From bcfaaffa3751f8c7883e41c162ba4030fd9bd21a Mon Sep 17 00:00:00 2001
From: Jesse Morgan <jesse@jesterpm.net>
Date: Fri, 25 Oct 2013 01:36:27 +0000
Subject: Fixing ReplicatedRepository so that transactions may be entered when
the master is unavailable as long as no changes are made to replicated
storables.
---
.../repo/replicated/ReadOnlyTransaction.java | 91 ++++++++++
.../repo/replicated/ReplicatedRepository.java | 31 +++-
.../repo/replicated/ReplicationTrigger.java | 190 +++++++++++++--------
3 files changed, 234 insertions(+), 78 deletions(-)
create mode 100644 src/main/java/com/amazon/carbonado/repo/replicated/ReadOnlyTransaction.java
(limited to 'src/main/java/com/amazon/carbonado/repo')
diff --git a/src/main/java/com/amazon/carbonado/repo/replicated/ReadOnlyTransaction.java b/src/main/java/com/amazon/carbonado/repo/replicated/ReadOnlyTransaction.java
new file mode 100644
index 0000000..1666bf4
--- /dev/null
+++ b/src/main/java/com/amazon/carbonado/repo/replicated/ReadOnlyTransaction.java
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2006-2013 Amazon Technologies, Inc. or its affiliates.
+ * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
+ * of Amazon Technologies, Inc. or its affiliates. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.amazon.carbonado.repo.replicated;
+
+import java.util.concurrent.TimeUnit;
+
+import com.amazon.carbonado.IsolationLevel;
+import com.amazon.carbonado.PersistException;
+import com.amazon.carbonado.Transaction;
+
+/**
+ * ReadOnlyTransaction wraps an another transaction. It's only function is to
+ * serve as a marker for the ReplicatedStorage triggers that no write
+ * operations are allowed.
+ *
+ * @author Jesse Morgan
+ */
+class ReadOnlyTransaction implements Transaction {
+ private final Transaction mTxn;
+
+ public ReadOnlyTransaction(Transaction txn) {
+ mTxn = txn;
+ }
+
+ @Override
+ public void commit() throws PersistException {
+ mTxn.commit();
+ }
+
+ @Override
+ public void exit() throws PersistException {
+ mTxn.exit();
+ }
+
+ @Override
+ public void setForUpdate(boolean forUpdate) {
+ mTxn.setForUpdate(forUpdate);
+ }
+
+ @Override
+ public boolean isForUpdate() {
+ return mTxn.isForUpdate();
+ }
+
+ @Override
+ public void setDesiredLockTimeout(int timeout, TimeUnit unit) {
+ mTxn.setDesiredLockTimeout(timeout, unit);
+ }
+
+ @Override
+ public IsolationLevel getIsolationLevel() {
+ return mTxn.getIsolationLevel();
+ }
+
+ @Override
+ public void detach() {
+ mTxn.detach();
+ }
+
+ @Override
+ public void attach() {
+ mTxn.attach();
+ }
+
+ @Override
+ public boolean preCommit() throws PersistException {
+ return mTxn.preCommit();
+ }
+
+ @Override
+ public String toString() {
+ return "ReadOnlyTransaction wrapping { " + mTxn.toString() + " }";
+ }
+}
+
diff --git a/src/main/java/com/amazon/carbonado/repo/replicated/ReplicatedRepository.java b/src/main/java/com/amazon/carbonado/repo/replicated/ReplicatedRepository.java
index 6cf0d6c..cfe021d 100644
--- a/src/main/java/com/amazon/carbonado/repo/replicated/ReplicatedRepository.java
+++ b/src/main/java/com/amazon/carbonado/repo/replicated/ReplicatedRepository.java
@@ -70,6 +70,7 @@ import com.amazon.carbonado.spi.StoragePool;
import com.amazon.carbonado.txn.TransactionPair;
+import com.amazon.carbonado.util.BelatedCreationException;
import com.amazon.carbonado.util.Throttle;
/**
@@ -243,18 +244,36 @@ class ReplicatedRepository
}
public Transaction enterTransaction() {
- return new TransactionPair(mMasterRepository.enterTransaction(),
- mReplicaRepository.enterTransaction());
+ Transaction master;
+ try {
+ master = mMasterRepository.enterTransaction();
+ } catch (BelatedCreationException e) {
+ return new ReadOnlyTransaction(mReplicaRepository.enterTransaction());
+ }
+
+ return new TransactionPair(master, mReplicaRepository.enterTransaction());
}
public Transaction enterTransaction(IsolationLevel level) {
- return new TransactionPair(mMasterRepository.enterTransaction(level),
- mReplicaRepository.enterTransaction(level));
+ Transaction master;
+ try {
+ master = mMasterRepository.enterTransaction(level);
+ } catch (BelatedCreationException e) {
+ return new ReadOnlyTransaction(mReplicaRepository.enterTransaction(level));
+ }
+
+ return new TransactionPair(master, mReplicaRepository.enterTransaction(level));
}
public Transaction enterTopTransaction(IsolationLevel level) {
- return new TransactionPair(mMasterRepository.enterTopTransaction(level),
- mReplicaRepository.enterTopTransaction(level));
+ Transaction master;
+ try {
+ master = mMasterRepository.enterTopTransaction(level);
+ } catch (BelatedCreationException e) {
+ return new ReadOnlyTransaction(mReplicaRepository.enterTopTransaction(level));
+ }
+
+ return new TransactionPair(master, mReplicaRepository.enterTopTransaction(level));
}
public IsolationLevel getTransactionIsolationLevel() {
diff --git a/src/main/java/com/amazon/carbonado/repo/replicated/ReplicationTrigger.java b/src/main/java/com/amazon/carbonado/repo/replicated/ReplicationTrigger.java
index 4b01679..1b88e3e 100644
--- a/src/main/java/com/amazon/carbonado/repo/replicated/ReplicationTrigger.java
+++ b/src/main/java/com/amazon/carbonado/repo/replicated/ReplicationTrigger.java
@@ -83,99 +83,133 @@ class ReplicationTrigger<S extends Storable> extends Trigger<S> {
@Override
public Object beforeInsert(S replica) throws PersistException {
- return beforeInsert(replica, false);
+ return beforeInsert(null, replica, false);
}
@Override
public Object beforeTryInsert(S replica) throws PersistException {
- return beforeInsert(replica, true);
+ return beforeInsert(null, replica, true);
}
- private Object beforeInsert(S replica, boolean forTry) throws PersistException {
- final S master = mMasterStorage.prepare();
- replica.copyAllProperties(master);
+ @Override
+ public Object beforeInsert(Transaction txn, S replica) throws PersistException {
+ return beforeInsert(txn, replica, false);
+ }
- try {
- if (forTry) {
- if (!master.tryInsert()) {
- throw abortTry();
+ @Override
+ public Object beforeTryInsert(Transaction txn, S replica) throws PersistException {
+ return beforeInsert(txn, replica, true);
+ }
+
+ private Object beforeInsert(Transaction txn, S replica, boolean forTry) throws PersistException {
+ if (txn instanceof ReadOnlyTransaction) {
+ // This operation was intended to take place in a transaction, but
+ // the master repository was unavailable when the transaction was
+ // entered.
+ throw new PersistException("Current transaction is read-only.");
+ }
+
+ final S master = mMasterStorage.prepare();
+ replica.copyAllProperties(master);
+
+ try {
+ if (forTry) {
+ if (!master.tryInsert()) {
+ throw abortTry();
+ }
+ } else {
+ master.insert();
}
- } else {
- master.insert();
+ } catch (UniqueConstraintException e) {
+ // This may be caused by an inconsistency between replica and
+ // master. Here's one scenerio: user called tryLoad and saw the
+ // entry does not exist. So instead of calling update, he/she calls
+ // insert. If the master entry exists, then there is an
+ // inconsistency. The code below checks for this specific kind of
+ // error and repairs it by inserting a record in the replica.
+
+ // Here's another scenerio: Unique constraint was caused by an
+ // inconsistency with the values of the alternate keys. User
+ // expected alternate keys to have unique values, as indicated by
+ // replica.
+
+ repair(replica);
+
+ // Throw exception since we don't know what the user's intentions
+ // really are.
+ throw e;
}
- } catch (UniqueConstraintException e) {
- // This may be caused by an inconsistency between replica and
- // master. Here's one scenerio: user called tryLoad and saw the
- // entry does not exist. So instead of calling update, he/she calls
- // insert. If the master entry exists, then there is an
- // inconsistency. The code below checks for this specific kind of
- // error and repairs it by inserting a record in the replica.
- // Here's another scenerio: Unique constraint was caused by an
- // inconsistency with the values of the alternate keys. User
- // expected alternate keys to have unique values, as indicated by
- // replica.
+ // Master may have applied sequences to unitialized primary keys, so
+ // copy primary keys to replica. Mark properties as dirty to allow
+ // primary key to be changed.
+ replica.markPropertiesDirty();
- repair(replica);
+ // Copy all properties in order to trigger constraints that
+ // master should have resolved.
+ master.copyAllProperties(replica);
- // Throw exception since we don't know what the user's intentions
- // really are.
- throw e;
+ return null;
}
- // Master may have applied sequences to unitialized primary keys, so
- // copy primary keys to replica. Mark properties as dirty to allow
- // primary key to be changed.
- replica.markPropertiesDirty();
+ @Override
+ public Object beforeUpdate(S replica) throws PersistException {
+ return beforeUpdate(null, replica, false);
+ }
- // Copy all properties in order to trigger constraints that
- // master should have resolved.
- master.copyAllProperties(replica);
+ @Override
+ public Object beforeTryUpdate(S replica) throws PersistException {
+ return beforeUpdate(null, replica, true);
+ }
- return null;
- }
+ @Override
+ public Object beforeUpdate(Transaction txn, S replica) throws PersistException {
+ return beforeUpdate(txn, replica, false);
+ }
- @Override
- public Object beforeUpdate(S replica) throws PersistException {
- return beforeUpdate(replica, false);
- }
+ @Override
+ public Object beforeTryUpdate(Transaction txn, S replica) throws PersistException {
+ return beforeUpdate(txn, replica, true);
+ }
- @Override
- public Object beforeTryUpdate(S replica) throws PersistException {
- return beforeUpdate(replica, true);
- }
+ private Object beforeUpdate(Transaction txn, S replica, boolean forTry) throws PersistException {
+ if (txn instanceof ReadOnlyTransaction) {
+ // This operation was intended to take place in a transaction, but
+ // the master repository was unavailable when the transaction was
+ // entered.
+ throw new PersistException("Current transaction is read-only.");
+ }
- private Object beforeUpdate(S replica, boolean forTry) throws PersistException {
- final S master = mMasterStorage.prepare();
- replica.copyPrimaryKeyProperties(master);
- replica.copyVersionProperty(master);
- replica.copyDirtyProperties(master);
+ final S master = mMasterStorage.prepare();
+ replica.copyPrimaryKeyProperties(master);
+ replica.copyVersionProperty(master);
+ replica.copyDirtyProperties(master);
- try {
- if (forTry) {
- if (!master.tryUpdate()) {
- // Master record does not exist. To ensure consistency,
- // delete record from replica.
- if (tryDeleteReplica(replica)) {
- // Replica was inconsistent, but caller might be in a
- // transaction and rollback the repair. Run repair
- // again in separate thread to ensure it sticks.
- repair(replica);
- }
- throw abortTry();
- }
- } else {
- try {
- master.update();
- } catch (PersistNoneException e) {
- // Master record does not exist. To ensure consistency,
- // delete record from replica.
- if (tryDeleteReplica(replica)) {
- // Replica was inconsistent, but caller might be in a
- // transaction and rollback the repair. Run repair
- // again in separate thread to ensure it sticks.
- repair(replica);
+ try {
+ if (forTry) {
+ if (!master.tryUpdate()) {
+ // Master record does not exist. To ensure consistency,
+ // delete record from replica.
+ if (tryDeleteReplica(replica)) {
+ // Replica was inconsistent, but caller might be in a
+ // transaction and rollback the repair. Run repair
+ // again in separate thread to ensure it sticks.
+ repair(replica);
+ }
+ throw abortTry();
}
+ } else {
+ try {
+ master.update();
+ } catch (PersistNoneException e) {
+ // Master record does not exist. To ensure consistency,
+ // delete record from replica.
+ if (tryDeleteReplica(replica)) {
+ // Replica was inconsistent, but caller might be in a
+ // transaction and rollback the repair. Run repair
+ // again in separate thread to ensure it sticks.
+ repair(replica);
+ }
throw e;
}
}
@@ -199,6 +233,18 @@ class ReplicationTrigger<S extends Storable> extends Trigger<S> {
@Override
public Object beforeDelete(S replica) throws PersistException {
+ return beforeDelete(null, replica);
+ }
+
+ @Override
+ public Object beforeDelete(Transaction txn, S replica) throws PersistException {
+ if (txn instanceof ReadOnlyTransaction) {
+ // This operation was intended to take place in a transaction, but
+ // the master repository was unavailable when the transaction was
+ // entered.
+ throw new PersistException("Current transaction is read-only.");
+ }
+
S master = mMasterStorage.prepare();
replica.copyPrimaryKeyProperties(master);
--
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