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Added the Voldemort Client automated re-bootstrap mechanism
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Chinmay Soman
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Lei Gao
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Jun 27, 2012
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125 changes: 125 additions & 0 deletions
125
src/java/voldemort/client/AsyncMetadataVersionManager.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| package voldemort.client; | ||
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| import java.lang.Thread.UncaughtExceptionHandler; | ||
| import java.util.Random; | ||
| import java.util.concurrent.Callable; | ||
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| import org.apache.log4j.Level; | ||
| import org.apache.log4j.Logger; | ||
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| import voldemort.versioning.Versioned; | ||
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| /* | ||
| * The AsyncMetadataVersionManager is used to track the Metadata version on the | ||
| * cluster and if necessary Re-bootstrap the client. | ||
| * | ||
| * During initialization, it will retrieve the current version of the store (or | ||
| * the entire stores.xml depending upon granularity) and then periodically check | ||
| * whether this has been updated. During init if the initial version turns out | ||
| * to be null, it means that no change has been done to that store since it was | ||
| * created. In this case, we assume version '0'. | ||
| */ | ||
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| public class AsyncMetadataVersionManager implements Runnable { | ||
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| private final Logger logger = Logger.getLogger(this.getClass()); | ||
| private Versioned<Long> currentVersion; | ||
| private final SystemStore<String, Long> sysStore; | ||
| private final String systemKey = "stores.xml"; | ||
| private volatile boolean isRunning; | ||
| private final Callable<Void> storeClientThunk; | ||
| private long asyncMetadataCheckInterval; | ||
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| // Random delta generator | ||
| final int DELTA_MAX = 1000; | ||
| Random randomGenerator = new Random(System.currentTimeMillis()); | ||
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| public AsyncMetadataVersionManager(SystemStore<String, Long> systemStore, | ||
| long asyncMetadataCheckInterval, | ||
| Callable<Void> storeClientThunk) { | ||
| this(null, systemStore, asyncMetadataCheckInterval, storeClientThunk); | ||
| } | ||
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| public AsyncMetadataVersionManager(Versioned<Long> initialVersion, | ||
| SystemStore<String, Long> systemStore, | ||
| long asyncMetadataCheckInterval, | ||
| Callable<Void> storeClientThunk) { | ||
| this.sysStore = systemStore; | ||
| if(initialVersion == null) { | ||
| this.currentVersion = sysStore.getSysStore("stores.xml"); | ||
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| // If the received store version is null, assume version 0 | ||
| if(currentVersion == null) | ||
| currentVersion = new Versioned<Long>((long) 0); | ||
| } else { | ||
| currentVersion = initialVersion; | ||
| } | ||
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| // Initialize and start the background check thread | ||
| isRunning = true; | ||
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| Thread checkVersionThread = new Thread(this, "AsyncVersionCheckThread"); | ||
| checkVersionThread.setDaemon(true); | ||
| checkVersionThread.setUncaughtExceptionHandler(new UncaughtExceptionHandler() { | ||
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| public void uncaughtException(Thread t, Throwable e) { | ||
| if(logger.isEnabledFor(Level.ERROR)) | ||
| logger.error("Uncaught exception in Metadata Version check thread:", e); | ||
| } | ||
| }); | ||
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| this.storeClientThunk = storeClientThunk; | ||
| this.asyncMetadataCheckInterval = asyncMetadataCheckInterval; | ||
| checkVersionThread.start(); | ||
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| } | ||
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| public void destroy() { | ||
| isRunning = false; | ||
| } | ||
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| public void run() { | ||
| while(!Thread.currentThread().isInterrupted() && isRunning) { | ||
| try { | ||
| Thread.sleep(asyncMetadataCheckInterval); | ||
| } catch(InterruptedException e) { | ||
| break; | ||
| } | ||
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| Versioned<Long> newVersion = this.sysStore.getSysStore(systemKey); | ||
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| // If version obtained is null, the store is untouched. Continue | ||
| if(newVersion == null) { | ||
| logger.info("Metadata unchanged after creation ..."); | ||
| continue; | ||
| } | ||
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| logger.info("MetadataVersion check => Obtained " + systemKey + " version : " | ||
| + newVersion); | ||
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| if(!newVersion.equals(currentVersion)) { | ||
| logger.info("Metadata version mismatch detected."); | ||
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| // Determine a random delta delay between 0 to 1000 (ms) | ||
| int delta = randomGenerator.nextInt(DELTA_MAX); | ||
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| try { | ||
| logger.info("Sleeping for delta : " + delta + " (ms) before re-bootstrapping."); | ||
| Thread.sleep(delta); | ||
| } catch(InterruptedException e) { | ||
| break; | ||
| } | ||
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| // Invoke callback for bootstrap | ||
| try { | ||
| this.storeClientThunk.call(); | ||
| } catch(Exception e) { | ||
| e.printStackTrace(); | ||
| } | ||
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| // Update the current version | ||
| currentVersion = newVersion; | ||
| } | ||
| } | ||
| } | ||
| } |
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