com.graphaware.writer.neo4j

Class SingleThreadedWriter

java.lang.Object

com.google.common.util.concurrent.AbstractScheduledService

com.graphaware.writer.service.QueueBackedScheduledService<RunnableFuture<?>>

com.graphaware.writer.neo4j.SingleThreadedWriter

All Implemented Interfaces:

com.google.common.util.concurrent.Service, Neo4jWriter, Writer

Direct Known Subclasses:

BatchWriter, TxPerTaskWriter

public abstract class SingleThreadedWriter
extends QueueBackedScheduledService<RunnableFuture<?>>
implements Neo4jWriter

A Neo4jWriter that maintains a queue of tasks and writes to the database in a single thread by constantly pulling the tasks from the head of the queue.

If the queue capacity is full, tasks are dropped and a warning is logged.

Note that start() must be called in order to start processing the queue and stop() should be called before the application is shut down.

Nested Class Summary

Nested classes/interfaces inherited from class com.google.common.util.concurrent.AbstractScheduledService

com.google.common.util.concurrent.AbstractScheduledService.CustomScheduler, com.google.common.util.concurrent.AbstractScheduledService.Scheduler

Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service

com.google.common.util.concurrent.Service.Listener, com.google.common.util.concurrent.Service.State

Field Summary

Fields

Modifier and Type	Field and Description
protected org.neo4j.graphdb.GraphDatabaseService	database

Fields inherited from class com.graphaware.writer.service.QueueBackedScheduledService

DEFAULT_QUEUE_CAPACITY, queue

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SingleThreadedWriter(org.neo4j.graphdb.GraphDatabaseService database) Construct a new writer with a default queue capacity of QueueBackedScheduledService.DEFAULT_QUEUE_CAPACITY.
protected	SingleThreadedWriter(org.neo4j.graphdb.GraphDatabaseService database, int queueCapacity) Construct a new writer.

Method Summary

Modifier and Type	Method and Description
protected <T> T	block(RunnableFuture<T> futureTask, String id, int waitMillis) Block until the given task is executed, or until a timeout occurs.
protected abstract <T> RunnableFuture<T>	createTask(Callable<T> task) Create a runnable future from the given task.
protected <T> T	offer(Callable<T> task, String id, int waitMillis) Offer a task to the queue for processing.
void	start() Start the processing of tasks.
void	stop() Stop the processing of tasks.
<T> T	write(Callable<T> task, String id, int waitMillis)
void	write(Runnable task)
void	write(Runnable task, String id)

Methods inherited from class com.graphaware.writer.service.QueueBackedScheduledService

equals, hashCode, logEmptyQueue, loggingFrequencyMs, offer, scheduler, shutDown

Methods inherited from class com.google.common.util.concurrent.AbstractScheduledService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, executor, failureCause, isRunning, runOneIteration, serviceName, startAsync, startUp, state, stopAsync, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

database

protected final org.neo4j.graphdb.GraphDatabaseService database

Constructor Detail

SingleThreadedWriter

protected SingleThreadedWriter(org.neo4j.graphdb.GraphDatabaseService database)

Construct a new writer with a default queue capacity of QueueBackedScheduledService.DEFAULT_QUEUE_CAPACITY.

Parameters:

database - to write to.

SingleThreadedWriter

protected SingleThreadedWriter(org.neo4j.graphdb.GraphDatabaseService database,
                               int queueCapacity)

Construct a new writer.

Parameters:

database - to write to.

queueCapacity - capacity of the queue.

Method Detail

start

@PostConstruct
public void start()

Start the processing of tasks.

Specified by:

start in interface Writer

Overrides:

start in class QueueBackedScheduledService<RunnableFuture<?>>

stop

@PreDestroy
public void stop()

Stop the processing of tasks.

Specified by:

stop in interface Writer

Overrides:

stop in class QueueBackedScheduledService<RunnableFuture<?>>

write

public void write(Runnable task)

Specified by:

write in interface Neo4jWriter

write

public void write(Runnable task,
                  String id)

Specified by:

write in interface Neo4jWriter

write

public <T> T write(Callable<T> task,
                   String id,
                   int waitMillis)

Specified by:

write in interface Neo4jWriter

offer

protected final <T> T offer(Callable<T> task,
                            String id,
                            int waitMillis)

Offer a task to the queue for processing.

Type Parameters:

T - type of the processing result.

Parameters:

task - to process.

id - of the task for logging purposes.

waitMillis - how many milliseconds to block and wait for the task to be executed. Use 0 (or less) for no blocking, i.e. for situations where the caller isn't interested in the result.

Returns:

result of the processing or null if the caller decided not to wait, or if the processing took longer than the waitMillis argument, or if the queue is too full and the #offer(RunnableFuture) has not been overridden to block in such situations.

createTask

protected abstract <T> RunnableFuture<T> createTask(Callable<T> task)

Create a runnable future from the given task.

Parameters:

task - task.

Returns:

future.

block

protected final <T> T block(RunnableFuture<T> futureTask,
                            String id,
                            int waitMillis)

Block until the given task is executed, or until a timeout occurs.

Type Parameters:

T - type of the task's result.

Parameters:

futureTask - to wait for.

id - of the task for logging.

waitMillis - how long to wait before giving up.

Returns:

result of the task. null if timed out.