Add option to memory profiling and limit page cache (#158)

tap/settings.go

@@ -1,5 +1,18 @@
 package tap
 
+import (
+	"os"
+	"strconv"
+)
+
+const (
+	MemoryProfilingEnabledEnvVarName          = "MEMORY_PROFILING_ENABLED"
+	MaxBufferedPagesTotalEnvVarName           = "MAX_BUFFERED_PAGES_TOTAL"
+	MaxBufferedPagesPerConnectionEnvVarName   = "MAX_BUFFERED_PAGES_PER_CONNECTION"
+	MaxBufferedPagesTotalDefaultValue         = 5000
+	MaxBufferedPagesPerConnectionDefaultValue = 5000
+)
+
 type globalSettings struct {
 	filterPorts       []int
 	filterAuthorities []string
@@ -29,3 +42,23 @@ func GetFilterIPs() []string {
 	copy(addresses, gSettings.filterAuthorities)
 	return addresses
 }
+
+func GetMaxBufferedPagesTotal() int {
+	valueFromEnv, err := strconv.Atoi(os.Getenv(MaxBufferedPagesTotalEnvVarName))
+	if err != nil {
+		return MaxBufferedPagesTotalDefaultValue
+	}
+	return valueFromEnv
+}
+
+func GetMaxBufferedPagesPerConnection() int {
+	valueFromEnv, err := strconv.Atoi(os.Getenv(MaxBufferedPagesPerConnectionEnvVarName))
+	if err != nil {
+		return MaxBufferedPagesPerConnectionDefaultValue
+	}
+	return valueFromEnv
+}
+
+func GetMemoryProfilingEnabled() bool {
+	return os.Getenv(MemoryProfilingEnabledEnvVarName) == "1"
+}