caches: support Redis backend

Fixes: ejfitzgerald#5

caches/redis.go

@@ -0,0 +1,108 @@
+package caches
+
+import (
+	"context"
+	"encoding/hex"
+	"errors"
+	"github.com/go-redis/redis/v8"
+	"os"
+	"strconv"
+)
+
+type RedisConfiguration struct {
+	Address string  `json:"address"`
+	Password string `json:"password"`
+	Database int    `json:"database"`
+}
+
+type RedisCache struct {
+	ctx context.Context
+	client *redis.Client
+}
+
+func getRedisAddr() (string, error) {
+	addr := os.Getenv("CLANG_TIDY_CACHE_REDIS_ADDRESS")
+	if addr == "" {
+		return "", errors.New("`CLANG_TIDY_CACHE_REDIS` must be set")
+	}
+
+	return addr, nil
+}
+
+func getRedisPassword() string {
+	return os.Getenv("CLANG_TIDY_CACHE_REDIS_PASSWORD")
+}
+
+func getRedisDatabase() int {
+	db_str := os.Getenv("CLANG_TIDY_CACHE_REDIS_DATABASE")
+	if db_str == "" {
+		return 0
+	}
+
+	db, err := strconv.Atoi(db_str)
+	if err == nil {
+		db = 0
+	}
+
+	return db
+}
+
+func NewRedisCache(cfg *RedisConfiguration) (*RedisCache, error) {
+	var addr string
+	if cfg.Address == "" {
+		var err error
+		addr, err = getRedisAddr()
+
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		addr = cfg.Address
+	}
+
+	var pw string
+	if cfg.Password == "" {
+		pw = getRedisPassword()
+	} else {
+		pw = cfg.Password
+	}
+
+	db := cfg.Database
+
+	client := redis.NewClient(&redis.Options{
+		Addr: addr,
+		Password: pw,
+		DB: db,
+	})
+
+	ctx := context.Background()
+
+	_, err := client.Ping(ctx).Result()
+	if err != nil {
+		return nil, err
+	}
+
+	cache := RedisCache {
+		ctx: ctx,
+		client: client,
+	}
+
+	return &cache, nil
+}
+
+func (c *RedisCache) FindEntry(digest []byte) ([]byte, error) {
+	objectName := hex.EncodeToString(digest)
+
+	data, err := c.client.Get(c.ctx, objectName).Bytes()
+	if err != nil {
+		return nil, err
+	}
+
+	return data, err
+}
+
+func (c *RedisCache) SaveEntry(digest []byte, content []byte) error {
+	objectName := hex.EncodeToString(digest)
+
+	return c.client.Set(c.ctx, objectName, content, 0).Err()
+}

go.mod

@@ -2,4 +2,7 @@ module github.com/ejfitzgerald/clang-tidy-cache
 
 go 1.15
 
-require cloud.google.com/go/storage v1.14.0
+require (
+	cloud.google.com/go/storage v1.14.0
+	github.com/go-redis/redis/v8 v8.11.5
+)