IORuntime Configuration

It is possible to configure your IORuntime externally, at runtime.

JVM

You can set these as system properties via JVM arguments.

-Dcats.effect.propName=propValue

JS

On Node.js, these can be set via ordinary environment variables. For browsers (and generally any other runtime) you can instead define globals in your JavaScript bundle:

process.env.CATS_EFFECT_PROPNAME = propValue;
// alias for compatibility with Create React App
process.env.REACT_APP_CATS_EFFECT_PROPNAME = propValue;

This can be done for example with the EnvironmentPlugin for Webpack or Create React App.

System Property (JVM) / ENV Variable (JS)	Value (default)	Description
cats.effect.detectBlockedThreads N/A	Boolean (false)	Whether or not we should detect blocked threads.
cats.effect.logNonDaemonThreadsOnExit N/A	Boolean (true)	Whether or not we should check for non-daemon threads on JVM exit.
cats.effect.logNonDaemonThreads.sleepIntervalMillis N/A	Long (10000L)	Time to sleep between checking for presence of non-daemon threads.
cats.effect.warnOnNonMainThreadDetected N/A	Boolean (true)	Print a warning message when IOApp main runs on a non-main thread
cats.effect.cancelation.check.threshold CATS_EFFECT_CANCELATION_CHECK_THRESHOLD	Int (512)	Configure how often cancellation is checked. By default, every 512 iterations of the run loop.
cats.effect.auto.yield.threshold.multiplier CATS_EFFECT_AUTO_YIELD_THRESHOLD_MULTIPLIER	Int (2)	autoYieldThreshold = autoYieldThresholdMultiplier x cancelationCheckThreshold. See thread model.
cats.effect.tracing.exceptions.enhanced CATS_EFFECT_TRACING_EXCEPTIONS_ENHANCED	Boolean (true)	Augment the stack traces of caught exceptions to include frames from the asynchronous stack traces. See tracing.
cats.effect.tracing.buffer.size CATS_EFFECT_TRACING_BUFFER_SIZE	Int (16)	Number of stack frames retained in the tracing buffer. Will be rounded up to next power of two.
cats.effect.shutdown.hook.timeout CATS_EFFECT_SHUTDOWN_HOOK_TIMEOUT	Duration (Inf)	If your IOApp encounters a Ctrl+C or System.exit, how long it should wait for fiber cancellation before forcibly stopping.
cats.effect.cpu.starvation.check.interval CATS_EFFECT_CPU_STARVATION_CHECK_INTERVAL	FiniteDuration (1.second)	The starvation checker repeatedly sleeps for this interval and then checks monotonic time when it awakens. It will then print a warning to stderr if it finds that the current time is greater than expected (see threshold below).
cats.effect.cpu.starvation.check.initialDelay CATS_EFFECT_CPU_STARVATION_CHECK_INITIAL_DELAY	Duration (10.seconds)	The initial delay before the CPU starvation checker starts running. Avoids spurious warnings due to the JVM not being warmed up yet. Set to Duration.Inf to disable CPU starvation checking.
cats.effect.cpu.starvation.check.threshold CATS_EFFECT_CPU_STARVATION_CHECK_THRESHOLD	Double (0.1)	The starvation checker will print a warning if it finds that it has been asleep for at least interval * (1 + threshold) (where interval from above is the expected time to be asleep for). Sleeping for too long is indicative of fibers hogging a worker thread either by performing blocking operations on it or by cedeing insufficiently frequently.