备忘录
批量杀线程
#!/bin/bash
ps -ef|grep $1|grep -v grep|awk '{print $2}'|xargs -r kill -9
MySQL
创建用户并且授权读写Schema
create user ${USERNAME} IDENTIFIED by '${PASSWORD}';
show grants for ${USERNAME};
grant all on ${SCHEMA}.* to ${USERNAME};
flush privileges;
MongoDB 权限配置
管理员权限配置
db.createUser({user:"root",pwd:"123456",roles: [{ role:"root", db:"admin"}]})
用户配置样例
db.createUser({
user: "someuser",
pwd: "somepassword",
roles:[
{ role: "readWrite", db: "somedb" }
]
})
删除用户
db.dropUser("username")
MongoDB 慢查询相关
查找当前大于10.0秒的、且最慢的一个查询的详情
mongo --quiet --eval "let limit_time = 10.0;" slow_query.js
统计大于10秒的慢查数量
mongo --quiet --eval "db.currentOp().inprog.filter(x=>x['secs_running']>10).length"
一般统计大于5秒,15秒,30秒,60秒,300秒的慢查数量。
查询Running总时间
这个指标可以从侧面反应数据库的操作体验和压力。
mongo --quiet --eval "db.currentOp().inprog.map(x=>x.microsecs_running/1000000.0).reduce((a,b)=>a+b)"
// 检查大于 limit_time 秒的慢查询数据
// let limit_time = 10.0;
// 上一句在eval里面执行来达到动态设置的效果
db.currentOp().inprog.filter(
x=>x["microsecs_running"]>(limit_time*1000000)
).sort(
// 取最慢的一条进行展示
(a,b)=>{
const va = a["microsecs_running"];
const vb = b["microsecs_running"];
if(a==b){
return 0;
}else{
if(a>b){
return -1;
}else{
return 1;
}
}
}
)
杀死超时任务
let over_time = 60.0;// Over 1 min
db.currentOp().inprog.forEach(
opInfo=>{
try{
const opId = opInfo["opid"];
const opDuration = opInfo["secs_running"];
if(opDuration>over_time){
db.killOp(opId);
console.log(`Operation ${opId} killed, details: ${JSON.stringify(opInfo)}`)
}
}catch(err){
console.error("Error while executing killing filter.")
console.error(err)
}
}
)
Python Tricks
Lazy Evaluation
From the blog Python 延迟初始化(lazy property)
class lazy(object):
def __init__(self, func):
self.func = func
def __get__(self, instance, cls):
val = self.func(instance)
setattr(instance, self.func.__name__, val)
return val
def lazy_property(func):
attr_name = "_lazy_" + func.__name__
@property
def _lazy_property(self):
if not hasattr(self, attr_name):
setattr(self, attr_name, func(self))
return getattr(self, attr_name)
return _lazy_property
Comparing with the lazy, it more like cache the result, maybe can also simply replaced by lru_cache
. We have to ensure the return value won't change while using it.
Example of Async wait
import asyncio
from asyncio import Future
from typing import Dict
futures: Dict[str, Future] = {}
@app.get("/test/lock/{task_id}")
async def test_lock(task_id: str):
result = asyncio.get_event_loop().create_future()
# Put the task in Queue
futures[task_id] = result
return {
"result": await result
}
@app.get("/test/release/{task_id}")
async def test_release(task_id: str):
if task_id not in futures:
raise Exception("Task not found")
# Set result while the task finished
futures[task_id].set_result(f"{task_id} is done")
return {
"task": task_id
}
FFMPEG
Convert MP4 File to MP3 File
ffmpeg -i ${MP4_FILE} -vn \
-acodec libmp3lame -ac 2 -ab 320k -ar 48000 \
${MP3_FILE}
Replace -ab {bitrate}
to -ac 2 -qscale:a 4
to use VBR
Convert to H264 mp4 file
ffmpeg -vcodec h264 -acodec copy -movflags +faststart -pix_fmt yuv420p -crf 23 -i input.mp4 output.mp4
Merge subtitle (srt) file and video
ffmpeg -i ${INPUT_VIDEO} -f srt -i ${SUBTITLE_FILE} -c:v copy -c:a copy -c:s srt ${OUTPUT_VIDEO}
# -c:s can also be copy
树莓派
RPI3 Ubuntu 摄像头
只能使用32位的系统
在
/boot/firmware/config.txt
里增加start_x=1
执行
sudo snap install picamera-streaming-demo
以后重启系统打开 http://:8000/ 即可查看
参考资料:
RPI3 Wifi
Edit
/etc/netplan/xxxxxx.yaml
:
# This file is generated from information provided by
# the datasource. Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
version: 2
ethernets:
eth0:
optional: true
dhcp4: true
# add wifi setup information here ...
wifis:
wlan0:
optional: true
access-points:
"YOUR-SSID-NAME":
password: "YOUR-NETWORK-PASSWORD"
dhcp4: true
sudo netplan --debug try
# (continue even if there are errors)
sudo netplan --debug generate
# (provides more details in case of issues with the previous command)
sudo netplan --debug apply
# (if no issues during the previous commands)
Reference: How to setup the Raspberry Pi 3 onboard WiFi for Ubuntu Server 18.04 with netplan?
Encryption
SAML2 key/pem generator
openssl req -x509 -sha256 -nodes -days 3650 -newkey rsa:2048 -keyout encryption.key -out encryption.pem
openssl req -x509 -sha256 -nodes -days 3650 -newkey rsa:2048 -keyout signing.key -out signing.pem
K8S
创建一个管理员账户的配置文件
首先创建一个Service Account
apiVersion: v1
kind: ServiceAccount
metadata:
name: <Account Name>
namespace: default
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: admin-user
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: cluster-admin
subjects:
- kind: ServiceAccount
name: <Account Name>
namespace: default
获取账户详情 kubectl describe serviceaccount <Account Name>
随后获取secret的名字,格式一般是 <Account Name>-token-<随机字符串>
最后获取Token:
kubectl describe secret <Token Secret Name>
apiVersion: v1
kind: Config
users:
- name: <Account Name>
user:
token: "<TOKEN>"
clusters:
- name: <Cluster Name>
cluster:
api-version: v1
server: <API ENDPOINT>
contexts:
- name: <Cluster Name>
context:
cluster: <Cluster Name>
user: <Account Name>
current-context: <Cluster Name>
Java/Scala/Kotlin
Maven Settings
Mainly ~/.m2/settings.xml
.
<?xml version="1.0" encoding="UTF-8"?>
<settings xmlns="http://maven.apache.org/SETTINGS/1.1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd">
<servers>
<server>
<id>nexus-snapshots</id>
<username>{username}</username>
<password>{password}</password>
</server>
<server>
<id>nexus-releases</id>
<username>{username}</username>
<password>{password}</password>
</server>
</servers>
<mirrors>
<mirror>
<id>central</id>
<name>central</name>
<url>https://nexus.xxxx.com/repository/maven/</url>
<mirrorOf>*</mirrorOf>
</mirror>
</mirrors>
</settings>
Glances
屏蔽多余的设备
在使用snap的时候经常会有一些奇怪的设备,包括loop{x}
或者是/snap/
之类的,这个时候只要在配置文件里加上
[fs]
hide=/boot.*,/snap.*
[diskio]
hide=loop.*
[network]
hide=docker.*,lo,veth.*
就可以屏蔽这些设备。
官方文档:
https://glances.readthedocs.io/en/latest/aoa/diskio.html
https://glances.readthedocs.io/en/latest/aoa/fs.html
配置文件的位置 https://glances.readthedocs.io/en/latest/config.html
Git
自动使用SSH代替HTTP
来源:https://www.digitalocean.com/community/tutorials/how-to-use-a-private-go-module-in-your-own-project
在~/.gitconfig
加入这一段:
[url "ssh://[email protected]/"]
insteadOf = https://github.com/
不仅可以用于导入私有的Go模块,还可以用于Brew安装的时候自动拉取Repo。
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