[feature] simpler cache size configuration (#2051)

* add automatic cache max size generation based on ratios of a singular fixed memory target

Signed-off-by: kim <grufwub@gmail.com>

* remove now-unused cache max-size config variables

Signed-off-by: kim <grufwub@gmail.com>

* slight ratio tweak

Signed-off-by: kim <grufwub@gmail.com>

* remove unused visibility config var

Signed-off-by: kim <grufwub@gmail.com>

* add secret little ratio config trick

Signed-off-by: kim <grufwub@gmail.com>

* fixed a word

Signed-off-by: kim <grufwub@gmail.com>

* update cache library to remove use of TTL in result caches + slice cache

Signed-off-by: kim <grufwub@gmail.com>

* update other cache usages to use correct interface

Signed-off-by: kim <grufwub@gmail.com>

* update example config to explain the cache memory target

Signed-off-by: kim <grufwub@gmail.com>

* update env parsing test with new config values

Signed-off-by: kim <grufwub@gmail.com>

* do some ratio twiddling

Signed-off-by: kim <grufwub@gmail.com>

* add missing header

* update envparsing with latest defaults

Signed-off-by: kim <grufwub@gmail.com>

* update size calculations to take into account result cache, simple cache and extra map overheads

Signed-off-by: kim <grufwub@gmail.com>

* tweak the ratios some more

Signed-off-by: kim <grufwub@gmail.com>

* more nan rampaging

Signed-off-by: kim <grufwub@gmail.com>

* fix envparsing script

Signed-off-by: kim <grufwub@gmail.com>

* update cache library, add sweep function to keep caches trim

Signed-off-by: kim <grufwub@gmail.com>

* sweep caches once a minute

Signed-off-by: kim <grufwub@gmail.com>

* add a regular job to sweep caches and keep under 80% utilisation

Signed-off-by: kim <grufwub@gmail.com>

* remove dead code

Signed-off-by: kim <grufwub@gmail.com>

* add new size library used to libraries section of readme

Signed-off-by: kim <grufwub@gmail.com>

* add better explanations for the mem-ratio numbers

Signed-off-by: kim <grufwub@gmail.com>

* update go-cache

Signed-off-by: kim <grufwub@gmail.com>

* library version bump

Signed-off-by: kim <grufwub@gmail.com>

* update cache.result{} size model estimation

Signed-off-by: kim <grufwub@gmail.com>

---------

Signed-off-by: kim <grufwub@gmail.com>

vendor/github.com/DmitriyVTitov/size/size.go

@@ -0,0 +1,142 @@
+// Package size implements run-time calculation of size of the variable.
+// Source code is based on "binary.Size()" function from Go standard library.
+// size.Of() omits size of slices, arrays and maps containers itself (24, 24 and 8 bytes).
+// When counting maps separate calculations are done for keys and values.
+package size
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// Of returns the size of 'v' in bytes.
+// If there is an error during calculation, Of returns -1.
+func Of(v interface{}) int {
+	// Cache with every visited pointer so we don't count two pointers
+	// to the same memory twice.
+	cache := make(map[uintptr]bool)
+	return sizeOf(reflect.Indirect(reflect.ValueOf(v)), cache)
+}
+
+// sizeOf returns the number of bytes the actual data represented by v occupies in memory.
+// If there is an error, sizeOf returns -1.
+func sizeOf(v reflect.Value, cache map[uintptr]bool) int {
+	switch v.Kind() {
+
+	case reflect.Array:
+		sum := 0
+		for i := 0; i < v.Len(); i++ {
+			s := sizeOf(v.Index(i), cache)
+			if s < 0 {
+				return -1
+			}
+			sum += s
+		}
+
+		return sum + (v.Cap()-v.Len())*int(v.Type().Elem().Size())
+
+	case reflect.Slice:
+		// return 0 if this node has been visited already
+		if cache[v.Pointer()] {
+			return 0
+		}
+		cache[v.Pointer()] = true
+
+		sum := 0
+		for i := 0; i < v.Len(); i++ {
+			s := sizeOf(v.Index(i), cache)
+			if s < 0 {
+				return -1
+			}
+			sum += s
+		}
+
+		sum += (v.Cap() - v.Len()) * int(v.Type().Elem().Size())
+
+		return sum + int(v.Type().Size())
+
+	case reflect.Struct:
+		sum := 0
+		for i, n := 0, v.NumField(); i < n; i++ {
+			s := sizeOf(v.Field(i), cache)
+			if s < 0 {
+				return -1
+			}
+			sum += s
+		}
+
+		// Look for struct padding.
+		padding := int(v.Type().Size())
+		for i, n := 0, v.NumField(); i < n; i++ {
+			padding -= int(v.Field(i).Type().Size())
+		}
+
+		return sum + padding
+
+	case reflect.String:
+		s := v.String()
+		hdr := (*reflect.StringHeader)(unsafe.Pointer(&s))
+		if cache[hdr.Data] {
+			return int(v.Type().Size())
+		}
+		cache[hdr.Data] = true
+		return len(s) + int(v.Type().Size())
+
+	case reflect.Ptr:
+		// return Ptr size if this node has been visited already (infinite recursion)
+		if cache[v.Pointer()] {
+			return int(v.Type().Size())
+		}
+		cache[v.Pointer()] = true
+		if v.IsNil() {
+			return int(reflect.New(v.Type()).Type().Size())
+		}
+		s := sizeOf(reflect.Indirect(v), cache)
+		if s < 0 {
+			return -1
+		}
+		return s + int(v.Type().Size())
+
+	case reflect.Bool,
+		reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Int, reflect.Uint,
+		reflect.Chan,
+		reflect.Uintptr,
+		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128,
+		reflect.Func:
+		return int(v.Type().Size())
+
+	case reflect.Map:
+		// return 0 if this node has been visited already (infinite recursion)
+		if cache[v.Pointer()] {
+			return 0
+		}
+		cache[v.Pointer()] = true
+		sum := 0
+		keys := v.MapKeys()
+		for i := range keys {
+			val := v.MapIndex(keys[i])
+			// calculate size of key and value separately
+			sv := sizeOf(val, cache)
+			if sv < 0 {
+				return -1
+			}
+			sum += sv
+			sk := sizeOf(keys[i], cache)
+			if sk < 0 {
+				return -1
+			}
+			sum += sk
+		}
+		// Include overhead due to unused map buckets.  10.79 comes
+		// from https://golang.org/src/runtime/map.go.
+		return sum + int(v.Type().Size()) + int(float64(len(keys))*10.79)
+
+	case reflect.Interface:
+		return sizeOf(v.Elem(), cache) + int(v.Type().Size())
+
+	}
+
+	return -1
+}