Madan Jampani | 12390c1 | 2014-11-12 00:35:56 -0800 | [diff] [blame^] | 1 | package org.onlab.onos.store.service.impl; |
| 2 | |
| 3 | import java.util.UUID; |
| 4 | import java.util.concurrent.CompletableFuture; |
| 5 | import java.util.concurrent.ExecutionException; |
| 6 | import java.util.concurrent.TimeUnit; |
| 7 | import java.util.concurrent.TimeoutException; |
| 8 | import java.util.concurrent.atomic.AtomicBoolean; |
| 9 | |
| 10 | import org.joda.time.DateTime; |
| 11 | import org.onlab.onos.cluster.ClusterService; |
| 12 | import org.onlab.onos.store.service.DatabaseService; |
| 13 | import org.onlab.onos.store.service.Lock; |
| 14 | import org.onlab.onos.store.service.OptimisticLockException; |
| 15 | |
| 16 | /** |
| 17 | * A distributed lock implementation. |
| 18 | */ |
| 19 | public class DistributedLock implements Lock { |
| 20 | |
| 21 | private final DistributedLockManager lockManager; |
| 22 | private final DatabaseService databaseService; |
| 23 | private final String path; |
| 24 | private DateTime lockExpirationTime; |
| 25 | private AtomicBoolean isLocked = new AtomicBoolean(false); |
| 26 | private byte[] lockId; |
| 27 | |
| 28 | public DistributedLock( |
| 29 | String path, |
| 30 | DatabaseService databaseService, |
| 31 | ClusterService clusterService, |
| 32 | DistributedLockManager lockManager) { |
| 33 | |
| 34 | this.path = path; |
| 35 | this.databaseService = databaseService; |
| 36 | this.lockManager = lockManager; |
| 37 | this.lockId = |
| 38 | (UUID.randomUUID().toString() + "::" + clusterService.getLocalNode().id().toString()).getBytes(); |
| 39 | } |
| 40 | |
| 41 | @Override |
| 42 | public String path() { |
| 43 | return path; |
| 44 | } |
| 45 | |
| 46 | @Override |
| 47 | public void lock(int leaseDurationMillis) { |
| 48 | |
| 49 | if (isLocked() && lockExpirationTime.isAfter(DateTime.now().plusMillis(leaseDurationMillis))) { |
| 50 | // Nothing to do. |
| 51 | // Current expiration time is beyond what is requested. |
| 52 | return; |
| 53 | } else { |
| 54 | tryLock(Long.MAX_VALUE, leaseDurationMillis); |
| 55 | } |
| 56 | } |
| 57 | |
| 58 | @Override |
| 59 | public boolean tryLock(int leaseDurationMillis) { |
| 60 | try { |
| 61 | databaseService.putIfAbsent(DistributedLockManager.ONOS_LOCK_TABLE_NAME, path, lockId); |
| 62 | return true; |
| 63 | } catch (OptimisticLockException e) { |
| 64 | return false; |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | @Override |
| 69 | public boolean tryLock( |
| 70 | long waitTimeMillis, |
| 71 | int leaseDurationMillis) { |
| 72 | if (tryLock(leaseDurationMillis) == false) { |
| 73 | CompletableFuture<Void> future = |
| 74 | lockManager.lockIfAvailable(this, waitTimeMillis, leaseDurationMillis); |
| 75 | try { |
| 76 | future.get(waitTimeMillis, TimeUnit.MILLISECONDS); |
| 77 | } catch (ExecutionException | InterruptedException e) { |
| 78 | // TODO: ExecutionException could indicate something |
| 79 | // wrong with the backing database. |
| 80 | // Throw an exception? |
| 81 | return false; |
| 82 | } catch (TimeoutException e) { |
| 83 | return false; |
| 84 | } |
| 85 | } |
| 86 | lockExpirationTime = DateTime.now().plusMillis(leaseDurationMillis); |
| 87 | return true; |
| 88 | } |
| 89 | |
| 90 | @Override |
| 91 | public boolean isLocked() { |
| 92 | if (isLocked.get()) { |
| 93 | // We rely on local information to check |
| 94 | // if the expired. |
| 95 | // This should should make this call |
| 96 | // light weight, which still retaining the same |
| 97 | // safety guarantees. |
| 98 | if (DateTime.now().isAfter(lockExpirationTime)) { |
| 99 | isLocked.set(false); |
| 100 | return false; |
| 101 | } |
| 102 | } |
| 103 | return true; |
| 104 | } |
| 105 | |
| 106 | @Override |
| 107 | public void unlock() { |
| 108 | if (!isLocked()) { |
| 109 | return; |
| 110 | } else { |
| 111 | databaseService.removeIfValueMatches(DistributedLockManager.ONOS_LOCK_TABLE_NAME, path, lockId); |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | @Override |
| 116 | public boolean extendExpiration(int leaseDurationMillis) { |
| 117 | if (isLocked() && lockExpirationTime.isAfter(DateTime.now().plusMillis(leaseDurationMillis))) { |
| 118 | return true; |
| 119 | } else { |
| 120 | return tryLock(leaseDurationMillis); |
| 121 | } |
| 122 | } |
| 123 | } |