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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.jaxrs.client;
import com.yahoo.vespa.applicationmodel.HostName;
import javax.ws.rs.ProcessingException;
import java.io.IOException;
import java.util.Objects;
import java.util.Set;
import java.util.function.Function;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* A {@link JaxRsStrategy} that will retry on failures, looping twice over all available server hosts before giving up.
*
* @author <a href="mailto:bakksjo@yahoo-inc.com">Oyvind Bakksjo</a>
*/
public class RetryingJaxRsStrategy<T> implements JaxRsStrategy<T> {
private static final Logger logger = Logger.getLogger(RetryingJaxRsStrategy.class.getName());
private static final int NUM_LOOP_ATTEMPTS = 2;
private final Set<HostName> hostNames;
private final int port;
private final JaxRsClientFactory jaxRsClientFactory;
private final Class<T> apiClass;
private String pathPrefix;
public RetryingJaxRsStrategy(
final Set<HostName> hostNames,
final int port,
final JaxRsClientFactory jaxRsClientFactory,
final Class<T> apiClass,
final String pathPrefix) {
if (hostNames.isEmpty()) {
throw new IllegalArgumentException("hostNames argument must not be empty");
}
Objects.requireNonNull(jaxRsClientFactory, "jaxRsClientFactory argument may not be null");
Objects.requireNonNull(apiClass, "apiClass argument may not be null");
Objects.requireNonNull(pathPrefix, "pathPrefix argument may not be null");
this.hostNames = hostNames;
this.port = port;
this.jaxRsClientFactory = jaxRsClientFactory;
this.apiClass = apiClass;
this.pathPrefix = pathPrefix;
}
@Override
public <R> R apply(final Function<T, R> function) throws IOException {
ProcessingException sampleException = null;
for (int i = 0; i < NUM_LOOP_ATTEMPTS; ++i) {
for (final HostName hostName : hostNames) {
final T jaxRsClient = jaxRsClientFactory.createClient(apiClass, hostName, port, pathPrefix);
try {
return function.apply(jaxRsClient);
} catch (ProcessingException e) {
sampleException = e;
logger.log(Level.WARNING, "Failed REST API call (in retry loop)", e);
}
}
}
final String message = String.format(
"Giving up invoking REST API after %d tries against hosts %s.%s",
NUM_LOOP_ATTEMPTS,
hostNames,
sampleException == null ? "" : ", sample error: " + sampleException.getMessage());
assert sampleException != null;
throw new IOException(message, sampleException);
}
}
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