# The Graph

使用 graphQL 數據結構，讓你可以監聽區塊鏈節點的事件或數據，並且發佈到 graph node 上面。之後可以讓大家 Query 使用。需要自己寫一個 subgraph 的邏輯，然後發布到 graph node上。官方有提供 名為[ studio node](https://thegraph.com/studio/) 的 graph node。也可以在自己本地架設。

### 官方文件

<https://thegraph.com/docs/en/>

### 本地架設 Graph node 教學

<https://thegraph.academy/developers/local-development/>

### 探索已發佈的 Subgraph

{% embed url="<https://thegraph.com/explorer>" %}

## 使用 OpenZeppelin 範例

<https://github.com/OpenZeppelin/openzeppelin-subgraphs>

<https://docs.openzeppelin.com/subgraphs/0.1.x/>

將以上 clone 到你的專案或是 `npm install @openzeppelin/subgraphs`，之後 copy node\_module 裡面 config file，然後放到你的專案內

之後輸入以下（要把 --config 後的路徑改成剛的 config file）

```
npx graph-compiler \
  --config configs/sample.json \
  --include node_modules/@openzeppelin/subgraphs/src/datasources \
  --export-schema \
  --export-subgraph
```

![](https://3415061728-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M0u4DA5jITnh37VYXmj%2Fuploads%2F53MmXQQyTxuIY1gyHXyB%2F%E6%88%AA%E5%9C%96%202022-02-07%20%E4%B8%8B%E5%8D%883.09.07.png?alt=media\&token=942db4f6-b897-4c78-a2b3-bf1fc4afa416)

之後要去把 編譯出來的 yaml 改名為 subgraph.yaml，然後增加 network 與 contract address 等 config field

ERC721 的 subgraph.yaml 範例：

```
specVersion: 0.0.2
schema:
  file: erc721.schema.graphql
dataSources:
  - kind: ethereum/contract
    name: erc721
    network: mainnet
    source:
      abi: IERC721
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.5
      language: wasm/assemblyscript
      entities:
        - ERC721Contract
      abis:
        - name: IERC721
          file: ../node_modules/@openzeppelin/contracts/build/contracts/IERC721Metadata.json
      eventHandlers:
        - event: Approval(indexed address,indexed address,indexed uint256)
          handler: handleApproval
        - event: ApprovalForAll(indexed address,indexed address,bool)
          handler: handleApprovalForAll
        - event: Transfer(indexed address,indexed address,indexed uint256)
          handler: handleTransfer
      file: ../node_modules/@openzeppelin/subgraphs/src/datasources/erc721.ts

```

之後看你要部署到 studio 還是自己 host 的節點，如果要部署到 studio 就先去 <https://thegraph.com/studio/> create subgraph 然後從 cli auth 後 deploy

```
graph deploy --studio <yaml 內 dataSources 的 name>
```

部署到 local 節點就參考：<https://thegraph.academy/developers/local-development/>

## 查看目前 subgraph 健康度

hosted service 可用此 endpoint `https://api.thegraph.com/index-node/graphq`

```
indexingStatusForCurrentVersion(subgraphName: "org/subgraph") {
  synced
  health
  fatalError {
    message
    block {
      number
      hash
    }
    handler
  }
  chains {
    chainHeadBlock {
      number
    }
    latestBlock {
      number
    }
  }
}
```

## 相關事項

graph-cli 版本 0.16 後有改變指令，如果要用舊版 cli 部署到 studio 或 host-service 可以如下使用 --node 參數

> const HOSTED\_SERVICE\_URL = '<https://api.thegraph.com/deploy/>'
>
> const SUBGRAPH\_STUDIO\_URL = '<https://api.studio.thegraph.com/deploy/>'

```
npx graph deploy --access-token=<...> --node https://api.thegraph.com/deploy/ --ipfs https://api.thegraph.com/ipfs <github username>/<subgraph name>
```

## 相關範例

#### OpenZeppelin:

<https://github.com/OpenZeppelin/openzeppelin-subgraphs>

#### NFT:

<https://github.com/dabit3/custom-nft-subgraph-workshop>

<https://github.com/dabit3/bored-ape-yacht-club-api-and-subgraph>

&#x20;<https://github.com/dabit3/building-a-subgraph-workshop>

#### DeFi:

<https://github.com/token-terminal/tt-subgraphs>

&#x20;<https://github.com/messari/subgraphs>