本页面介绍了如何使用 Spanner 客户端库为事务设置超时。如果事务无法在给定的超时值内完成，则会失败并显示 DEADLINE_EXCEEDED 错误。
您可以为事务和 RPC 请求语句设置超时值。为事务设置的超时值大于在事务中执行的语句的超时值并不会增加语句的超时值，因为语句受其自身的超时值限制。
此外，如果在执行 Commit 请求期间发生超时错误，事务仍有可能已提交。
您可以使用 Go、Java、Python 和 Node.js 客户端库设置事务超时。
Go
import (
"context"
"errors"
"fmt"
"io"
"time"
"cloud.google.com/go/spanner"
"google.golang.org/api/iterator"
"google.golang.org/grpc/codes"
)
func transactionTimeout(w io.Writer, db string) error {
ctx := context.Background()
client, err := spanner.NewClient(ctx, db)
if err != nil {
return err
}
defer client.Close()
// Create a context with a 60-second timeout and use this context to run a read/write transaction.
// This context timeout will be applied to the entire transaction, and the transaction will fail
// if it cannot finish within the specified timeout value. The Spanner client library applies the
// (remainder of the) timeout to each statement that is executed in the transaction.
ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
defer cancel()
_, err = client.ReadWriteTransaction(ctx, func(ctx context.Context, txn *spanner.ReadWriteTransaction) error {
selectStmt := spanner.Statement{
SQL: `SELECT SingerId, FirstName, LastName FROM Singers ORDER BY LastName, FirstName`,
}
// The context that is passed in to the transaction function should be used for each statement
// is executed.
iter := txn.Query(ctx, selectStmt)
defer iter.Stop()
for {
row, err := iter.Next()
if errors.Is(err, iterator.Done) {
break
}
if err != nil {
return err
}
var singerID int64
var firstName, lastName string
if err := row.Columns(&singerID, &firstName, &lastName); err != nil {
return err
}
fmt.Fprintf(w, "%d %s %s\n", singerID, firstName, lastName)
}
stmt := spanner.Statement{
SQL: `INSERT INTO Singers (SingerId, FirstName, LastName)
VALUES (38, 'George', 'Washington')`,
}
rowCount, err := txn.Update(ctx, stmt)
if err != nil {
return err
}
fmt.Fprintf(w, "%d record(s) inserted.\n", rowCount)
return nil
})
// Check if an error was returned by the transaction.
// The spanner.ErrCode(err) function will return codes.OK if err == nil.
code := spanner.ErrCode(err)
if code == codes.OK {
fmt.Fprintf(w, "Transaction with timeout was executed successfully\n")
} else if code == codes.DeadlineExceeded {
fmt.Fprintf(w, "Transaction timed out\n")
} else {
fmt.Fprintf(w, "Transaction failed with error code %v\n", code)
}
return err
}
Java
import com.google.cloud.spanner.DatabaseClient;
import com.google.cloud.spanner.DatabaseId;
import com.google.cloud.spanner.ResultSet;
import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerOptions;
import com.google.cloud.spanner.Statement;
import io.grpc.Context;
import io.grpc.Context.CancellableContext;
import io.grpc.Deadline;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/**
* Sample showing how to set a timeout for an entire transaction for the Cloud Spanner Java client.
*/
class TransactionTimeoutExample {
static void executeTransactionWithTimeout() {
// TODO(developer): Replace these variables before running the sample.
String projectId = "my-project";
String instanceId = "my-instance";
String databaseId = "my-database";
executeTransactionWithTimeout(projectId, instanceId, databaseId, 60L, TimeUnit.SECONDS);
}
// Execute a read/write transaction with a timeout for the entire transaction.
static void executeTransactionWithTimeout(
String projectId,
String instanceId,
String databaseId,
long timeoutValue,
TimeUnit timeoutUnit) {
try (Spanner spanner = SpannerOptions.newBuilder().setProjectId(projectId).build()
.getService()) {
DatabaseClient client =
spanner.getDatabaseClient(DatabaseId.of(projectId, instanceId, databaseId));
// Create a gRPC context with a deadline and with cancellation.
// gRPC context deadlines require the use of a scheduled executor.
ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
try (CancellableContext context =
Context.current()
.withDeadline(Deadline.after(timeoutValue, timeoutUnit), executor)
.withCancellation()) {
context.run(
() -> {
client
.readWriteTransaction()
.run(
transaction -> {
try (ResultSet resultSet =
transaction.executeQuery(
Statement.of(
"SELECT SingerId, FirstName, LastName\n"
+ "FROM Singers\n"
+ "ORDER BY LastName, FirstName"))) {
while (resultSet.next()) {
System.out.printf(
"%d %s %s\n",
resultSet.getLong("SingerId"),
resultSet.getString("FirstName"),
resultSet.getString("LastName"));
}
}
String sql =
"INSERT INTO Singers (SingerId, FirstName, LastName)\n"
+ "VALUES (20, 'George', 'Washington')";
long rowCount = transaction.executeUpdate(Statement.of(sql));
System.out.printf("%d record inserted.%n", rowCount);
return null;
});
});
}
}
}
}Node.js
/**
* TODO(developer): Uncomment the following lines before running the sample.
*/
// const projectId = 'my-project-id';
// const instanceId = 'my-instance';
// const databaseId = 'my-database';
// Imports the Google Cloud client library
const {Spanner} = require('@google-cloud/spanner');
// Creates a client
const spanner = new Spanner({
projectId: projectId,
});
async function executeTransactionWithTimeout() {
// Gets a reference to a Cloud Spanner instance and database.
const instance = spanner.instance(instanceId);
const database = instance.database(databaseId);
const options = {
timeout: 60000, // 60 seconds timeout
};
try {
await database.runTransactionAsync(options, async tx => {
const [results] = await tx.run(
'SELECT SingerId, FirstName, LastName FROM Singers ORDER BY LastName, FirstName',
);
results.forEach(result => {
console.log(
`${result[0].name}: ${result[0].value.value}, ${result[1].name}: ${result[1].value}, ${result[2].name}: ${result[2].value}`,
);
});
const sql =
"INSERT INTO Singers (SingerId, FirstName, LastName) VALUES (100, 'George', 'Washington')";
const [rowCount] = await tx.runUpdate(sql);
console.log(`${rowCount} record inserted.`);
await tx.commit();
});
} catch (err) {
console.error('ERROR:', err);
} finally {
await database.close();
}
}
executeTransactionWithTimeout();Python
# instance_id = "your-spanner-instance"
# database_id = "your-spanner-db-id"
spanner_client = spanner.Client()
instance = spanner_client.instance(instance_id)
database = instance.database(database_id)
def read_then_write(transaction):
# Read records.
results = transaction.execute_sql(
"SELECT SingerId, FirstName, LastName FROM Singers ORDER BY LastName, FirstName"
)
for result in results:
print("SingerId: {}, FirstName: {}, LastName: {}".format(*result))
# Insert a record.
row_ct = transaction.execute_update(
"INSERT INTO Singers (SingerId, FirstName, LastName) "
" VALUES (100, 'George', 'Washington')"
)
print("{} record(s) inserted.".format(row_ct))
# configure transaction timeout to 60 seconds
database.run_in_transaction(read_then_write, timeout_secs=60)