如何在 Ubuntu Docker 映像旁邊啟動 Postgresql 數據庫容器？

Question

如何使用 docker-compose 在一個容器中啟動 PostgreSQL，並允許 Ubuntu 22 容器訪問它？

我的docker-compose.yml看起來像：

version: "3.6"
services:
  db:
    image: postgres:14-alpine
    environment:
      - POSTGRES_USER=test
      - POSTGRES_PASSWORD=test
      - POSTGRES_DB=test
    command: -c fsync=off -c synchronous_commit=off -c full_page_writes=off --max-connections=200 --shared-buffers=4GB --work-mem=20MB
    tmpfs:
      - /var/lib/postgresql
  app_test:
    build:
      context: ..
      dockerfile: Dockerfile
      shm_size: '2gb'
    volumes:
      - /dev/shm:/dev/shm

我的Dockerfile只運行一個 Django 單元測試套件，該套件使用相同的憑據連接到 PostgreSQL 數據庫。 但是，看起來數據庫會定期崩潰或停止和啟動，從而中斷與測試的連接。

當我運行時：

docker-compose -f docker-compose.yml -p myproject up --build --exit-code-from myproject_app

我得到 output 喜歡：

Successfully built 45c74650b75f
Successfully tagged myproject_app:latest
Creating myproject_app_test_1 ... done
Creating myproject_db_1       ... done
Attaching to myproject_app_test_1, myproject_db_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
db_1        | selecting default time zone ... UTC
db_1        | creating configuration files ... ok
app_test_1  | SITE not set. Defaulting to myproject.
app_test_1  | Initialized settings for site "myproject".
db_1        | running bootstrap script ... ok
db_1        | performing post-bootstrap initialization ... sh: locale: not found
db_1        | 2022-09-23 02:06:54.175 UTC [30] WARNING:  no usable system locales were found
db_1        | 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....2022-09-23 02:06:56.736 UTC [36] LOG:  starting PostgreSQL 14.4 on x86_64-pc-linux-musl, compiled by gcc (Alpine 11.2.1_git20220219) 11.2.1 20220219, 64-bit
db_1        | 2022-09-23 02:06:56.737 UTC [36] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1        | 2022-09-23 02:06:56.743 UTC [37] LOG:  database system was shut down at 2022-09-23 02:06:56 UTC
db_1        | 2022-09-23 02:06:56.750 UTC [36] 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        | 2022-09-23 02:06:57.100 UTC [36] LOG:  received fast shutdown request
db_1        | 2022-09-23 02:06:57.101 UTC [36] LOG:  aborting any active transactions
db_1        | 2022-09-23 02:06:57.104 UTC [36] LOG:  background worker "logical replication launcher" (PID 43) exited with exit code 1
db_1        | 2022-09-23 02:06:57.105 UTC [38] LOG:  shutting down
db_1        | waiting for server to shut down....2022-09-23 02:06:57.222 UTC [36] 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        | 2022-09-23 02:06:57.566 UTC [1] LOG:  starting PostgreSQL 14.4 on x86_64-pc-linux-musl, compiled by gcc (Alpine 11.2.1_git20220219) 11.2.1 20220219, 64-bit
db_1        | 2022-09-23 02:06:57.568 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1        | 2022-09-23 02:06:57.569 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db_1        | 2022-09-23 02:06:57.571 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1        | 2022-09-23 02:06:57.576 UTC [50] LOG:  database system was shut down at 2022-09-23 02:06:57 UTC
db_1        | 2022-09-23 02:06:57.583 UTC [1] LOG:  database system is ready to accept connections
db_1        | 2022-09-23 02:06:58.805 UTC [57] ERROR:  relation "django_site" does not exist at character 78
db_1        | 2022-09-23 02:06:58.805 UTC [57] STATEMENT:  SELECT "django_site"."id", "django_site"."domain", "django_site"."name" FROM "django_site" WHERE "django_site"."id" = 2 LIMIT 21

為什么顯示正在shutting down和database system was shut down ，意味着數據庫重新啟動了幾次？ 為什么 Django 無法訪問它來初始化架構？

Answer 1

在 docker-compose 中使用數據庫時，您總是需要等待它們完全啟動。 您的程序需要 ping 並等待（在第一次嘗試連接可能仍在啟動的數據庫失敗后不會崩潰），或者您可以使用著名的 now wait-for-it.sh 腳本。

下面是第二種方法的示例。

Dockerfile：

FROM debian:stable

WORKDIR /scripts

RUN apt-get update && apt-get install -y curl telnet

# there are many versions on the internet, I just picked one
RUN curl -sO https://raw.githubusercontent.com/vishnubob/wait-for-it/master/wait-for-it.sh && chmod a+x *.sh

ENTRYPOINT ["/scripts/wait-for-it.sh"]

它只准備一個帶有 wait-for-it.sh 腳本和 telnet 的圖像（以測試數據庫連接）

docker-compose.yml

version: "3.6"

services:
  db:
    image: postgres:14-alpine
    environment:
      - POSTGRES_USER=test
      - POSTGRES_PASSWORD=test
      - POSTGRES_DB=test
    command: -c fsync=off -c synchronous_commit=off -c full_page_writes=off --max-connections=200 --shared-buffers=4GB --work-mem=20MB
    tmpfs:
      - /var/lib/postgresql

  test:
    build:
      context: .
    command: db:5432 -t 3000 -- telnet db 5432

test服務將等待數據庫可用，然后再啟動它的主進程。

最好的測試方法：

在一個終端開始：

docker-compose up test

在第二個終端：

# make the operation even longer
docker rmi postgres:14-alpine

# start database
docker-compose up db

數據庫在啟動過程中重啟的原因在評論中有很好的解釋。