Basic implementation of Caching Middleware (#39)

* Basic implementation of Caching Middleware

* Minor fix

* Added comments

* Update CACHING.md

* Update CACHING.md

* Update CACHING.md

* Add response parser

* Integrate response parser and adjust tests accordingly

* Fix tests

* Improve tests

* CR's fixes

* CR's fixes

* Change Key Structure

* Update CACHING.md

* Rename ChainID -> CachePrefix and add validation

* Add is_cache_enabled boolean flag

* Added test for cache disabled scenario

* CR's fixes

* Improve tests

* Update healthcheck

* CR's fixes

* CR's fixes: improve logging

* Fixes after merge

* Improve IsCacheable method

* Improve logging

* CR's fixes

* Fix JSON-RPC response's ID flow

* Remove deprecated TODO

* Small fix

.env

@@ -47,6 +47,8 @@ TEST_SERVICE_LOG_LEVEL=ERROR
 # endpoint the proxy service should use for querying
 # evm blockchain information related to proxied requests
 TEST_EVM_QUERY_SERVICE_URL=http://kava-validator:8545
+# TEST_REDIS_ENDPOINT_URL is an url of redis
+TEST_REDIS_ENDPOINT_URL=localhost:6379
 
 ##### Kava Node Config
 
@@ -100,6 +102,19 @@ METRIC_PARTITIONING_ROUTINE_DELAY_FIRST_RUN_SECONDS=10
 METRIC_PARTITIONINING_PREFILL_PERIOD_DAYS=7
 # Used by `ready` script to ensure metric partitions have been created.
 MINIMUM_REQUIRED_PARTITIONS=30
+# CACHE_ENABLED specifies if cache should be enabled. By default cache is disabled.
+CACHE_ENABLED=true
+# REDIS_ENDPOINT_URL is an url of redis
+REDIS_ENDPOINT_URL=redis:6379
+REDIS_PASSWORD=
+# CACHE_TTL_SECONDS is a TTL for cached evm requests
+# CACHE_TTL_SECONDS should be specified in seconds
+CACHE_TTL_SECONDS=600
+# CACHE_PREFIX is used as prefix for any key in the cache, key has such structure:
+# <cache_prefix>:evm-request:<method_name>:sha256:<sha256(body)>
+# Possible values are testnet, mainnet, etc...
+# CACHE_PREFIX must not contain colon symbol
+CACHE_PREFIX=local-chain
 
 ##### Database Config
 POSTGRES_PASSWORD=password

.gitignore

@@ -17,10 +17,11 @@ kava-proxy-service
 cover.html
 
 # Dependency directories (remove the comment below to include it)
-# vendor/
+vendor/
 
 # ignore editor files
 .vscode/
+.idea/
 
 # ignore e2e test validator files
 docker/shared/genesis.json

architecture/CACHING.md

@@ -0,0 +1,90 @@
+## Caching Middleware Architecture
+
+Package `cachemdw` is responsible for caching EVM requests and provides corresponding middleware
+
+package can work with any underlying storage which implements simple `cache.Cache` interface
+
+package provides two different middlewares:
+- `IsCachedMiddleware` (should be run before proxy middleware)
+- `CachingMiddleware`  (should be run after proxy middleware)
+
+`IsCachedMiddleware` is responsible for setting response in the context if it's in the cache
+
+`CachingMiddleware` is responsible for caching response by taking a value from context (should be set by `ProxyMiddleware`) and setting in the cache
+
+## CachingMiddleware
+
+`CachingMiddleware` returns kava-proxy-service compatible middleware which works in the following way:
+- tries to get decoded request from context (previous middleware should set it)
+- checks few conditions:
+  - if request isn't already cached
+  - if request is cacheable
+  - if response is present in context
+- if all above is true - caches the response
+- calls next middleware
+
+## IsCachedMiddleware
+
+`IsCachedMiddleware` returns kava-proxy-service compatible middleware which works in the following way:
+- tries to get decoded request from context (previous middleware should set it)
+- tries to get response from the cache
+  - if present sets cached response in context, marks as cached in context and forwards to next middleware
+  - if not present marks as uncached in context and forwards to next middleware
+- next middleware should check whether request was cached and act accordingly:
+
+## What requests are cached?
+
+As of now we cache requests which has `specific block number` in request, for example:
+```json
+{
+	"jsonrpc":"2.0",
+	"method":"eth_getBlockByNumber",
+	"params":[
+		"0x1b4", // specific block number
+		true
+	],
+	"id":1
+}
+```
+
+we don't cache requests without `specific block number` or requests which uses magic tags as a block number: "latest", "pending", "earliest", etc...
+
+## Cache Invalidation
+
+### Keys Structure
+
+Keys have such format:
+
+`<cache_prefix>:evm-request:<method_name>:sha256:<sha256(body)>`
+
+For example:
+
+`local-chain:evm-request:eth_getBlockByHash:sha256:2db366278f2cb463f92147bd888bdcad528b44baa94b7920fdff35f4c11ee617`
+
+### Invalidation for specific method
+
+If you want to invalidate cache for specific method you may run such command:
+
+`redis-cli KEYS "<cache_prefix>:evm-request:<method_name>:sha256:*" | xargs redis-cli DEL`
+
+For example:
+
+`redis-cli KEYS "local-chain:evm-request:eth_getBlockByNumber:sha256:*" | xargs redis-cli DEL`
+
+### Invalidation for all methods
+
+If you want to invalidate cache for all methods you may run such command:
+
+`redis-cli KEYS "<cache_prefix>:evm-request:*" | xargs redis-cli DEL`
+
+For example:
+
+`redis-cli KEYS "local-chain:evm-request:*" | xargs redis-cli DEL`
+
+## Architecture Diagrams
+
+### Serve request from the cache (avoiding call to actual backend)
+![image](https://github.com/Kava-Labs/kava-proxy-service/assets/37836031/1bd8cb8e-6a9e-45a6-b698-3f99eaab2aa2)
+
+### Serve request from the backend and then cache the response
+![image](https://github.com/Kava-Labs/kava-proxy-service/assets/37836031/b0eb5cb9-51da-43f9-bb7d-b94bf482f366)

clients/cache/cache.go

@@ -0,0 +1,16 @@
+package cache
+
+import (
+	"context"
+	"errors"
+	"time"
+)
+
+var ErrNotFound = errors.New("value not found in the cache")
+
+type Cache interface {
+	Set(ctx context.Context, key string, data []byte, expiration time.Duration) error
+	Get(ctx context.Context, key string) ([]byte, error)
+	Delete(ctx context.Context, key string) error
+	Healthcheck(ctx context.Context) error
+}

clients/cache/inmemory.go

@@ -0,0 +1,101 @@
+package cache
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// InMemoryCache is an in-memory implementation of the Cache interface.
+type InMemoryCache struct {
+	data  map[string]cacheItem
+	mutex sync.RWMutex
+}
+
+// Ensure InMemoryCache implements the Cache interface.
+var _ Cache = (*InMemoryCache)(nil)
+
+// cacheItem represents an item stored in the cache.
+type cacheItem struct {
+	data       []byte
+	expiration time.Time
+}
+
+// NewInMemoryCache creates a new instance of InMemoryCache.
+func NewInMemoryCache() *InMemoryCache {
+	return &InMemoryCache{
+		data: make(map[string]cacheItem),
+	}
+}
+
+// Set sets the value of a key in the cache.
+func (c *InMemoryCache) Set(
+	ctx context.Context,
+	key string,
+	data []byte,
+	expiration time.Duration,
+) error {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	expiry := time.Now().Add(expiration)
+
+	if expiration == 0 {
+		// 100 years in the future to prevent expiry
+		expiry = time.Now().AddDate(100, 0, 0)
+	}
+
+	c.data[key] = cacheItem{
+		data:       data,
+		expiration: expiry,
+	}
+
+	return nil
+}
+
+// Get retrieves the value of a key from the cache.
+func (c *InMemoryCache) Get(ctx context.Context, key string) ([]byte, error) {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
+
+	item, ok := c.data[key]
+	if !ok || time.Now().After(item.expiration) {
+		// Not a real ttl but just replicates it for fetching
+		delete(c.data, key)
+
+		return nil, ErrNotFound
+	}
+
+	return item.data, nil
+}
+
+// GetAll returns all the non-expired data in the cache.
+func (c *InMemoryCache) GetAll(ctx context.Context) map[string][]byte {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
+
+	result := make(map[string][]byte)
+
+	for key, item := range c.data {
+		if time.Now().After(item.expiration) {
+			delete(c.data, key)
+		} else {
+			result[key] = item.data
+		}
+	}
+
+	return result
+}
+
+// Delete removes a key from the cache.
+func (c *InMemoryCache) Delete(ctx context.Context, key string) error {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	delete(c.data, key)
+	return nil
+}
+
+func (c *InMemoryCache) Healthcheck(ctx context.Context) error {
+	return nil
+}

clients/cache/redis.go

@@ -0,0 +1,114 @@
+package cache
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/kava-labs/kava-proxy-service/logging"
+	"github.com/redis/go-redis/v9"
+)
+
+type RedisConfig struct {
+	Address  string
+	Password string
+	DB       int
+}
+
+// RedisCache is an implementation of Cache that uses Redis as the caching backend.
+type RedisCache struct {
+	client *redis.Client
+	*logging.ServiceLogger
+}
+
+var _ Cache = (*RedisCache)(nil)
+
+func NewRedisCache(
+	cfg *RedisConfig,
+	logger *logging.ServiceLogger,
+) (*RedisCache, error) {
+	client := redis.NewClient(&redis.Options{
+		Addr:     cfg.Address,
+		Password: cfg.Password,
+		DB:       cfg.DB,
+	})
+
+	return &RedisCache{
+		client:        client,
+		ServiceLogger: logger,
+	}, nil
+}
+
+// Set sets the value for the given key in the cache with the given expiration.
+func (rc *RedisCache) Set(
+	ctx context.Context,
+	key string,
+	value []byte,
+	expiration time.Duration,
+) error {
+	rc.Logger.Trace().
+		Str("key", key).
+		Str("value", string(value)).
+		Dur("expiration", expiration).
+		Msg("setting value in redis")
+
+	return rc.client.Set(ctx, key, value, expiration).Err()
+}
+
+// Get gets the value for the given key in the cache.
+func (rc *RedisCache) Get(
+	ctx context.Context,
+	key string,
+) ([]byte, error) {
+	rc.Logger.Trace().
+		Str("key", key).
+		Msg("getting value from redis")
+
+	val, err := rc.client.Get(ctx, key).Bytes()
+	if err == redis.Nil {
+		rc.Logger.Trace().
+			Str("key", key).
+			Msgf("value not found in redis")
+		return nil, ErrNotFound
+	}
+	if err != nil {
+		rc.Logger.Error().
+			Str("key", key).
+			Err(err).
+			Msg("error during getting value from redis")
+		return nil, err
+	}
+
+	rc.Logger.Trace().
+		Str("key", key).
+		Str("value", string(val)).
+		Msg("successfully got value from redis")
+
+	return val, nil
+}
+
+// Delete deletes the value for the given key in the cache.
+func (rc *RedisCache) Delete(ctx context.Context, key string) error {
+	rc.Logger.Trace().
+		Str("key", key).
+		Msg("deleting value from redis")
+
+	return rc.client.Del(ctx, key).Err()
+}
+
+func (rc *RedisCache) Healthcheck(ctx context.Context) error {
+	rc.Logger.Trace().Msg("redis healthcheck was called")
+
+	// Check if we can connect to Redis
+	_, err := rc.client.Ping(ctx).Result()
+	if err != nil {
+		rc.Logger.Error().
+			Err(err).
+			Msg("can't ping redis")
+		return fmt.Errorf("error connecting to Redis: %v", err)
+	}
+
+	rc.Logger.Trace().Msg("redis healthcheck was successful")
+
+	return nil
+}