nim-namespaced-logging/tests/thread_safety.nim

## Run each scenario in its own ThreadSanitizer-instrumented process.
## Success means no race was reported; a crash is not required to expose UB.
import std/[atomics, locks, os]
import ../src/namespaced_logging

const iterations = 1_000
var start: Atomic[bool]
var cloneLock: Lock
var ready: Atomic[int]

proc awaitStart() =
  while not start.load():
    discard

proc serviceWorker(service: LogService) {.thread.} =
  awaitStart()
  for i in 0 ..< iterations:
    let local = service.threadLocalRef()
    let logger = local.getLogger("worker")
    doAssert logger.isEnabled(lvlInfo)

proc independentWorker() {.thread.} =
  awaitStart()
  var service = initLogService()
  service.setThreshold("worker", lvlInfo)
  for i in 0 ..< iterations:
    let local = service.threadLocalRef()
    let logger = local.getLogger("worker")
    doAssert logger.isEnabled(lvlInfo)

type
  AppenderLifetimes = object
    created, destroyed: Atomic[int]
  TrackedAppenderObj = object of LogAppender
    lifetimes: ptr AppenderLifetimes
  TrackedAppender = ref TrackedAppenderObj

proc `=destroy`(app: TrackedAppenderObj) =
  if app.lifetimes != nil:
    app.lifetimes.destroyed.atomicInc()
  `=destroy`(app.namespace)

proc trackedAppender(lifetimes: ptr AppenderLifetimes): TrackedAppender =
  lifetimes.created.atomicInc()
  TrackedAppender(lifetimes: lifetimes)

method clone(app: TrackedAppender): LogAppender {.gcsafe.} =
  trackedAppender(app.lifetimes)

proc lifetimeWorker(source: ptr LogService) {.thread.} =
  # Borrow the original only until this thread owns a local service. The
  # readiness barrier lets the parent release it before we continue.
  let local = source[].threadLocalRef()
  ready.atomicInc()
  awaitStart()
  for i in 0 ..< iterations:
    var handle = local.service
    var copied = handle
    handle = LogService()
    var moved = move(copied)
    moved.setThreshold("worker", lvlInfo)
    let nested = moved.threadLocalRef()
    doAssert nested.getLogger("worker").isEnabled(lvlInfo)
  # Local caches and the last shared owner are destroyed on worker threads.

proc reconfigureWorker(service: LogService) {.thread.} =
  var handle = service
  let local = service.threadLocalRef()
  awaitStart()
  for i in 0 ..< iterations:
    handle.setThreshold("worker", lvlInfo)
    local.ensureFreshness()
    doAssert local.getLogger("worker").isEnabled(lvlInfo)

type
  CustomState = ref object
    value: int
  StatefulAppender = CustomLogAppender[CustomState]

proc ignoreMessage(state: CustomState, msg: LogMessage) {.gcsafe, noconv.} =
  discard

proc stateWorker(source: ptr StatefulAppender) {.thread.} =
  awaitStart()
  for i in 0 ..< iterations:
    var copied: StatefulAppender
    withLock cloneLock:
      copied = StatefulAppender(clone(source[]))
    doAssert copied.state.value == 42

proc makeFormatter(prefix: string): LogMessageFormatter =
  result = proc(msg: LogMessage): string {.gcsafe.} = prefix & msg.msg

proc formatterWorker(source: ptr ConsoleLogAppender) {.thread.} =
  awaitStart()
  # This formatter only needs msg. Avoid clock/timezone initialization so
  # sanitizer diagnostics identify closure ownership rather than libc state.
  let msg = LogMessage(msg: "message")
  for i in 0 ..< iterations:
    var copied: ConsoleLogAppender
    withLock cloneLock:
      copied = ConsoleLogAppender(clone(source[]))
    doAssert copied.formatter(msg) == "prefix: message"

proc main() =
  doAssert paramCount() == 1
  initLock(cloneLock)
  defer: deinitLock(cloneLock)
  case paramStr(1)
  of "independent":
    var workers: array[4, Thread[void]]
    for i in 0 ..< workers.len:
      createThread(workers[i], independentWorker)
    start.store(true)
    joinThreads(workers)
  of "service":
    var service = initLogService()
    service.setThreshold("worker", lvlInfo)
    service.addAppender(initConsoleLogAppender())
    var workers: array[4, Thread[LogService]]
    for i in 0 ..< workers.len:
      createThread(workers[i], serviceWorker, service)
    # No parent-side copying/configuration changes overlap the workers.
    # The parent retains service and all thread argument storage until join.
    start.store(true)
    joinThreads(workers)
  of "custom-state":
    var source = initCustomLogAppender(CustomState(value: 42), ignoreMessage)
    var workers: array[4, Thread[ptr StatefulAppender]]
    for i in 0 ..< workers.len:
      createThread(workers[i], stateWorker, addr source)
    start.store(true)
    joinThreads(workers)
  of "service-lifetime":
    var lifetimes: AppenderLifetimes
    var service = initLogService()
    block:
      let original = trackedAppender(addr lifetimes)
      service.addAppender(original)
    var workers: array[4, Thread[ptr LogService]]
    for i in 0 ..< workers.len:
      createThread(workers[i], lifetimeWorker, addr service)
    while ready.load() != workers.len:
      discard
    # Thread arguments contain only a borrowed pointer, so there are no hidden
    # owning handles in Thread.data keeping the control block alive here.
    service = LogService()
    start.store(true)
    joinThreads(workers)
    doAssert lifetimes.created.load() > workers.len
    doAssert lifetimes.destroyed.load() == lifetimes.created.load()
  of "service-reconfigure":
    var service = initLogService()
    service.addAppender(initConsoleLogAppender())
    var workers: array[4, Thread[LogService]]
    for i in 0 ..< workers.len:
      createThread(workers[i], reconfigureWorker, service)
    start.store(true)
    joinThreads(workers)
  of "formatter":
    var source = initConsoleLogAppender()
    source.formatter = makeFormatter("prefix: ")
    var workers: array[4, Thread[ptr ConsoleLogAppender]]
    for i in 0 ..< workers.len:
      createThread(workers[i], formatterWorker, addr source)
    start.store(true)
    joinThreads(workers)
  else:
    raise newException(ValueError, "unknown thread safety scenario")

# The pointer-based scenarios borrow immutable source appenders whose owner
# outlives all workers. This isolates clone/destruction races from LogService
# copying and from ordinary unsynchronized application-state mutation.
main()