如何使用Go和Docker等待PostgreSQL数据库？

huangapple
go评论125阅读模式
英文:

How to wait postgres db using go with docker?

问题

我使用docker-compose部署了一个使用gorm和postgres的Go应用程序。

我通过另一个容器服务进行了数据库创建和数据迁移。这里只列出了应用程序和数据库容器的问题。

docker-compose.yml

  1.   app:
  2.     build: ./app
  3.     command: ["/bin/wait-for-it.sh", "db:5432", "--", "/bin/main"]
  4.     volumes:
  5.       - ./app/:/app/
  6.     ports:
  7.       - 8080:8080
  8.     environment:
  9.       - DB_USER=postgres
  10.       - DB_NAME=mydb
  11.       - DB_PASS=password
  12.     depends_on:
  13.       - db
  14.     links:
  15.       - db
  17.   db:
  18.     image: postgres:13-alpine
  19.     environment:
  20.       - POSTGRES_PASSWORD=password
  21.       - POSTGRES_DB=mydb

Dockerfile

  1. FROM golang:1.16.3-alpine3.13 AS builder
  2. WORKDIR /app
  3. COPY . .
  4. RUN CGO_ENABLED=0 GOOS=linux go build -o main
  6. FROM alpine:3.13
  7. RUN apk update && apk --no-cache add bash
  8. COPY --from=builder /app /bin/.
  9. RUN ["chmod", "+x", "/bin/wait-for-it.sh"]

db/db.go

  1. package db
  3. import (
  4.     "fmt"
  5.     "os"
  7.     "gorm.io/driver/postgres"
  8.     "gorm.io/gorm"
  9. )
  11. var (
  12.     db *gorm.DB
  13. )
  15. func Init() {
  16.     conn := fmt.Sprintf("host=db port=5432 user=%s password=%s dbname=%s sslmode=disable", os.Getenv("DB_USER"), os.Getenv("DB_PASS"), os.Getenv("DB_NAME"))
  18.     _, err := gorm.Open(postgres.Open(conn), &gorm.Config{})
  19.     if err != nil {
  20.         panic(err)
  21.     }
  22. }
  24. func GetDB() *gorm.DB {
  25.     return db
  26. }

models/post.go

  1. package models
  3. type Post struct {
  4.     ID    int    `json:"id" gorm:"primary_key"`
  5.     Title string `json:"title"`
  6.     Body  string `json:"body"`
  7. }

main.go

  1.    1   │ package main
  2.    2   │
  3.    3   │ import (
  4.    4   │     "app/db"
  5.    5   │     "app/models"
  6.    6   │     "fmt"
  7.    7   │ )
  8.    8   │
  9.    9   │ func main() {
  10.   10   │     db.Init()
  11.   11   │
  12.   12   │     db := db.GetDB()
  13.   13   │
  14.   14   │     var posts []models.Post
  15.   15   │     db.Find(&posts)
  16.   16   │     fmt.Println(posts)
  17.   17   │ }

在构建docker-compose时，它首先尝试连接数据库，但似乎数据库尚未可达。即使添加了wait-for-it，也无法解决问题。

  1. app_1   | wait-for-it.sh: waiting 15 seconds for db:5432
  2. db_1    |
  3. db_1    | PostgreSQL Database directory appears to contain a database; Skipping initialization
  4. db_1    |
  5. app_1   | wait-for-it.sh: db:5432 is available after 0 seconds
  6. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  starting PostgreSQL 13.2 on x86_64-pc-linux-musl, compiled by gcc (Alpine 10.2.1_pre1) 10.2.1 20201203, 64-bit
  7. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
  8. app_1   | panic: runtime error: invalid memory address or nil pointer dereference
  9. app_1   | [signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x59c446]
  10. app_1   |
  11. app_1   | goroutine 1 [running]:
  12. app_1   | gorm.io/gorm.(*DB).getInstance(0x0, 0xc000026038)
  13. app_1   | 	/go/pkg/mod/gorm.io/gorm@v1.21.10/gorm.go:355 +0x26
  14. app_1   | gorm.io/gorm.(*DB).Find(0x0, 0x868220, 0xc00000c018, 0x0, 0x0, 0x0, 0xc000094058)
  15. app_1   | 	/go/pkg/mod/gorm.io/gorm@v1.21.10/finisher_api.go:159 +0x2f
  16. app_1   | main.main()
  17. app_1   | 	/app/main.go:15 +0x7f
  18. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  listening on IPv6 address "::", port 5432
  19. db_1    | 2021-06-02 03:53:03.734 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
  20. db_1    | 2021-06-02 03:53:03.741 UTC [22] LOG:  database system was shut down at 2021-06-02 03:52:34 UTC
  21. db_1    | 2021-06-02 03:53:03.747 UTC [1] LOG:  database system is ready to accept connections
  22. myapp_app_1 exited with code 2

如何正确设置？

/app/main.go:15有什么问题吗？它应该正常工作并获取数据。

英文:

I deployed a go with gorm app using postgres by docker-compose.

I did db creation and data migration by an another container service. Here only listed the app and db container issues.

docker-compose.yml

  1.   app:
  2.     build: ./app
  3.     command: ["/bin/wait-for-it.sh", "db:5432", "--", "/bin/main"]
  4.     volumes:
  5.       - ./app/:/app/
  6.     ports:
  7.       - 8080:8080
  8.     environment:
  9.       - DB_USER=postgres
  10.       - DB_NAME=mydb
  11.       - DB_PASS=password
  12.     depends_on:
  13.       - db
  14.     links:
  15.       - db
  17.   db:
  18.     image: postgres:13-alpine
  19.     environment:
  20.       - POSTGRES_PASSWORD=password
  21.       - POSTGRES_DB=mydb

Dockerfile

  1. FROM golang:1.16.3-alpine3.13 AS builder
  2. WORKDIR /app
  3. COPY . .
  4. RUN CGO_ENABLED=0 GOOS=linux go build -o main
  6. FROM alpine:3.13
  7. RUN apk update && apk --no-cache add bash
  8. COPY --from=builder /app /bin/.
  9. RUN ["chmod", "+x", "/bin/wait-for-it.sh"]

db/db.go

  1. package db
  3. import (
  4.     "fmt"
  5.     "os"
  7.     "gorm.io/driver/postgres"
  8.     "gorm.io/gorm"
  9. )
  11. var (
  12.     db *gorm.DB
  13. )
  15. func Init() {
  16.     conn := fmt.Sprintf("host=db port=5432 user=%s password=%s dbname=%s sslmode=disable", os.Getenv("DB_USER"), os.Getenv("DB_PASS"), os.Getenv("DB_NAME"))
  18.     _, err := gorm.Open(postgres.Open(conn), &gorm.Config{})
  19.     if err != nil {
  20.         panic(err)
  21.     }
  22. }
  24. func GetDB() *gorm.DB {
  25.     return db
  26. }

models/post.go

  1. package models
  3. type Post struct {
  4.     ID    int    `json:"id" gorm:"primary_key"`
  5.     Title string `json:"title"`
  6.     Body  string `json:"body"`
  7. }

main.go

  1.    1   │ package main
  2.    2   │
  3.    3   │ import (
  4.    4   │     "app/db"
  5.    5   │     "app/models"
  6.    6   │     "fmt"
  7.    7   │ )
  8.    8   │
  9.    9   │ func main() {
  10.   10   │     db.Init()
  11.   11   │
  12.   12   │     db := db.GetDB()
  13.   13   │
  14.   14   │     var posts []models.Post
  15.   15   │     db.Find(&posts)
  16.   16   │     fmt.Println(posts)
  17.   17   │ }

When start to build docker-compose, it tried to connect db first, but it seems that db didn't become reachable yet. Even added wait-for-it doesn't work.

  1. app_1   | wait-for-it.sh: waiting 15 seconds for db:5432
  2. db_1    |
  3. db_1    | PostgreSQL Database directory appears to contain a database; Skipping initialization
  4. db_1    |
  5. app_1   | wait-for-it.sh: db:5432 is available after 0 seconds
  6. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  starting PostgreSQL 13.2 on x86_64-pc-linux-musl, compiled by gcc (Alpine 10.2.1_pre1) 10.2.1 20201203, 64-bit
  7. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
  8. app_1   | panic: runtime error: invalid memory address or nil pointer dereference
  9. app_1   | [signal SIGSEGV: segmentation violation code=0x1 addr=0x28 pc=0x59c446]
  10. app_1   |
  11. app_1   | goroutine 1 [running]:
  12. app_1   | gorm.io/gorm.(*DB).getInstance(0x0, 0xc000026038)
  13. app_1   | 	/go/pkg/mod/gorm.io/gorm@v1.21.10/gorm.go:355 +0x26
  14. app_1   | gorm.io/gorm.(*DB).Find(0x0, 0x868220, 0xc00000c018, 0x0, 0x0, 0x0, 0xc000094058)
  15. app_1   | 	/go/pkg/mod/gorm.io/gorm@v1.21.10/finisher_api.go:159 +0x2f
  16. app_1   | main.main()
  17. app_1   | 	/app/main.go:15 +0x7f
  18. db_1    | 2021-06-02 03:53:03.731 UTC [1] LOG:  listening on IPv6 address "::", port 5432
  19. db_1    | 2021-06-02 03:53:03.734 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
  20. db_1    | 2021-06-02 03:53:03.741 UTC [22] LOG:  database system was shut down at 2021-06-02 03:52:34 UTC
  21. db_1    | 2021-06-02 03:53:03.747 UTC [1] LOG:  database system is ready to accept connections
  22. myapp_app_1 exited with code 2

How to set it correctly?

Does /app/main.go:15 anything incorrect? It should work and get data normally.

答案1

得分: 1

你需要在你的命令中添加等待时间：

  1. 命令: ["/bin/wait-for-it.sh", "db:5432", "-t", "600000000", "--", "/bin/main"]

这里的时间是等待的最长时间，当数据库启动并运行时，应用程序/bin/main将立即执行。

当你不使用-t参数运行时，默认等待时间为15秒。

更多信息请参考这里。

英文:

you need to add the Time for waiting in your command:

  1. command: ["/bin/wait-for-it.sh", "db:5432", "-t", "600000000", "--", "/bin/main"]

the time is here the maximun time for waiting, the app /bin/main will be excuted as soon the DB is up and running.

when you run without -t the default is 15 seconds

more info Here

huangapple
  • 本文由 发表于 2021年6月2日 13:44:00
  • 转载请务必保留本文链接：https://go.coder-hub.com/67799504.html
  • docker
  • docker-compose
  • go
  • go-gorm
  • postgresql
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