Feature/set block number cache

README.md

@@ -244,7 +244,7 @@ export const getTxAllowList = (): Array<TransactionAllow> => {
 |  lte  |  txValue <= condition is allowed  |
 
 #### Transaction access rate limit(Option)
-If you set transaction access rate limit, follow [Transaction access rate limit](https://github.com/oasysgames/verse-proxy/blob/master/docs/RateLimit.md)
+If you set transaction access rate limit, follow [Transaction access rate limit](/docs/RateLimit.md)
 
 ### Set contract deployer
 You can control deployer of a verse at `src/config/transactionAllowList.ts`.
@@ -300,4 +300,9 @@ VERSE_READ_NODE_URL=[YOUR_VERSE_REPLICA_URL]
 ### Check Master-Verse-Node
 To check the behavior of requests to the Master-Verse-Node, an endpoint named `/master` is provided.
 
-All transactions sent to `/master` are sent to the Master-Verse-Node.
+All transactions sent to `/master` are sent to the Master-Verse-Node.
+
+## Reduce Metamask Access
+By returning the cache of blockNumber to the metamask, the number of accesses to the metamask can be reduced.
+For more detail, check the following doc.
+[Reduce Metamask Access](/docs/MetamaskAccess.md)

docs/MetamaskAccess.md

@@ -0,0 +1,47 @@
+# Reduce Metamask Access
+By returning the cache of block number to the metamask, the number of accesses to the metamask can be reduced.
+
+This approach is only applicable to browsers built on Chromium (chrome, brave, and Microsoft Edge based on Chromium).
+
+## Context
+When the metamask is open in the browser, the metamask checks the block number with `eth_blockNumber` once every 5~6 seconds.
+
+And metamask does the following when block number is updated.
+- Execute `eth_getBalance` for all accounts registered in the metamask.
+- Check the balance of all ERC20 accounts registered by the current account(ERC20.balanceOf).
+
+Oasys Verse updates the block number each time a transaction is executed.
+Therefore, each time a transaction is executed, there is access to update the balance of the metamask as explained above.
+
+## How to Reduce
+When there is a request for block number from metamask, the following actions should be taken
+- If a block number cache exists, it is returned.
+- If the cache of block number does not exist, request `eth_blockNumber` from verse to get the latest block number.
+
+It will prevent a metamask balance update request from occurring each time the transaction updates the block number.
+
+We create block number cache for each user using IP address and user-agent.
+
+## Update block number Cache
+The block number cache will be updated in the following cases.
+
+- When `eth_blockNumber` is requested by metamask after the block numberCache has been deleted by the expiration
+- The user block number cache is updated when a user executes a transaction by `eth_sendRawTransaction`.
+
+In other words, if there is a change in your ERC20 balance due to a transaction you executed, you can see the change in your token balance immediately after the transaction is executed.
+
+## Concern
+Returning a block number cache to the metamask raises the following concerns.
+
+While a block numberCache is being returned, it is impossible to confirm that another account's transaction has changed your account's token balance.
+
+In other words, if the expiration of block numberCache is too long, you can only confirm that your account's token balance has changed once the cache_expire expires.
+
+In addition, when a view function of a contract connected to Metamask (such as ERC20) is executed, the result is cached in Metamask.
+If periodic block number checks do not progress the block number, the result of the cache is returned. Therefore, you cannot check the result of the latest view function.
+
+## Setup
+It can be enabled by setting block numberCache's expiration from the environment variable.
+```bash
+BLOCK_NUMBER_CACHE_EXPIRE_SEC=15 # 15 seconds
+```

package.json

@@ -31,6 +31,7 @@
     "body-parser": "^1.20.2",
     "ethers": "^5.7.1",
     "ioredis": "^5.3.1",
+    "nestjs-real-ip": "^2.2.0",
     "reflect-metadata": "^0.1.13",
     "rimraf": "^3.0.2",
     "rxjs": "^7.2.0"

src/app.module.ts

@@ -1,4 +1,4 @@
-import { Module } from '@nestjs/common';
+import { CacheModule, Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
 import { HttpModule } from '@nestjs/axios';
 import { ProxyController } from './controllers';
@@ -19,6 +19,7 @@ import configuration from './config/configuration';
       load: [configuration],
     }),
     HttpModule,
+    CacheModule.register(),
   ],
   controllers: [ProxyController],
   providers: [

src/config/configuration.ts

@@ -4,6 +4,9 @@ export default () => ({
     process.env.VERSE_URL ||
     'http://localhost:8545',
   verseReadNodeUrl: process.env.VERSE_READ_NODE_URL,
+  blockNumberCacheExpire: process.env.BLOCK_NUMBER_CACHE_EXPIRE_SEC
+    ? parseInt(process.env.BLOCK_NUMBER_CACHE_EXPIRE_SEC, 10)
+    : undefined,
   datastore: process.env.DATASTORE ?? '',
   allowedMethods: [
     /^net_version$/,