8000 Use reflection to install system signal handlers in JVM applications by kyri-petrou · Pull Request #9251 · zio/zio · GitHub
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Use reflection to install system signal handlers in JVM applications #9251

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Merged
merged 4 commits into from
Oct 22, 2024
+134 −22
Merged

Use reflection to install system signal handlers in JVM applications #9251

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1645618
Use reflection to install system signal handlers
kyri-petrou Oct 18, 2024
1e5a7a5
Use `java.util.logging.Logger` for warnings and cleanup
kyri-petrou Oct 19, 2024
b5b6403
Make Signal a Scala class
kyri-petrou Oct 20, 2024
810bbd3
Use `nonEmpty` instead
kyri-petrou Oct 20, 2024
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1 change: 1 addition & 0 deletions core/jvm/src/main/resources/META-INF/native-image/dev.zio/zio/native-image.properties
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Args = -H:DynamicProxyConfigurationResources=${.}/sun-misc-signal-proxy-config.json
7 changes: 7 additions & 0 deletions ...vm/src/main/resources/META-INF/native-image/dev.zio/zio/sun-misc-signal-proxy-config.json
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[
{
"interfaces": [
"sun.misc.SignalHandler"
]
}
]
24 changes: 2 additions & 22 deletions core/jvm/src/main/scala/zio/internal/PlatformSpecific.scala
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Expand Up @@ -38,28 +38,8 @@ private[zio] trait PlatformSpecific {
* Adds a signal handler for the specified signal (e.g. "INFO"). This method
* never fails even if adding the handler fails.
*/
final def addSignalHandler(signal: String, action: () => Unit)(implicit unsafe: zio.Unsafe): Unit = {
import sun.misc.Signal
import sun.misc.SignalHandler

final case class ZIOSignalHandler(action: () => Unit) extends SignalHandler {
private[zio] var signalHandler: SignalHandler = null
override def handle(signal: Signal): Unit = {
action()
if (signalHandler != SignalHandler.SIG_DFL && signalHandler != SignalHandler.SIG_IGN) {
signalHandler.handle(signal)
}
}
}

try {
val zioSignal = new Signal(signal)
val zioSignalHandler = ZIOSignalHandler(action)
zioSignalHandler.signalHandler = Signal.handle(zioSignal, zioSignalHandler)
} catch {
case _: Throwable => ()
}
}
final def addSignalHandler(signal: String, action: () => Unit)(implicit unsafe: zio.Unsafe): Unit =
Signal.handle(signal, _ => action())

// Check the classpath to see if we're running in an unforked sbt environment.
private val isUnforkedInSbt =
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124 changes: 124 additions & 0 deletions core/jvm/src/main/scala/zio/internal/Signal.scala
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package zio.internal

import java.lang.invoke.MethodHandle
import java.lang.invoke.MethodHandles
import java.lang.invoke.MethodType
import java.lang.reflect.{InvocationHandler, Method, Proxy}
import java.util.function.Consumer
import java.util.logging.Logger

/**
* * This class is used to handle system signals in a platform-specific way. It
* attemps to use the sun.misc.Signal and sun.misc.SignalHandler classes if they
* are available. If they are not available, it will gracefully degrade to a
* no-op.
*
* '''IMPLEMENTATION NOTE''': This class uses reflection to access the
* sun.misc.Signal and sun.misc.SignalHandler. This is necessary because the
* sun.misc.Signal and sun.misc.SignalHandler classes might not be available in
* some JVMs.
*/
private object Signal {

private val signalHandler: Signal.SignalHandler = {
val logger = Logger.getLogger("zio.internal.Signal")
val signalClass = findClass("sun.misc.Signal")
val signalHandlerClass = findClass("sun.misc.SignalHandler")

var constructorHandle: MethodHandle = null
var staticMethodHandle: MethodHandle = null

if ((signalClass ne null) && (signalHandlerClass ne null)) {
val lookup = MethodHandles.lookup()
constructorHandle = initSignalConstructorMethodHandle(lookup, signalClass)
staticMethodHandle = initHandleStaticMethodHandle(lookup, signalClass, signalHandlerClass)
} else {
constructorHandle = null
staticMethodHandle = null
}

if ((signalHandlerClass ne null) && (constructorHandle ne null) && (staticMethodHandle ne null))
new SignalHandler.SunMiscSignalHandler(signalHandlerClass, constructorHandle, staticMethodHandle)
else {
logger.warning(
"sun.misc.Signal and sun.misc.SignalHandler are not available on this platform. Defaulting to no-op signal handling implementation; ZIO fiber dump functionality might not work as expected."
)
new SignalHandler.NoOpSignalHandler
}
}

private[internal] def handle(signal: String, handler: Consumer[AnyRef]): Unit =
signalHandler.handle(signal, handler)

private def findClass(name: String): Class[?] =
try {
Class.forName(name)
} catch {
case _: ClassNotFoundException => null
}

private def initSignalConstructorMethodHandle(
lookup: MethodHandles.Lookup,
signalClass: Class[?]
): MethodHandle = {
val signalConstructorMethodType = MethodType.methodType(classOf[Unit], classOf[String])
try {
lookup.findConstructor(signalClass, signalConstructorMethodType)
} catch {
case _: Exception => null
}
}

private def initHandleStaticMethodHandle(
lookup: MethodHandles.Lookup,
signalClass: Class[?],
signalHandlerClass: Class[?]
) =
try {
val handleStaticMethodType = MethodType.methodType(signalHandlerClass, signalClass, signalHandlerClass)
lookup.findStatic(signalClass, "handle", handleStaticMethodType)
} catch {
case _: Exception => null
}

private abstract sealed class SignalHandler {
def handle(signal: String, handler: Consumer[AnyRef]): Unit
}

private object SignalHandler {

final class SunMiscSignalHandler(
signalHandlerClass: Class[?],
constuctorMethodHandle: MethodHandle,
staticMethodHandle: MethodHandle
) extends Signal.SignalHandler {

override def handle(signal: String, handler: Consumer[AnyRef]): Unit = {
val invocationHandler = initInvocationHandler(handler)
val proxy = Proxy.newProxyInstance(
Signal.getClass.getClassLoader,
Array(signalHandlerClass),
invocationHandler
)
try {
val s = constuctorMethodHandle.invoke(signal)
staticMethodHandle.invoke(s, proxy)
} catch {
// Gracefully degrade to a no-op
case _: Throwable => ()
}
}

private def initInvocationHandler(handler: Consumer[AnyRef]): InvocationHandler =
(proxy: Any, method: Method, args: Array[AnyRef]) => {
if (args.nonEmpty) handler.accept(args(0))
null
}

}

final class NoOpSignalHandler extends SignalHandler {
override def handle(signal: String, handler: Consumer[AnyRef]): Unit = ()
}
}
}
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