连接被拒绝：服务器是否在主机“ db”172.21.0.2上运行并在端口5432上接受web_1 TCP / IP连接？

如何解决连接被拒绝：服务器是否在主机“ db”172.21.0.2上运行并在端口5432上接受web_1 TCP / IP连接？

我知道这是一个典型的问题，但是我需要社区的帮助来解决。当我运行docker-compose时，连接被拒绝：服务器是否在主机“ db”（172.21.0.2）上运行并在端口5432上接受web_1 TCP / IP连接？ docker-compose的Web部分失败，但是db运行。我可以使用localhost：5432连接到数据库。这不是一个等待问题，因为tiangolo / uvicorn-gunicorn：python3.8-alpine3.10实现了一个等待机制-dockerize。有人知道问题出在哪里吗？也许有人能为我指出正确的方向？ 所以我的Dockerfile是

FROM tiangolo/uvicorn-gunicorn:python3.8-alpine3.10

# copy requirements file
COPY ./requirements.txt /usr/src/app/requirements.txt

# install dependencies
RUN set -eux \
    && apk add --no-cache --virtual .build-deps build-base \
        libressl-dev libffi-dev gcc musl-dev python3-dev \
        postgresql-dev openssl \
    && pip install --upgrade pip setuptools wheel \
    && pip install -r /usr/src/app/requirements.txt \
    && rm -rf /root/.cache/pip

# copy project
COPY . /app

我的docker-compose是：

version: '3.7'

services:
    db:
        image: postgres:13-alpine
        volumes:
            - postgres_data:/var/lib/postgresql/data/
        ports:
            - 5432:5432
        environment:
            - POSTGRES_USER=postgres
            - POSTGRES_PASSWORD=postgres
            - POSTGRES_DB=api

    web:
        build: ./src  
        ports:
            - 80:80
        depends_on:
            - db
        environment:
            - DATABASE_URL=postgresql://postgres:postgres@db/api

volumes:
    postgres_data:

我使用dockerize添加了一个等待，但是Web部分失败：

Attaching to gunicorn_db_1,gunicorn_web_1
db_1   | The files belonging to this database system will be owned by user "postgres".
db_1   | This user must also own the server process.
db_1   |
db_1   | The database cluster will be initialized with locale "en_US.utf8".
db_1   | The default database encoding has accordingly been set to "UTF8".
db_1   | The default text search configuration will be set to "english".
db_1   |
db_1   | Data page checksums are disabled.
db_1   |
db_1   | fixing permissions on existing directory /var/lib/postgresql/data ... ok
db_1   | creating subdirectories ... ok
db_1   | selecting dynamic shared memory implementation ... posix
db_1   | selecting default max_connections ... 100
db_1   | selecting default shared_buffers ... 128MB
web_1  | 2020/08/30 15:33:51 Waiting for: tcp://db:5432
web_1  | 2020/08/30 15:33:51 Problem with dial: dial tcp 172.21.0.2:5432: connect: connection refused. Sleeping 30s
db_1   | selecting default time zone ... Etc/UTC
db_1   | creating configuration files ... ok
db_1   | running bootstrap script ... ok
db_1   | performing post-bootstrap initialization ... ok
db_1   | syncing data to disk ... initdb: warning: enabling "trust" authentication for local connections
db_1   | You can change this by editing pg_hba.conf or using the option -A,or
db_1   | --auth-local and --auth-host,the next time you run initdb.
db_1   | ok
db_1   |
db_1   |
db_1   | Success. You can now start the database server using:
db_1   |
db_1   |     pg_ctl -D /var/lib/postgresql/data -l logfile start
db_1   |
db_1   | waiting for server to start....2020-08-30 15:33:53.037 UTC [45] LOG:  starting PostgreSQL 13beta3 (Debian 13~beta3-1.pgdg100+1) on x86_64-pc-linux-gnu,compiled by gcc (Debian 8.3.0-6) 8.3.0,64-bit
db_1   | 2020-08-30 15:33:53.044 UTC [45] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1   | 2020-08-30 15:33:53.059 UTC [46] LOG:  database system was shut down at 2020-08-30 15:33:52 UTC
db_1   | 2020-08-30 15:33:53.066 UTC [45] LOG:  database system is ready to accept connections
db_1   |  done
db_1   | server started
db_1   | CREATE DATABASE
db_1   |
db_1   |
db_1   | /usr/local/bin/docker-entrypoint.sh: ignoring /docker-entrypoint-initdb.d/*
db_1   |
db_1   | 2020-08-30 15:33:53.399 UTC [45] LOG:  received fast shutdown request
db_1   | waiting for server to shut down....2020-08-30 15:33:53.404 UTC [45] LOG:  aborting any active transactions
db_1   | 2020-08-30 15:33:53.407 UTC [45] LOG:  background worker "logical replication launcher" (PID 52) exited with exit code 1
db_1   | 2020-08-30 15:33:53.409 UTC [47] LOG:  shutting down
db_1   | 2020-08-30 15:33:53.438 UTC [45] LOG:  database system is shut down
db_1   |  done
db_1   | server stopped
db_1   |
db_1   | PostgreSQL init process complete; ready for start up.
db_1   |
db_1   | 2020-08-30 15:33:53.530 UTC [1] LOG:  starting PostgreSQL 13beta3 (Debian 13~beta3-1.pgdg100+1) on x86_64-pc-linux-gnu,64-bit
db_1   | 2020-08-30 15:33:53.531 UTC [1] LOG:  listening on IPv4 address "0.0.0.0",port 5432
db_1   | 2020-08-30 15:33:53.531 UTC [1] LOG:  listening on IPv6 address "::",port 5432
db_1   | 2020-08-30 15:33:53.539 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1   | 2020-08-30 15:33:53.549 UTC [63] LOG:  database system was shut down at 2020-08-30 15:33:53 UTC
db_1   | 2020-08-30 15:33:53.559 UTC [1] LOG:  database system is ready to accept connections
web_1  | 2020/08/30 15:34:21 Connected to tcp://db:5432
gunicorn_web_1 exited with code 0

解决方法

乍看之下，两个文件对我来说似乎都很不错，实际上添加一个依赖项应该可以解决此问题，但是根据无法正常工作的文档显示。它表示容器之间的依赖关系，但这并不意味着容器将等待其他容器准备就绪。

对于撰写的旧版本，我们可以添加运行状况检查

healthcheck:
  test: ["-U postgres"]
  interval: 3s
  timeout: 30s
  retries: 1

但是，由于不再受支持，因此最好的选择是向该服务添加手动等待/睡眠。

有一个广泛使用的bash脚本（wait for it），可用于测试并等待TCP主机和端口的可用性。还建议使用Compose Documentation中的解决方案。您可以将wait for it复制到文件中并立即开始使用。

web:
    command: /wait-for-it.sh db:5432

您还可能需要检查一下：Wait for it usage with docker

,

所以，我的问题只发生在金枪鱼上。现在，我选择unicorn + nginx作为反向代理，而不选择gunicorn：）

,

只需将 Docker-Compose 的版本更改为版本：“3.5” 这解决了问题