org.spf4j.concurrent.jdbc

Class JdbcSemaphore

java.lang.Object

org.spf4j.concurrent.jdbc.JdbcSemaphore

All Implemented Interfaces:

AutoCloseable, PermitSupplier, Semaphore

@Beta
public final class JdbcSemaphore
extends Object
implements AutoCloseable, Semaphore

A jdbc table based semaphore implementation. Similar with a semaphore implemented with zookeeper, we rely on heartbeats to detect dead members. If you have a zookeeper instance accessible you should probably use a semaphore implemented with it... If you are already connecting to a database. this should be a reliable and low overhead (no calls from DBA) implementation. (at leat that is my goal) Using a crappy database will give you crappy results. There are 3 tables involved: SEMAPHORES - keep track of available and total permits by semaphore. PERMITS_BY_OWNER - keeps track of all permits by owner. HEARTBEATS - keeps heartbeats by owner to detect - dead owners. All table names and columns are customizable to adapt this implementation to different naming conventions.

Author:

zoly

Constructor Summary

Constructors

Constructor and Description
JdbcSemaphore(DataSource dataSource, SemaphoreTablesDesc semTableDesc, String semaphoreName, int nrPermits, int jdbcTimeoutSeconds, boolean strictReservations)
JdbcSemaphore(DataSource dataSource, SemaphoreTablesDesc semTableDesc, String semaphoreName, int nrPermits, int jdbcTimeoutSeconds, boolean strictReservations, int acquirePollMillis)
JdbcSemaphore(DataSource dataSource, String semaphoreName, int nrPermits)
JdbcSemaphore(DataSource dataSource, String semaphoreName, int nrPermits, boolean strict) create a JDBC Semaphore.

Method Summary

Modifier and Type	Method and Description
int	availablePermits()
void	close()
protected void	finalize()
List<OwnerPermits>	getDeadOwnerPermits(int wishPermits)
int	getJdbcTimeoutSeconds()
void	increasePermits(int nrPermits)
boolean	isIsHealthy()
int	permitsOwned()
void	reducePermits(int nrPermits)
void	registerJmx()
void	release(int nrReservations) release a number of permits.
void	releaseAll()
int	releaseDeadOwnerPermits(int wishPermits) Attempts to release permits for this semaphore owned by dead owners.
int	removeDeadHeartBeatAndNotOwnerRows(long timeoutSeconds)
String	toString()
int	totalPermits()
boolean	tryAcquire(int nrPermits, long deadlineNanos)
void	unregisterJmx()
void	updatePermits(int nrPermits)

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.spf4j.concurrent.Semaphore

release, toSemaphore

Methods inherited from interface org.spf4j.concurrent.PermitSupplier

acquire, acquire, tryAcquire, tryAcquire

Constructor Detail

JdbcSemaphore

public JdbcSemaphore(DataSource dataSource,
                     String semaphoreName,
                     int nrPermits)
              throws InterruptedException,
                     SQLException

Parameters:

dataSource - the jdbc data source with the Semaphores table. Please be sensible, no "test on borrow" pools.

semaphoreName - number of initial permits, if semaphore already exists the existing nr of permits is kept.

nrPermits - the number of initial permits.

Throws:

InterruptedException

SQLException

JdbcSemaphore

public JdbcSemaphore(DataSource dataSource,
                     String semaphoreName,
                     int nrPermits,
                     boolean strict)
              throws InterruptedException,
                     SQLException

create a JDBC Semaphore. create one instance / process.

Parameters:

dataSource - the data source to use for sync.

semaphoreName - the semaphore name.

nrPermits - number of initial permits.

strict - if true, if semaphore already exists and the total permits is different that param nrPermits an IllegalArgumentException will be thrown.

Throws:

InterruptedException

SQLException

JdbcSemaphore

public JdbcSemaphore(DataSource dataSource,
                     SemaphoreTablesDesc semTableDesc,
                     String semaphoreName,
                     int nrPermits,
                     int jdbcTimeoutSeconds,
                     boolean strictReservations)
              throws InterruptedException,
                     SQLException

Throws:

InterruptedException

SQLException

JdbcSemaphore

public JdbcSemaphore(DataSource dataSource,
                     SemaphoreTablesDesc semTableDesc,
                     String semaphoreName,
                     int nrPermits,
                     int jdbcTimeoutSeconds,
                     boolean strictReservations,
                     int acquirePollMillis)
              throws InterruptedException,
                     SQLException

Throws:

InterruptedException

SQLException

Method Detail

registerJmx

public void registerJmx()

unregisterJmx

public void unregisterJmx()

tryAcquire

@CheckReturnValue
public boolean tryAcquire(int nrPermits,
                                            long deadlineNanos)
                                     throws InterruptedException

Specified by:

tryAcquire in interface PermitSupplier

Throws:

InterruptedException

release

public void release(int nrReservations)

Description copied from interface: Semaphore

release a number of permits.

Specified by:

release in interface Semaphore

Parameters:

nrReservations - the number of permits to release.

releaseAll

public void releaseAll()

availablePermits

public int availablePermits()
                     throws SQLException,
                            InterruptedException

Throws:

SQLException

InterruptedException

permitsOwned

public int permitsOwned()
                 throws SQLException,
                        InterruptedException

Throws:

SQLException

InterruptedException

totalPermits

public int totalPermits()
                 throws SQLException,
                        InterruptedException

Throws:

SQLException

InterruptedException

getDeadOwnerPermits

@Nonnull
public List<OwnerPermits> getDeadOwnerPermits(int wishPermits)
                                                throws SQLException,
                                                       InterruptedException

Throws:

SQLException

InterruptedException

releaseDeadOwnerPermits

@CheckReturnValue
public int releaseDeadOwnerPermits(int wishPermits)
                                              throws InterruptedException,
                                                     SQLException

Attempts to release permits for this semaphore owned by dead owners.

Parameters:

wishPermits - - How many permits we would like to get released.

Returns:

- the number of permits we actually released.

Throws:

SQLException - - something went wrong with the db.

InterruptedException - - thrown if thread is interrupted.

updatePermits

public void updatePermits(int nrPermits)
                   throws SQLException,
                          InterruptedException

Throws:

SQLException

InterruptedException

reducePermits

public void reducePermits(int nrPermits)
                   throws SQLException,
                          InterruptedException

Throws:

SQLException

InterruptedException

increasePermits

public void increasePermits(int nrPermits)
                     throws SQLException,
                            InterruptedException

Throws:

SQLException

InterruptedException

removeDeadHeartBeatAndNotOwnerRows

public int removeDeadHeartBeatAndNotOwnerRows(long timeoutSeconds)
                                       throws SQLException,
                                              InterruptedException

Throws:

SQLException

InterruptedException

toString

public String toString()

Overrides:

toString in class Object

close

public void close()

Specified by:

close in interface AutoCloseable

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable

getJdbcTimeoutSeconds

public int getJdbcTimeoutSeconds()

isIsHealthy

public boolean isIsHealthy()