(Nodejs + Restify) 发送后无法设置 headers - 承诺拒绝警告

Question

UnhandledPromiseRejectionWarning：未处理的承诺拒绝（拒绝 ID：1）：错误：发送后无法设置 headers。 当我连续点击 API 或在请求完成之前再次点击 API 时会发生此错误。 参考了很多解决方案都无法得到合适的answer.pls，帮我解决一下。

exports.getRecords = function(req, res) {

        db.task(t => {
                return t.batch([
                    t.any(selectQuery),
                    t.any(recordCountQuery)
                ]);
            })
            .then(data => {

                //create a formatted object based on the two queries with recordCount
                var output = {};

                output.meta = data[1][0];
                let petData = data[0];

                /*
                 * Checks If the pet details available and then processing the pets Data
                 * To get the existing image URL.
                 */

                if (!util.isNullOrUndefined(petData)) {
                    //Iterating over the Array of pets and process each pets with promises()
                    Promise.all(petData.map(pet => {

                            //Processing each pet
                            return processUtil.getvalidData(pet)
                                .then(pet => pet);
                        }))
                        .then(results => {
                            //After processing all the pets send the output
                            output.data = results;
                            res.json(output);
                        })
                };
            })
            .catch(function(err) {
                if (util.isError(err)) {
                    res.error('NotFoundError', err);
                } // return 404
                else {
                    res.error('InternalServerError', err);
                }; //else 500

            });
    };

这是两个响应的控制台日志

单次点击的响应日志

    "15" "TRACE" "services-data" "lynd-PC" "sr"  "4596ec40" "" "GET" "/data/2" "request received"
    "16" "TRACE" "services-data" "lynd-PC" ""    "4596ec40" "" "GET" "/data/2" ""
    "17" "TRACE" "services-data" "lynd-PC" ""    "4596ec40" "" "GET" "/data/2" ""
    "18" "TRACE" "services-data" "lynd-PC" "ss"  "4596ec40" "200" "GET" "/data/2" "response sent"

在请求完成之前我们两次点击 API 时的响应日志。

"15" "TRACE" "services-data" "lynd-PC" "sr"  "1a85afb7" "" "GET" "/data/2" "request received"
"15" "TRACE" "services-data" "lynd-PC" ""    "1a85afb7" "" "GET" "/data/2" ""
"16" "TRACE" "services-data" "lynd-PC" ""    "1a85afb7" "" "GET" "/data/2" ""
"17" "TRACE" "services-data" "lynd-PC" "ss"  "1a85afb7" "500" "GET" "/data/2" "response sent"
"18" "TRACE" "services-data" "lynd-PC" ""    "1a85afb7" "" "GET" "/data/2" ""
(node:3860) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): Error: Can't set headers after they are sent.

Answer 1

首先，您的代码中 Promise.all() 没有拒绝处理程序。您可以通过更改以下内容将其链接到父承诺链（它确实有一个拒绝处理程序）：

Promise.all(petData.map(pet => {

对此：

return Promise.all(petData.map(pet => {

因此，这将解决一次未处理拒绝的机会。或者，您可以将自己的拒绝句柄添加到 Promise.all() 承诺中，如果您更愿意为其设置单独的拒绝处理程序。

您似乎还有多个代码路径不会发送任何响应。如果这种情况：

if (!util.isNullOrUndefined(petData)) {

不满足（意味着它不进入 if 块），那么您的代码将不会发送任何响应，这通常是编码错误，因为每个请求都需要发送一个响应。

(Nodejs + Restify) 发送后无法设置 headers - 承诺拒绝警告

(Nodejs + Restify) Can't set headers after they are sent - promise rejection warning

javascript

node.js

promise

restify