Thread-safety for the registry

chronicles/topics_registry.nim

@@ -1,4 +1,4 @@
-import macros, tables
+import locks, macros, tables
 from options import LogLevel
 
 type
@@ -16,31 +16,45 @@ type
     topicStatesTable*: Table[string, ptr Topic]
 
 var
-  gActiveLogLevel: LogLevel
+  registryLock: Lock
-  gTotalEnabledTopics: int
+  gActiveLogLevel       {.guard: registryLock.}: LogLevel
-  gTotalRequiredTopics: int
+  gTotalEnabledTopics   {.guard: registryLock.}: int
-  gTopicStates = initTable[string, ptr Topic]()
+  gTotalRequiredTopics  {.guard: registryLock.}: int
+  gTopicStates          {.guard: registryLock.} = initTable[string, ptr Topic]()
+  mainThreadId = getThreadId()
+
+initLock(registryLock)
+
+template lockRegistry(body: untyped) =
+  when compileOption("threads"):
+    withLock registryLock: body
+  else:
+    body
 
 proc setLogLevel*(lvl: LogLevel) =
+  lockRegistry:
     gActiveLogLevel = lvl
 
 proc clearTopicsRegistry* =
+  lockRegistry:
     gTotalEnabledTopics = 0
     gTotalRequiredTopics = 0
     for val in gTopicStates.values:
       val.state = Normal
 
-iterator topicStates*: (string, TopicState) =
-  for name, topic in gTopicStates:
-    yield (name, topic.state)
-
 proc registerTopic*(name: string, topic: ptr Topic): ptr Topic =
+  # As long as sequences are thread-local, modifying the `gTopicStates`
+  # sequence must be done only from the main thread:
+  doAssert getThreadId() == mainThreadId
+
+  lockRegistry:
     gTopicStates[name] = topic
     return topic
 
 proc setTopicState*(name: string,
                     newState: TopicState,
                     logLevel = LogLevel.NONE): bool =
+  lockRegistry:
     if not gTopicStates.hasKey(name):
       return false
 
@@ -63,6 +77,7 @@ proc setTopicState*(name: string,
 
 proc topicsMatch*(logStmtLevel: LogLevel,
                   logStmtTopics: openarray[ptr Topic]): bool =
+  lockRegistry:
     var
       hasEnabledTopics = gTotalEnabledTopics > 0
       enabledTopicsMatch = false
@@ -88,5 +103,6 @@ proc topicsMatch*(logStmtLevel: LogLevel,
     return normalTopicsMatch
 
 proc getTopicState*(topic: string): ptr Topic =
+  lockRegistry:
     return gTopicStates.getOrDefault(topic)