在Google App Engine开发服务器中自定义HighRepJobPolicy

Question

我在App Engine开发服务器中使用自定义HighRepJobPolicy。当我在单元测试中使用同一类工作得很好：

LocalDatastoreServiceTestConfig datastoreConfig = new LocalDatastoreServiceTestConfig(); 
datastoreConfig.setAlternateHighRepJobPolicyClass(CustomHighRepJobPolicy.class); 

但是当我尝试通过增加JVM标签

-Ddatastore.high_replication_job_policy_class=foo.bar.CustomHighRepJobPolicy 

我得到一个ClassNotFoundException使用这个类在Java开发服务器：

Caused by: java.lang.ClassNotFoundException: foo.bar.CustomHighRepJobPolicy 
     at java.net.URLClassLoader$1.run(URLClassLoader.java:217) 
     at java.security.AccessController.doPrivileged(Native Method) 
     at java.net.URLClassLoader.findClass(URLClassLoader.java:205) 
     at java.lang.ClassLoader.loadClass(ClassLoader.java:321) 
     at com.google.appengine.tools.development.DevAppServerClassLoader.loadClass(DevAppServerClassLoader.java:87) 
     at java.lang.ClassLoader.loadClass(ClassLoader.java:266) 
     at java.lang.Class.forName0(Native Method) 
     at java.lang.Class.forName(Class.java:186) 
     at com.google.appengine.api.datastore.dev.LocalDatastoreService.initHighRepJobPolicy(LocalDatastoreService.java:426) 
     ... 66 more 

这是预期的工作，或有其他人尝试过吗？我问，因为我无法通过Google找到任何有关此信息，并且App Engine docs仅提及DefaultHighRepJobPolicy。

Answer 1

Looks like you were early to the party：

public class LocalCustomPolicyHighRepDatastoreTest { 
    private static final class CustomHighRepJobPolicy implements HighRepJobPolicy { 
     static int count = 0; 
     @Override 
     public boolean shouldApplyNewJob(Key entityGroup) { 
      // every other new job fails to apply 
      return count++ % 2 == 0; 
     } 

     @Override 
     public boolean shouldRollForwardExistingJob(Key entityGroup) { 
      // every other existing job fails to apply 
      return count++ % 2 == 0; 
     } 
    } 

    private final LocalServiceTestHelper helper = 
     new LocalServiceTestHelper(new LocalDatastoreServiceTestConfig() 
      .setAlternateHighRepJobPolicyClass(CustomHighRepJobPolicy.class)); 

    @Before 
    public void setUp() { 
     helper.setUp(); 
    } 

    @After 
    public void tearDown() { 
     helper.tearDown(); 
    } 

    @Test 
    public void testEventuallyConsistentGlobalQueryResult() { 
     DatastoreService ds = DatastoreServiceFactory.getDatastoreService(); 
     ds.put(new Entity("yam")); // applies 
     ds.put(new Entity("yam")); // does not apply 
     // first global query only sees the first Entity 
     assertEquals(1, ds.prepare(new Query("yam")).countEntities(withLimit(10))); 
     // second global query sees both Entities because we "groom" (attempt to 
     // apply unapplied jobs) after every query 
     assertEquals(2, ds.prepare(new Query("yam")).countEntities(withLimit(10))); 
    } 
}