logging: add Multi

Excluding go version 1.9 as only go version1.13 onwards are supported.

.travis.yml

@@ -1,8 +1,17 @@
+arch:
+   - amd64
+   - ppc64le
 sudo: false
 language: go
 go:
   - tip
   - 1.9
+jobs:
+ exclude:
+  - go: 1.9
+    arch: amd64
+  - go: 1.9
+    arch: ppc64le
 script: 
   - go get golang.org/x/lint/golint
   - go get golang.org/x/tools/cmd/cover

config/config.go

@@ -1,6 +1,11 @@
 // Package config implements a simple global configuration system that
 // supports a file with key=value pairs and environment variables. Note
 // that the config system is global.
+//
+// This package is intended to be used for small daemons: some configuration
+// file is optionally populated at program start, then this is used to
+// transparently look up configuration values from either that file or the
+// environment.
 package config
 
 import (
@@ -82,3 +87,24 @@ func GetDefault(key, def string) string {
 	}
 	return def
 }
+
+// Require retrieves a value from either a configuration file or the
+// environment. If the key isn't present, it will call log.Fatal, printing
+// the missing key.
+func Require(key string) string {
+	if v, ok := vars[key]; ok {
+		return v
+	}
+
+	v, ok := os.LookupEnv(prefix + key)
+	if !ok {
+		var envMessage string
+		if prefix != "" {
+			envMessage = " (note: looked for the key " + prefix + key
+			envMessage += " in the local env)"
+		}
+		log.Fatalf("missing required configuration value %s%s", key, envMessage)
+	}
+
+	return v
+}

logging/log.go

@@ -277,3 +277,60 @@ func (lw *LogWriter) SetLevel(l Level) {
 
 // Close is a no-op that satisfies the Logger interface.
 func (lw *LogWriter) Close() error { return nil }
+
+// Multi allows combining of loggers.
+type Multi struct {
+	loggers []Logger
+}
+
+func NewMulti(loggers ...Logger) *Multi {
+	return &Multi{loggers: loggers}
+}
+
+func (m *Multi) Debug(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Debug(actor, event, attrs)
+	}
+}
+
+func (m *Multi) Info(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Info(actor, event, attrs)
+	}
+}
+
+func (m *Multi) Warn(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Warn(actor, event, attrs)
+	}
+}
+
+func (m *Multi) Error(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Error(actor, event, attrs)
+	}
+}
+
+func (m *Multi) Critical(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Critical(actor, event, attrs)
+	}
+}
+
+func (m *Multi) Fatal(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.Fatal(actor, event, attrs)
+	}
+}
+
+func (m *Multi) FatalCode(exitcode int, actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.FatalCode(exitcode, actor, event, attrs)
+	}
+}
+
+func (m *Multi) FatalNoDie(actor, event string, attrs map[string]string) {
+	for _, l := range m.loggers {
+		l.FatalNoDie(actor, event, attrs)
+	}
+}

rand/rand.go

@@ -0,0 +1,49 @@
+// Package rand contains utilities for interacting with math/rand, including
+// seeding from a random sed.
+package rand
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	mrand "math/rand"
+)
+
+// CryptoUint64 generates a cryptographically-secure 64-bit integer.
+func CryptoUint64() (uint64, error) {
+	bs := make([]byte, 8)
+	_, err := rand.Read(bs)
+	if err != nil {
+		return 0, err
+	}
+
+	return binary.BigEndian.Uint64(bs), nil
+}
+
+// Seed initialises the non-cryptographic PRNG with a random,
+// cryptographically secure value. This is done just as a good
+// way to make this random. The returned 64-bit value is the seed.
+func Seed() (uint64, error) {
+	seed, err := CryptoUint64()
+	if err != nil {
+		return 0, err
+	}
+
+	// NB: this is permitted.
+	mrand.Seed(int64(seed))
+	return seed, nil
+}
+
+// Int is a wrapper for math.Int so only one package needs to be imported.
+func Int() int {
+	return mrand.Int()
+}
+
+// Intn is a wrapper for math.Intn so only one package needs to be imported.
+func Intn(max int) int {
+	return mrand.Intn(max)
+}
+
+// Intn2 returns a random value between min and max, inclusive.
+func Intn2(min, max int) int {
+	return Intn(max-min) + min
+}

rand/rand_test.go

@@ -0,0 +1,74 @@
+package rand
+
+import (
+	"fmt"
+	mrand "math/rand"
+	"testing"
+)
+
+func TestCryptoUint64(t *testing.T) {
+	n1, err := CryptoUint64()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	n2, err := CryptoUint64()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// This has such a low chance of occurring that it's likely to be
+	// indicative of a bad CSPRNG.
+	if n1 == n2 {
+		t.Fatalf("repeated random uint64s: %d", n1)
+	}
+}
+
+func TestIntn(t *testing.T) {
+	expected := []int{3081, 4887, 4847, 1059, 3081}
+	mrand.Seed(1)
+	for i := 0; i < 5; i++ {
+		n := Intn2(1000, 5000)
+
+		if n != expected[i] {
+			fmt.Printf("invalid sequence at %d: expected %d, have %d", i, expected[i], n)
+		}
+	}
+}
+
+func TestSeed(t *testing.T) {
+	seed1, err := Seed()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var seed2 uint64
+	n1 := Int()
+	tries := 0
+
+	for {
+		seed2, err = Seed()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if seed1 != seed2 {
+			break
+		}
+
+		tries++
+
+		if tries > 3 {
+			t.Fatal("can't generate two unique seeds")
+		}
+	}
+
+	n2 := Int()
+
+	// Again, this not impossible, merely statistically improbably and a
+	// potential canary for RNG issues.
+	if n1 == n2 {
+		t.Fatalf("repeated integers fresh from two unique seeds: %d/%d -> %d",
+			seed1, seed2, n1)
+	}
+}