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Retry exponential backoff #775 (#829)

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* Spatial partition

* Retry with exponential backoff

* retry exponential backoff

* branch error
This commit is contained in:
AnaghaSasikumar 2019-02-04 11:57:13 +05:30 committed by Ilkka Seppälä
parent a6749cb63e
commit 10cb191533
3 changed files with 246 additions and 0 deletions
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16
retry/src/main/java/com/iluwatar/retry/App.java
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@ -71,6 +71,7 @@ public final class App {
noErrors();
errorNoRetry();
errorWithRetry();
errorWithRetryExponentialBackoff();
}
private static void noErrors() throws Exception {
@ -102,4 +103,19 @@ public final class App {
+ "the result %s after a number of attempts %s", customerId, retry.attempts()
));
}
private static void errorWithRetryExponentialBackoff() throws Exception {
final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
new FindCustomer("123", new CustomerNotFoundException("not found")),
6, //6 attempts
30000, //30 s max delay between attempts
e -> CustomerNotFoundException.class.isAssignableFrom(e.getClass())
);
op = retry;
final String customerId = op.perform();
LOG.info(String.format(
"However, retrying the operation while ignoring a recoverable error will eventually yield "
+ "the result %s after a number of attempts %s", customerId, retry.attempts()
));
}
}

115
retry/src/main/java/com/iluwatar/retry/RetryExponentialBackoff.java Normal file
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@ -0,0 +1,115 @@
/*
* The MIT License (MIT)
*
* Copyright (c) 2014-2016 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package com.iluwatar.retry;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Predicate;
/**
* Decorates {@link BusinessOperation business operation} with "retry" capabilities.
*
* @author George Aristy (george.aristy@gmail.com)
* @param <T> the remote op's return type
*/
public final class RetryExponentialBackoff<T> implements BusinessOperation<T> {
private final BusinessOperation<T> op;
private final int maxAttempts;
private final long maxDelay;
private final AtomicInteger attempts;
private final Predicate<Exception> test;
private final List<Exception> errors;
/**
* Ctor.
*
* @param op the {@link BusinessOperation} to retry
* @param maxAttempts number of times to retry
* @param ignoreTests tests to check whether the remote exception can be ignored. No exceptions
* will be ignored if no tests are given
*/
@SafeVarargs
public RetryExponentialBackoff(
BusinessOperation<T> op,
int maxAttempts,
long maxDelay,
Predicate<Exception>... ignoreTests
) {
this.op = op;
this.maxAttempts = maxAttempts;
this.maxDelay = maxDelay;
this.attempts = new AtomicInteger();
this.test = Arrays.stream(ignoreTests).reduce(Predicate::or).orElse(e -> false);
this.errors = new ArrayList<>();
}
/**
* The errors encountered while retrying, in the encounter order.
*
* @return the errors encountered while retrying
*/
public List<Exception> errors() {
return Collections.unmodifiableList(this.errors);
}
/**
* The number of retries performed.
*
* @return the number of retries performed
*/
public int attempts() {
return this.attempts.intValue();
}
@Override
public T perform() throws BusinessException {
do {
try {
return this.op.perform();
} catch (BusinessException e) {
this.errors.add(e);
if (this.attempts.incrementAndGet() >= this.maxAttempts || !this.test.test(e)) {
throw e;
}
try {
Random rand = new Random();
long testDelay = (long) Math.pow(2, this.attempts()) * 1000 + rand.nextInt(1000);
long delay = testDelay < this.maxDelay ? testDelay : maxDelay;
Thread.sleep(delay);
} catch (InterruptedException f) {
//ignore
}
}
}
while (true);
}
}

115
retry/src/test/java/com/iluwatar/retry/RetryExponentialBackoffTest.java Normal file
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@ -0,0 +1,115 @@
/*
* The MIT License (MIT)
*
* Copyright (c) 2014-2016 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package com.iluwatar.retry;
import org.junit.jupiter.api.Test;
import static org.hamcrest.CoreMatchers.hasItem;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
/**
* Unit tests for {@link Retry}.
*
* @author George Aristy (george.aristy@gmail.com)
*/
public class RetryExponentialBackoffTest {
/**
* Should contain all errors thrown.
*/
@Test
public void errors() throws Exception {
final BusinessException e = new BusinessException("unhandled");
final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
() -> {
throw e;
},
2,
0
);
try {
retry.perform();
} catch (BusinessException ex) {
//ignore
}
assertThat(
retry.errors(),
hasItem(e)
);
}
/**
* No exceptions will be ignored, hence final number of attempts should be 1 even if we're asking
* it to attempt twice.
*/
@Test
public void attempts() {
final BusinessException e = new BusinessException("unhandled");
final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
() -> {
throw e;
},
2,
0
);
try {
retry.perform();
} catch (BusinessException ex) {
//ignore
}
assertThat(
retry.attempts(),
is(1)
);
}
/**
* Final number of attempts should be equal to the number of attempts asked because we are
* asking it to ignore the exception that will be thrown.
*/
@Test
public void ignore() throws Exception {
final BusinessException e = new CustomerNotFoundException("customer not found");
final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
() -> {
throw e;
},
2,
0,
ex -> CustomerNotFoundException.class.isAssignableFrom(ex.getClass())
);
try {
retry.perform();
} catch (BusinessException ex) {
//ignore
}
assertThat(
retry.attempts(),
is(2)
);
}
}