feat: Add ability to set Redis database and prefix in config (#614)

## Which problem is this PR solving?

In a blue/green deployment model, two refinery clusters might want to
share the same instance of redis. It's also possible that multiple apps
want to share one redis. This permits that by:
- allowing the redis "database" (an integer from 0-15) to be specified
in the configuration
- allowing the redis "prefix" (a string used in the name of the keys
stored in redis) to be set as well. It already existed but was hardcoded
to "refinery".

## Short description of the changes

- Add RedisDatabase and RedisPrefix to the PeerManagement section of
config.
- Add tests
- Add documentation

Fixes #544

config/config.go

@@ -57,6 +57,13 @@ type Config interface {
 	// management.
 	GetRedisPassword() (string, error)
 
+	// GetRedisPrefix returns the prefix string used in the keys for peer
+	// management.
+	GetRedisPrefix() string
+
+	// GetRedisDatabase returns the ID of the Redis database to use for peer management.
+	GetRedisDatabase() int
+
 	// GetUseTLS returns true when TLS must be enabled to dial the Redis instance to
 	// use for peer management.
 	GetUseTLS() (bool, error)

config/config_test.go

@@ -379,6 +379,8 @@ func TestPeerManagementType(t *testing.T) {
 	[PeerManagement]
 		Type = "redis"
 		Peers = ["http://refinery-1231:8080"]
+		RedisPrefix = "testPrefix"
+		RedisDatabase = 9
 	`, "")
 	defer os.Remove(rules)
 	defer os.Remove(config)
@@ -389,6 +391,14 @@ func TestPeerManagementType(t *testing.T) {
 	if d, _ := c.GetPeerManagementType(); d != "redis" {
 		t.Error("received", d, "expected", "redis")
 	}
+
+	if s := c.GetRedisPrefix(); s != "testPrefix" {
+		t.Error("received", s, "expected", "testPrefix")
+	}
+
+	if db := c.GetRedisDatabase(); db != 9 {
+		t.Error("received", db, "expected", 9)
+	}
 }
 
 func TestAbsentTraceKeyField(t *testing.T) {

config/file_config.go

@@ -100,6 +100,8 @@ type PeerManagementConfig struct {
 	RedisHost               string
 	RedisUsername           string
 	RedisPassword           string
+	RedisPrefix             string `validate:"required"`
+	RedisDatabase           int    `validate:"gte=0,lte=15"`
 	UseTLS                  bool
 	UseTLSInsecure          bool
 	IdentifierInterfaceName string
@@ -152,6 +154,7 @@ func NewConfig(config, rules string, errorCallback func(error)) (Config, error)
 	c.SetDefault("CompressPeerCommunication", true)
 	c.SetDefault("APIKeys", []string{"*"})
 	c.SetDefault("PeerManagement.Peers", []string{"http://127.0.0.1:8081"})
+	c.SetDefault("PeerManagement.RedisPrefix", "refinery")
 	c.SetDefault("PeerManagement.Type", "file")
 	c.SetDefault("PeerManagement.UseTLS", false)
 	c.SetDefault("PeerManagement.UseTLSInsecure", false)
@@ -507,13 +510,27 @@ func (f *fileConfig) GetRedisUsername() (string, error) {
 	return f.config.GetString("PeerManagement.RedisUsername"), nil
 }
 
+func (f *fileConfig) GetRedisPrefix() string {
+	f.mux.RLock()
+	defer f.mux.RUnlock()
+
+	return f.config.GetString("PeerManagement.RedisPrefix")
+}
+
 func (f *fileConfig) GetRedisPassword() (string, error) {
 	f.mux.RLock()
 	defer f.mux.RUnlock()
 
 	return f.config.GetString("PeerManagement.RedisPassword"), nil
 }
 
+func (f *fileConfig) GetRedisDatabase() int {
+	f.mux.RLock()
+	defer f.mux.RUnlock()
+
+	return f.config.GetInt("PeerManagement.RedisDatabase")
+}
+
 func (f *fileConfig) GetUseTLS() (bool, error) {
 	f.mux.RLock()
 	defer f.mux.RUnlock()

config/mock.go

@@ -42,6 +42,8 @@ type MockConfig struct {
 	GetRedisUsernameVal           string
 	GetRedisPasswordErr           error
 	GetRedisPasswordVal           string
+	GetRedisDatabaseVal           int
+	GetRedisPrefixVal             string
 	GetUseTLSErr                  error
 	GetUseTLSVal                  bool
 	GetUseTLSInsecureErr          error
@@ -224,6 +226,20 @@ func (m *MockConfig) GetRedisPassword() (string, error) {
 	return m.GetRedisPasswordVal, m.GetRedisPasswordErr
 }
 
+func (m *MockConfig) GetRedisPrefix() string {
+	m.Mux.RLock()
+	defer m.Mux.RUnlock()
+
+	return m.GetRedisPrefixVal
+}
+
+func (m *MockConfig) GetRedisDatabase() int {
+	m.Mux.RLock()
+	defer m.Mux.RUnlock()
+
+	return m.GetRedisDatabaseVal
+}
+
 func (m *MockConfig) GetUseTLS() (bool, error) {
 	m.Mux.RLock()
 	defer m.Mux.RUnlock()

config_complete.toml

@@ -219,6 +219,20 @@ Metrics = "honeycomb"
 # Not eligible for live reload.
 # RedisPassword = ""
 
+# RedisPrefix is a string used as a prefix for the keys in redis while storing
+# the peer membership. It might be useful to set this in any situation where
+# multiple refinery clusters or multiple applications want to share a single
+# Redis instance. It may not be blank.
+# Default = "refinery"
+# RedisPrefix = "customPrefix"
+
+# RedisDatabase is an integer from 0-15 indicating the database number to use
+# for the Redis instance storing the peer membership. It might be useful to set
+# this in any situation where multiple refinery clusters or multiple
+# applications want to share a single Redis instance.
+# Default = 0
+# RedisDatabase = 1
+
 # UseTLS enables TLS when connecting to redis for peer cluster membership management, and sets the MinVersion to 1.2.
 # Not eligible for live reload.
 # UseTLS = false

internal/peer/redis.go

@@ -91,7 +91,7 @@ func newRedisPeers(ctx context.Context, c config.Config, done chan struct{}) (Pe
 
 	peers := &redisPeers{
 		store: &redimem.RedisMembership{
-			Prefix: "refinery",
+			Prefix: c.GetRedisPrefix(),
 			Pool:   pool,
 		},
 		peers:      make([]string, 1),
@@ -225,7 +225,7 @@ func buildOptions(c config.Config) []redis.DialOption {
 	options := []redis.DialOption{
 		redis.DialReadTimeout(1 * time.Second),
 		redis.DialConnectTimeout(1 * time.Second),
-		redis.DialDatabase(0), // TODO enable multiple databases for multiple samproxies
+		redis.DialDatabase(c.GetRedisDatabase()),
 	}
 
 	username, _ := c.GetRedisUsername()