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PgAsyncTransactionManagerExample.java
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PgAsyncTransactionManagerExample.java
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/*
* Copyright 2022 Google Inc.
*
* 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.example.spanner;
//[START spanner_postgresql_async_transaction_manager]
import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.cloud.spanner.AbortedException;
import com.google.cloud.spanner.AsyncTransactionManager;
import com.google.cloud.spanner.AsyncTransactionManager.AsyncTransactionStep;
import com.google.cloud.spanner.AsyncTransactionManager.CommitTimestampFuture;
import com.google.cloud.spanner.AsyncTransactionManager.TransactionContextFuture;
import com.google.cloud.spanner.DatabaseClient;
import com.google.cloud.spanner.DatabaseId;
import com.google.cloud.spanner.Key;
import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerOptions;
import com.google.cloud.spanner.Statement;
import com.google.cloud.spanner.Struct;
import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.MoreExecutors;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
class PgAsyncTransactionManagerExample {
static void asyncTransactionManager()
throws InterruptedException, ExecutionException, TimeoutException {
// TODO(developer): Replace these variables before running the sample.
String projectId = "my-project";
String instanceId = "my-instance";
String databaseId = "my-database";
try (Spanner spanner =
SpannerOptions.newBuilder().setProjectId(projectId).build().getService()) {
DatabaseClient client =
spanner.getDatabaseClient(DatabaseId.of(projectId, instanceId, databaseId));
asyncTransactionManager(client);
}
}
static void asyncTransactionManager(DatabaseClient client)
throws InterruptedException, ExecutionException, TimeoutException {
ExecutorService executor = Executors.newSingleThreadExecutor();
AsyncTransactionStep<List<Struct>, long[]> updateCounts;
try (AsyncTransactionManager mgr = client.transactionManagerAsync()) {
TransactionContextFuture txn = mgr.beginAsync();
// Loop to retry aborted errors.
while (true) {
try {
updateCounts =
txn.then(
(transaction, v) -> {
// Execute two reads in parallel and return the result of these as the input
// for the next step of the transaction.
ApiFuture<Struct> album1BudgetFut =
transaction.readRowAsync(
"Albums", Key.of(1, 1), ImmutableList.of("MarketingBudget"));
ApiFuture<Struct> album2BudgetFut =
transaction.readRowAsync(
"Albums", Key.of(2, 2), ImmutableList.of("MarketingBudget"));
return ApiFutures.allAsList(
Arrays.asList(album1BudgetFut, album2BudgetFut));
},
executor)
// The input of the next step of the transaction is the return value of the
// previous step, i.e. a list containing the marketing budget of two Albums.
.then(
(transaction, budgets) -> {
long album1Budget = budgets.get(0).getLong(0);
long album2Budget = budgets.get(1).getLong(0);
long transfer = 200_000;
if (album2Budget >= transfer) {
album1Budget += transfer;
album2Budget -= transfer;
Statement updateStatement1 =
Statement.newBuilder(
"UPDATE Albums "
+ "SET MarketingBudget = $1 "
+ "WHERE SingerId = 1 and AlbumId = 1")
.bind("p1")
.to(album1Budget)
.build();
Statement updateStatement2 =
Statement.newBuilder(
"UPDATE Albums "
+ "SET MarketingBudget = $1 "
+ "WHERE SingerId = 2 and AlbumId = 2")
.bind("p1")
.to(album2Budget)
.build();
return transaction.batchUpdateAsync(
ImmutableList.of(updateStatement1, updateStatement2));
} else {
return ApiFutures.immediateFuture(new long[] {0L, 0L});
}
},
executor);
// Commit after the updates.
CommitTimestampFuture commitTsFut = updateCounts.commitAsync();
// Wait for the transaction to finish and execute a retry if necessary.
commitTsFut.get();
break;
} catch (AbortedException e) {
txn = mgr.resetForRetryAsync();
}
}
}
// Calculate the total update count.
ApiFuture<Long> totalUpdateCount =
ApiFutures.transform(
updateCounts,
input -> Arrays.stream(input).sum(),
MoreExecutors.directExecutor());
System.out.printf("%d records updated.%n", totalUpdateCount.get(30L, TimeUnit.SECONDS));
executor.shutdown();
}
}
//[END spanner_postgresql_async_transaction_manager]