Mengelola koneksi database

Halaman ini menyediakan praktik terbaik dan contoh kode khusus bahasa untuk membantu Anda membuat aplikasi yang menggunakan koneksi database Cloud SQL secara efektif.

Contoh ini adalah kutipan dari aplikasi web lengkap yang tersedia untuk Anda di GitHub. Pelajari lebih lanjut.

Untuk petunjuk langkah demi langkah cara menjalankan contoh aplikasi web yang terhubung ke Cloud SQL, ikuti link untuk lingkungan Anda:

Kumpulan koneksi

Kumpulan koneksi adalah cache koneksi database yang digunakan bersama dan digunakan kembali untuk meningkatkan latensi dan performa koneksi. Saat memerlukan koneksi database, aplikasi Anda akan meminjam salah satu dari kumpulan data tersebut untuk sementara; setelah selesai dengan koneksi, aplikasi akan menampilkan koneksi ke kumpulan, yang dapat digunakan kembali saat berikutnya aplikasi memerlukan koneksi database.

Koneksi terbuka dan tertutup

Jika menggunakan kumpulan koneksi, Anda harus membuka dan menutup koneksi dengan benar, sehingga koneksi Anda selalu dikembalikan ke kumpulan setelah selesai digunakan. Koneksi yang tidak ditampilkan atau "bocor" tidak digunakan kembali, karena menghabiskan resource dan dapat menyebabkan bottleneck performa untuk aplikasi Anda.

Python

# Preparing a statement before hand can help protect against injections.
stmt = sqlalchemy.text(
    "INSERT INTO votes (time_cast, candidate) VALUES (:time_cast, :candidate)"
)
try:
    # Using a with statement ensures that the connection is always released
    # back into the pool at the end of statement (even if an error occurs)
    with db.connect() as conn:
        conn.execute(stmt, parameters={"time_cast": time_cast, "candidate": team})
        conn.commit()
except Exception as e:
    # If something goes wrong, handle the error in this section. This might
    # involve retrying or adjusting parameters depending on the situation.
    # ...

Java

// Using a try-with-resources statement ensures that the connection is always released back
// into the pool at the end of the statement (even if an error occurs)
try (Connection conn = pool.getConnection()) {

  // PreparedStatements can be more efficient and project against injections.
  String stmt = "INSERT INTO votes (time_cast, candidate) VALUES (?, ?);";
  try (PreparedStatement voteStmt = conn.prepareStatement(stmt);) {
    voteStmt.setTimestamp(1, now);
    voteStmt.setString(2, team);

    // Finally, execute the statement. If it fails, an error will be thrown.
    voteStmt.execute();
  }
} catch (SQLException ex) {
  // If something goes wrong, handle the error in this section. This might involve retrying or
  // adjusting parameters depending on the situation.
  // ...
}

Node.js

/**
 * Insert a vote record into the database.
 *
 * @param {object} pool The Knex connection object.
 * @param {object} vote The vote record to insert.
 * @returns {Promise}
 */
const insertVote = async (pool, vote) => {
  try {
    return await pool('votes').insert(vote);
  } catch (err) {
    throw Error(err);
  }
};

C#

using Npgsql;
using System;

namespace CloudSql
{
    public class PostgreSqlTcp
    {
        public static NpgsqlConnectionStringBuilder NewPostgreSqlTCPConnectionString()
        {
            // Equivalent connection string:
            // "Uid=<DB_USER>;Pwd=<DB_PASS>;Host=<INSTANCE_HOST>;Database=<DB_NAME>;"
            var connectionString = new NpgsqlConnectionStringBuilder()
            {
                // Note: Saving credentials in environment variables is convenient, but not
                // secure - consider a more secure solution such as
                // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
                // keep secrets safe.
                Host = Environment.GetEnvironmentVariable("INSTANCE_HOST"),     // e.g. '127.0.0.1'
                // Set Host to 'cloudsql' when deploying to App Engine Flexible environment
                Username = Environment.GetEnvironmentVariable("DB_USER"), // e.g. 'my-db-user'
                Password = Environment.GetEnvironmentVariable("DB_PASS"), // e.g. 'my-db-password'
                Database = Environment.GetEnvironmentVariable("DB_NAME"), // e.g. 'my-database'

                // The Cloud SQL proxy provides encryption between the proxy and instance.
                SslMode = SslMode.Disable,
            };
            connectionString.Pooling = true;
            // Specify additional properties here.
            return connectionString;
        }
    }
}

Go

insertVote := "INSERT INTO votes(candidate, created_at) VALUES($1, NOW())"
_, err := db.Exec(insertVote, team)

Ruby

@vote = Vote.new candidate: candidate

# ActiveRecord creates and executes your SQL and automatically
# handles the opening and closing of the database connection.
if @vote.save
  render json: "Vote successfully cast for \"#{@vote.candidate}\" at #{@vote.time_cast} PST!"
else
  render json: @vote.errors, status: :unprocessable_entity
end

PHP

// Use prepared statements to guard against SQL injection.
$sql = 'INSERT INTO votes (time_cast, candidate) VALUES (NOW(), :voteValue)';

try {
    $statement = $conn->prepare($sql);
    $statement->bindParam('voteValue', $value);

    $res = $statement->execute();
} catch (PDOException $e) {
    throw new RuntimeException(
        'Could not insert vote into database. The PDO exception was ' .
        $e->getMessage(),
        $e->getCode(),
        $e
    );
}

Jumlah koneksi

Setiap koneksi database menggunakan resource sisi klien dan server. Selain itu, Cloud SQL memberlakukan batasan koneksi secara keseluruhan yang tidak boleh dilampaui. Membuat dan menggunakan lebih sedikit koneksi akan mengurangi overhead dan membantu Anda tetap berada di bawah batas koneksi.

Python

# Pool size is the maximum number of permanent connections to keep.
pool_size=5,
# Temporarily exceeds the set pool_size if no connections are available.
max_overflow=2,
# The total number of concurrent connections for your application will be
# a total of pool_size and max_overflow.

Java

// maximumPoolSize limits the total number of concurrent connections this pool will keep. Ideal
// values for this setting are highly variable on app design, infrastructure, and database.
config.setMaximumPoolSize(5);
// minimumIdle is the minimum number of idle connections Hikari maintains in the pool.
// Additional connections will be established to meet this value unless the pool is full.
config.setMinimumIdle(5);

Node.js

// 'max' limits the total number of concurrent connections this pool will keep. Ideal
// values for this setting are highly variable on app design, infrastructure, and database.
config.pool.max = 5;
// 'min' is the minimum number of idle connections Knex maintains in the pool.
// Additional connections will be established to meet this value unless the pool is full.
config.pool.min = 5;

C#

// MaxPoolSize sets maximum number of connections allowed in the pool.
connectionString.MaxPoolSize = 5;
// MinPoolSize sets the minimum number of connections in the pool.
connectionString.MinPoolSize = 0;

Go

// Set maximum number of connections in idle connection pool.
db.SetMaxIdleConns(5)

// Set maximum number of open connections to the database.
db.SetMaxOpenConns(7)

Ruby

# 'pool' is the maximum number of permanent connections to keep.
pool: 5

PHP

PDO saat ini tidak menawarkan fungsi apa pun untuk mengonfigurasi batas koneksi.

Backoff eksponensial

Jika aplikasi Anda mencoba terhubung ke database dan tidak berhasil, database tersebut mungkin tidak tersedia untuk sementara. Dalam hal ini, mengirim permintaan koneksi berulang akan menyia-nyiakan source. Sebaiknya, tunggu sebelum mengirim permintaan koneksi tambahan agar database dapat diakses kembali. Penggunaan backoff eksponensial atau mekanisme penundaan lainnya akan mencapai sasaran ini.

Percobaan ulang ini hanya dapat dilakukan saat pertama kali menghubungkan, atau saat pertama kali mengambil koneksi dari kumpulan data. Jika terjadi error di tengah transaksi, aplikasi harus melakukan percobaan ulang, dan harus mencoba lagi dari awal transaksi. Jadi, meskipun kumpulan data Anda dikonfigurasi dengan benar, aplikasi mungkin masih melihat error jika koneksi terputus.

Python

# SQLAlchemy automatically uses delays between failed connection attempts,
# but provides no arguments for configuration.

Java

// Hikari automatically delays between failed connection attempts, eventually reaching a
// maximum delay of `connectionTimeout / 2` between attempts.

Node.js

// 'knex' uses a built-in retry strategy which does not implement backoff.
// 'createRetryIntervalMillis' is how long to idle after failed connection creation before trying again
config.pool.createRetryIntervalMillis = 200; // 0.2 seconds

C#

Policy
    .Handle<NpgsqlException>()
    .WaitAndRetry(new[]
    {
        TimeSpan.FromSeconds(1),
        TimeSpan.FromSeconds(2),
        TimeSpan.FromSeconds(5)
    })
    .Execute(() => connection.Open());

Go

Paket database/sql saat ini tidak menawarkan fungsi apa pun untuk mengonfigurasi backoff eksponensial.

Ruby

# ActiveRecord automatically uses delays between failed connection attempts,
# but provides no arguments for configuration.

PHP

PDO saat ini tidak menawarkan fungsi apa pun untuk mengonfigurasi backoff eksponensial.

Waktu tunggu koneksi habis

Ada banyak alasan mengapa upaya koneksi mungkin tidak berhasil. Jaringan komunikasi tidak terjamin, dan database mungkin tidak dapat merespons untuk sementara. Pastikan aplikasi Anda menangani koneksi yang rusak atau gagal dengan baik.

Python

# 'pool_timeout' is the maximum number of seconds to wait when retrieving a
# new connection from the pool. After the specified amount of time, an
# exception will be thrown.
pool_timeout=30,  # 30 seconds

Java

// setConnectionTimeout is the maximum number of milliseconds to wait for a connection checkout.
// Any attempt to retrieve a connection from this pool that exceeds the set limit will throw an
// SQLException.
config.setConnectionTimeout(10000); // 10 seconds
// idleTimeout is the maximum amount of time a connection can sit in the pool. Connections that
// sit idle for this many milliseconds are retried if minimumIdle is exceeded.
config.setIdleTimeout(600000); // 10 minutes

Node.js

// 'acquireTimeoutMillis' is the number of milliseconds before a timeout occurs when acquiring a
// connection from the pool. This is slightly different from connectionTimeout, because acquiring
// a pool connection does not always involve making a new connection, and may include multiple retries.
// when making a connection
config.pool.acquireTimeoutMillis = 60000; // 60 seconds
// 'createTimeoutMillis` is the maximum number of milliseconds to wait trying to establish an
// initial connection before retrying.
// After acquireTimeoutMillis has passed, a timeout exception will be thrown.
config.pool.createTimeoutMillis = 30000; // 30 seconds
// 'idleTimeoutMillis' is the number of milliseconds a connection must sit idle in the pool
// and not be checked out before it is automatically closed.
config.pool.idleTimeoutMillis = 600000; // 10 minutes

C#

// Timeout sets the time to wait (in seconds) while
// trying to establish a connection before terminating the attempt.
connectionString.Timeout = 15;

Go

Paket database/sql saat ini tidak menawarkan fungsi apa pun untuk mengonfigurasi waktu tunggu koneksi. Waktu tunggu dikonfigurasi pada level driver.

Ruby

# 'timeout' is the maximum number of seconds to wait when retrieving a
# new connection from the pool. After the specified amount of time, an
# ActiveRecord::ConnectionTimeoutError will be raised.
timeout: 5000

PHP

// Here we set the connection timeout to five seconds and ask PDO to
// throw an exception if any errors occur.
[
    PDO::ATTR_TIMEOUT => 5,
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
]

Durasi koneksi

Membatasi masa aktif koneksi dapat membantu mencegah terakumulasinya koneksi yang diabaikan. Anda dapat menggunakan kumpulan koneksi untuk membatasi masa pakai koneksi.

Python

# 'pool_recycle' is the maximum number of seconds a connection can persist.
# Connections that live longer than the specified amount of time will be
# re-established
pool_recycle=1800,  # 30 minutes

Java

// maxLifetime is the maximum possible lifetime of a connection in the pool. Connections that
// live longer than this many milliseconds will be closed and reestablished between uses. This
// value should be several minutes shorter than the database's timeout value to avoid unexpected
// terminations.
config.setMaxLifetime(1800000); // 30 minutes

Node.js

Library Node.js 'knex' saat ini tidak menawarkan fungsi apa pun untuk mengontrol durasi koneksi.

C#

// ConnectionIdleLifetime sets the time (in seconds) to wait before
// closing idle connections in the pool if the count of all
// connections exceeds MinPoolSize.
connectionString.ConnectionIdleLifetime = 300;

Go

// Set Maximum time (in seconds) that a connection can remain open.
db.SetConnMaxLifetime(1800 * time.Second)

Ruby

ActiveRecord saat ini tidak menawarkan fungsi apa pun untuk mengontrol durasi koneksi.

PHP

PDO saat ini tidak menawarkan fungsi apa pun untuk mengontrol durasi koneksi.

Untuk melihat permohonan lengkap, klik link di bawah.

Python

Lihat aplikasi lengkap untuk bahasa pemrograman Python.

Java

Lihat aplikasi lengkap untuk bahasa pemrograman Java.

Node.js

Lihat aplikasi lengkap untuk bahasa pemrograman Node.js.

C#

Lihat aplikasi lengkap untuk bahasa pemrograman C#.

Go

Lihat aplikasi lengkap untuk bahasa pemrograman Go.

Ruby

Lihat aplikasi lengkap untuk bahasa pemrograman Ruby.

PHP

Lihat aplikasi lengkap untuk bahasa pemrograman PHP.

Langkah selanjutnya