Clarify shared logging state and owning handle types

README.md

@@ -266,7 +266,7 @@ usability in multithreaded environments. The design centers on two key types:
 #### LogService (Value Type)
 ```nim
 type LogService* = object
-  global: GlobalLogService
+  shared: ptr SharedLogServiceState
 ```
 
 The *LogService* object is intended to support uses cases such as:
@@ -288,7 +288,7 @@ The *LogService* object is intended to support uses cases such as:
 #### ThreadLocalLogService (Reference Type)
 ```nim
 type ThreadLocalLogService* = ref object
-  shared: LogService
+  serviceHandle: LogService
   configVersion: int
   appenders: seq[LogAppender]
   thresholds: TableRef[string, Level]
@@ -321,7 +321,7 @@ during regular operation and support both the configuration functions of
 > *ThreadLocalLogService* objects should **never** be shared outside the
 > context of the thread in which they were initialized.
 
-#### GlobalLogService (Internal)
+#### SharedLogServiceState (Internal)
 
 Under the hood *LogService* holds a pointer to a manually allocated shared
 control block that serves as the single source of truth for logging
@@ -376,12 +376,12 @@ changes:
 ```nim
 proc ensureFreshness*(ls: ThreadLocalLogService) =
   # Cheap atomic check first
-  if ls.configVersion == ls.global.configVersion.load():
+  if ls.configVersion == ls.shared.configVersion.load():
     return  # No changes, return immediately
 
   # Only acquire lock and copy if versions differ
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
-    ls.configVersion = ls.global.configVersion.load
+    ls.configVersion = ls.shared.configVersion.load
     # Sync state...
 ```
 

src/namespaced_logging.nim

@@ -7,7 +7,7 @@ from std/logging import Level
 export Level
 
 type
-  GlobalLogServiceObj = object
+  SharedLogServiceState = object
     owners: Atomic[int]         # Lifetime of independently owned service handles
     configVersion: Atomic[int]  # To signal the need for threads to update
     lock: Lock                  # To protect reads/writes across threads
@@ -19,8 +19,6 @@ type
     errorHandler: ErrorHandlerFunc
     errorHandlerLock: Lock
 
-  GlobalLogService = ptr GlobalLogServiceObj
-
 
   ErrorHandlerFunc* =
     proc (err: ref Exception, msg: string) {.gcsafe,nimcall.}
@@ -30,13 +28,13 @@ type
     ## Copyable shared configuration handle with an atomic lifetime.
     ## Each thread must own its own handle; do not concurrently assign to or
     ## destroy the same handle variable while another thread reads it.
-    global: GlobalLogService
+    shared: ptr SharedLogServiceState
 
 
   ThreadLocalLogService* = ref object
     ## Cache confined to the thread that creates it. Appender clones must
     ## themselves respect thread ownership of custom state and formatters.
-    shared: LogService
+    serviceHandle: LogService
     configVersion: int
     appenders: seq[LogAppender]
     thresholds: TableRef[string, Level]
@@ -133,52 +131,52 @@ type
 
 const UninitializedConfigVersion = low(int)
 
-proc retainGlobal(gls: GlobalLogService) {.inline.} =
+proc retainSharedState(state: ptr SharedLogServiceState) {.inline.} =
-  if gls != nil:
+  if state != nil:
-    discard gls.owners.fetchAdd(1, moRelaxed)
+    discard state.owners.fetchAdd(1, moRelaxed)
 
 
-proc releaseGlobal(gls: GlobalLogService) =
+proc releaseSharedState(state: ptr SharedLogServiceState) =
-  if gls != nil and gls.owners.fetchSub(1, moAcquireRelease) == 1:
+  if state != nil and state.owners.fetchSub(1, moAcquireRelease) == 1:
     # The last owner has exclusive access to the control block. Its managed
     # fields must be destroyed explicitly because it is manually allocated.
-    `=destroy`(gls.appenders)
+    `=destroy`(state.appenders)
-    `=destroy`(gls.thresholds)
+    `=destroy`(state.thresholds)
-    deinitLock(gls.errorHandlerLock)
+    deinitLock(state.errorHandlerLock)
-    deinitLock(gls.lock)
+    deinitLock(state.lock)
-    deallocShared(gls)
+    deallocShared(state)
 
 
 proc `=destroy`*(ls: LogService) =
-  releaseGlobal(ls.global)
+  releaseSharedState(ls.shared)
 
 
 proc `=copy`*(dest: var LogService, source: LogService) =
-  if dest.global == source.global: return
+  if dest.shared == source.shared: return
-  retainGlobal(source.global)
+  retainSharedState(source.shared)
-  releaseGlobal(dest.global)
+  releaseSharedState(dest.shared)
-  dest.global = source.global
+  dest.shared = source.shared
 
 
 proc `=dup`*(source: LogService): LogService =
-  retainGlobal(source.global)
+  retainSharedState(source.shared)
-  result.global = source.global
+  result.shared = source.shared
 
 
 proc `=wasMoved`*(ls: var LogService) =
-  ls.global = nil
+  ls.shared = nil
 
 
 # The compiler-generated sink operation transfers the pointer after releasing
 # the destination. It does not retain the transferred owner.
-template global(ls: ThreadLocalLogService): untyped =
+template shared(ls: ThreadLocalLogService): untyped =
-  ls.shared.global
+  ls.serviceHandle.shared
 
 
 proc service*(ls: ThreadLocalLogService): LogService =
   ## Obtain an independently owned shared handle, e.g. to pass to a worker.
   ## This replaces copying ls[] when ThreadLocalLogService was ref LogService.
-  ls.shared
+  ls.serviceHandle
 
 
 var consoleLogging {.global.}: LogWriterThreadState[ConsoleMessage]
@@ -274,7 +272,7 @@ proc shutdownThreadedFileLogging() =
 proc ensureFreshness*(ls: var LogService) =
   ## A shared handle has no cached configuration. Retained for callers that
   ## previously refreshed LogService values; only local services need refresh.
-  if ls.global == nil:
+  if ls.shared == nil:
     raise newException(ValueError,
       "LogService not properly initialized. Use initLogService")
 
@@ -284,7 +282,7 @@ proc ensureFreshness*(ls: ThreadLocalLogService) =
   ## against the global log service definition. This uses an atomic version
   ## number to allow the check to be inexpensive, only incurring the more
   ## expensive copy operations if there are actual changes.
-  if ls.isNil or ls.global.isNil:
+  if ls.isNil or ls.shared.isNil:
     raise newException(ValueError,
       "LogService not properly initialized. Use initLogService to obtain a" &
       "properly initialized LogService object")
@@ -293,23 +291,24 @@ proc ensureFreshness*(ls: ThreadLocalLogService) =
   # particular, do not iterate a seq through a function-returned expression:
   # that can create an owning temporary and register its shared appender refs
   # with this thread's ORC cycle collector even while the lock is held.
-  let gls = ls.shared.global
+  let state = ls.serviceHandle.shared
-  if ls.configVersion == gls.configVersion.load(): return
+  if ls.configVersion == state.configVersion.load(): return
 
-  withLock gls.lock:
+  withLock state.lock:
-    ls.configVersion = gls.configVersion.load
+    ls.configVersion = state.configVersion.load
 
     ls.appenders = @[]
-    for a in gls.appenders: ls.appenders.add(clone(a))
+    for a in state.appenders: ls.appenders.add(clone(a))
 
     ls.thresholds = newTable[string, Level]()
-    for ns, t in pairs(gls.thresholds): ls.thresholds[ns] = t
+    for ns, t in pairs(state.thresholds): ls.thresholds[ns] = t
 
 
-proc initGlobalLogService(
+proc initSharedLogServiceState(
     rootLevel = lvlAll,
-    errorHandler = defaultErrorHandlerFunc): GlobalLogService =
+    errorHandler = defaultErrorHandlerFunc): ptr SharedLogServiceState =
-  result = cast[GlobalLogService](allocShared0(sizeof(GlobalLogServiceObj)))
+  result = cast[ptr SharedLogServiceState](
+    allocShared0(sizeof(SharedLogServiceState)))
   result.owners.store(1)
   result.configVersion.store(0)
   initLock(result.lock)
@@ -335,26 +334,26 @@ proc initLogService*(
   ## Multiple calls to *initLogService* will result in completely independent
   ## *LogService* objects with their own synchronized configuration and global
   ## state.
-  result.global = initGlobalLogService(rootLevel, errorHandler)
+  result.shared = initSharedLogServiceState(rootLevel, errorHandler)
 
 
 proc threadLocalRef*(ls: LogService): ThreadLocalLogService =
   ## Build a fresh cache in the calling thread, retaining only the shared
   ## handle. Never copy another thread's cached appender or threshold refs.
-  result = ThreadLocalLogService(shared: ls,
+  result = ThreadLocalLogService(serviceHandle: ls,
     configVersion: UninitializedConfigVersion)
   ensureFreshness(result)
 
 
 proc reportLoggingError(
-    gls: GlobalLogService,
+    state: ptr SharedLogServiceState,
     err: ref Exception,
     msg: string) =
 
   var handler: ErrorHandlerFunc
 
-  withLock gls.errorHandlerLock:
+  withLock state.errorHandlerLock:
-    handler = gls.errorHandler
+    handler = state.errorHandler
 
   if not handler.isNil:
     try: handler(err, msg)
@@ -398,23 +397,23 @@ proc setErrorHandler*(
 
   if errHandler.isNil: return
 
-  withLock ls.global.errorHandlerLock:
+  withLock ls.shared.errorHandlerLock:
-    ls.global.errorHandler = errHandler
+    ls.shared.errorHandler = errHandler
 
 
 proc setErrorHandler*(
     ls: ThreadLocalLogService,
     errHandler = defaultErrorHandlerFunc) {.gcsafe.} =
-  setErrorHandler(ls.shared, errHandler)
+  setErrorHandler(ls.serviceHandle, errHandler)
 
 
 proc setRootThreshold*(ls: var LogService, lvl: Level) {.gcsafe.} =
-  ls.global.rootLevel.store(lvl)
+  ls.shared.rootLevel.store(lvl)
-  ls.global.configVersion.atomicInc
+  ls.shared.configVersion.atomicInc
 
 
 proc setRootThreshold*(ls: ThreadLocalLogService, lvl: Level) {.gcsafe.} =
-  setRootThreshold(ls.shared, lvl)
+  setRootThreshold(ls.serviceHandle, lvl)
 
 
 func formatSimpleTextLog*(msg: LogMessage): string {.gcsafe.} = msg.msg
@@ -424,24 +423,24 @@ func formatJsonStructuredLog*(msg: LogMessage): string {.gcsafe.} = $(%msg)
 
 
 proc setThreshold*(ls: var LogService, scope: string, lvl: Level) {.gcsafe.} =
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
-    ls.global.thresholds[scope] = lvl
+    ls.shared.thresholds[scope] = lvl
-    ls.global.configVersion.atomicInc
+    ls.shared.configVersion.atomicInc
 
 
 proc setThreshold*(ls: ThreadLocalLogService, scope: string, lvl: Level) {.gcsafe.} =
-  setThreshold(ls.shared, scope, lvl)
+  setThreshold(ls.serviceHandle, scope, lvl)
   ensureFreshness(ls)
 
 
 proc setThresholds*(ls: var LogService, thresholds: TableRef[string, Level]) {.gcsafe.} =
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
-    for k,v in thresholds: ls.global.thresholds[k] = v
+    for k,v in thresholds: ls.shared.thresholds[k] = v
-    ls.global.configVersion.atomicInc
+    ls.shared.configVersion.atomicInc
 
 
 proc setThresholds*(ls: ThreadLocalLogService, thresholds: TableRef[string, Level]) {.gcsafe.} =
-  setThresholds(ls.shared, thresholds)
+  setThresholds(ls.serviceHandle, thresholds)
   ensureFreshness(ls)
 
 proc getLogger*(
@@ -479,8 +478,8 @@ proc getLogger*(
 
 
 proc appenders*(ls: var LogService): seq[LogAppender] {.gcsafe.} =
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
-    for a in ls.global.appenders: result.add(clone(a))
+    for a in ls.shared.appenders: result.add(clone(a))
 
 proc appenders*(ls: ThreadLocalLogService): seq[LogAppender] {.gcsafe.} =
   for a in ls.appenders: result.add(clone(a))
@@ -488,34 +487,34 @@ proc appenders*(ls: ThreadLocalLogService): seq[LogAppender] {.gcsafe.} =
 proc addAppender*(ls: var LogService, appender: LogAppender) {.gcsafe.} =
   ## Add a log appender to the shared configuration. Local services refresh
   ## their cached state on their next freshness check.
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
     var copiedAppender = clone(appender)
-    ls.global.appenders.add(copiedAppender)
+    ls.shared.appenders.add(copiedAppender)
-    ls.global.configVersion.atomicInc
+    ls.shared.configVersion.atomicInc
 
 
 proc addAppender*(ls: ThreadLocalLogService, appender: LogAppender) {.gcsafe.} =
-  addAppender(ls.shared, appender)
+  addAppender(ls.serviceHandle, appender)
   ensureFreshness(ls)
 
 
 proc clearAppenders*(ls: var LogService) {.gcsafe.} =
   ## Remove all shared appenders. Local services refresh their cached state
   ## on their next freshness check.
-  withLock ls.global.lock:
+  withLock ls.shared.lock:
-    ls.global.appenders = @[]
+    ls.shared.appenders = @[]
-    ls.global.configVersion.atomicInc
+    ls.shared.configVersion.atomicInc
 
 
 proc clearAppenders*(ls: ThreadLocalLogService) {.gcsafe.} =
-  clearAppenders(ls.shared)
+  clearAppenders(ls.serviceHandle)
 
 
 func getEffectiveThreshold(logger: Logger): Level {.gcsafe.} =
   ## Get the effective logging level threshold for a logger. This is the most
   ## specific level that is set for the logger or any of its parents. The root
   ## logger is used as the default if no other level is set.
-  result = logger.threadSvc.global.rootLevel.load
+  result = logger.threadSvc.shared.rootLevel.load
 
   # Check for exact match first
   if logger.threadSvc.thresholds.hasKey(logger.scope):
@@ -738,7 +737,7 @@ method appendLogMessage[T](
       raise newException(ValueError, "CustomLogAppender.appendLogMessage: doLogMessage is nil")
     else: cla.doLogMessage(cla.state, msg)
   except Exception:
-    ls.global.reportLoggingError(
+    ls.shared.reportLoggingError(
       getCurrentException(),
       "unable to append to CustomLogAppender")
 
@@ -822,7 +821,7 @@ method appendLogMessage(
     else:
       cla.appendLogMessageSingleThreaded(ls, msg)
   except Exception:
-    ls.global.reportLoggingError(
+    ls.shared.reportLoggingError(
       getCurrentException(),
       "unable to append to ConsoleLogAppender")
 
@@ -892,7 +891,7 @@ method appendLogMessage(
     else:
       fla.appendLogMessageSingleThreaded(ls, msg)
   except Exception:
-    ls.global.reportLoggingError(
+    ls.shared.reportLoggingError(
       getCurrentException(),
       "unable to append to FileLogAppender")
 
@@ -958,22 +957,22 @@ when isMainModule:
   import std/[files, tempfiles, unittest]
   import ./namespaced_logging/testutil
 
-  suite "GlobalLogService Initialization":
+  suite "LogService Initialization":
 
     test "initLogService creates valid service":
       let ls = initLogService()
       let local = ls.threadLocalRef()
       check:
-        ls.global != nil
+        ls.shared != nil
-        ls.global.owners.load() == 2
+        ls.shared.owners.load() == 2
-        ls.global.configVersion.load() == 0
+        ls.shared.configVersion.load() == 0
-        ls.global.rootLevel.load() == lvlAll
+        ls.shared.rootLevel.load() == lvlAll
         local.configVersion >= 0
-        local.configVersion == ls.global.configVersion.load
+        local.configVersion == ls.shared.configVersion.load
 
     test "initLogService with custom root level":
       let ls = initLogService(lvlInfo)
-      check ls.global.rootLevel.load() == lvlInfo
+      check ls.shared.rootLevel.load() == lvlInfo
 
     test "threadLocalRef builds independent caches for an unchanged service":
       var service = initLogService()
@@ -982,7 +981,7 @@ when isMainModule:
       let first = service.threadLocalRef()
       let second = service.threadLocalRef()
       check:
-        first.global == second.global
+        first.shared == second.shared
         first.configVersion == second.configVersion
         cast[pointer](first.thresholds) != cast[pointer](second.thresholds)
         first.thresholds["worker"] == second.thresholds["worker"]
@@ -996,7 +995,7 @@ when isMainModule:
 
     test "setRootThreshold updates level":
       ls.setRootThreshold(lvlError)
-      check ls.global.rootLevel.load() == lvlError
+      check ls.shared.rootLevel.load() == lvlError
 
     test "setThreshold adds namespace threshold":
       ls.setThreshold("api", lvlWarn)
@@ -1004,9 +1003,9 @@ when isMainModule:
 
     test "ensureFreshness syncs configuration":
       # Modify global state directly
-      withLock ls.global.lock:
+      withLock ls.shared.lock:
-        ls.global.thresholds["test"] = lvlError
+        ls.shared.thresholds["test"] = lvlError
-        ls.global.configVersion.atomicInc()
+        ls.shared.configVersion.atomicInc()
 
       # Local state should be out of sync
       check not ls.thresholds.hasKey("test")
@@ -1021,18 +1020,18 @@ when isMainModule:
       ls.setThreshold("api", lvlWarn)
 
       check:
-        ls.configVersion == ls.global.configVersion.load
+        ls.configVersion == ls.shared.configVersion.load
         ls.configVersion != ls2.configVersion
-        ls2.configVersion != ls.global.configVersion.load
+        ls2.configVersion != ls.shared.configVersion.load
         ls.thresholds["api"] == lvlWarn
-        ls.global.thresholds["api"] == lvlWarn
+        ls.shared.thresholds["api"] == lvlWarn
         not ls2.thresholds.contains("api")
 
       ls2.ensureFreshness()
 
       check:
         ls.configVersion == ls2.configVersion
-        ls2.configVersion == ls.global.configVersion.load
+        ls2.configVersion == ls.shared.configVersion.load
         ls2.thresholds["api"] == lvlWarn
 
     test "ensureFreshness syncs configuration across threads":
@@ -1083,13 +1082,13 @@ when isMainModule:
       joinThreads(tA, tB)
 
     test "configuration version incrementing":
-      let initialVersion = ls.global.configVersion.load()
+      let initialVersion = ls.shared.configVersion.load()
 
       ls.setRootThreshold(lvlWarn)
-      check ls.global.configVersion.load() > initialVersion
+      check ls.shared.configVersion.load() > initialVersion
 
       ls.setThreshold("test", lvlError)
-      check ls.global.configVersion.load() > initialVersion + 1
+      check ls.shared.configVersion.load() > initialVersion + 1
 
 
   suite "Logger Creation and Usage":