Gitea/modules/cache/cache.go

// Copyright 2017 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package cache

import (
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"strconv"
	"time"

	"gitea.dev/modules/setting"
	"gitea.dev/modules/util"
)

var defaultCache StringCache

// Init start cache service
func Init() error {
	if defaultCache == nil {
		c, err := NewStringCache(setting.CacheService.Cache)
		if err != nil {
			return err
		}
		for range 10 {
			if err = c.Ping(); err == nil {
				break
			}
			time.Sleep(time.Second)
		}
		if err != nil {
			return err
		}
		defaultCache = c
	}
	return nil
}

const (
	testCacheKey = "DefaultCache.TestKey"
	// SlowCacheThreshold marks cache tests as slow
	// set to 30ms per discussion: https://github.com/go-gitea/gitea/issues/33190
	// TODO: Replace with metrics histogram
	SlowCacheThreshold = 30 * time.Millisecond
)

// Test performs delete, put and get operations on a predefined key
// returns
func Test() (time.Duration, error) {
	if defaultCache == nil {
		return 0, errors.New("default cache not initialized")
	}

	testData := hex.EncodeToString(make([]byte, 500))

	start := time.Now()

	if err := defaultCache.Delete(testCacheKey); err != nil {
		return 0, fmt.Errorf("expect cache to delete data based on key if exist but got: %w", err)
	}
	if err := defaultCache.Put(testCacheKey, testData, 10); err != nil {
		return 0, fmt.Errorf("expect cache to store data but got: %w", err)
	}
	testVal, hit := defaultCache.Get(testCacheKey)
	if !hit {
		return 0, errors.New("expect cache hit but got none")
	}
	if testVal != testData {
		return 0, errors.New("expect cache to return same value as stored but got other")
	}

	return time.Since(start), nil
}

// GetCache returns the currently configured cache
func GetCache() StringCache {
	return defaultCache
}

// GetString returns the key value from cache with callback when no key exists in cache
func GetString(key string, getFunc func() (string, error)) (string, error) {
	if defaultCache == nil || setting.CacheService.TTL <= 0 {
		return getFunc()
	}
	cached, exist := defaultCache.Get(key)
	if !exist {
		value, err := getFunc()
		if err != nil {
			return value, err
		}
		return value, defaultCache.Put(key, value, setting.CacheService.TTLSeconds())
	}
	return cached, nil
}

// GetInt64 returns key value from cache with callback when no key exists in cache
func GetInt64(key string, getFunc func() (int64, error)) (int64, error) {
	s, err := GetString(key, func() (string, error) {
		v, err := getFunc()
		return strconv.FormatInt(v, 10), err
	})
	if err != nil {
		return 0, err
	}
	if s == "" {
		return 0, nil
	}
	return strconv.ParseInt(s, 10, 64)
}

// Remove key from cache
func Remove(key string) {
	if defaultCache == nil {
		return
	}
	_ = defaultCache.Delete(key)
}

// SafeCacheKey returns a cache-safe key for the input string
// Some caches like memcached have char & length limits.
// Caller must make sure the prefix is valid and well-designed.
// If prefix is already too long, the returned key will still exceed the limit, then just let the cache report an error.
func SafeCacheKey(prefix, input string) string {
	// memcached has a limit 250 for key length, so we use 230 to leave some room for other prefixes and separators
	return safeCacheKey(prefix, input, 230)
}

func safeCacheKey(prefix, input string, limit int) string {
	safeAsKey := len(prefix)+len(input)+3 <= limit
	if safeAsKey {
		for i := 0; i < len(input); i++ {
			if c := input[i]; c <= ' ' || c >= 127 {
				safeAsKey = false
				break
			}
		}
	}
	sep, key := ":s-", input
	if !safeAsKey {
		hashBytes := sha256.Sum256(util.UnsafeStringToBytes(input))
		sep, key = ":h-", hex.EncodeToString(hashBytes[:])
	}
	return prefix + sep + key
}