tfsdklog: Introduce outside context level checks for logging functions

.changes/unreleased/ENHANCEMENTS-20230418-201952.yaml

@@ -0,0 +1,6 @@
+kind: ENHANCEMENTS
+body: 'tfsdklog: Improved logging performance 20x when logs would be skipped due to
+  logging level'
+time: 2023-04-18T20:19:52.460485-04:00
+custom:
+  Issue: "149"

tfsdklog/levels.go

@@ -0,0 +1,81 @@
+package tfsdklog
+
+import (
+	"sync"
+
+	"github.com/hashicorp/go-hclog"
+)
+
+var (
+	// rootLevel stores the effective level of the root SDK logger during
+	// NewRootSDKLogger where the value is deterministically chosen based on
+	// environment variables, etc. This call generally happens with each new
+	// provider RPC request. If the environment variable values changed during
+	// runtime between calls, then inflight provider requests checking this
+	// value would receive the most up-to-date value which would potentially
+	// differ with the actual in-context logger level. This tradeoff would only
+	// effect the inflight requests and should not be an overall performance
+	// concern in the case of this level causing more context checks until the
+	// request is over.
+	rootLevel hclog.Level = hclog.NoLevel
+
+	// rootLevelMutex is a read-write mutex that protects rootLevel from
+	// triggering the data race detector.
+	rootLevelMutex = sync.RWMutex{}
+
+	// subsystemLevels stores the effective level of all subsystem SDK loggers
+	// during NewSubsystem where the value is deterministically chosen based on
+	// environment variables, etc. This call generally happens with each new
+	// provider RPC request. If the environment variable values changed during
+	// runtime between calls, then inflight provider requests checking this
+	// value would receive the most up-to-date value which would potentially
+	// differ with the actual in-context logger level. This tradeoff would only
+	// effect the inflight requests and should not be an overall performance
+	// concern in the case of this level causing more context checks until the
+	// request is over.
+	subsystemLevels map[string]hclog.Level = make(map[string]hclog.Level)
+
+	// subsystemLevelsMutex is a read-write mutex that protects the
+	// subsystemLevels map from concurrent read and write panics.
+	subsystemLevelsMutex = sync.RWMutex{}
+)
+
+// subsystemWouldLog returns true if the subsystem SDK logger would emit a log
+// at the given level. This is performed outside the context-based logger for
+// performance.
+func subsystemWouldLog(subsystem string, level hclog.Level) bool {
+	subsystemLevelsMutex.RLock()
+
+	setLevel, ok := subsystemLevels[subsystem]
+
+	subsystemLevelsMutex.RUnlock()
+
+	if !ok {
+		return false
+	}
+
+	return wouldLog(setLevel, level)
+}
+
+// rootWouldLog returns true if the root SDK logger would emit a log at the
+// given level. This is performed outside the context-based logger for
+// performance.
+func rootWouldLog(level hclog.Level) bool {
+	rootLevelMutex.RLock()
+
+	setLevel := rootLevel
+
+	rootLevelMutex.RUnlock()
+
+	return wouldLog(setLevel, level)
+}
+
+// wouldLog returns true if the set level would emit a log at the given
+// level. This is performed outside the context-based logger for performance.
+func wouldLog(setLevel, checkLevel hclog.Level) bool {
+	if checkLevel == hclog.Off {
+		return false
+	}
+
+	return checkLevel >= setLevel
+}