If I started a process using Scala Process/ProcessBuilder. How can I get the pid of the process that was created?
I could not find any mention of the pid in the official docs:
http://www.scala-lang.org/api/2.10.4/index.html#scala.sys.process.Process
http://www.scala-lang.org/api/2.10.4/index.html#scala.sys.process.ProcessBuilder
http://www.scala-lang.org/api/2.10.4/index.html#scala.sys.process.package
2016: same question; I've been clicking through related questions for a few minutes, but still couldn't find any solution that is generally agreed upon. Here is a Scala version inspired by LRBH10's Java code in the answer linked by wingedsubmariner:
import scala.sys.process.Process
def pid(p: Process): Long = {
val procField = p.getClass.getDeclaredField("p")
procField.synchronized {
procField.setAccessible(true)
val proc = procField.get(p)
try {
proc match {
case unixProc
if unixProc.getClass.getName == "java.lang.UNIXProcess" => {
val pidField = unixProc.getClass.getDeclaredField("pid")
pidField.synchronized {
pidField.setAccessible(true)
try {
pidField.getLong(unixProc)
} finally {
pidField.setAccessible(false)
}
}
}
// If someone wants to add support for Windows processes,
// this would be the right place to do it:
case _ => throw new RuntimeException(
"Cannot get PID of a " + proc.getClass.getName)
}
} finally {
procField.setAccessible(false)
}
}
}
// little demo
val proc = Process("echo 'blah blah blaaah'").run()
println(pid(proc))
WARNING: scala code runner is essentially just a bash script, so when you use it to launch scala programs, it will do thousand things before actually starting the java process. Therefore, the PID of the java-process that you are actually interested in will be much larger than what the above code snippet returns. So this method is essentially useless if you start your processes with scala. Use java directly, and explicitly add Scala library to the classpath.
The scala.sys.io.process classes are wrappers around the Java classes for starting processes, and unfortunately it is difficult to obtain the PID from this API. See the stackoverlow question for this, How to get PID of process I've just started within java program?.
Related
I will start mentioning I am very new to Scala but I have now to maintain a legacy code where some new feature are being tried to be include.
I have the following code:
Where a list is coming as a parameter where a new output needs to be processed. However it seems like code is not waiting for the response to the external service when processing.
def historyBet(jackpotListUser : List[JackpotBetHistory])(implicit MC: AppMarkerContext) : List[LegacyJackpotHistoryResponse] =
for {
bet <- jackpotListUser
prize = jackpotIntegratorService.findJackpotByJackpotHumanId(bet.jackpotHumanId) match {
case Some(jackpot : JackpotResponse) =>
...
extra code extracting price from jackpot : JackpotResponse
...
extra code generating result with prize
} yield result
How can I do a call to jackpotIntegratorService.findJackpotByJackpotHumanId to execute at that time. instead of returning something that F[Option....?
def findJackpotByJackpotHumanId(
jackpotHumanId: JackpotHumanId
)(implicit MC: AppMarkerContext): F[Option[JackpotResponse]] =
jackpotIntegratorRepo.findJackpotByJackpotHumanId(jackpotHumanId)
where it is finally implemented as:
override def findJackpotByJackpotHumanId(
jackpotHumanId: JackpotHumanId
)(implicit mc: AppMarkerContext): IO[Option[JackpotResponse]] =
... code calling an API which return the IO.
Thanks!
I thought I could do IO.await somewhere... but not sure where or how...
because in the "historyBet" function I got a F[] when it was an IO... so what is the syntax to be able to wait for the response and the continue?
Extra Comment:
The real issue we notice is that the method call is starting (the logs shows part of it) but the caller with in the maps continues too.
prize = jackpotIntegratorService.findJackpotByJackpotHumanId
this part of the code continues even when prize, which we want the final object JackpotResponse, not the IO or F.
So, if your method needs to call an IO then it must return an IO unless you unsafeRunSync them... but, as the name suggest, you should not do that.
So the return type is now: IO[List[LegacyJackpotHistoryResponse]
And can be implemented like this:
def historyBet(jackpotListUser: List[JackpotBetHistory])(implicit MC: AppMarkerContext): IO[List[LegacyJackpotHistoryResponse]] =
jackpotListUser.traverse { bet =>
jackpotIntegratorService.findJackpotByJackpotHumanId(bet.jackpotHumanId).map {
case Some(jackpot) =>
// ...
case None =>
// ...
}
}
I'm writing Selenium tests with ScalaTest's Selenium DSL and I'm running into timeouts I can't explain. To make matters more complicated, they only seem to happen some of the time.
The problem occurs whenever I access an Element after a page load or some Javascript rendering. It looks like this:
click on "editEmployee"
eventually {
textField(name("firstName")).value = "Steve"
}
My PatienceConfig is configured like this:
override implicit val patienceConfig: PatienceConfig =
PatienceConfig(timeout = Span(5, Seconds), interval = Span(50, Millis))
The test fails with the following error:
- should not display the old data after an employee was edited *** FAILED ***
The code passed to eventually never returned normally. Attempted 1 times over 10.023253653000001 seconds.
Last failure message: WebElement 'firstName' not found.. (EditOwnerTest.scala:24)
It makes sense that it doesn't succeed immediately, because the click causes some rendering, and the textfield may not be available right away. However, it shouldn't take 10 seconds to make an attempt to find it, right?
Also, I find it very interesting that the eventually block tried it only once, and that it took almost precisely 10 seconds. This smells like a timeout occurred somewhere, and it's not my PatienceConfig, because that was set to time out after 5 seconds.
With this workaround, it does work:
click on "editEmployee"
eventually {
find(name("firstName")).value // from ScalaTest's `OptionValues`
}
textField(name("firstName")).value = "Steve"
I did some digging in the ScalaTest source, and I've noticed that all calls that have this problem (it's not just textField), eventually call webElement at some point. The reason why the workaround works, is because it doesn't call webElement. webElement is defined like this:
def webElement(implicit driver: WebDriver, pos: source.Position = implicitly[source.Position]): WebElement = {
try {
driver.findElement(by)
}
catch {
case e: org.openqa.selenium.NoSuchElementException =>
// the following is avoid the suite instance to be bound/dragged into the messageFun, which can cause serialization problem.
val queryStringValue = queryString
throw new TestFailedException(
(_: StackDepthException) => Some("WebElement '" + queryStringValue + "' not found."),
Some(e),
pos
)
}
}
I've copied that code into my project and played around with it, and it looks like constructing and/or throwing the exception is where most of the 10 seconds are spent.
(EDIT Clarification: I've actually seen the code actually spend its 10 seconds inside the catch block. The implicit wait is set to 0, and besides, if I remove the catch block everything simply works as expected.)
So my question is, what can I do to avoid this strange behaviour? I don't want to have to insert superfluous calls to find all the time, because it's easily forgotten, especially since, as I said, the error occurs only some of the time. (I haven't been able to determine when the behaviour occurs and when it doesn't.)
It is clear that the textField(name("firstName")).value = "Steve" ends up calling the WebElement as you have found out.
Since the issue in the op is happening where ever web elements are involved (which in turn implies that webdriver is involved), I think it is safe to assume that the issue is related to the implicit wait on the Web driver.
implicitlyWait(Span(0, Seconds))
The above should ideally fix the issue. Also, making implicit wait to be 0 is a bad practice. Any web page might have some loading issues. The page load is handled by Selenium outside its wait conditions. But slow element load (may be due to ajax calls) could result in failure. I usually keep 10 seconds as my standard implicit wait. For scenarios which require more wait, explicit waits can be used.
def implicitlyWait(timeout: Span)(implicit driver: WebDriver): Unit = {
driver.manage.timeouts.implicitlyWait(timeout.totalNanos, TimeUnit.NANOSECONDS)
}
Execution Flow:
name("firstName") ends up having value as Query {Val by = By.className("firstName") }.
def name(elementName: String): NameQuery = new NameQuery(elementName)
case class NameQuery(queryString: String) extends Query { val by = By.name(queryString) }
Query is fed to the textField method which calls the Query.webElement as below.
def textField(query: Query)(implicit driver: WebDriver, pos: source.Position): TextField = new TextField(query.webElement)(pos)
sealed trait Query extends Product with Serializable {
val by: By
val queryString: String
def webElement(implicit driver: WebDriver, pos: source.Position = implicitly[source.Position]): WebElement = {
try {
driver.findElement(by)
}
catch {
case e: org.openqa.selenium.NoSuchElementException =>
// the following is avoid the suite instance to be bound/dragged into the messageFun, which can cause serialization problem.
val queryStringValue = queryString
throw new TestFailedException(
(_: StackDepthException) => Some("WebElement '" + queryStringValue + "' not found."),
Some(e),
pos
)
}
}
}
I don't know ScalaTest's specifics, but such strange timeouts usually occur when you're mixing up implicit and explicit waits together.
driver.findElement uses implicit waits internally. And depending on specified explicit waits timeout, you may face with summing both together.
Ideally, implicit waits should be set to 0 to avoid such issues.
i'm trying to get a clean and gracefull shutdown, and for some reason, it wont execute. iv'e tried:
sys addShutdownHook{
logger.warn("SHUTTING DOWN...")
// irrelevant logic here...
}
and also:
Runtime.getRuntime.addShutdownHook(ThreadOperations.delayOnThread{
logger.warn("SHUTTING DOWN...")
// irrelevant logic here...
}
)
where ThreadOperations.delayOnThread definition is:
object ThreadOperations {
def startOnThread(body: =>Unit) : Thread = {
onThread(true, body)
}
def delayOnThread(body: =>Unit) : Thread = {
onThread(false, body)
}
private def onThread(runNow : Boolean, body: =>Unit) : Thread = {
val t=new Thread {
override def run=body
}
if(runNow){t.start}
t
}
// more irrelevant operations...
}
but when i run my program (executable jar, double activation), the hook does not start. so what am i doing wrong? what is the right way to add a shutdown hook in scala? is it in any way related to the fact i'm using double activation?
double activation is done like that:
object Gate extends App {
val givenArgs = if(args.isEmpty){
Array("run")
}else{
args
}
val jar = Main.getClass.getProtectionDomain().getCodeSource().getLocation().getFile;
val dir = jar.dropRight(jar.split(System.getProperty("file.separator")).last.length + 1)
val arguments = Seq("java", "-cp", jar, "boot.Main") ++ givenArgs.toSeq
Process(arguments, new java.io.File(dir)).run();
}
(scala version: 2.9.2 )
thanks.
In your second attempt, your shutdown hook you seems to just create a thread and never start it (so it just gets garbage collected and does nothing). Did I miss something? (EDIT: yes I did, see comment. My bad).
In the first attempt, the problem might just be that the underlying log has some caching, and the application exits before the log is flushed.
Solved it.
For some reason, I thought that run as opposed to ! would detach the process. It actually hangs on because there are open streams left to the Process, which is returned from run (or maybe it just hangs for another reason, 'cause exec doesn't hang, but returns a Process with open streams to and from the child process, much like run). For this reason, the original process was still alive, and I accidentally sent the signals to it. Of course, it did not contain a handler, or a shutdown hook, so nothing happened.
The solution was to use Runtime.getRuntime.exec(arguments.toArray) instead of Process(arguments, new java.io.File(dir)).run();, close the streams in the Gate object, and send the ^C signal to the right process.
I tried to run the groovy script. But unfortunately the script does not ask me for the input and through null pointer exceptions. Please help me what I need to do for this.
static startShell() {
client = new Client()
// TODO add Windows compatibility check
def historyFile = new File(System.getProperty("user.home"), "kitty.history")
historyFile.createNewFile()
def history = new History(historyFile)
def reader = new ConsoleReader()
reader.setBellEnabled(false)
reader.setUseHistory(true)
reader.setDefaultPrompt(PROMPT)
reader.setHistory(history)
reader.addCompletor(new SimpleCompletor(commands as String[]))
LOOP: while (true) {
def input = reader?.readLine().trim()
if (input.length() == 0)
continue
if (["exit", "quit"].contains(input.tokenize().get(0)))
break LOOP
try {
inputHandler(input)
}
catch (Exception e) {
println e.getMessage()
}
I also tried by replacing the reader? with reader also.
Error:
kitty> Caught: java.lang.NullPointerException: Cannot invoke method trim() on null object
at org.apache.kitty.CmdShell.startShell(CmdShell.groovy:100)
at org.apache.kitty.CmdShell.main(CmdShell.groovy:79)
Please Help
I believe this is related to this question:
java.io.Console support in Eclipse IDE
Essentially, Eclipse does not support Console Reader for running applications - though I'm confused as to how Andrew Eisenberg got a working result in Eclipse if that is the case.
Can you simplify your program into something that I can run? I tried something very simple and I was able to have it run both on the command line and inside Eclipse.
Here's the script I created:
import jline.ConsoleReader
def reader = new ConsoleReader()
LOOP: while (true) {
def input = reader?.readLine().trim()
if (input.length() == 0)
continue
if (["exit", "quit"].contains(input.tokenize().get(0)))
break LOOP
println "You said: " + input
}
Can you try running this and see if this works for you?
This page has a description of Map's getOrElseUpdate usage method:
object WithCache{
val cacheFun1 = collection.mutable.Map[Int, Int]()
def fun1(i:Int) = i*i
def catchedFun1(i:Int) = cacheFun1.getOrElseUpdate(i, fun1(i))
}
So you can use catchedFun1 which will check if cacheFun1 contains key and return value associated with it. Otherwise, it will invoke fun1, then cache fun1's result in cacheFun1, then return fun1's result.
I can see one potential danger - cacheFun1 can became to large. So cacheFun1 must be cleaned somehow by garbage collector?
P.S. What about scala.collection.mutable.WeakHashMap and java.lang.ref.* ?
See the Memo pattern and the Scalaz implementation of said paper.
Also check out a STM implementation such as Akka.
Not that this is only local caching so you might want to lookinto a distributed cache or STM such as CCSTM, Terracotta or Hazelcast
Take a look at spray caching (super simple to use)
http://spray.io/documentation/1.1-SNAPSHOT/spray-caching/
makes the job easy and has some nice features
for example :
import spray.caching.{LruCache, Cache}
//this is using Play for a controller example getting something from a user and caching it
object CacheExampleWithPlay extends Controller{
//this will actually create a ExpiringLruCache and hold data for 48 hours
val myCache: Cache[String] = LruCache(timeToLive = new FiniteDuration(48, HOURS))
def putSomeThingInTheCache(#PathParam("getSomeThing") someThing: String) = Action {
//put received data from the user in the cache
myCache(someThing, () => future(someThing))
Ok(someThing)
}
def checkIfSomeThingInTheCache(#PathParam("checkSomeThing") someThing: String) = Action {
if (myCache.get(someThing).isDefined)
Ok(s"just $someThing found this in the cache")
else
NotFound(s"$someThing NOT found this in the cache")
}
}
On the scala mailing list they sometimes point to the MapMaker in the Google collections library. You might want to have a look at that.
For simple caching needs, I'm still using Guava cache solution in Scala as well.
Lightweight and battle tested.
If it fit's your requirements and constraints generally outlined below, it could be a great option:
Willing to spend some memory to improve speed.
Expecting that keys will sometimes get queried more than once.
Your cache will not need to store more data than what would fit in RAM. (Guava caches are local to a single run of your application.
They do not store data in files, or on outside servers.)
Example for using it will be something like this:
lazy val cachedData = CacheBuilder.newBuilder()
.expireAfterWrite(60, TimeUnit.MINUTES)
.maximumSize(10)
.build(
new CacheLoader[Key, Data] {
def load(key: Key): Data = {
veryExpansiveDataCreation(key)
}
}
)
To read from it, you can use something like:
def cachedData(ketToData: Key): Data = {
try {
return cachedData.get(ketToData)
} catch {
case ee: Exception => throw new YourSpecialException(ee.getMessage);
}
}
Since it hasn't been mentioned before let me put on the table the light Spray-Caching that can be used independently from Spray and provides expected size, time-to-live, time-to-idle eviction strategies.
We are using Scaffeine (Scala + Caffeine), and you can read abouts its pros/cons compared to other frameworks over here.
You add your sbt,
"com.github.blemale" %% "scaffeine" % "4.0.1"
Build your cache
import com.github.blemale.scaffeine.{Cache, Scaffeine}
import scala.concurrent.duration._
val cachedItems: Cache[String, Int] =
Scaffeine()
.recordStats()
.expireAtferWrite(60.seconds)
.maximumSize(500)
.build[String, Int]()
cachedItems.put("key", 1) // Add items
cache.getIfPresent("key") // Returns an option