There is nothing faster.1 There is nothing more correct. HikariCP is a "zero-overhead" production-quality connection pool. Coming in at roughly 50Kb, the library is extremely light.
Using a stub-JDBC implementation to isolate and measure the overhead of HikariCP, 60+ Million JDBC operations were performed in 10ms on a commodity PC.2 The next fastest connection pool (Tomcat) was 1874ms. Apache DBCP and C3P0 failed to successfully execute the benchmark.
| Pool | Med (ms) | Avg (ms) | Max (ms) |
|---|---|---|---|
| BoneCP | 4635 | 3060 | 6747 |
| Tomcat | 1874 | 1719 | 1882 |
| HikariCP | 10 | 9 | 13 |
1We contend HikariCP is near the theoretical maximum on current JVM technology.
2400 threads, 50 connection pool. Measurements in nanoseconds and converted to milliseconds.
See benchmarks here. See how we do it here.
3Benchmark numbers updated periodically to reflect latest developments.
Or look at this:
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>1.2.8</version>
<scope>compile</scope>
</dependency>The following are the various properties that can be configured in the pool, their behavior, and their defaults. HikariCP uses milliseconds for all time values, be careful.
Rather than coming out of the box with almost nothing configured, HikariCP comes with sane defaults that let a great many deployments run without any additional tweaking (except for the DataSource and DataSource properties).
acquireIncrement
This property controls the maximum number of connections that are acquired at one time, with
the exception of pool initialization. Default: 1
acquireRetries
This is a per-connection attempt retry count used during new connection creation (acquisition).
If a connection creation attempt fails there will be a wait of acquireRetryDelay
milliseconds followed by another attempt, up to the number of retries configured by this
property. Default: 3
acquireRetryDelay
This property controls the number of milliseconds to delay between attempts to acquire a
connection to the database. If acquireRetries is 0, this property has no effect.
Default: 750
autoCommit
This property controls the default auto-commit behavior of connections returned from the pool.
It is a boolean value. Default: true
connectionInitSql
This property sets a SQL statement that will be executed after every new connection creation
before adding it to the pool. If this SQL is not valid or throws an exception, it will be
treated as a connection failure and the standard retry logic will be followed. Default: none
connectionTestQuery
This is for "legacy" databases that do not support the JDBC4 Connection.isValid() API. This
is the query that will be executed just before a connection is given to you from the pool to
validate that the connection to the database is still alive. It is database dependent and
should be a query that takes very little processing by the database (eg. "VALUES 1"). See
the jdbc4ConnectionTest property for a more efficent alive test. One of either this
property or jdbc4ConnectionTest must be specified. Default: none
connectionTimeout
This property controls the maximum number of milliseconds that a client (that's you) will wait
for a connection from the pool. If this time is exceeded without a connection becoming
available, a SQLException will be thrown. Default: 5000
dataSource
This property is only available via programmatic configuration. This property allows you
to directly set the instance of the DataSource to be wrapped by the pool, rather than
having HikariCP construct it via reflection. When this property is specified, the
dataSourceClassName property and all DataSource-specific properties will be ignored.
Default: none
dataSourceClassName
This is the name of the DataSource class provided by the JDBC driver. Consult the
documentation for your specific JDBC driver to get this class name. Note XA data sources
are not supported. XA requires a real transaction manager like bitronix.
Default: none
idleTimeout
This property controls the maximum amount of time (in milliseconds) that a connection is
allowed to sit idle in the pool. Whether a connection is retired as idle or not is subject
to a maximum variation of +30 seconds, and average variation of +15 seconds. A connection
will never be retired as idle before this timeout. A value of 0 means that idle connections
are never removed from the pool. Default: 600000 (10 minutes)
jdbc4ConnectionTest
This property is a boolean value that determines whether the JDBC4 Connection.isValid() method
is used to check that a connection is still alive. This value is mutually exclusive with the
connectionTestQuery property, and this method of testing connection validity should be
preferred if supported by the JDBC driver. Default: true
leakDetectionThreshold
This property controls the amount of time that a connection can be out of the pool before a
message is logged indicating a possible connection leak. A value of 0 means leak detection
is disabled. While the default is 0, and other connection pool implementations state that
leak detection is "not for production" as it imposes a high overhead, at least in the case
of HikariCP the imposed overhead is only 5μs (microseconds) split between getConnection()
and close(). Maybe other pools are doing it wrong, but feel free to use leak detection under
HikariCP in production environments if you wish. Default: 0
maxLifetime
This property controls the maximum lifetime of a connection in the pool. When a connection
reaches this timeout, even if recently used, it will be retired from the pool. An in-use
connection will never be retired, only when it is idle will it be removed. We strongly
recommend setting this value, and using something reasonable like 30 minutes or 1 hour. A
value of 0 indicates no maximum lifetime (infinite lifetime), subject of course to the
idleTimeout setting. Default: 1800000 (30 minutes)
maximumPoolSize
This property controls the maximum size that the pool is allowed to reach, including both
idle and in-use connections. Basically this value will determine the maximum number of
actual connections to the database backend. A reasonable value for this is best determined
by your execution environment. When the pool reaches this size, and no idle connections are
available, calls to getConnection() will block for up to connectionTimeout milliseconds
before timing out. Default: 60
minimumPoolSize
This property controls the minimum number of connections that HikariCP tries to maintain in
the pool, including both idle and in-use connections. If the connections dip below this
value, HikariCP will make a best effort to restore them quickly and efficiently. A reasonable
value for this is best determined by your execution environment. Default: 10
poolName
This property represents a user-defined name for the connection pool and appears mainly
in a JMX management console to identify pools and pool configurations. Default: auto-generated
transactionIsolation
This property controls the default transation isolation level of connections returned from
the pool. If this property is not specified, the default transaction isolation level defined
by the JDBC driver is used. Typically, the JDBC driver default transaction isolation level
should be used. Only use this property if you have specific isolation requirements that are
common for all queries, otherwise simply set the isolation level manually when creating or
preparing statements. The value of this property is the constant name from the Connection
class such as TRANSACTION_READ_COMMITTED, TRANSACTION_REPEATABLE_READ, etc. Default: none
DataSource properies can be set on the HikariConfig object through the use of the addDataSourcePropery
method, like so:
config.addDataSourceProperty("url", "jdbc:hsqldb:mem:test");
config.addDataSourceProperty("user", "SA");
config.addDataSourceProperty("password", "");See the Initialization section below for further examples.
HikariCP has plenty of "knobs" to turn as you can see above, but comparatively less than some other pools. This is a design philosophy. The HikariCP design asthetic is Minimalism.
We're not going to (overly) question the design decisions of other pools, but we will say that some other pools seem to implement a lot of "gimmicks" that proportedly improve performance. HikariCP achieves high-performance even in pools beyond realistic deployment sizes.
In keeping with the simple is better or less is more design philosophy, some knobs and features are intentionally left out. Here are two, and the rationale.
Statement Cache
Most major database JDBC drivers already have a Statement cache that can be configured (Oracle,
MySQL, PostgreSQL, Derby, etc). A statement cache in the pool would add unneeded weight and no
additional functionality. It is simply unnecessary with modern database drivers to implement a
cache at the pool level.
Log Statement Text / Slow Query Logging
Like Statement caching, most major database vendors support statement logging through
properties of their own driver. This includes Oracle, MySQL, Derby, MSSQL, and others. We
consider this a "development-time" feature. For those few databases that do not support it,
jdbcdslog-exp is a good option. It is easy to
wrap HikariCP around jdbcdslog. It also provides some nice additional stuff like timing,
logging slow queries only, and PreparedStatement bound parameter logging. Great stuff during
development and pre-Production.
HikariConfig config = new HikariConfig();
config.setMaximumPoolSize(100);
config.setDataSourceClassName("com.mysql.jdbc.jdbc2.optional.MysqlDataSource");
config.addDataSourceProperty("url", "jdbc:mysql://localhost/database");
config.addDataSourceProperty("user", "bart");
config.addDataSourceProperty("password", "51mp50n");
HikariDataSource ds = new HikariDataSource(config);or property file based:
HikariConfig config = new HikariConfig("some/path/hikari.properties");
HikariDataSource ds = new HikariDataSource(config);Example property file:
acquireIncrement=3
acquireRetryDelay=1000
connectionTestQuery=SELECT 1
dataSourceClassName=org.postgresql.ds.PGSimpleDataSource
dataSource.username=test
dataSource.password=test
dataSource.databaseName=mydb
dataSource.serverName=localhostor java.util.Properties based:
Properties props = new Properties();
props.setProperty("maximumPoolSize", 100);
props.setProperty("dataSourceClassName", "org.postgresql.ds.PGSimpleDataSource");
props.setProperty("dataSource.username", "test");
props.setProperty("dataSource.password", "test");
props.setProperty("dataSource.databaseName", "mydb");
props.setProperty("dataSource.logWriter", new PrintWriter(System.out));
HikariConfig config = new HikariConfig(props);
HikariDataSource ds = new HikariDataSource(config);Don't forget the Wiki for additional information such as:
The following properties are also configurable in real-time as the pool is running via a JMX management console such as JConsole:
acquireIncrementacquireRetriesacquireRetryDelayconnectionTimeoutidleTimeoutmaxLifetimeminimumPoolSizemaximumPoolSize
Google discussion group HikariCP here, growing FAQ.
- Java 7 and above1. If you need legacy Java support, I recommend the Tomcat pool.
- Javassist 3.18.1+ library
- slf4j library
Please perform changes and submit pull requests from the dev branch instead of master. Please set your editor to use spaces instead of tabs, and adhere to the apparent style of the code you are editing. The dev branch is always more "current" than the master if you are looking to live life on the edge.