package com.hubspot.singularity.data;
import static com.google.common.base.Preconditions.checkState;
import io.dropwizard.lifecycle.Managed;
import javax.inject.Singleton;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.atomic.AtomicValue;
import org.apache.curator.framework.recipes.atomic.DistributedAtomicInteger;
import org.apache.curator.retry.RetryOneTime;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import com.google.inject.Inject;
@Singleton
public class ExecutorIdGenerator implements Managed {
private volatile DistributedAtomicInteger distributedGenerator = null;
private final char[] alphabet;
private static final String COUNTER_PATH = "/executors/counter";
private final CuratorFramework curator;
@Inject
public ExecutorIdGenerator(CuratorFramework curator) {
this.curator = curator;
this.alphabet = buildAlphabet();
}
@Override
public void start() {
this.distributedGenerator = new DistributedAtomicInteger(curator, COUNTER_PATH, new RetryOneTime(1));
}
@Override
public void stop() {
}
public String getNextExecutorId() {
checkState(distributedGenerator != null, "never started!");
try {
AtomicValue<Integer> atomic = distributedGenerator.increment();
Preconditions.checkState(atomic.succeeded(), "Atomic increment did not succeed");
return convertUsingAlphabet(atomic.postValue());
} catch (Throwable t) {
throw Throwables.propagate(t);
}
}
private String convertUsingAlphabet(int number) {
final StringBuilder bldr = new StringBuilder();
while (number > 0) {
int remainder = number % alphabet.length;
bldr.append(alphabet[remainder]);
number = number / alphabet.length;
}
return bldr.toString();
}
private char[] buildAlphabet() {
final char[] alphabet = new char[36];
int c = 0;
// add integers
for (int i = 48; i < 58; i++) {
alphabet[c++] = (char) i;
}
// add letters
for (int i = 97; i < 123; i++) {
alphabet[c++] = (char) i;
}
return alphabet;
}
}