Mysql2::Error::ConnectionError: Can't connect to MySQL server on 'mysql' (111 "Connection refused")

Question

i am running the docker-compose for my sample applications, and this file consist of mysql database and the application image. i am getting the following error.

    $ docker logs -f sample-application
    Can't connect to MySQL server on 'mysql' (111 "Connection refused")
    Couldn't create database for {"adapter"=>"mysql2", "encoding"=>"utf8", "pool"=>5, "reconnect"=>true, "database"=>"datagen", "username"=>"root", "password"=>"password", "host"=>"mysql", "port"=>3306}
    rake aborted!
    Mysql2::Error::ConnectionError: Can't connect to MySQL server on 'mysql' (111 "Connection refused")
    /usr/local/bundle/gems/mysql2-0.5.2/lib/mysql2/client.rb:90:in `connect'
    /usr/local/bundle/gems/mysql2-0.5.2/lib/mysql2/client.rb:90:in `initialize'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/mysql2_adapter.rb:22:in `new'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/mysql2_adapter.rb:22:in `mysql2_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:809:in `new_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:853:in `checkout_new_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:832:in `try_to_checkout_new_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:793:in `acquire_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:521:in `checkout'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:380:in `connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:1008:in `retrieve_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/connection_handling.rb:90:in `connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/mysql_database_tasks.rb:6:in `connection'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/mysql_database_tasks.rb:14:in `create'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:119:in `create'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:139:in `block in create_current'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:316:in `block in each_current_configuration'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:313:in `each'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:313:in `each_current_configuration'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/tasks/database_tasks.rb:138:in `create_current'
    /usr/local/bundle/gems/activerecord-5.2.1/lib/active_record/railties/databases.rake:29:in `block (2 levels) in <top (required)>'
    /usr/local/bundle/gems/rake-12.3.1/exe/rake:27:in `<top (required)>'
    Tasks: TOP => db:create
    (See full trace by running task with --trace)

Here is database components for mysql docker-compose yaml file


version: '3.1'

services:
sample-service:
    image: service:latest
    hostname: sample-service
    container_name: sample-service
    depends_on:
      - sample-application
    ports:
      - "8080:8080"
    networks:
      - $NETWORK_NAME

mysql:
    image: mysql:5.7
    hostname: mysql
    container_name: mysql
    ports:
      - "3306:3306"
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_DATABASE=foo
      - MYSQL_USER=root
      - MYSQL_PASSWORD=password
    networks:
      - $NETWORK_NAME

sample-application:
    image: sample:latest 
    hostname: mysql
    container_name: sample-application
    depends_on:
      - mysql
    ports:
      - "3000:3000"
    environment:
      - RAILS_ENV=production
      - DATABASE_HOST=mysql
      - DATABASE_USER=root
      - DATABASE_NAME=foo
      - DATABASE_PORT=3306
    networks:
      - $NETWORK_NAME

networks:
  datagen:
    external: true

I am able to ping mysql from application docker container image. The connection is successfull and at the same time i am able to access the mysql image from some other machine also.

So there is no issue in the mysql image but i am unable to connect to mysql host when running using docker compose. The environmental variable which i passes is also correct.

I looked into various issues in stackoverflow and tried to change the bind address. But i dont see it in my mysql container image.


    bash-4.2# find / -name "*.cnf"
    /var/lib/mysql/auto.cnf
    /usr/share/mysql/my-default.cnf
    /etc/pki/tls/openssl.cnf
    /etc/my.cnf
    /healthcheck.cnf
    bash-4.2# cat /etc/my.cnf
    # For advice on how to change settings please see
    # http://dev.mysql.com/doc/refman/5.6/en/server-configuration-defaults.html

    [mysqld]
    #
    # Remove leading # and set to the amount of RAM for the most important data
    # cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
    # innodb_buffer_pool_size = 128M
    #
    # Remove leading # to turn on a very important data integrity option: logging
    # changes to the binary log between backups.
    # log_bin
    #
    # Remove leading # to set options mainly useful for reporting servers.
    # The server defaults are faster for transactions and fast SELECTs.
    # Adjust sizes as needed, experiment to find the optimal values.
    # join_buffer_size = 128M
    # sort_buffer_size = 2M
    # read_rnd_buffer_size = 2M
    skip-host-cache
    skip-name-resolve
    datadir=/var/lib/mysql
    socket=/var/lib/mysql/mysql.sock
    secure-file-priv=/var/lib/mysql-files
    user=mysql

    # Disabling symbolic-links is recommended to prevent assorted security risks
    symbolic-links=0

    log-error=/var/log/mysqld.log
    pid-file=/var/run/mysqld/mysqld.pid

@grapes i have added the complete docker-compose file as per your suggestion — klee
– klee, Commented Jan 16, 2019 at 11:47
Are you really using a variable as the network name for your containers or is it a copy and paste issue? Also, please indent the docker-compose.yml correctly. — whites11
– whites11, Commented Jan 16, 2019 at 12:01
@whites11 Its a copy and paste issue. i am able to download the images and i guess its not an issue — klee
– klee, Commented Jan 16, 2019 at 12:05

grapes · Accepted Answer · 2019-01-16 12:03:04Z

1

You really need external network? The only possible reason is that you want to connect other containers to it. Otherwise don't use it - you will be able to access containers from host just through port exposal mechanism.

If you are not going to access database from outside docker-compose, consider following changes to file:

removed useless stuff
removed ports (inside user-defined network you don't need exposing)

docker-compose.yml

version: '3.1'

services:
  mysql:
    image: mysql:5.7
    environment:
      - MYSQL_ROOT_PASSWORD=password
      - MYSQL_DATABASE=foo
      - MYSQL_USER=root
      - MYSQL_PASSWORD=password

  sample-application:
    image: sample:latest 
    depends_on:
      - mysql
    environment:
      - RAILS_ENV=production
      - DATABASE_HOST=mysql
      - DATABASE_USER=root
      - DATABASE_NAME=foo
      - DATABASE_PORT=3306

  sample-service:
    image: service:latest
    depends_on:
      - sample-application

With such configuration you can access services inside network by their names, e.g. mysql, sample-service and sample-application

Btw strange situation when service depends on application and not vice versa

answered Jan 16, 2019 at 12:03

grapes

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2 Comments

klee Over a year ago

my application is able to connect with database sometime alone. sometimes application is not connecting with the database and i am getting the previous error as well.

grapes Over a year ago

Check that your db is ready. It is often that database takes longer time to start and you try to connect while it is not yet running. Put some timeout or better user kits like wait-for which check that remote tcp port is open

FullStackEngineer · Accepted Answer · 2019-12-25 14:44:03Z

0

If you are using rails to connect to Mysql, make sure the db host in database.yml is same as the name of the service(in this case mysql) in docker-compose, that is how it knows to connect to mysql container. Remove all containers and images and build from beginning just to make sure no configuration is cached.

answered Dec 25, 2019 at 14:44

FullStackEngineer

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