MariaDB R2DBC connector

Non-blocking MariaDB and MySQL client.

MariaDB and MySQL client, 100% Java, compatible with Java8+, apache 2.0 licensed.

• Driver permits ed25519, PAM authentication that comes with MariaDB.
• use MariaDB 10.5 returning fonction to permit Statement.returnGeneratedValues

Driver follow R2DBC 1.0.0 specifications

Documentation

See documentation for native or with Spring Data R2DBC use.

Quick Start

The MariaDB Connector is available through maven using :

		<dependency>
				<groupId>org.mariadb</groupId>
				<artifactId>r2dbc-mariadb</artifactId>
				<version>1.3.0</version>
		</dependency>

Factory can be created using ConnectionFactory or using connection URL.

Using builder

MariadbConnectionConfiguration conf = MariadbConnectionConfiguration.builder()
						.host("localhost")
						.port(3306)
						.username("myUser")
						.password("MySuperPassword")
						.database("db")
						.build();
MariadbConnectionFactory factory = new MariadbConnectionFactory(conf);

//OR

ConnectionFactory factory = ConnectionFactories.get("r2dbc:mariadb://user:password@host:3306,host2:3302/myDB?option1=value");

Basic example:

		MariadbConnectionConfiguration conf = MariadbConnectionConfiguration.builder()
						.host("localhost")
						.port(3306)
						.username("myUser")
						.password("MySuperPassword")
						.database("db")
						.build();
		MariadbConnectionFactory factory = new MariadbConnectionFactory(conf);

		MariadbConnection connection = factory.create().block();
		connection.createStatement("SELECT * FROM myTable WHERE val = ?")
						.bind(0, "myVal") // setting parameter
						.execute()
						.flatMap(r -> r.map((row, metadata) -> {
							return "value=" + row.get(0, String.class);
						}));
		connection.close().subscribe();

Connection options

option	description	type	default
username	User to access database.	string
password	User password.	string
host	IP address or DNS of the database server. Multiple host can be set, separate by comma. If first host is not reachable (timeout is connectTimeout), driver use next hosts.Not used when using option socketPath.	string	"localhost"
port	Database server port number. Not used when using option socketPath	integer	3306
database	Default database to use when establishing the connection.	string
connectTimeout	Sets the connection timeout	Duration	10s
tcpKeepAlive	Sets socket keep alive	Boolean	false
tcpAbortiveClose	This option can be used in environments where connections are created and closed in rapid succession. Often, it is not possible to create a socket in such an environment after a while, since all local “ephemeral” ports are used up by TCP connections in TCP_WAIT state. Using tcpAbortiveClose works around this problem by resetting TCP connections (abortive or hard close) rather than doing an orderly close.	boolean	false
socket	Permits connections to the database through the Unix domain socket for faster connection whe server is local.	string
allowMultiQueries	Allows you to issue several SQL statements in a single call. (That is, INSERT INTO a VALUES('b'); INSERT INTO c VALUES('d');). This may be a security risk as it allows for SQL Injection attacks.	boolean	false
connectionAttributes	When performance_schema is active, permit to send server some client information. Those information can be retrieved on server within tables performance_schema.session_connect_attrs and performance_schema.session_account_connect_attrs. This can permit from server an identification of client/application per connection	Map<String,String>
sessionVariables	Permits to set session variables upon successful connection	Map<String,String>
tlsProtocol	Force TLS/SSL protocol to a specific set of TLS versions (example "TLSv1.2", "TLSv1.3").	List	java default
serverSslCert	Permits providing server's certificate in DER form, or server's CA certificate. This permits a self-signed certificate to be trusted. Can be used in one of 3 forms : serverSslCert=/path/to/cert.pem (full path to certificate) serverSslCert=classpath:relative/cert.pem (relative to current classpath) as verbatim DER-encoded certificate string "------BEGIN CERTIFICATE-----"	String
clientSslCert	Permits providing client's certificate in DER form (use only for mutual authentication). Can be used in one of 3 forms : clientSslCert=/path/to/cert.pem (full path to certificate) clientSslCert=classpath:relative/cert.pem (relative to current classpath) as verbatim DER-encoded certificate string "------BEGIN CERTIFICATE-----"	String
clientSslKey	client private key path(for mutual authentication)	String
clientSslPassword	client private key password	charsequence
sslMode	ssl requirement. Possible value are DISABLE, // NO SSL TRUST, // Encryption, but no certificate and hostname validation (DEVELOPMENT ONLY) VERIFY_CA, // Encryption, certificates validation, BUT no hostname validation VERIFY_FULL, // Standard SSL use: Encryption, certificate validation and hostname validation TUNNEL, // Connect over a pre-created SSL tunnel. See sslContextBuilderCustomizer options and sslTunnelDisableHostVerification	SslMode	DISABLE
rsaPublicKey	only for MySQL server Server RSA public key, for SHA256 authentication	String
cachingRsaPublicKey	only for MySQL server Server caching RSA public key, for cachingSHA256 authentication	String
allowPublicKeyRetrieval	only for MySQL server Permit retrieved Server RSA public key from server. This can create a security issue	boolean	true
allowPipelining	Permit to send queries to server without waiting for previous query to finish	boolean	true
useServerPrepStmts	Permit to indicate to use text or binary protocol for query with parameter	boolean	false
prepareCacheSize	if useServerPrepStmts = true, cache the prepared informations in a LRU cache to avoid re-preparation of command. Next use of that command, only prepared identifier and parameters (if any) will be sent to server. This mainly permit for server to avoid reparsing query.	int	256
pamOtherPwd	Permit to provide additional password for PAM authentication with multiple authentication step. If multiple passwords, value must be URL encoded.	string
autocommit	Set default autocommit value on connection initialization"	Boolean	true
tinyInt1isBit	Convert Bit(1)/TINYINT(1) default to boolean type	boolean	true
restrictedAuth	if set, restrict authentication plugin to secure list. Default provided plugins are mysql_native_password, mysql_clear_password, client_ed25519, dialog, sha256_password and caching_sha2_password	string
loopResources	permits to share netty EventLoopGroup among multiple async libraries/framework	LoopResources
sslContextBuilderCustomizer	Permits to customized SSL context builder.	UnaryOperator
sslTunnelDisableHostVerification	Disable hostname verification during SSLHandshake when SslMode.TUNNEL is set	boolean
permitRedirect	Permit server redirection	boolean	true
timezone	permits to force session timezone in case of client having a different timezone compare to server. The option timezone can have 3 types of value: * 'disabled' (default) : connector doesn't change time_zone. * 'auto': client will use client default timezone. * '': connector will set connection variable to value. Since 1.2.0	String	'disabled'
skipPostCommands	Permit to indicate that commands after connections must be skipped. This permit to avoid unnecessary command on connection creation, and when using RDV proxy not to have session pinning. Use with care, because connector expects server to have : 1.connection exchanges to be UT8(mb3/mb4). 2.autocommit set to true. 3.transaction isolation defaulting to REPEATABLE-READ	boolean	'false'

Compatibility

Connector is compatible with R2DBC 1.0.0 spec. For 0.9.1 spec compatibility, use artifact-id r2dbc-mariadb-0.9.1-spec example

		<dependency>
				<groupId>org.mariadb</groupId>
				<artifactId>r2dbc-mariadb-0.9.1-spec</artifactId>
				<version>1.3.0</version>
		</dependency>

Failover

Failover occurs when a connection to a primary database server fails and the connector opens up a connection to another database server. For example, server A has the current connection. After a failure (server crash, network down …) the connection will switch to another server (B).

Load balancing allows load to be distributed over multiple servers : When initializing a connection or after a failed connection, the connector will attempt to connect to a host. The connection is selected randomly among the valid hosts. Thereafter, all statements will run on that database server until the connection will be closed (or fails). Example: when creating a pool of 60 connections, each one will use a random host. With 3 master hosts, the pool will have about 20 connections to each host.

ConnectionFactory factory = ConnectionFactories.get("r2dbc:mariadb:sequential://user:password@host:3306,host2:3302/myDB?option1=value");

Failover behaviour

Failover parameter is set (i.e. prefixing connection string with r2dbc:mariadb:[sequential|loadbalancing]://... or using HaMode builder).

There can be multiple fail causes. When a failure occurs many things will be done:

• connection recovery (re-establishing connection transparently)
• re-execute command/transaction if possible

During failover, the fail host address will be put on a blacklist (shared by JVM) for 60 seconds. Connector will always try to connect non blacklisted host first, but can retry to connect blacklisted host before 60s if all hosts are blacklisted.

re-execution

The driver will try to reconnect to any valid host (not blasklisted, or if all primary host are blacklisted trying blacklisted hosts). If reconnection fail, an Exception with be thrown with SQLState "08XXX". If using a pool, this connection will be discarded.

on successful reconnection, there will be different cases.

If driver identify that command can be replayed without issue (for example connection.isValid(), a PREPARE/ROLLBACK command), driver will execute command without throwing any error.

Driver cannot transparently handle all cases : imagine that the failover occurs when executing an INSERT command without a transaction: driver cannot know that command has been received and executed on server. In those case, an SQLException with be thrown with SQLState "25S03".

Option transactionReplay :

Most of the time, queries occurs in transaction (ORM for example doesn't permit using auto-commit), so redo transaction implementation will solve most of failover cases transparently for user point of view.

Redo transaction approach is to save commands in transaction. When a failover occurs during a transaction, the connector can automatically reconnect and replay transaction, making failover completely transparent.

There is some limitations :

driver will buffer up commands in a transaction until some inner limit. huge command will temporarily disable transaction buffering for current transaction. Commands must be idempotent only (queries can be "replayable")

Tracker

To file an issue or follow the development, see JIRA.