javascript - 在 NodeJs Promise while 循环中停止多个服务控制器查询

Question

我正在尝试从节点脚本启动 Windows 服务。该服务有挂起的坏习惯，有时需要重试才能成功启动。我有一个承诺，而循环设置（请随时提出更好的方法）。我遇到的问题是，每个循环的sc.pollInterval输出都会在控制台中写入重复的结果。下面是我在控制台中看到的重复内容的示例，这是在循环的第二次迭代之后，我希望它只显示该内容一次。

sc \\abnf34873 start ColdFusion 10 Application Server

sc \\abnf34873 queryex ColdFusion 10 Application Server

SERVICE_NAME: ColdFusion 10 Application Server
        TYPE               : 10  WIN32_OWN_PROCESS
        STATE              : 2  START_PENDING
                                (NOT_STOPPABLE, NOT_PAUSABLE, IGNORES_SHUTDOWN)
        WIN32_EXIT_CODE    : 0  (0x0)
        SERVICE_EXIT_CODE  : 0  (0x0)
        CHECKPOINT         : 0x0
        WAIT_HINT          : 0x7d0
        PID                : 0
        FLAGS              :

SERVICE_NAME: ColdFusion 10 Application Server
        TYPE               : 10  WIN32_OWN_PROCESS
        STATE              : 2  START_PENDING
                                (NOT_STOPPABLE, NOT_PAUSABLE, IGNORES_SHUTDOWN)
        WIN32_EXIT_CODE    : 0  (0x0)
        SERVICE_EXIT_CODE  : 0  (0x0)
        CHECKPOINT         : 0x0
        WAIT_HINT          : 0x7d0
        PID                : 13772
        FLAGS              :

这是我的代码。基本上，我将尝试启动服务 3 次。如果没有，那么我会抛出错误。需要注意的一件事是，当我尝试启动服务但它卡在“Start_pending”状态时，我终止了该进程，然后尝试再次启动它。

var retryCount = 0;

// Start the colfusion service
gulp.task('start-coldfusion-service', function(done) {
    var serviceStarted = false;
    console.log("Starting coldfusion service..");
    // This says we're going to ask where it's at every 30 seconds until it's in the desired state.
    sc.pollInterval(30);
    sc.timeout(60);
    retryCount = 0;

    tryServiceStart().then(function(result) {
          // process final result here
        done();
    }).catch(function(err) {
        // process error here
    });
});


function tryServiceStart() {
    return startService().then(function(serviceStarted) {
        if (serviceStarted == false) {
            console.log("Retry Count: " + retryCount);
            // Try again..
            return tryServiceStart();
        } else {
             return result;
        }
    });
}

function startService() {
    return new Promise(function(resolve, reject) {
        var started = true;
        // Make sure the coldfusion service exists on the target server
        sc.query(targetServer, { name: 'ColdFusion 10 Application Server'}).done(function(services) {
            // if the service exists and it is currentl stopped, then we're going to start it.
            if (services.length == 1) {
                var pid = services[0].pid;
                if (services[0].state.name == 'STOPPED') {
                    sc.start(targetServer, 'ColdFusion 10 Application Server')
                        .catch(function(error) {
                            started = false;
                            console.log("Problem starting Coldfusion service! error message: " + error.message);
                            console.log("retrying...");
                            retryCount++;
                            if (parseInt(retryCount) > 2) {
                                throw Error(error.message);
                            }
                       })
                       .done(function(displayName) {
                            if (started) {
                                console.log('Coldfusion service started successfully!');
                            }
                            resolve(started);
                       });
                } else if (services[0].state.name == 'START_PENDING') {
                    kill(pid, {force: true}).catch(function (err) {
                        console.log('Problem killing process..');
                    }).then(function() {
                        console.log('Killed hanging process..');
                        resolve(false);
                    });
                }
            } else {
                console.log("Could not find the service in a stopped state.");
                resolve(false);
            }
        });
   });
}

score 1 · Accepted Answer

不太清楚为什么你会在控制台中得到重复的结果，但是下面是一些关于如何更好地编写代码的想法，主要是通过在最低级别进行承诺。

非常接近最初的概念，我最终得到了这个......

Promisify sc 命令

sc 命令返回类似于 promise 的东西，但使用 .done() 方法，该方法很可能不具备真正的 .then() 的全部功能
承诺每个命令为.xxxAsync()
通过采用每个命令的.doneas .then， Promise.resolve() 应该能够同化命令返回的类似 Promise 的东西。

;(function() {
    commands.forEach(command => {
        sc[command].then = sc[command].done;
        sc[command + 'Async'] = function() {
            return Promise.resolve(sc[command](...arguments)); 
        };
    }).
}(['start', 'query'])); // add other commands as required

gulp.task()

如果服务已打开，则承诺链遵循其成功路径，否则遵循其错误路径
无需测试 aresult以检测成功路径中的错误情况。

gulp.task('start-coldfusion-service', function(done) {
    console.log('Starting coldfusion service..');
    // This says we're going to ask where it's at every 30 seconds until it's in the desired state.
    sc.pollInterval(30);
    sc.timeout(60);
    tryServiceStart(2) // tryServiceStart(maxRetries)
    .then(done) // success! The service was started.
    .catch(function(err) {
        // the only error to end up here should be 'Maximum tries reached'.
        console.err(err);
        // process error here if necessary
    });
});

尝试服务启动（）

在此处安排重试

function tryServiceStart(maxRetries) {
    return startService()
    // .then(() => {}) // success! No action required here, just stay on the success path.
    .catch((error) => {
        // all throws from startService() end up here
        console.error(error); // log intermediate/final error
        if(--maxRetries > 0) {
            return tryServiceStart();
        } else {
            throw new Error('Maximum tries reached');
        }
    });
}

启动服务（）

通过调用sc.query()和sc.start()
console.log()被清除以支持投掷。
抛出的错误将被捕获并重新登录tryServiceStart()

function startService() {
    // Make sure the coldfusion service exists on the target server
    return sc.queryAsync(targetServer, { name: 'ColdFusion 10 Application Server'})
    .then((services) => {
        // if the service exists and it is currently stopped, then start it.
        if (services.length == 1) {
            switch(services[0].state.name) {
                case 'STOPPED':
                    return sc.startAsync(targetServer, 'ColdFusion 10 Application Server')
                    .catch((error) => {
                        throw new Error("Problem starting Coldfusion service! error message: " + error.message);
                    });
                break;
                case 'START_PENDING':
                    return kill(services[0].pid, { 'force': true })
                    .then(() => {
                        throw new Error('Killed hanging process..'); // successful kill but still an error as far as startService() is concerned.
                    })
                    .catch((err) => {
                        throw new Error('Problem killing process..');
                    });
                break;
                default:
                    throw new Error("Service not in a stopped state.");
            }
        } else {
            throw new Error('Could not find the service.');
        }
    });
}

仅检查语法错误，因此很可能需要调试。

提供 FWIW。酌情采用/突袭。

score 0 · Accepted Answer

I have found another npm package called promise-retry that seems to have addressed the issue I was having. At the same time, I believe it made my code a little more clear as to what it's doing.

gulp.task('start-coldfusion-service', function(done) {
    var serviceStarted = false;
    console.log("Starting coldfusion service..");
    // Since starting a service on another server isn't exactly fast, we have to poll the status of it.
    // This says we're going to ask where it's at every 30 seconds until it's in the desired state.
    sc.pollInterval(30);
    sc.timeout(60);     

    promiseRetry({retries: 3}, function (retry, number) {
        console.log('attempt number', number);

        return startService()
        .catch(function (err) {
            console.log(err);
            if (err.code === 'ETIMEDOUT') {
                retry(err);
            } else if (err === 'killedProcess') {
                retry(err);
            }

            throw Error(err);
        });
    })
    .then(function (value) {
        done();
    }, function (err) {
        console.log("Unable to start the service after 3 tries!");
        process.exit();
    });

});

function startService() {
    var errorMsg = "";
    return new Promise(function(resolve, reject) {
        var started = true;
        // Make sure the coldfusion service exists on the target server
        sc.query(targetServer, { name: 'ColdFusion 10 Application Server'}).done(function(services) {
            // if the service exists and it is currentl stopped, then we're going to start it.
            if (services.length == 1) {
                var pid = services[0].pid;
                if (services[0].state.name == 'STOPPED') {
                    sc.start(targetServer, 'ColdFusion 10 Application Server')
                        .catch(function(error) {
                            started = false;
                            errorMsg = error;
                            console.log("Problem starting Coldfusion service! error message: " + error.message);
                            console.log("retrying...");
                       })
                       .done(function(displayName) {
                            if (started) {
                                console.log('Coldfusion service started successfully!');
                                resolve(started);
                            } else {
                                reject(errorMsg);
                            }
                       });
                } else if (services[0].state.name == 'START_PENDING') {
                    kill(pid, {force: true}).catch(function (err) {
                        console.log('Problem killing process..');
                    }).then(function() {
                        console.log('Killed hanging process..');
                        reject("killedProcess");
                    });
                } else {
                    // Must already be started..
                    resolve(true);
                }
            } else {
                console.log("Could not find the service in a stopped state.");
                resolve(false);
            }
        });

   });

}

javascript - 在 NodeJs Promise while 循环中停止多个服务控制器查询

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