docker containers can not connect to each other-CodePudding

I have a django-rest-framwork app which uses PosgreSql as db. So I am using docker containers for them one image for django-rest-framwork and one for PosgreSql, and then docker compose file to handle them.

db service refrese to PostgreSQL
backend refers to Django Rest app

I have a docker-compose file

version: '3.9'
services:
  
  db:
    image: postgres:latest
    restart: always
    ports:
      - "5432:5432"
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=85842475DB
      - POSTGRES_DB=sports_center_db
      - POSTGRES_PORT=5432
  
  backend:
    build: ./api
    depends_on:
      - db
    ports:
      - "8000:8000"
    environment:
      - DB_NAME=sports_center_db
      - DB_USER_NAME=postgres
      - DB_PASSWORD=85842475DB
      - DB_HOST=db
      - DB_PORT=5432

It builds correctly but when I ran docker compose up I got following logs

[ ] Running 2/2
 ⠿ Container sports_center-db-1       Created                                                                                                   0.1s
 ⠿ Container sports_center-backend-1  Created                                                                                                   0.1s
Attaching to sports_center-backend-1, sports_center-db-1
sports_center-db-1       | The files belonging to this database system will be owned by user "postgres".
sports_center-db-1       | This user must also own the server process.
sports_center-db-1       | 
sports_center-db-1       | The database cluster will be initialized with locale "en_US.utf8".
sports_center-db-1       | The default database encoding has accordingly been set to "UTF8".
sports_center-db-1       | The default text search configuration will be set to "english".
sports_center-db-1       | 
sports_center-db-1       | Data page checksums are disabled.
sports_center-db-1       | 
sports_center-db-1       | fixing permissions on existing directory /var/lib/postgresql/data ... ok
sports_center-db-1       | creating subdirectories ... ok
sports_center-db-1       | selecting dynamic shared memory implementation ... posix
sports_center-db-1       | selecting default max_connections ... 100
sports_center-db-1       | selecting default shared_buffers ... 128MB
sports_center-db-1       | selecting default time zone ... Etc/UTC
sports_center-db-1       | creating configuration files ... ok
sports_center-db-1       | running bootstrap script ... ok
sports_center-db-1       | performing post-bootstrap initialization ... ok
sports_center-backend-1  | Exception in thread django-main-thread:
sports_center-backend-1  | Traceback (most recent call last):
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 282, in ensure_connection
sports_center-backend-1  |     self.connect()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 263, in connect
sports_center-backend-1  |     self.connection = self.get_new_connection(conn_params)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/postgresql/base.py", line 215, in get_new_connection
sports_center-backend-1  |     connection = Database.connect(**conn_params)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/psycopg2/__init__.py", line 122, in connect
sports_center-backend-1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
sports_center-backend-1  | psycopg2.OperationalError: connection to server at "db" (172.18.0.2), port 5432 failed: Connection refused
sports_center-backend-1  |  Is the server running on that host and accepting TCP/IP connections?
sports_center-backend-1  | 
sports_center-backend-1  | 
sports_center-backend-1  | The above exception was the direct cause of the following exception:
sports_center-backend-1  | 
sports_center-backend-1  | Traceback (most recent call last):
sports_center-backend-1  |   File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
sports_center-backend-1  |     self.run()
sports_center-backend-1  |   File "/usr/lib/python3.10/threading.py", line 953, in run
sports_center-backend-1  |     self._target(*self._args, **self._kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/autoreload.py", line 64, in wrapper
sports_center-backend-1  |     fn(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/core/management/commands/runserver.py", line 137, in inner_run
sports_center-backend-1  |     self.check_migrations()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/core/management/base.py", line 564, in check_migrations
sports_center-backend-1  |     executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/migrations/executor.py", line 18, in __init__
sports_center-backend-1  |     self.loader = MigrationLoader(self.connection)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/migrations/loader.py", line 58, in __init__
sports_center-backend-1  |     self.build_graph()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/migrations/loader.py", line 235, in build_graph
sports_center-backend-1  |     self.applied_migrations = recorder.applied_migrations()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/migrations/recorder.py", line 81, in applied_migrations
sports_center-backend-1  |     if self.has_table():
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/migrations/recorder.py", line 57, in has_table
sports_center-backend-1  |     with self.connection.cursor() as cursor:
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 323, in cursor
sports_center-backend-1  |     return self._cursor()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 299, in _cursor
sports_center-backend-1  |     self.ensure_connection()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 281, in ensure_connection
sports_center-backend-1  |     with self.wrap_database_errors:
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/utils.py", line 91, in __exit__
sports_center-backend-1  |     raise dj_exc_value.with_traceback(traceback) from exc_value
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 282, in ensure_connection
sports_center-backend-1  |     self.connect()
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/base/base.py", line 263, in connect
sports_center-backend-1  |     self.connection = self.get_new_connection(conn_params)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/utils/asyncio.py", line 26, in inner
sports_center-backend-1  |     return func(*args, **kwargs)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/django/db/backends/postgresql/base.py", line 215, in get_new_connection
sports_center-backend-1  |     connection = Database.connect(**conn_params)
sports_center-backend-1  |   File "/usr/local/lib/python3.10/dist-packages/psycopg2/__init__.py", line 122, in connect
sports_center-backend-1  |     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
sports_center-backend-1  | django.db.utils.OperationalError: connection to server at "db" (172.18.0.2), port 5432 failed: Connection refused
sports_center-backend-1  |  Is the server running on that host and accepting TCP/IP connections?
sports_center-backend-1  | 
sports_center-db-1       | syncing data to disk ... ok
sports_center-db-1       | 
sports_center-db-1       | 
sports_center-db-1       | Success. You can now start the database server using:
sports_center-db-1       | 
sports_center-db-1       |     pg_ctl -D /var/lib/postgresql/data -l logfile start
sports_center-db-1       | 
sports_center-db-1       | initdb: warning: enabling "trust" authentication for local connections
sports_center-db-1       | initdb: hint: You can change this by editing pg_hba.conf or using the option -A, or --auth-local and --auth-host, the next time you run initdb.
sports_center-db-1       | waiting for server to start....2022-10-16 19:57:48.569 UTC [48] LOG:  starting PostgreSQL 15.0 (Debian 15.0-1.pgdg110 1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
sports_center-db-1       | 2022-10-16 19:57:48.575 UTC [48] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
sports_center-db-1       | 2022-10-16 19:57:48.596 UTC [51] LOG:  database system was shut down at 2022-10-16 19:57:41 UTC
sports_center-db-1       | 2022-10-16 19:57:48.607 UTC [48] LOG:  database system is ready to accept connections
sports_center-db-1       |  done
sports_center-db-1       | server started
sports_center-db-1       | CREATE DATABASE
sports_center-db-1       | 
sports_center-db-1       | 
sports_center-db-1       | /usr/local/bin/docker-entrypoint.sh: ignoring /docker-entrypoint-initdb.d/*
sports_center-db-1       | 
sports_center-db-1       | waiting for server to shut down...2022-10-16 19:57:48.814 UTC [48] LOG:  received fast shutdown request
sports_center-db-1       | .2022-10-16 19:57:48.820 UTC [48] LOG:  aborting any active transactions
sports_center-db-1       | 2022-10-16 19:57:48.823 UTC [48] LOG:  background worker "logical replication launcher" (PID 54) exited with exit code 1
sports_center-db-1       | 2022-10-16 19:57:48.824 UTC [49] LOG:  shutting down
sports_center-db-1       | 2022-10-16 19:57:48.830 UTC [49] LOG:  checkpoint starting: shutdown immediate
sports_center-db-1       | 2022-10-16 19:57:49.416 UTC [49] LOG:  checkpoint complete: wrote 918 buffers (5.6%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.047 s, sync=0.516 s, total=0.592 s; sync files=250, longest=0.009 s, average=0.003 s; distance=4217 kB, estimate=4217 kB
sports_center-db-1       | 2022-10-16 19:57:49.442 UTC [48] LOG:  database system is shut down
sports_center-db-1       |  done
sports_center-db-1       | server stopped
sports_center-db-1       | 
sports_center-db-1       | PostgreSQL init process complete; ready for start up.
sports_center-db-1       | 
sports_center-db-1       | 2022-10-16 19:57:49.580 UTC [1] LOG:  starting PostgreSQL 15.0 (Debian 15.0-1.pgdg110 1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
sports_center-db-1       | 2022-10-16 19:57:49.581 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
sports_center-db-1       | 2022-10-16 19:57:49.581 UTC [1] LOG:  listening on IPv6 address "::", port 5432
sports_center-db-1       | 2022-10-16 19:57:49.593 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
sports_center-db-1       | 2022-10-16 19:57:49.609 UTC [63] LOG:  database system was shut down at 2022-10-16 19:57:49 UTC
sports_center-db-1       | 2022-10-16 19:57:49.621 UTC [1] LOG:  database system is ready to accept connections
sports_center-db-1       | 2022-10-16 20:02:49.708 UTC [61] LOG:  checkpoint starting: time
sports_center-db-1       | 2022-10-16 20:02:53.897 UTC [61] LOG:  checkpoint complete: wrote 44 buffers (0.3%); 0 WAL file(s) added, 0 removed, 0 recycled; write=4.131 s, sync=0.029 s, total=4.190 s; sync files=12, longest=0.006 s, average=0.003 s; distance=252 kB, estimate=252 kB

As I understand containers can not connect to each other. Any error or if I missing something here in the compose file, please tell me why this is happening and how to solve it.

CodePudding user response：

Your application started before the database finished initializing. Depends_on waits for the other container to start, but there's still a delay before it's available. There are several possible solutions:

Configure the app to retry connecting to the database.
Configure the app to wait for the database using a command like wait-for-it.
Adjust the depends_on condition to also wait on the healthcheck:

version: "2.4"
services:
  web:
    build: .
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_started
  redis:
    image: redis
  db:
    image: postgres
    healthcheck:
      test: "exit 0"

CodePudding user response：

EDIT: as suggested by BMitch, maybe you need to create a network.

Initial answer:

Maybe you need to link them ?

Try adding the following to the backend:

    links:
      - db