/**
* Tests a somewhat contrived upgrade scenario with persistent classes A and B that can be
* embedded in an entity without changing the entity class definition or version. For example, if
* a field of type Animal has subclasses Cat and Dog, these subclasses will not be known to the
* DPL until an instance of them is stored. When a new subclass is defined in the app, a metadata
* upgrade will not occur until an instance is stored.
*
* <p>The contrived scenario is:
*
* <p>+ App initially contains persistent class A, but no instance of A is stored. Neither the
* Master nor Replica DPL is aware of class A.
*
* <p>+ App is modified to contain new persistent class B.
*
* <p>+ Replica is upgraded, but does not enter Replica Upgrade Mode because class A and B are not
* yet used or referenced.
*
* <p>+ Master writes record containing instance of A, but Replica does not read it. Replica
* metadata is stale. It so happens that A is assigned format ID 200 by the Master.
*
* <p>+ Master is bounced and former Replica is elected Master.
*
* <p>+ New Master attempts to write record with instances of B, and updates its metadata, and
* happens to assign B format ID 200. If the metadata previously written by the old Master is
* overwritten, then metadata corruption will occur. Class A and B will have been assigned the
* same format ID.
*
* <p>+ When any node reads record containing A, some sort of exception will probably occur as a
* result of the incorrect format ID, or perhaps incorrect data will be returned.
*
* <p>This problem should be avoided because the new Master should detect that its metadata is
* stale, and refresh it prior to writing the new metadata. It detects this, even though it is not
* in Replica Upgrade Mode, by reading the metadata before updating it, and checking to see if it
* has changed since it was last read. See PersistCatalog.writeDataCheckStale.
*
* <p>The scenario is contrived in the sense that it is very unlikely that an instance of A will
* happen to be written by the Master for the very first time during the upgrade process. But it
* does provide a test case for the detection of metadata changes in PersistCatalog.writeData.
*/
@Test
public void testRefreshBeforeWrite() throws Exception {
doInitDuringOpen = false;
open();
masterApp.insertNullAnimal();
replicaApp1.readNullAnimal();
replicaApp2.readNullAnimal();
/* Replicas upgraded to v1 but do not enter Replica Upgrade Mode. */
bounceReplica1(1);
bounceReplica2(1);
assertFalse(replicaApp1.getStore().isReplicaUpgradeMode());
assertFalse(replicaApp2.getStore().isReplicaUpgradeMode());
masterApp.insertDogAnimal();
bounceMaster(1);
masterApp.insertCatAnimal();
masterApp.readDogAnimal();
masterApp.readCatAnimal();
replicaApp1.readDogAnimal();
replicaApp1.readCatAnimal();
replicaApp2.readDogAnimal();
replicaApp2.readCatAnimal();
close();
}
