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It is believed that many inexperienced people have no idea about how to use GraphQL in Geth. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

1. What's wrong with JSON-RPC API?

Let's take a look at what's wrong with the classic JSON-RPC API.

As its name suggests, JSON-RPC is a remote procedure call protocol that is designed to call remote functions and return the results of calculations. JSON-RPC is a fairly broad protocol, and you need to design your own calling interface on top of it.

But the problem with JSON-RPC is that it does not support flexible queries, which leads to a double waste of computing resources and data transfer:

Even if the user only needs part of the data, the RPC call still needs to return a large amount of data, resulting in a waste of bandwidth. For example, you call eth_getBlock only to get the miner's address, but it still needs to return the complete block data.

If a user repeatedly calls a RPC interface, even if only a little bit of data is returned for each call, the node's CPU will be wasted. For example, when you call the eth_getTransactionReceipt interface to poll the receipt for a transaction.

For JSON-RPC API in Ethernet Fong, the above problem is further magnified due to the structural characteristics of blockchain data. Executing a query (such as eth_getBalance) multiple times needs to ensure that the query is in the same world state or even on the same node: when you use multiple nodes for load balancing, different backend nodes may have different synchronization delays, which may return different content for the same RPC request.

In order to solve these problems, EIP 1767 proposed the GraphQL interface of Ethernet Fong nodes. Geth introduced support for EIP 1767 in version 1.9.0, and realized complete native GraphQL support.

2. What is GraphQL?

GraphSQL is a new query language proposed to solve the problems existing in REST API. GraphQL maps data object relationships to a graph (Graph) and designs a query language (Query Language) to traverse the relationships in the diagram-- which is the source of the GraphQL name.

This article is very suitable for developers who are not familiar with GraphQL to quickly understand the basic concepts of GraphQL and how to use NodeJS technology stack to implement GraphQL server and client: from SQL to GraphQL.

3. Enable GraphQL support for Geth

Native support for GraphQL introduced by Geth 1.9.0. When starting geth, use the-- graphql command line flag to open the GraphQL API interface. For example, execute the following command to access the ethernet G ö rli test chain and turn on GraphQL API support:

~ $geth-- goerli-- graphql4, Geth GraphQL browser

Once the GraphQL support of Geth is enabled, you can test it through the GraphQL browser preset by Geth. The GraphQL service listens on port 8547 by default, and the API access path is / graphql. You can access Geth's GraphQL browser using the following URL:

Http://localhost:8547

The interface is shown below, and on the far left is the entered GraphQL query:

For ease of viewing, the GraphQL query statement on the left is listed here:

{logs (filter: {fromBlock: 0, addresses: ["0xf105795bf5d1b1894e70bd04dc846898ab19fa62"], topics: [["0x0f0c27adfd84b60b6f456b0e87cdccb1e5fb9603991588d87fa99f5b6b61e670"]]}) {transaction {hash from {address} block {number timestamp}

You can interpret the above GraphQL statement as follows:

Query log logs

Query criteria: specifying using filter object

Return field: transaction, whose structure is shown above

5. Compare JSON-RPC API and Geth GraphQL with examples

Suppose we want to query the miner accounts of the latest 10 blocks and the balance of these accounts. The implementation code using JSON-RPC is as follows:

Async function main () {const lastBlock = await web3.eth.getBlockNumber () result = [] for (let I = lastBlock; I > = lastBlock-10; iMurb -) {let block = await web3.eth.getBlock (I) let blockRes = {} blockRes.number = I blockRes.miner = {} blockRes.miner.address = block.miner blockRes.miner.balance = await web3.eth.getBalance (block.miner) result.push (blockRes)} console.log (result);}

We need to do 10 cycles to check each block's miner account number and its balance one by one. In each cycle, we need to call RPC API twice to query the chunk data and the account balance, so a total of 10 calls 2 = 20 calls are required.

Here is a GraphQL query that gets the same data:

{blocks (from:lastBlock-10, to:lastBlock) {number miner {address balance}

You can type and execute the above query in the Geth GraphQL browser. Shockingly, we only made one call to complete the task we had done with 20 previous calls with JSON-RPC!

6. Backward compatibility of Geth GraphQL

The current GraphQL syntax support is included in the schema.go file in the Geth source code. The following table lists the current implementation status of Geth GraphQL, where the brief description column describes the Geth GraphQL statement corresponding to JSON-RPC:

JSON-RPC GraphQL status briefly indicates that eth_blockNumber has implemented {block {number}} eth_call has implemented {call (data: {to: "0x...", data: "0x..."}) {data status gasUsed}} eth_estimateGas has implemented {estimateGas (data: {to: "0x..." Data: "0x..."} eth_gasPrice has been implemented {gasPrice} eth_getBalance has been implemented {account (address: "0x...") {balance} eth_getBlockByHash has been implemented {block (hash: "0x...") {...} eth_getBlockByNumber has been implemented {block (number: 123) {...} eth_getBlockTransactionCountByHash has been implemented {block (hash) : "0x...") {transactionCount}} eth_getBlockTransactionCountByNumber implemented {block (number: X) {transactionCounnt}} eth_getCode implemented {account (address: "0x...") {code}} eth_getLogs implemented {logs (filter: {...}) {...} or {block (...) {logs (filter: {...}) { ...} eth_getStorageAt has implemented {account (address: "0x...") {storage (slot: "0x...")} eth_getTransactionByBlockHashAndIndex has implemented {block (hash: "0x...") {transactionAt (index: X) {...} eth_getTransactionByBlockNumberAndIndex has implemented {block (number: n) {transactionAt (index: X) {... } eth_getTransactionByHash has implemented {transaction (hash: "0x...") {...}} eth_getTransactionCount has implemented {account (address: "0x...") {transactionCount}} eth_getTransactionReceipt has implemented {transaction (hash: "0x...") {...} eth_getUncleByBlockHashAndIndex has implemented {block (hash: "0x...") {ommerAt (index) : X) {...} eth_getUncleByBlockNumberAndIndex implemented {block (number: n) {ommerAt (index: X) {...} eth_getUncleCountByBlockHash implemented {block (hash: "0x...") {ommerCount}} eth_getUncleCountByBlockNumber implemented {block (number: X) {ommerCount}} eth_protocolVersion implemented {protocolVersion} eth_sendRawTransaction implemented mutation {sendRawTransaction ( Data: data)} eth_syncing has implemented {syncing {...}} eth_getCompilers has not implemented JSON-RPC obsolete compiler function eth_compileLLL has not implemented JSON-RPC obsolete compiler function eth_compileSolidity has not implemented JSON-RPC obsolete compiler function eth_compileSerpent has not implemented JSON-RPC obsolete compiler function eth_newFilter has not implemented filter function may be stipulated in future EIP Eth_newBlockFilter does not implement filter function may stipulate in future EIP that eth_newPendingTransactionFilter does not implement filter function may agree in future EIP that eth_uninstallFilter does not implement filter function may agree in future EIP that eth_getFilterChanges does not implement filter function may agree in future EIP that eth_getFilterLogs does not implement filter function may agree on eth_accounts unrealized account function in future EIP Can not belong to the node core API eth_sign unrealized account function does not belong to the node core API eth_sendTransaction unrealized account function does not belong to the node core API eth_coinbase unrealized mining related functions will be defined separately eth_getWork unrealized mining related functions will be defined separately eth_hashRate unrealized mining related functions will be defined separately eth_mining unrealized mining related functions Eth_submitHashrate unrealized mining related functions will be defined separately eth_submitWork unrealized mining related functions will be defined separately

After reading the above, have you mastered how to use GraphQL in Geth? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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