Redis – Django Celery Beat cannot connect to postgres database from inside docker container

My docker contianer django server, postgres, celery worker and celery beat. Running the application by itself there is no issue with connecting to the database however when the timed task to update the database runs I get an error

celery_1       | django.db.utils.OperationalError: could not connect to server: No such file or directory

celery_1       |        Is the server running locally and accepting
celery_1       |        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

below are my files

docker-compose.yaml

version: "3"

services:
  redis:
    image: redis:alpine
  db:
    image: postgres:10-alpine
    environment:
      - POSTGRES_DB=app
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=supersecretpassword
    ports:
      - "5432:5432"
    volumes:
      - "db:/var/lib/postgresql/data"

  pgadmin:
    image: dpage/pgadmin4
    depends_on:
      - db
    ports:
      - "5555:80"
    environment:
      - PGADMIN_DEFAULT_EMAIL=dev@localhost
      - PGADMIN_DEFAULT_PASSWORD=password

  dj-dividend:
    container_name: dividend
    build: backend
    command: sh -c "python manage.py wait_for_db && python manage.py makemigrations && python manage.py migrate && python manage.py runserver 0.0.0.0:80"
    environment:
      - DB_HOST=db
      - DB_NAME=app
      - DB_USER=postgres
      - DB_PASS=supersecretpassword
    volumes:
      - ./backend:/code
    ports:
      - "80:80"
    depends_on:
      - db
      - redis
  celery:
    build: backend
    command: celery -A backend worker -l info
    volumes:
      - ./backend:/code
    depends_on:
      - db
      - redis
  celery-beat:
    build: backend
    command: celery -A backend beat -l info
    volumes:
      - ./backend:/code
    depends_on:
      - db
      - redis
      - celery
volumes:
  db:

settings.py

import os
from celery.schedules import crontab

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/2.2/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = '1a0@6lsfxtfrt0n=#q1&up6hf$px-$ug^n%^v!n)^iwp_n*7c%'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = ['*']


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'dividends',
    'rest_framework',
    'django_celery_beat',
    'core'

]
CORS_ORIGIN_ALLOW_ALL = True


MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'corsheaders.middleware.CorsMiddleware',
]

ROOT_URLCONF = 'backend.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'backend.wsgi.application'


# Database
# https://docs.djangoproject.com/en/2.2/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': os.environ.get('DB_HOST'),
        'NAME': os.environ.get('DB_NAME'),
        'USER': os.environ.get('DB_USER'),
        'PASSWORD': os.environ.get('DB_PASS'),
    }
}


# Password validation
# https://docs.djangoproject.com/en/2.2/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/2.2/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/2.2/howto/static-files/

STATIC_URL = '/static/'

#Celery

CELERY_BROKER_URL = "redis://redis:6379"
CELERY_RESULT_BACKEND = "redis://redis:6379"
CELERY_ACCEPT_CONTENT = ['application/json']
CELERY_TASK_SERIALIZER = 'json'
CELERY_RESULT_SERIALIZER = 'json'
CELERY_BEAT_SCHEDULE = {
    "get_stocks": {
        'task': 'dividends.tasks.get_stocks',
        'schedule': crontab(minute="*/1") #every minute
    }
}

Dockerfile

FROM python:3.7

# Set environment variables
ENV PYTHONUNBUFFERED 1

COPY requirements.txt /

# Install dependencies.
RUN pip install -r /requirements.txt

# Set work directory.
RUN mkdir /code
WORKDIR /code

# Copy project code.
COPY . /code/

EXPOSE 80

tasks.py

from celery import shared_task
from .utils import get_stock_data

from .models import Stock


@shared_task(default_retry_delay=5, max_retries=3)
def get_stocks():
    for stock in Stock.objects.all().values_list('ticker'):
        try:
            get_stock_data(stock[0])
        except:
            continue

celery.py

from celery import Celery
import os

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'backend.settings')

app = Celery('backend')
app.config_from_object('django.conf:settings', namespace='CELERY')

app.autodiscover_tasks()