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MariaDB R2DBC connector

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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 0.9.1 specifications


See documentation for native or with Spring Data R2DBC use.

Quick Start

The MariaDB Connector is available through maven using :


Factory can be created using ConnectionFactory or using connection URL.

Using builder

MariadbConnectionConfiguration conf = MariadbConnectionConfiguration.builder()
MariadbConnectionFactory factory = new MariadbConnectionFactory(conf);


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

Basic example:

    MariadbConnectionConfiguration conf = MariadbConnectionConfiguration.builder()
    MariadbConnectionFactory factory = new MariadbConnectionFactory(conf);

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

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
socketTimeout Sets the socket timeout Duration
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
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-----"
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-----"
clientSslKey client private key path(for mutual authentication) String
clientSslPassword client private key password charsequence
sslMode ssl requirement. Possible value are
  • 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
rsaPublicKey only for MySQL server
Server RSA public key, for SHA256 authentication
cachingRsaPublicKey only for MySQL server
Server caching RSA public key, for cachingSHA256 authentication
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


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.


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")


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