javascript - 在 catch block 中抛出错误 Q Promise 不拒绝 Promise

Question

我有以下函数被另一个函数调用:

 function fetchAllRecords(client, item, region, offset, savedCount, totalCount) {
  offset = offset || 1;
  savedCount = savedCount || 0;
  totalCount = totalCount || 0;
  return processQueue(client, item, offset, region).then(function (result) {
    return associate(result, item, region)
  }).then(function (success) {
    return saveBatch(item, success.allResources, region);
  }).then(function (result) {
    savedCount += result.savedCount;
    totalCount += result.totalCount;
    if (debugmode) {
      console.log(savedCount + '/' + totalCount);
    }
    offset += item.limit;
    return fetchAllRecords(client, item, region, offset, savedCount, totalCount);
  }).catch(function (err) {
    if (err == 'done')
      return 'done';

    // All of the above steps have built-in retry so we assume there's a non-recoverable error in this batch and move to next
    if (err.message === 'LIMIT_EXCEEDED') {
      offset += item.limit;
      return fetchAllRecords(client, item, region, offset, savedCount, totalCount);
    }
    else {
******************* Problem Line ********************
      console.log('Miscellenious error in fetachAllRecords, moving to next resource');
      console.log(JSON.stringify(err));
      throw new Error('Misc');
    }
  });
}

并且在另一个函数中像这样调用它

function processResource(client, item, debugmode, region) {
  var deferred = q.defer();
  if (item.resource === "Property" && region === "ccmls") {
    var cities = cities.list;
    item.query = item.query + ' ,(City=|' + cities.join() + ')';
  }
  fetchAllRecords(client, item, region)
    .then(function (result) {
      if (debugmode) {
        console.log('fetchAllRecords: ' + item.resource + '.' + item.class + ' completed...');
      }
      deferred.resolve(result);
    })
    .catch(function (err) {
      console.log(item.resource + '.' + item.class + ' failed with error: ' + JSON.stringify(err));
      deferred.reject(err);
    });
  return deferred.promise;
}

在上面的问题行中，应该拒绝 fetchAllRecords 并在 processResource 中拒绝 fetchAllResources catch 处理程序应该被调用，但由于某种奇怪的原因，问题行在 throw 之后不断被调用，并且在被调用十几次(随机)后，它最终拒绝了 processResource< 中的 fetchAllResources 返回的 promise 。我在这里遗漏了一些明显的东西吗？另外请评论我使用 Promise 的风格，可以吗还是我需要更多练习？

Answer 1

您会收到大量日志，因为您使用递归方法，并在每个级别处理和重新抛出错误。同步写的，完全一样

function fetchAll(offset) {
    if (offset > 5) throw new Error("message"); // let's say the inner one throws
    try {
        return fetchAll(offset+1);
    } catch(e) {
        console.error(e.message);
        throw e;
    }
}
fetchAll(0);

您也希望在这里收到 5 条消息，对吧？

解决方案是不再处理内部结果中的错误。要通过 promise 实现这一目标，请查看 difference between .then(…).catch(…) and .then(…, …) - 你想要后者:

function fetchAllRecords(client, item, region, offset=1, savedCount=0, totalCount=0) {
  return processQueue(client, item, offset, region).then(function (result) {
    return associate(result, item, region)
  }).then(function (success) {
    return saveBatch(item, success.allResources, region);
  }).then(function (result) {
    savedCount += result.savedCount;
    totalCount += result.totalCount;
    if (debugmode) {
      console.log(savedCount + '/' + totalCount);
    }
    offset += item.limit;
    return fetchAllRecords(client, item, region, offset, savedCount, totalCount);
  }, function (err) {
// ^^
    if (err == 'done')
      return 'done';

    if (err.message === 'LIMIT_EXCEEDED') {
      offset += item.limit;
      return fetchAllRecords(client, item, region, offset, savedCount, totalCount);
    } else {
      console.log('Miscellenious error in fetchAllRecords, moving to next resource');
      console.log(JSON.stringify(err));
      throw new Error('Misc');
    }
  });
}
function processResource(client, item, debugmode, region) {
  if (item.resource === "Property" && region === "ccmls") {
    var cities = cities.list;
    item.query = item.query + ' ,(City=|' + cities.join() + ')';
  }
  return fetchAllRecords(client, item, region)
  .then(function (result) {
    if (debugmode) {
      console.log('fetchAllRecords: ' + item.resource + '.' + item.class + ' completed...');
    }
    return result;
  }, function (err) {
    console.log(item.resource + '.' + item.class + ' failed with error: ' + JSON.stringify(err));
    throw err;
  });
}