如何在 Docker 个容器之间建立连接

Question

当我尝试将我的 goLang GORM 服务连接到 Docker Postgress 容器时遇到连接问题。我认为问题出在连接字符串底部的 golang 代码上。

docker-compose up
Recreating postgress_postgre_1 ... done
Attaching to postgres
postgres   | 2018-12-11 21:08:48.283 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
postgres   | 2018-12-11 21:08:48.283 UTC [1] LOG:  listening on IPv6 address "::", port 5432
postgres   | 2018-12-11 21:08:48.291 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgres   | 2018-12-11 21:08:48.316 UTC [20] LOG:  database system was shut down at 2018-12-11 21:08:44 UTC
postgres   | 2018-12-11 21:08:48.328 UTC [1] LOG:  database system is ready to accept connections

=== 当我运行 golang 我得到...恐慌：无法连接数据库

=============== docker-compose.yml

version: '3.6'
services:
  postgre:
    image: postgres:11.1-alpine
    ports:
      - '5432:5432'
    network_mode: bridge
    container_name: postgres

    environment:
      POSTGRES_USER: 'user'
      POSTGRES_PASSWORD: 'password'
      POSTGRESS_DB: 'db_amex01'
    volumes:
      - ./init:/docker-entrypoint-initdb.d/

==== main.go

主要包

import (
    "fmt"
    "log"
    "net/http"

    "github.com/gorilla/mux"
    "github.com/jinzhu/gorm"

    // _ "github.com/jinzhu/gorm/dialects/sqlite"
    _ "github.com/jinzhu/gorm/dialects/postgres"
)

// _ "github.com/jinzhu/gorm/blob/master/dialects/postgres"

type ToDo struct {
    gorm.Model
    ID          int    `json:"id"`
    TASK_STRING string `json:"task_string"`
    DONE        bool   `json:"done"`
}

var db *gorm.DB
var err error

func main() {
    const (
        host     = "localhost"
        port     = 5432
        user     = "postgres"
        password = "password"
        dbname   = "db_amex01"
    )


// this is the problem I believe I am having...

    db, err := gorm.Open("postgres", "host='postgres' port=5432 user=user dbname='db_amex01' password='password'")



    defer db.Close()

    if err != nil {
        panic("failed to connect database")
    }

    defer db.Close()

Answer 1

您似乎正在放弃从 gorm.Open() 返回的错误。要确切知道为什么 gorm 无法打开连接，您需要输出错误。

而不是：

panic("failed to connect database")

使用：

panic("failed to connect database: " + err)

乍一看，可能是你的主机配置错误

host='postgres' port=5432 user=user dbname='db_amex01' password='password'

应该是：

host=localhost port=5432 user=user dbname=db_amex01 password=password

但是如果没有来自 gorm.Open()

的错误就很难判断

还有一点要注意；在第一次检查错误之前不要调用 db.Close()。在出现错误的情况下，db 可能是 nil，导致对 db 的任何方法的调用出现恐慌。您还在发布的代码片段中两次调用 db.Close() 。不要这样做。 Golang 关于 io.Closer 的文档：

Closer is the interface that wraps the basic Close method.

The behavior of Close after the first call is undefined. Specific implementations may document their own behavior.

编辑（2018 年 12 月 12 日）：

当我在本地运行你的代码时，我从 gorm 得到的错误是关于 SSL 的，因为你是运行你的 postgres 服务器，通过 docker-compose 没有任何 SSL 配置.您可以将 sslmode=disable 标志添加到您的连接字符串以解决此问题。

您的 docker-compose.yml 中还有一个拼写错误：POSTGRESS_DB 应该是 POSTGRES_DB。

这是我在本地运行获得的完整工作示例：

docker-compose.yml:

version: '3.6'
services:
  postgres:
    image: postgres:11.1-alpine
    ports:
      - '5432:5432'
    environment:
      POSTGRES_USER: 'test_user'
      POSTGRES_PASSWORD: 'test_password'
      POSTGRES_DB: 'test_database'
    volumes:
      - ./init:/docker-entrypoint-initdb.d/

main.go:

package main

import (
    "fmt"
    "log"

    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/postgres"
)

const (
    host     = "localhost"
    port     = "5432"
    user     = "test_user"
    password = "test_password"
    dbname   = "test_database"
)

func main() {
    url := fmt.Sprintf("postgres://%s:%s@%s:%s/%s?sslmode=disable",
        user,
        password,
        host,
        port,
        dbname,
    )

    db, err := gorm.Open("postgres", url)
    if err != nil {
        log.Fatalf("error connecting to database: %v", err)
    }
    defer db.Close()

    if err := db.DB().Ping(); err != nil {
        log.Fatalf("error pinging database: %v", err)
    }

    fmt.Println("Success!")
}

Answer 2

您的撰写文件中有错字，您将服务命名为 postgre 但连接到 postgres。 Docker 使用服务名称作为共享网络上的 DNS 别名，因此这会中断您的连接尝试。要修复，只需重命名您的服务：

version: '3.6'
services:
  postgres:
    image: postgres:11.1-alpine
    ports:
      - '5432:5432'
    environment:
      POSTGRES_USER: 'user'
      POSTGRES_PASSWORD: 'password'
      POSTGRESS_DB: 'db_amex01'
    volumes:
      - ./init:/docker-entrypoint-initdb.d/

如何在 Docker 个容器之间建立连接

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