实现GAE和GKE k8s cron job的秒级调度单位
mrdulin opened this issue · comments
实现GAE和GKE k8s cron job的秒级调度单位
问题
如何实现Google App Engine和Google Kubernetes Engine定时作业(cron job
)的秒级调度(schedule
)单位?
不同于node-schedule
拥有秒级调度单位,可以将定时作业精确在某一秒执行。GAE
和GKE
的定时作业只能精确到分钟(min
)。
在GAE
的定时作业文档中,schedule
格式可以知道,时间单位的有效值包括:
minutes
或mins
hours
在GKE
的定时作业文档中,CronJob 使用所需的 schedule
字段,该字段接受 Unix 标准 crontab
格式的时间。所有 CronJob 时间均采用世界协调时间 (UTC):
- 第一个值表示分钟(0 到 59 之间)
- 第二个值表示小时(0 到 23 之间)
- 第三个值表示一个月中的某天(1 到 31 之间)
- 第四个值表示月份(1 到 12 之间)
- 第五个值表示星期(0 到 6 之间)
以及k8s Cron Job文档中的调度(schedule)都是Unix标准crontab
格式的时间,GKE
使用kubernetes
,简称k8s
,来管理compute engine
集群(kubernetes
集群)。
解决方案
GAE
cron job
我们可以先尝试设置GAE
定时作业的schedule
为every 1 seconds
,看看是什么效果。
server.js
:
const express = require('express');
const pkg = require('./package.json');
const app = express();
function validateCronRequest(req, res, next) {
console.log('X-Appengine-Cron', req.get('X-Appengine-Cron'), typeof req.get('X-Appengine-Cron'));
if (req.get('X-Appengine-Cron') !== 'true') {
return res.status(403);
}
next();
}
app.get('/version', (req, res) => {
res.send(`version: ${pkg.version}`);
});
app.get('/cronjob/sync', validateCronRequest, (req, res) => {
res.sendStatus(200);
});
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
console.log(`Server listening on port ${PORT}...`);
});
app.yaml
:
runtime: nodejs8
service: cronjob-sec-unit
cron.yaml
:
cron:
- description: 'sync job'
url: /cronjob/sync
schedule: every 1 seconds
target: cronjob-sec-unit
首先部署GAE
service
:
gcloud app deploy
部署成功后,去GCP
console - App Engine查看
紧接着部署GAE
定时作业:
gcloud app deploy ./cron.yaml
报错
ERROR: (gcloud.app.deploy) An error occurred while parsing file: [/Users/ldu020/workspace/nodejs-gcp/src/app-engine/cron-jobs-second-unit-schedule/cron.yaml]
Unable to assign value 'every 1 seconds' to attribute 'schedule':
schedule 'every 1 seconds' failed to parse: line 1:8 mismatched input u'second' expecting set None
in "/Users/ldu020/workspace/nodejs-gcp/src/app-engine/cron-jobs-second-unit-schedule/cron.yaml", line 4, column 15
错误说“不能将every 1 seconds
赋值给schedule
,解析every 1 seconds
失败”。可见,GAE
定时作业schedule
并不支持秒级单位。
修改cron.yaml
,将schedule
设置为every 1 mins
:
cron:
- description: 'sync job'
url: /cronjob/sync
schedule: every 1 mins
target: cronjob-sec-unit
再次部署,部署成功后查看GCP
控制台:
查看该定时作业在Stackdriver Logging
中的logs,验证该定时作业运行是否正常。
通过日志的时间戳可以看到,该定时作业每分钟执行一次。
查看App Engine
部署的service的logs:
该service运行正常,路由/cronjob/sync
每分钟被定时作业调用一次。
接下来实现秒级调度单位的定时作业,本质上是将定时作业的最小调度单位——1分钟,再次划分成一系列秒级时间序列。对Node.js
异步流程控制库async熟悉的同学可以马上想到用timeSeries
函数。我们这里将定时作业设置为10秒执行一次,修改后的代码如下:
server.js
:
const express = require('express');
const async = require('async');
const pkg = require('./package.json');
const app = express();
const OUTER_SCHEDULE = 60; // 1 minute
const INNER_SCHEDULE = 10; // 10 seconds
function validateCronRequest(req, res, next) {
// console.log('X-Appengine-Cron', req.get('X-Appengine-Cron'), typeof req.get('X-Appengine-Cron'));
if (process.env.NODE_ENV === 'production') {
if (req.get('X-Appengine-Cron') !== 'true') {
return res.status(403);
}
}
next();
}
app.get('/version', (req, res) => {
res.send(`version: ${pkg.version}`);
});
app.get('/cronjob/sync', validateCronRequest, async (req, res) => {
// Update database every 1 minute
// await updateDB();
// Update database every 10 seconds
try {
await updateDBTimeSeries();
} catch (error) {
console.error(error);
}
res.sendStatus(200);
});
function sleep(ms) {
return new Promise((resolve) => setTimeout(resolve, ms));
}
async function updateDB() {
return new Promise((resolve) => {
process.nextTick(() => {
console.log('Update database success.');
resolve();
});
});
}
async function updateDBEveryTenSeconds(item, n, next) {
// console.log('item: ', item);
await updateDB();
if (item < n - 1) {
await sleep(INNER_SCHEDULE * 1000);
}
next();
}
async function updateDBTimeSeries() {
const n = OUTER_SCHEDULE / INNER_SCHEDULE;
return new Promise((resolve, reject) => {
async.timesSeries(
n,
(item, next) => updateDBEveryTenSeconds(item, n, next),
(error, results) => {
if (error) {
return reject(error);
}
console.log('A round update database operations done.');
resolve(results);
}
);
});
}
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
console.log(`Server listening on port ${PORT}...`);
});
部署后,查看App Engine
service的日志:
可以看到,我们的调度任务每10秒执行一次,通过async.timeSeries
方法将GAE
定时作业的schedule
(1分钟),划分出了6段。
GKE cron job
同理,我们也可以在GKE
的定时作业上实现秒级调度单位。
src/index.js
:
const async = require('async');
const OUTER_SCHEDULE = 60;
const INNER_SCHEDULE = 10;
async function main() {
try {
await updateDBTimeSeries();
console.log('A round update database operations done.');
} catch (error) {
console.error(error);
}
}
function sleep(ms) {
return new Promise((resolve) => setTimeout(resolve, ms));
}
async function updateDB() {
return new Promise((resolve) => {
process.nextTick(() => {
console.log('Update database success.');
resolve();
});
});
}
async function updateDBEveryTenSeconds(item, n, next) {
await updateDB();
if (item < n - 1) {
await sleep(INNER_SCHEDULE * 1000);
}
next();
}
async function updateDBTimeSeries() {
const n = OUTER_SCHEDULE / INNER_SCHEDULE;
return new Promise((resolve, reject) => {
async.timesSeries(
n,
(item, next) => updateDBEveryTenSeconds(item, n, next),
(error, results) => {
if (error) {
return reject(error);
}
resolve(results);
}
);
});
}
main();
示例代码和GAE
例子的代码差不多,去掉了express
启动的HTTP
server的代码。
k8s/cronjobs/update-db.yaml
:
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: update-db
spec:
schedule: '*/1 * * * *'
startingDeadlineSeconds: 10
concurrencyPolicy: Forbid
successfulJobsHistoryLimit: 1
failedJobsHistoryLimit: 1
jobTemplate:
spec:
template:
metadata:
labels:
run: update-db
spec:
restartPolicy: Never
containers:
- name: cron-job-second-unit-schedule
image: asia.gcr.io/shadowsocks-218808/cron-job-second-unit-schedule:1.1
env:
- name: NODE_ENV
value: 'production'
- name: K8S_POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
ports:
- containerPort: 8080
protocol: TCP
设置schedule
为*/1 * * * *
,表示每分钟执行一次作业,具体执行什么作业?执行容器CMD
指令指定的启动脚本,即npm start
,即node ./src/index.js
。
Dockerfile
:
FROM node:8.9-alpine
WORKDIR /app
COPY ./ /app/
RUN apk update \
&& apk add curl --no-cache \
&& npm i -g npm@latest \
&& npm i --production
CMD [ "npm", "start" ]
package.json
:
"scripts": {
"start": "node ./src/index.js"
},
下面关于打包docker
image
,还有GKE
的使用和k8s cron job
的部署简单说下。
打包docker
image
:
docker build -t cron-job-second-unit-schedule:1.1 .
设置docker
tag
docker tag cron-job-second-unit-schedule:1.1 asia.gcr.io/shadowsocks-218808/cron-job-second-unit-schedule:1.1
push
该docker
image
到GCR
registry:
docker push asia.gcr.io/shadowsocks-218808/cron-job-second-unit-schedule:1.1
The push refers to repository [asia.gcr.io/shadowsocks-218808/cron-job-second-unit-schedule]
2a9069409556: Pushed
4a18dd75bba0: Pushed
fbe45ea1c2a6: Layer already exists
f846841ed47f: Layer already exists
0198944a9875: Layer already exists
9dfa40a0da3b: Layer already exists
1.1: digest: sha256:81e4b2b5ddda93781bf368372d8697cad5619ca7ffa763cdd1eb0a49893622d1 size: 1577
使用gcloud
命令行工具创建kubernetes cluster
:
☁ cron-job-second-unit-schedule [master] ⚡ gcloud container clusters create nodejs-gcp --num-nodes=3
Creating cluster nodejs-gcp in us-west1-a... Cluster is being health-checked (master is healthy)...done.
Created [https://container.googleapis.com/v1/projects/shadowsocks-218808/zones/us-west1-a/clusters/nodejs-gcp].
To inspect the contents of your cluster, go to: https://console.cloud.google.com/kubernetes/workload_/gcloud/us-west1-a/nodejs-gcp?project=shadowsocks-218808
kubeconfig entry generated for nodejs-gcp.
NAME LOCATION MASTER_VERSION MASTER_IP MACHINE_TYPE NODE_VERSION NUM_NODES STATUS
nodejs-gcp us-west1-a 1.11.7-gke.12 35.199.144.38 n1-standard-1 1.11.7-gke.12 3 RUNNING
为kubectl
命令设置默认集群,将kubectl
的context
设置为新创建的这个cluster
☁ cron-job-second-unit-schedule [master] ⚡ gcloud container clusters get-credentials nodejs-gcp
Fetching cluster endpoint and auth data.
kubeconfig entry generated for nodejs-gcp.
部署k8s
cron job:
☁ cron-job-second-unit-schedule [master] ⚡ kaf ./k8s/cronjobs/update-db.yaml
cronjob.batch "update-db" created
部署完成后,去GCP
控制台查看:
查看update-db
定时作业的container logs
:
可以看到该定时作业每10秒执行一次。
源码地址
GAE
: https://github.com/mrdulin/nodejs-gcp/tree/master/src/app-engine/cron-jobs-second-unit-schedule
GKE
: https://github.com/mrdulin/nodejs-gcp/tree/master/src/kubernetes-engine/cron-job-second-unit-schedule
顺便推荐个工具:https://crontab.guru/ - 输入*/1 * * * *
这样的crontab风格的schedule
,会输出文字表述的时间。