在Java中的OrientDB併發圖操作

我想在多線程環境（Java 8）中使用orientdb（v2.1.2），其中我更新多個線程內的頂點。我知道orientdb正在使用MVCC，因此這些操作可能會失敗並需要重新執行。在Java中的OrientDB併發圖操作

我寫了一個小單元測試，試圖通過等待線程內的循環障礙來引發這種情況。不幸的是，測試失敗，一個不起眼的異常，我不明白：

Sep 21, 2015 3:00:24 PM com.orientechnologies.common.log.OLogManager log 
INFO: OrientDB auto-config DISKCACHE=10,427MB (heap=3,566MB os=16,042MB disk=31,720MB) 
Thread [0] running 
Thread [1] running 
Sep 21, 2015 3:00:24 PM com.orientechnologies.common.log.OLogManager log 
WARNING: {db=tinkerpop} Requested command 'create edge type 'testedge_1442840424480' as subclass of 'E'' must be executed outside active transaction: the transaction will be committed and reopen right after it. To avoid this behavior execute it outside a transaction 
Sep 21, 2015 3:00:24 PM com.orientechnologies.common.log.OLogManager log 
WARNING: {db=tinkerpop} Requested command 'create edge type 'testedge_1442840424480' as subclass of 'E'' must be executed outside active transaction: the transaction will be committed and reopen right after it. To avoid this behavior execute it outside a transaction 
Exception in thread "Thread-4" com.orientechnologies.orient.core.exception.OSchemaException: Cluster with id 11 already belongs to class testedge_1442840424480 
    at com.orientechnologies.orient.core.metadata.schema.OSchemaShared.checkClustersAreAbsent(OSchemaShared.java:1264) 
    at com.orientechnologies.orient.core.metadata.schema.OSchemaShared.doCreateClass(OSchemaShared.java:983) 
    at com.orientechnologies.orient.core.metadata.schema.OSchemaShared.createClass(OSchemaShared.java:415) 
    at com.orientechnologies.orient.core.metadata.schema.OSchemaShared.createClass(OSchemaShared.java:400) 
    at com.orientechnologies.orient.core.metadata.schema.OSchemaProxy.createClass(OSchemaProxy.java:100) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph$6.call(OrientBaseGraph.java:1387) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph$6.call(OrientBaseGraph.java:1384) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph.executeOutsideTx(OrientBaseGraph.java:1739) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph.createEdgeType(OrientBaseGraph.java:1384) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph.createEdgeType(OrientBaseGraph.java:1368) 
    at com.tinkerpop.blueprints.impls.orient.OrientBaseGraph.createEdgeType(OrientBaseGraph.java:1353) 
    at com.tinkerpop.blueprints.impls.orient.OrientVertex.addEdge(OrientVertex.java:928) 
    at com.tinkerpop.blueprints.impls.orient.OrientVertex.addEdge(OrientVertex.java:832) 
    at com.gentics.test.orientdb.OrientDBTinkerpopMultithreadingTest.lambda$0(OrientDBTinkerpopMultithreadingTest.java:31) 
    at com.gentics.test.orientdb.OrientDBTinkerpopMultithreadingTest$$Lambda$1/1446001495.run(Unknown Source) 
    at java.lang.Thread.run(Thread.java:745)

測試使用一個簡單的內存數據庫。我不知道爲什麼orientdb正在檢查一些集羣行動：

Cluster with id 11 already belongs to class testedge

不知怎的，纔會出現這個問題時，我嘗試創建具有相同標籤的兩條邊。

private OrientGraphFactory factory = new OrientGraphFactory("memory:tinkerpop").setupPool(5, 20); 

@Test 
public void testConcurrentGraphModifications() throws InterruptedException { 
    OrientGraph graph = factory.getTx(); 
    Vertex v = graph.addVertex(null); 
    graph.commit(); 
    CyclicBarrier barrier = new CyclicBarrier(2); 

    List<Thread> threads = new ArrayList<>(); 

    // Spawn two threads 
    for (int i = 0; i < 2; i++) { 
     final int threadNo = i; 
     threads.add(run(() -> { 
      System.out.println("Running thread [" + threadNo + "]"); 
      // Start a new transaction and modify vertex v 
      OrientGraph tx = factory.getTx(); 
      Vertex v2 = tx.addVertex(null); 
      v.addEdge("testedge", v2); 
      try { 
       barrier.await(); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
      tx.commit(); 
     })); 
    } 

    // Wait for all spawned threads 
    for (Thread thread : threads) { 
     thread.join(); 
    } 
} 

protected Thread run(Runnable runnable) { 
    Thread thread = new Thread(runnable); 
    thread.start(); 
    return thread; 
}

的測試用例完整的源可以在這裏找到：

https://github.com/Jotschi/orientdb-concurrency-test/blob/master/src/test/java/com/gentics/test/orientdb/OrientDBTinkerpopMultithreadingTest.java#L18

一般來說，我會是演示如何在使用orientdb時應對MVCC衝突例子非常感謝嵌入式多線程Java環境。

更新：

我注意到，當我通過tx.getVertex（vertex.getId（））我的線程中重新加載頂點問題不再occures（不是通過.reload（））。當我將頂點對象引用傳遞給我的線程並在那裏使用它時，我得到各種錯誤。我認爲OrientVertex類不是線程安全的。

來源

2015-09-21 Jotschi

你是對的全部圖形元素不是線程安全的。
當你創建邊緣時，你的異常的原因是，你在圖形數據庫的下面創建文檔，其中類別等於邊緣標籤。如果類不存在，則會自動提交事務並創建模式內的新類。當您同時添加邊並同時創建相同的類和結果時，每個類都映射到數據庫中的羣集（就像一個表），創建相同的羣集。因此，一個線程贏得其他失敗，並且已經創建了具有給定名稱的羣集。實際上，我建議您在運行時添加邊緣之前，先創建所有類的邊界標記（如果可能）。

還有一個建議。您應該考慮OrientGraph實例，就好像它是連接到服務器一樣。最好的用法如下：

設置池OrientGraphFactory交易之前
採集圖實例。
執行交易。
致電.shutdown（），請勿創建長時間存在的圖形實例。

來源

2015-10-02 18:13:36

在Java中的OrientDB併發圖操作

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