部署到AppEngine时未调用Ktor App的Main方法 [英] Ktor App's Main Method Not Called When Deployed to AppEngine

问题描述

在部署到AppEngine时，不会调用Ktor应用程序的 main 方法.应用程序的主要方法是根据 Timer 从API请求中检索内容并将该信息保存到客户端使用的Firestore数据库中的逻辑.

The Ktor application's main method is not called when deployed to AppEngine. In the applications's main method is logic to retrieve content from an API request based on a Timer and save that information to a Firestore database which a client consumes.

当前在 Jar 中部署到AppEngine时，此逻辑当前有效.但是，使用 Ktor 实施此操作将节省部署时间，并在需要端点时帮助将来验证后端服务.

This logic currently works when deployed in a Jar to AppEngine. However, implementing this with Ktor would save deploy time and help future proof the backend service if endpoints are required.

将应用程序部署到AppEngine后，将调用Ktor应用程序的 main 方法，这与在IntelliJ中运行时调用应用程序的main方法的方式类似.

The Ktor application's main method is called once the app is deployed to AppEngine similar to how an application's main method is called when ran in IntelliJ.

主要方法仅在调用应用程序的托管路由后才被调用.

The main method is only called once the app's hosted route is called.

即:https://[yourProjectName].appspot.com

主要方法

import io.ktor.application.Application
fun Application.main() {
    // App logic here.
}

build.gradle

buildscript {
ext.kotlin_version = '1.3.10'
ext.ktor_version = '1.0.0'
ext.appengine_version = '1.9.60'
ext.appengine_plugin_version = '1.3.4'
ext.junitJupiterVersion  = '5.0.3'

repositories {
    jcenter()
    mavenCentral()
}
dependencies {
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    classpath "com.google.cloud.tools:appengine-gradle-plugin:$appengine_plugin_version"
    classpath 'org.junit.platform:junit-platform-gradle-plugin:1.0.3'
    }
}

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.2.51'
}

apply plugin: 'java'
apply plugin: 'kotlin'
apply plugin: 'war'
apply plugin: 'com.google.cloud.tools.appengine'

sourceSets {
    main.kotlin.srcDirs = [ 'src/main/kotlin' ]
}

sourceCompatibility = 1.8

repositories {
    jcenter()
    mavenCentral()
    maven { url "https://kotlin.bintray.com/ktor" }
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    implementation "io.ktor:ktor-server-servlet:$ktor_version"
    implementation "io.ktor:ktor-html-builder:$ktor_version"
    providedCompile "com.google.appengine:appengine:$appengine_version"
    implementation 'com.squareup.retrofit2:retrofit:2.3.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
    implementation 'com.squareup.retrofit2:adapter-rxjava:2.3.0'
    implementation 'io.reactivex.rxjava2:rxjava:2.1.1'
    implementation 'com.google.firebase:firebase-admin:6.3.0'
    implementation 'com.google.apis:google-api-services-youtube:v3-rev204-1.23.0'
    testCompile group: 'junit', name: 'junit', version: '4.12'
    // JUnit Jupiter API and TestEngine implementation
    testCompile("org.junit.jupiter:junit-jupiter-api:${junitJupiterVersion}")
    testRuntime("org.junit.jupiter:junit-jupiter-engine:${junitJupiterVersion}")
    testCompile("org.assertj:assertj-core:3.10.0")
    // To avoid compiler warnings about @API annotations in JUnit code
    testCompileOnly('org.apiguardian:apiguardian-api:1.0.0')
}

kotlin.experimental.coroutines = 'enable'

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

task run(dependsOn: appengineRun)

appengine {
    deploy {
    version = 'media-staging-1201181257pm'
    }
}

src/main/resources/application.conf

ktor {
    application {
        modules = [ InitializationKt.main ]
    }
}

src/main/webapp/WEB-INF/

appengine-web.xml

<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
    <threadsafe>true</threadsafe>
    <runtime>java8</runtime>
</appengine-web-app>

web.xml

<?xml version="1.0" encoding="ISO-8859-1" ?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
    <servlet>
        <display-name>KtorServlet</display-name>
        <servlet-name>KtorServlet</servlet-name>
    <servlet-class>io.ktor.server.servlet.ServletApplicationEngine</servlet-class>
        <!-- path to application.conf file, required -->
        <init-param>
            <param-name>io.ktor.config</param-name>
            <param-value>application.conf</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>KtorServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

推荐答案

感谢您在 Kotlin Slack 回答了这个问题.

Thank you to Gabriel Machado on Kotlin Slack for answering this.

Gabriel建议使用 Cron Job strong> ，而不是 Timer Task (计时器任务)，因为基于Timer "线程可能存在问题. com/appengine/docs/standard/java/how-instances-are-managed"rel =" nofollow noreferrer>缩放类型.

Gabriel recommends using a Cron Job as opposed to a Timer Task because there may be issues with a Timer thread based on scaling type.

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