net.i2p.router

Class JobQueueScaler

java.lang.Object

net.i2p.router.JobQueueScaler

All Implemented Interfaces:

Runnable

class JobQueueScaler
extends Object
implements Runnable

Dynamic job runner scaling controller for the JobQueue. Monitors queue metrics (ready job count, lag) and automatically scales the number of JobQueueRunner threads up or down based on load conditions. Scaling Algorithm:

• Scale UP when: readyJobs > activeRunners * scaleUpJobsRatio OR maxLag > scaleUpLagThreshold
• Scale DOWN when: readyJobs < activeRunners AND maxLag < scaleDownLagThreshold (sustained)
• Bounds: min runners = max(4, cores), max runners = min(2 * router.maxJobRunners, RAM-based limit)

Feedback Mechanism:

• Captures pre-scale metrics before adding runners
• Compares post-scale metrics after 3 check intervals
• If lag INCREASED after scaling, automatically rolls back added runners
• After 2 failed scale attempts, stops scaling up until router restart
• Tracks memory usage to prevent OOM conditions

Sub-millisecond Lag Target: With very low lag targets (sub-ms), even small degradations are significant. The feedback system uses tight thresholds (20% increase = failure) to ensure we don't add runners that worsen performance.

Constructor Summary

Constructors

Constructor and Description
JobQueueScaler(RouterContext context, JobQueue jobQueue) Create a new JobQueueScaler.

Method Summary

Modifier and Type	Method and Description
int	getCurrentMaxRunners() Get the current maximum runner limit (may be up to 2x configured or RAM-limited).
boolean	isAlive() Check if the scaler is currently running.
void	run() Main scaling loop.
void	shutdown() Shutdown the scaler gracefully.
void	startup() Start the scaler thread.
void	updateMaxRunners(int configuredMax) Update the maximum runner limit (called when configuration changes).

Methods inherited from class java.lang.Object

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

Constructor Detail

JobQueueScaler

public JobQueueScaler(RouterContext context,
                      JobQueue jobQueue)

Create a new JobQueueScaler.

Parameters:

context - the router context

jobQueue - the job queue to scale

Method Detail

getCurrentMaxRunners

public int getCurrentMaxRunners()

Get the current maximum runner limit (may be up to 2x configured or RAM-limited).

isAlive

public boolean isAlive()

Check if the scaler is currently running.

run

public void run()

Main scaling loop.

Specified by:

run in interface Runnable

shutdown

public void shutdown()

Shutdown the scaler gracefully.

startup

public void startup()

Start the scaler thread.

updateMaxRunners

public void updateMaxRunners(int configuredMax)

Update the maximum runner limit (called when configuration changes).