Setac: A Phased Deterministic Testing Framework for Scala Actors. Samira Tasharofi Jun 02, 2011 Stanford, CA

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1 Setac: A Phased Deterministic Testing Framewrk fr Scala Actrs Samira Tasharfi Jun 02, 2011 Stanfrd, CA

2 Mtivatin Schedule is a surce f nn-determinism in cncurrent prgrams Shared memry: rder f accesses Message-passing: rder f messages The utput f the prgram might be different fr a given input depending n the schedule The bugs may nly shw up during sme specific schedules Systematic explratin can lead t state space explsin Setac Testing Framewrk 7/17/2011 2

3 Actr Mdel Actr is a cmputatinal entity with a mail bx and lcal state Deliver a message Append the message t the mail bx Prcess a message Extract a message frm the mail bx and execute that Determined by message handler In respnse t a message it prcesses: Changes its lcal state Sends messages t ther actrs Creates new actrs Setac Testing Framewrk 7/17/2011 3

4 Actrs in Scala Package scala.actrs in Scala library Develped by Philipp Haller Features Synchrnus and asynchrnus cmmunicatin Dynamic creatin/destrying f actrs Exceptin handling Remte actrs Custmizatin f the thread pl executing actrs Setac Testing Framewrk 7/17/2011 4

5 Example: BundedBuffer class BundedBuffer(maxSize: Int) extends Actr { var cntent = new Array[Int](size) var head, tail, cursize = 0 start verride def act() = lp { react { case Put(x) if (cursize < maxsize) => { cntent(tail) = x tail = (tail + 1) % size cursize += 1 case Get if (cursize > 0) => { val r = cntent(head) head = (head + 1) % size cursize -= 1 reply(r) class Prducer(buf: Actr) extends Actr { start verride def act() = lp { react { case Prduce(values) => values.freach(v => buf! Put(v)) class Cnsumer(buf: Actr) extends Actr { var tken = -1 start verride def act() = lp { react { case Cnsume(cunt) => fr (i <- 0 t cunt-1) tken = (buf!? Get).asInstanceOf[Int] Setac Testing Framewrk 7/17/2011 5

6 BufferTest class BufferTest def testbuffer() { val buf = new BundedBuffer(1) val cnsumer = new Cnsumer(buf) val prducer = new Prducer(buf) prducer Put(4), Put(5) Get, Get cnsumer 4, 5 buffer(1) prducer! Prduce(List(4, 5)) cnsumer! Cnsume(2) // cnsumer shuld receive 4 and 5 assert( ) Setac Testing Framewrk 7/17/2011 6

7 Buggy BundedBuffer class BundedBuffer(maxSize: Int) extends Actr { var cntent = new Array[Int](size) var head, tail, cursize = 0 start verride def act() = lp { Bug react { case Put(x) if (cursize <= maxsize) => { cntent(tail) = x tail = (tail + 1) % size cursize += 1 case Get if (cursize > 0) => { val r = cntent(head) head = (head + 1) % size cursize -= 1 reply(r) Setac Testing Framewrk 7/17/2011 7

8 Buggy BundedBuffer: Schedules in BufferTest class BundedBuffer(maxSize: Int) extends Actr { var cntent = new Array[Int](size) var head, tail, cursize = 0 start verride def act() = lp { react { case Put(x) if (cursize <= maxsize) => { cntent(tail) = x tail = (tail + 1) % size cursize += 1 case Get if (cursize > 0) => { val r = cntent(head) head = (head + 1) % size cursize -= 1 reply(r) Errr! cnsumer prducer buffer(1) Put(4) Get Put(5) Get Setac Testing Framewrk 7/17/2011 8

9 Crrect BundedBuffer: Checking Assertins in Test class BundedBuffer(maxSize: Int) extends Actr { var cntent = new Array[Int](size) var head, tail, cursize = 0 start verride def act() = lp { react { case Put(x) if (cursize < maxsize) => { cntent(tail) = x tail = (tail + 1) % size cursize += 1 case Get if (cursize > 0) => { val r = cntent(head) head = (head + 1) % size cursize -= 1 reply(r) class SimpleBufferTest def testbuffer() { val buf = new BundedBuffer(1) buf! Put(4) assert(buf.cursize == 1) Fails!! Put(4) Fails!! mailbx buffer assert lcal state cntent, head, tail, cursize Setac Testing Framewrk 7/17/2011 9

10 Testing Actr Prgrams Prblems: Hw t write unit tests fr Actr prgrams while cntrlling the schedule? Hw t check assertins at apprpriate times? Current Slutins: Using synchrnizatin cnstructs, e.g. Latches and Barriers Using Thread.sleep Setac Testing Framewrk 7/17/

11 BufferTest: A Test Schedule Cnsumer Prducer BundedeBuffer(1) Phase 1 Check assertins Get Phase 2 Check assertins 4 Put(4) Put(5) Phase 3 Check assertins 5 Get Setac Testing Framewrk 7/17/

12 Traditinal: BufferTest class BufferTest def testbuffer() { val putlatch = new CuntDwnLatch(2) val getlatch = new CuntDwnLatch(2) val buf = new BundedBuffer(1, putlatch, getlatch) val cnsumelatch = new CuntDwnLatch(1) val cnsumer = new Cnsumer(buf, cnsumelatch) val prducer = new Prducer(buf) Phase 1 cnsumer prducer buffer(1) Get //Phase 1 cnsumer! Cnsume(1) cnsumelatch.await() Thread.sleep(1000) assert(cnsumer.getstate == State.Blcked && buf.cursize == 0) // class Cnsumer(buf: Actr, cnsumelatch: CuntDwnLatch) extends Actr { var tken = -1 start verride def act() = lp { react { case Cnsume(cunt) => cnsumelatch.cuntdwn() fr (i <- 0 t cunt-1) tken = (buf!? Get).asInstanceOf[Int] Setac Testing Framewrk 7/17/

13 Traditinal: BufferTest (cnt) class BufferTest def testbuffer() { // //Phase 2 prducer! Prduce(List(4, 5)) putlatch.await() assert(cnsumer.tken == 4 && buf.cursize == 1) Phase 2 Phase 3 cnsumer prducer buffer(1) 4 5 Put(4) Put(5) Get // Phase 3 cnsumer! Cnsume(1) getlatch.await() assert(cnsumer.tken == 5 && buf.cursize == 0) class BundedBuffer(maxSize: Int, putlatch: CuntDwnLatch, getlatch: CuntDwnLatch) extends Actr { var cntent = new Array[Int](size) var head, tail, cursize = 0 start verride def act() = lp { react { case Put(x) if (cursize < maxsize) => { cntent(tail) = x tail = (tail + 1) % size cursize += 1 putlatch.cuntdwn() case Get if (cursize > 0) => { val r = cntent(head) head = (head + 1) % size cursize -= 1 reply(r) getlatch.cuntdwn() Setac Testing Framewrk 7/17/

14 Unreliable Traditinal BufferTest Prblems Thread.sleep Cmplexity and Deadlck pssibility Latches and Barriers Cstly Changing the prgram under test Setac Testing Framewrk 7/17/

15 Setac Specify tests with sme cnstraints n the schedule Partial rder f schedule messages Centralized schedule, less cmplexity Checking assertins when the system is stable There is n message that can be prcessed N prgress in the system N change in the run time envirnment Minimal changes in the prgram under test Setac Testing Framewrk 7/17/

16 Setac: BufferTest class BufferTest extends SetacTest def testbuffer() { val buf = new BundedBuffer(1) val cnsumer = new Cnsumer(buf) val prducer = new Prducer(buf) val put4 = createschedulemessage(prducer, buf, Put(4)) val put5 = createschedulemessage(prducer, buf, Put(5)) val gets = createmultipleschedulemessage(2, cnsumer, buf, Get) prducer! Prduce(List(4, 5)) cnsumer! Cnsume(2) //Phase 1 setschedule(gets(0)) assertwhenstable(cnsumer.isblcked && buf.cursize == 0) //Phase 2 setschedule(put4 -> put5) assertwhenstable(cnsumer.tken == 4 && buf.cursize == 1 && put5.isprcessed) // Phase 3 setschedule(gets(1)) assertwhenstable(cnsumer.tken == 5 && buf.cursize == 0) Setac Testing Framewrk 7/17/

17 Setac: BufferTest (cnt) class BundedBuffer(size: Int) extends TestActr { { // class Cnsumer(buf: Actr) extends TestActr { { // class Prducer(buf: Actr) extends TestActr { { // Setac Testing Framewrk 7/17/

18 Setac: BufferTest Remved Thread.sleep Mre reliable Remved synchrnizatin cnstructs, e.g. Latches Reduced cmplexity Minimized changes in the prgram under test Setac Testing Framewrk 7/17/

19 Setac APIs Fllws widely used style fr unit testing Integrated with Junit Refined ver time based n examples Checking assertins when system is stable Ttal and partial rder f schedule messages Status f Test messages Prcessed, delivered, etc. Status f actrs Mail bx: Number f messages, cntent f mail bx, etc. Executin Status: Blcked, Running, Suspended Setac Testing Framewrk 7/17/

20 Limitatins Handling nn-stable systems receivewithin, reactwithin, etc. in a lp Use assertafter API in Setac Managing annymus actrs E.g., Futures Handling actrs whse surce cde is nt available Setac Testing Framewrk 7/17/

21 Future Wrk Integrate Setac with Scala actr library T eliminate the required change in the prgram under test T remve sme f its limitatins Extend the slutin fr Akka actrs Integrate with ScalaTest Evaluate Setac n larger number f examples Speed, expressiveness Setac Testing Framewrk 7/17/

22 Cnclusins Large number f schedules in actr prgrams Only sme schedules might be imprtant t test It is nn-trivial t frce specific schedule and check assertins at apprpriate times Setac Sleeps - unreliable Latches hard t write/read Changes in the prgram under test- high cst Reliable Easy t write Very minimal changes in the prgram under test Open fr cllabratin Please try it: Setac Testing Framewrk 7/17/

Operating systems. Module 7 IPC (Interprocess communication) PART I. Tami Sorgente 1

Operating systems. Module 7 IPC (Interprocess communication) PART I. Tami Sorgente 1 Operating systems Mdule 7 IPC (Interprcess cmmunicatin) PART I Tami Srgente 1 INTERPROCESS COMMUNICATION Prcesses within a system may be independent r cperating Cperating prcess can affect r be affected