递归函数中重复执行的catch块

Question

我有一个递归函数，用于从 AWS 上的 CodeCommit 存储库获取 SQL 文件并按顺序运行它们。在运行下一个文件之前，我们需要等待上一个文件完成。如果 SQL 文件之一失败，我需要 catch 块来 return 关于失败文件的信息。

我目前在代码中看到的是，catch 块对存储库中的每个 SQL 文件重复一次。根据我的理解，'throw' 语句应该 return 到最初调用该函数的函数的 catch 块。谁能指出我在这里做错了什么？

const getFileData = async (newSQLFiles,processed=[]) => {
      try{
        if(newSQLFiles.length ===0){
          client.release();
          await pool.end().then(() => console.log('DB Connection pool closed.'))
          return processed;
        }
    
        var params = {
                filePath: newSQLFiles[0].relativePath, 
                repositoryName: 'testDBScripts' //Use environment variable
              };
    
        const data = await codecommit.getFile(params).promise();
        await runScripts(data);
        processed.push(newSQLFiles[0].relativePath)  
      }catch(err){
        console.log(err)
        throw [err,processed];
      }
      return await getFileData(newSQLFiles.slice(1),processed);
}

await getFileData(newSQLFiles)
.then(processed=>console.log("Following products are updated.",processed))
.catch(async ([e, file])=> {

    client.release();
    await pool.end().then(() => console.log('DB Connection pool closed.'))
    //await codePipelineJobFailed("SQL file " + file + " failed with : " + e)

    throw new Error("SQL file " + file + " failed with : " + e)}
)

Answer 1

在JavaScript中，当函数遇到return语句时，它将停止函数形式的进一步执行。可能它目前不起作用，因为在函数内的 catch 之后，您正在返回。

所以，为了解决您的问题，我想这样做：


const getFileData = async (newSQLFiles,processed=[]) => {
      try{
        if(newSQLFiles.length ===0){
          client.release();
          await pool.end().then(() => console.log('DB Connection pool closed.'))
          return processed;
        }
    
        var params = {
                filePath: newSQLFiles[0].relativePath, 
                repositoryName: 'testDBScripts' //Use environment variable
              };
    
        const data = await codecommit.getFile(params).promise();
        await runScripts(data);
        processed.push(newSQLFiles[0].relativePath)  
      }catch(err){
        console.log(err)
        throw [err,processed];
      }
      await getFileData(newSQLFiles.slice(1),processed);
}

await getFileData(newSQLFiles)
.then(processed=>console.log("Following products are updated.",processed))
.catch(async ([e, file])=> {

    client.release();
    await pool.end().then(() => console.log('DB Connection pool closed.'))
    //await codePipelineJobFailed("SQL file " + file + " failed with : " + e)

    throw new Error("SQL file " + file + " failed with : " + e)}
)

请注意，我已经从 try catch 块之后的函数范围中删除了 return。

Answer 2

您的代码包含许多关于如何在 JavaScript 中编写实用且健壮的异步程序的明显误解。关于下面的代码，我还有一些地方要更改，但我无法提供建议，因为未提供有关 codecommit.getFile 和 runScripts 的信息。如果您对此答案有任何疑问，我很乐意提供帮助 -

async function getFileData(files) {
  const result = []
  for (const f of files) {
    try {
      const data = await codecommit.getFile({
        filePath: f.relativePath,
        repositoryName: 'testDBScripts'
      }).promise()
      await runScripts(data)
      result.push(f.relativePath)
    }
    catch (e) {
      throw new Error("SQL file " + f + " failed with : " + e.message)
    }
  }
  return result
}

使用起来是这样的-

getFileData(newSQLFiles)
  .then(console.log, console.error)
  .finally(_ => client.release())
  .finally(_ => pool.end())

或者如果你更喜欢 catch，这也是一样的 -

getFileData(newSQLFiles)
  .then(console.log)
  .catch(console.error)
  .finally(_ => client.release())
  .finally(_ => pool.end())

注意 .finally 回调也可以 return 一个正确排序程序的承诺。请参阅下面的示例 -

const delay = (ms,x) =>
  new Promise(r => setTimeout(_ => console.log(x) || r(x), ms))
    
delay(1000,"a")
  .then(_ => delay(1000,"b"))
  .then(_ => delay(200, "result"))
  .finally(_ => delay(500,"client released"))
  .finally(_ => delay(1000,"pool closed"))
  .then(console.log, console.error)

a
b
result
client released
pool closed
result

如果序列中的任何承诺被拒绝或抛出错误，.finally 处理程序仍会被调用 -

const delay = (ms,x) =>
  new Promise(r => setTimeout(_ => console.log(x) || r(x), ms))
    
delay(1000,"a")
  .then(_ => Promise.reject(Error("SQL FAILURE")))
  .then(_ => delay(200, "result"))
  .finally(_ => delay(500,"client released"))
  .finally(_ => delay(1000,"pool closed"))
  .then(console.log, console.error)

a
client released
pool closed
Error: SQL FAILURE

递归函数中重复执行的catch块

Catch Block in Recursive Function Executing Repeatedly

javascript

recursion

async-await

aws-sdk