mirror of https://github.com/apache/jclouds.git
added convenience for retrying and getting a result
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parent
7b72ef5cfc
commit
269754c3c9
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@ -0,0 +1,43 @@
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package org.jclouds.predicates;
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import java.util.concurrent.Callable;
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public abstract class PredicateCallable<Result> implements PredicateWithResult<Void, Result>, Callable<Result> {
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Result lastResult;
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Exception lastFailure;
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@Override
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public boolean apply(Void input) {
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try {
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lastResult = call();
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onCompletion();
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return isAcceptable(lastResult);
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} catch (Exception e) {
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lastFailure = e;
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onFailure();
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return false;
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}
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}
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protected void onFailure() {
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}
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protected void onCompletion() {
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}
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protected boolean isAcceptable(Result result) {
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return result!=null;
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}
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@Override
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public Result getResult() {
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return lastResult;
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}
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@Override
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public Throwable getLastFailure() {
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return lastFailure;
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}
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}
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@ -0,0 +1,11 @@
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package org.jclouds.predicates;
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import com.google.common.base.Predicate;
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public interface PredicateWithResult<Input,Result> extends Predicate<Input> {
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Result getResult();
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Throwable getLastFailure();
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}
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@ -34,6 +34,11 @@ import com.google.common.base.Predicate;
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/**
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*
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* Retries a condition until it is met or a timeout occurs.
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* maxWait parameter is required.
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* Initial retry period and retry maxPeriod are optionally configurable,
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* defaulting to 50ms and 1000ms respectively,
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* with the retrier increasing the interval by a factor of 1.5 each time within these constraints.
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* All values taken as millis unless TimeUnit specified.
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*
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* @author Adrian Cole
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*/
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@ -92,6 +97,7 @@ public class RetryablePredicate<T> implements Predicate<T> {
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}
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protected long nextMaxInterval(long attempt, Date end) {
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// FIXME i think this should be pow(1.5, attempt) -- or alternatively newInterval = oldInterval*1.5
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long interval = (period * (long) Math.pow(attempt, 1.5));
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interval = interval > maxPeriod ? maxPeriod : interval;
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long max = end.getTime() - System.currentTimeMillis();
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@ -0,0 +1,36 @@
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package org.jclouds.predicates;
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import java.util.concurrent.TimeUnit;
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import com.google.common.base.Predicate;
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public class Retryables {
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public static <Input> boolean retry(Predicate<Input> predicate, Input input, long maxWaitMillis) {
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return new RetryablePredicate<Input>(predicate, maxWaitMillis).apply(input);
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}
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public static <Input> boolean retry(Predicate<Input> predicate, Input input, long maxWait, long period, TimeUnit unit) {
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return new RetryablePredicate<Input>(predicate, maxWait, period, unit).apply(input);
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}
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public static <Input> void assertEventually(Predicate<Input> predicate, Input input,
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long maxWaitMillis, String failureMessage) {
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if (!new RetryablePredicate<Input>(predicate, maxWaitMillis).apply(input))
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throw new AssertionError(failureMessage);
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}
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public static <Input,Result> Result retryGettingResultOrFailing(PredicateWithResult<Input,Result> predicate,
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Input input, long maxWaitMillis, String failureMessage) {
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if (!new RetryablePredicate<Input>(predicate, maxWaitMillis).apply(input))
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throw (AssertionError)new AssertionError(failureMessage).initCause(predicate.getLastFailure());
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return predicate.getResult();
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}
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public static <Input,Result> Result retryGettingResultOrFailing(PredicateWithResult<Input,Result> predicate,
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Input input, long maxWait, long period, TimeUnit unit, String failureMessage) {
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if (!new RetryablePredicate<Input>(predicate, maxWait, period, unit).apply(input))
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throw (AssertionError)new AssertionError(failureMessage).initCause(predicate.getLastFailure());
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return predicate.getResult();
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}
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}
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@ -0,0 +1,110 @@
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package org.jclouds.predicates;
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import static java.util.concurrent.TimeUnit.MILLISECONDS;
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import static org.jclouds.predicates.Retryables.retry;
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import static org.jclouds.predicates.Retryables.retryGettingResultOrFailing;
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import static org.testng.Assert.*;
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import org.testng.annotations.Test;
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@Test
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public class RetryablesTest {
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public static class FindX implements PredicateWithResult<String,Character> {
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Character result;
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Throwable lastFailure;
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int attempts=0;
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@Override
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public boolean apply(String input) {
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try {
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result = input.charAt(attempts++);
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return (result=='x');
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} catch (Exception e) {
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lastFailure = e;
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return false;
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}
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}
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public Character getResult() {
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return result;
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}
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public Throwable getLastFailure() {
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return lastFailure;
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}
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}
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public void testPredicateWithResult() {
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FindX findX = new FindX();
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assertFalse(findX.apply("hexy"));
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assertEquals((char)findX.getResult(), 'h');
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assertFalse(findX.apply("hexy"));
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assertTrue(findX.apply("hexy"));
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assertEquals((char)findX.getResult(), 'x');
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assertFalse(findX.apply("hexy"));
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assertNull(findX.getLastFailure());
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//now we get error
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assertFalse(findX.apply("hexy"));
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assertNotNull(findX.getLastFailure());
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assertEquals((char)findX.getResult(), 'y');
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}
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public void testRetry() {
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FindX findX = new FindX();
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assertTrue(retry(findX, "hexy", 1000, 1, MILLISECONDS));
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assertEquals(findX.attempts, 3);
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assertEquals((char)findX.getResult(), 'x');
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assertNull(findX.getLastFailure());
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//now we'll be getting errors
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assertFalse(retry(findX, "hexy", 100, 1, MILLISECONDS));
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assertEquals((char)findX.getResult(), 'y');
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assertNotNull(findX.getLastFailure());
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}
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public void testRetryGetting() {
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FindX findX = new FindX();
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assertEquals((char)retryGettingResultOrFailing(findX, "hexy", 1000, "shouldn't happen"), 'x');
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//now we'll be getting errors
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boolean secondRetrySucceeds=false;
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try {
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retryGettingResultOrFailing(findX, "hexy", 100, "expected");
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secondRetrySucceeds = true;
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} catch (AssertionError e) {
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assertTrue(e.toString().contains("expected"));
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}
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if (secondRetrySucceeds) fail("should have thrown");
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assertNotNull(findX.getLastFailure());
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assertFalse(findX.getLastFailure().toString().contains("expected"));
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}
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//using PredicateCallable we can repeat the above test, with the job expressed more simply
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public static class FindXSimpler extends PredicateCallable<Character> {
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String input = "hexy";
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int attempts=0;
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public Character call() {
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return input.charAt(attempts++);
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}
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public boolean isAcceptable(Character result) {
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return result=='x';
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}
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}
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public void testSimplerPredicateCallableRetryGetting() {
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FindXSimpler findX = new FindXSimpler();
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assertEquals((char)retryGettingResultOrFailing(findX, null, 1000, "shouldn't happen"), 'x');
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//now we'll be getting errors
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boolean secondRetrySucceeds=false;
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try {
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retryGettingResultOrFailing(findX, null, 100, "expected");
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secondRetrySucceeds = true;
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} catch (AssertionError e) {
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assertTrue(e.toString().contains("expected"));
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}
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if (secondRetrySucceeds) fail("should have thrown");
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assertNotNull(findX.getLastFailure());
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assertFalse(findX.getLastFailure().toString().contains("expected"));
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}
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}
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