2019年10月3日星期四

golang context 讓程式變髒了

為了解決goroutine間(特別是多層樹狀)取消( cancelation )
在 go 1.7 提供了 context standard library。
https://blog.golang.org/context

雖然提供了方便簡潔的操控goroutine的取消方法，並利用channel自動的通知取消給所有子執行緒。以及讓整顆樹的goroutine都能共享資料。

但官方希望我們不要二次封裝 context，而採用參數方式傳到每一個相關的function裡，連變數名稱都幫我們想好( ctx )，而且還建議放第一個參數。
這.... ，說真的，我不太能接受。

我們原本優雅的程式，讓這 ctx 污了整個code。

func doSomething(...interface{}) {
...
}

硬生生要變成這樣...

func doSomething(ctx context.Context, ...interface{}) {
...
   ctx.Done()
}

context 讓程式變髒了，就為了執行 ctx.Done()，ctx.Value(key)

@@

其實在讀完context的原始碼後，大概能理解原由。
雖然context source code寫得相當精要傳神，但個人認為其還是有許多的改善空間。

2019年9月24日星期二

golang sqlbuilder

https://github.com/eehsiao/sqlbuilder

sqlbuilder

sqlbuilder is a simple sql query string builder

sqlbuilder its recursive struct call, that you can easy to build sql string

ex: dao.Select().From().Join().Where().Limit()

SqlBuilder functions

build select :
- Select(f ...string)
  - f is a fileds list of strings
  - Select("filed1", "filed2", "filed3")
  - Select(lib.Struce4QuerySlice(DaoStructType)...)
    - the library ref : https://github.com/eehsiao/go-models-lib
- Distinct(b bool)
  - its default in builder is set false
- Top(i int)
  - only support mssql
- From(t ...string)
  - t is table name
- Where(c string)
  - c is condition, ex Where("field1=1 and filed2='b'")
- WhereAnd(c ...string)
- WhereOr(c ...string)
- Limit(i ...int)
  - support 2 parms
  - only support mysql
- Join(t string, c string)
  - t is table name
  - c is condition
- InnerJoin(t string, c string)
- LeftJoin(t string, c string)
- RightJoin(t string, c string)
- FullJoin(t string, c string)
- GroupBy(f ...string)
  - f is a fileds list of strings
- OrderBy(f ...string)
  - f is a fileds list of strings
- OrderByAsc(f ...string)
- OrderByDesc(f ...string)
- Having(s string)
  - s is having condition string
- BuildSelectSQL()
  - check and build sql string.
  - you can get sql string via BuildedSQL()
build update :
- Set(s map[string]interface{})
- FromOne(t string)
  - reset the table for only one
- BuildUpdateSQL()
  - check and build sql string.
  - you can get sql string via BuildedSQL()
build insert :
- Into(t string)
  - set the insert table
- Fields(f ...string)
  - f is a fileds list of strings
- Values(v ...[]interface{})
  - v is a values list of interface{}
- BuildInsertSQL()
  - check and build sql string.
  - you can get sql string via BuildedSQL()
build delete :
- BuildDeleteSQL()
  - check and build sql string.
  - you can get sql string via BuildedSQL()
common :
- ClearBuilder()
  - reset builder
- BuildedSQL()
  - return the builded sql string, if build success.
- SetDbName(s string)
- SetTbName(s string)
- SwitchPanicToErrorLog(b bool)
- PanicOrErrorLog(s string)

2019年9月17日星期二

Inter-Process Communication via websocket (golang)

github : https://github.com/eehsiao/websocket-ipc

websocket-ipc

Inter-Process Communication via websocket

how to be a deamon

install : install into service start : run as a deamon

sudo ./example install
sudo ./example start

how to stop deamon

when the deamon start

sudo ./example stop

how to remove deamon

when the deamon stop

sudo ./example remove

how to Communication

when the deamon start

sudo ./example {any string otherwise commands}

golang 連接mysql, redis 讀取資料的套件，簡單又好用

套件位置:
https://github.com/eehsiao/go-models-mysql
https://github.com/eehsiao/go-models-redis
https://github.com/eehsiao/go-models-lib
https://github.com/eehsiao/sqlbuilder
godoc:
https://godoc.org/github.com/eehsiao/go-models-mysql
https://godoc.org/github.com/eehsiao/go-models-redis
https://godoc.org/github.com/eehsiao/go-models-lib
https://godoc.org/github.com/eehsiao/sqlbuilder

go-models-mysql

go-models-mysql its lite and easy model.

Features

Field scanning has become easier since the original driver was extended. Assumption: we have 5 fields to scan

type Tb struct {
 field0 sql.NullString,
 field1 sql.NullString,
 field2 sql.NullString,
 field3 sql.NullString,
 field4 sql.NullString,
}

In original driver, it can't dynamic. how many fields, that you must write fields many how. it you have 20 fileds, you must write 20 times.

var tb Tb
err = rows.Scan(&tb.field0, &tb.field1, &tb.field2, &tb.field3, &tb.field4)

In go-models-mysql , you just fill struct nil pointer.

if val, err = myDao.ScanRowType(row, (*Tb)(nil)); err == nil {
 u, _ := val.(*Tb)
 fmt.Println("Tb", u)
}

DAO layer let you operate mysql more Intuitively.

Original driver (sql.DB) was extended, so you can operate original commands.
- ex: Query, QueryRow, Exec ....
Import the sqlbuilder that help access sql db easily.

 myDao.Select("Host", "User", "Select_priv").From("user").Where("User='root'").Limit(1)

Set the default table in DAO, that you can design your dao layer friendly.

 // set a struct for dao as default model (option)
 // (*UserTb)(nil) : nil pointer of the UserTb struct
 // "user" : is real table name in the db
 myUserDao.SetDefaultModel((*UserTb)(nil), "user")

 // call model's Get() , get all rows in user table
 // return (rows *sql.Rows, err error)
 rows, err = myDao.Get()

Requirements

Go 1.12 or higher.
database/sql package
go-sql-driver/mysql package

Go-Module

create go.mod file in your package folder, and fill below

module github.com/eehsiao/go-models-example

go 1.13

require (
 github.com/eehsiao/go-models-lib latest
 github.com/eehsiao/go-models-mysql latest
 github.com/eehsiao/go-models-redis latest
 github.com/eehsiao/sqlbuilder latest
 github.com/go-sql-driver/mysql v1.4.1
)

Docker

Easy to start the test evn. That you can run the example code.

$ docker-compose up -d

Usage

import (
    "database/sql"
 "fmt"

 mysql "github.com/eehsiao/go-models-mysql"
 redis "github.com/eehsiao/go-models-redis"
)

// UserTb : sql table struct that to store into mysql
type UserTb struct {
 Host       sql.NullString `TbField:"Host"`
 User       sql.NullString `TbField:"User"`
 SelectPriv sql.NullString `TbField:"Select_priv"`
}

//new mysql dao
myUserDao := &MyUserDao{
    Dao: mysql.NewDao().SetConfig("root", "mYaDmin", "127.0.0.1:3306", "mysql").OpenDB(),
}

// example 1 : directly use the sqlbuilder
myUserDao.Select("Host", "User", "Select_priv").From("user").Where("User='root'").Limit(1)
fmt.Println("sqlbuilder", myUserDao.BuildSelectSQL())
if row, err = myUserDao.GetRow(); err == nil {
    if val, err = myUserDao.ScanRowType(row, (*UserTb)(nil)); err == nil {
        u, _ := val.(*UserTb)
        fmt.Println("UserTb", u)
    }
}
    
// set a struct for dao as default model (option)
// (*UserTb)(nil) : nil pointer of the UserTb struct
// "user" : is real table name in the db
myUserDao.SetDefaultModel((*UserTb)(nil), "user")

// call model's Get() , get all rows in user table
// return (rows *sql.Rows, err error)
rows, err = myDao.Get()

// call model's GetRow() , get first row in user rows
// return (row *sql.Row, err error)
row, err = myDao.GetRow()

Example

1 build-in

example.go

The example will connect to local mysql and get user data. Then connect to local redis and set user data, and get back.

2 example

https://github.com/eehsiao/go-models-example/

How-to

How to design model data logical

MySQL

1.

create a table struct, and add the tag TbField:"real table filed"

TbField the tag is musted. read table filed also be same the table field.

type UserTb struct {
 Host       sql.NullString `TbField:"Host"`
 User       sql.NullString `TbField:"User"`
 SelectPriv sql.NullString `TbField:"Select_priv"`
}

2.

use Struce4QuerySlice to gen the sqlbuilder select fields

m := mysql.NewDao().SetConfig("root", "mYaDmin", "127.0.0.1:3306", "mysql").OpenDB()
m.Select(lib.Struce4QuerySlice(m.DaoStructType)...).From(m.TbName).Limit(3)

3.

scan the sql result to the struct of object

row, err = m.GetRow()
if val, err = m.ScanRowType(row, (*UserTb)(nil)); err == nil {
    u, _ := val.(*UserTb)
    fmt.Println("UserTb", u)
}

2019年9月16日星期一

golang go mod reading https://sum.golang.org/lookup/github.com/... 410 Gone (slove)

研究 go module 且跨多的module引用時, 發生

verifying github.com/eehsiao/go-models-lib@v0.0.1/go.mod: github.com/eehsiao/go-models-lib@v0.0.1/go.mod: reading https://sum.golang.org/lookup/github.com/eehsiao/go-models-lib@v0.0.1: 410 Gone

解決方法 (solve)

go mod tidy

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2019年10月3日 星期四