JobQueueScaler (Javadocs [I2P+ 2.13.0+]

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 avgLag < scaleDownLagThreshold (sustained)
- Bounds: min runners = max(4, cores), max runners = min(2 * router.maxJobRunners, RAM-based limit)
Resource Saturation Gates: Scale-up is suppressed (not just limited) when the bottleneck is resource saturation rather than thread count. Emergency signals (critical lag, wedged jobs, dropped jobs) override the suppression.
- CPU saturation: router.cpuLoad > 85%
- GC storm: router.gcPauseTime > 50 ms/min
- Network congestion: tunnel.buildSuccessRate < 50%
- Bandwidth saturation: bwLimiter.outboundDelayedTime > 500ms
Feedback Mechanism:
- Captures pre-scale metrics before adding runners
- Compares post-scale metrics after 2 check intervals
- If lag, maxLag, message delay, or ready jobs INCREASED after scaling, rolls back
- After 5 failed scale attempts, circuit breaker opens — stops scaling up
- Tracks memory usage to prevent OOM conditions

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

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

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`getCurrentMaxRunners()` Get the current maximum runner limit (may be up to 2x configured or RAM-limited).
`(package private) int`	`getMinRunnersDynamic()` Get the minimum number of runners (floor), dynamic - reads property each time.
`boolean`	`isAlive()` Check if the scaler is currently running.
`void`	`releaseRunners(int count, String reason)` Release previously requested runners.
`void`	`requestRunners(int count, String reason, long autoReleaseMs)` Request additional runners for an anticipated burst.
`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).
    Returns:
    the current max runners
  - getMinRunnersDynamic
```
int getMinRunnersDynamic()
```
    Get the minimum number of runners (floor), dynamic - reads property each time. On router startup, returns more runners to handle startup load.
  - isAlive
```
public boolean isAlive()
```
    Check if the scaler is currently running.
    Returns:
    whether alive
  - releaseRunners
```
public void releaseRunners(int count,
                           String reason)
```
    Release previously requested runners. Idempotent — releasing more than requested just floors the per-reason count at 0.
    Parameters:
    count - number of runners to release
    reason - must match the reason used in requestRunners
  - requestRunners
```
public void requestRunners(int count,
                           String reason,
                           long autoReleaseMs)
```
    Request additional runners for an anticipated burst. Called by subsystems (e.g., Tuner) that know demand is imminent. The floor prevents the scaler from reducing below active + requested until auto-decay or explicit release.
    Parameters:
    count - number of additional runners to reserve
    reason - label for tracking and logging
    autoReleaseMs - if > 0, auto-decay after this many ms
  - 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).

Class JobQueueScaler

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

JobQueueScaler

Method Detail

getCurrentMaxRunners

getMinRunnersDynamic

isAlive

releaseRunners

requestRunners

run

shutdown

startup

updateMaxRunners