.toMilliseconds() + "ms * 2^attempts <= " + spec.maxSleepTime.toMilliseconds() + "ms,retries=" + (spec.maxAttempts.value - 1), LatencySourceFactory.none());
src/java/org/apache/cassandra/service/RetryStrategy.java
72: * <li> {@code 10ms <= p95(rw)*1.8^attempts <= 100ms}
src/java/org/apache/cassandra/service/TimeoutStrategy.java
73: * <li> {@code 10ms <= p95(rw)*1.8^attempts <= 100ms}
```
The only user is repair, so not really a breaking change to paxos. If anyone was using this in paxos v2, the only impact is that it would have the first retry respect the min value rather than do `min * 2`, so LGTM
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "dcapwell (via GitHub)" <gi...@apache.org>.
dcapwell closed pull request #4549: [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config
URL: https://github.com/apache/cassandra/pull/4549
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "jyothsnakonisa (via GitHub)" <gi...@apache.org>.
jyothsnakonisa commented on code in PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#discussion_r2670026516
##########
test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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
+ *
+ * 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 org.apache.cassandra.service;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+public class TimeoutStrategyTest {
+
+ @Test
+ public void testParseLatencyModifierExponential() {
+ long expectedBaseLatencyMicros = TimeUnit.MILLISECONDS.toMicros(30);
+ String spec = "30ms * 2^attempts";
+ TimeoutStrategy.Wait w = org.apache.cassandra.service.TimeoutStrategy.parseWait(spec, TimeoutStrategy.LatencySourceFactory.none());
+
+ // Attempt 1: baseLatency * 2^(1-1) = baseLatency * 1
+ Assertions.assertThat(w.getMicros(1))
+ .isEqualTo(expectedBaseLatencyMicros);
+
+ // Attempt 2: baseLatency * 2^(2-1) = baseLatency * 2
+ Assertions.assertThat(w.getMicros(2))
+ .isEqualTo(expectedBaseLatencyMicros * 2);
+
+ // Attempt 3: baseLatency * 2^(3-1) = baseLatency * 4
+ Assertions.assertThat(w.getMicros(3))
+ .isEqualTo(expectedBaseLatencyMicros * 4);
+
+ // Edge case to check for 0 attempts: max(0, -1) = 0
+ Assertions.assertThat(w.getMicros(0))
+ .isEqualTo(expectedBaseLatencyMicros);
+ }
+}
Review Comment:
Please add new line
##########
src/java/org/apache/cassandra/service/TimeoutStrategy.java:
##########
@@ -97,7 +97,7 @@ interface LatencyModifierFactory
default LatencyModifier identity() { return (l, a) -> l; }
default LatencyModifier multiply(double constant) { return (l, a) -> saturatedCast(l * constant); }
default LatencyModifier multiplyByAttempts(double multiply) { return (l, a) -> saturatedCast(l * multiply * a); }
- default LatencyModifier multiplyByAttemptsExp(double base) { return (l, a) -> saturatedCast(l * pow(base, a)); }
+ default LatencyModifier multiplyByAttemptsExp(double base) { return (l, a) -> saturatedCast(l * pow(base, max(0, a-1))); }
Review Comment:
```suggestion
default LatencyModifier multiplyByAttemptsExp(double base) { return (l, a) -> saturatedCast(l * pow(base, max(0, a - 1))); }
```
Please fix formatting
##########
test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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
+ *
+ * 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 org.apache.cassandra.service;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+public class TimeoutStrategyTest {
+
+ @Test
+ public void testParseLatencyModifierExponential() {
Review Comment:
How about checking for Integer.MAX_VALUE & Integer.MIN_VALUE number of attempts for checking overflows?
Also, can you add another case for fractional base like `0.5`
##########
test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java:
##########
@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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
+ *
+ * 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 org.apache.cassandra.service;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+public class TimeoutStrategyTest {
+
+ @Test
+ public void testParseLatencyModifierExponential() {
+ long expectedBaseLatencyMicros = TimeUnit.MILLISECONDS.toMicros(30);
+ String spec = "30ms * 2^attempts";
+ TimeoutStrategy.Wait w = org.apache.cassandra.service.TimeoutStrategy.parseWait(spec, TimeoutStrategy.LatencySourceFactory.none());
Review Comment:
```suggestion
TimeoutStrategy.Wait w = TimeoutStrategy.parseWait(spec, TimeoutStrategy.LatencySourceFactory.none());
```
We don't need fully qualified class name
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Re: [PR] [CASSANDRA-21102] Fix off-by-one bug in exponential backoff for repair retry config [cassandra]
Posted by "dcapwell (via GitHub)" <gi...@apache.org>.
dcapwell commented on PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#issuecomment-3726436511
checkstyles fails
File Name Line Number Message
/workspace/cassandra/test/unit/org/apache/cassandra/service/TimeoutStrategyTest.java 24 Wrong order for 'java.util.concurrent.TimeUnit' import.
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