将 liquibase 集成到自定义 postgres 容器映像中

Question

I am trying to create a container image based on the official postgres image + my DB schema currently defined as liquibase XMLs.

This is how my Dockerfile looks:

FROM postgres:13.1


ENV POSTGRES_USER=myuser
ENV POSTGRES_PASSWORD=mypass
ENV POSTGRES_DB=mydb



# Copy the DB and user creation script which will then be automatically executed during the DB creation
ADD ./db_init.sql /docker-entrypoint-initdb.d/

# Temporary copy liquibase
ADD ./liquibase/ /liquibase/

# Copy and extract OpenJDK for liquibase 
ADD ./openjdk-11+28_linux-x64_bin.tar.gz /liquibase/

ENV JAVA_HOME=/liquibase/jdk-11


# Copy the changelog for the creation of the schema
ADD ./changelog/liquibase/ /liquibase/

# Execute liquibase
RUN /liquibase/liquibase --changeLogFile=/changelog/liquibase/index.xml --url=jdbc:postgresql://localhost:5432/$POSTGRES_DB --username=$POSTGRES_USER --password=$POSTGRES_PASSWORD --logLevel=info update


RUN rm -rf /liquibase

USER postgres

The build fails with:

[2020-12-15 10:37:23] SEVERE [liquibase.integration] Unexpected error running Liquibase: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: Connection could not be created to jdbc:postgresql://localhost:5432/sisdb with driver org.postgresql.Driver.  Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: Connection could not be created to jdbc:postgresql://localhost:5432/sisdb with driver org.postgresql.Driver.  Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at liquibase.integration.commandline.CommandLineUtils.createDatabaseObject(CommandLineUtils.java:131)
    at liquibase.integration.commandline.Main.doMigration(Main.java:1409)
    at liquibase.integration.commandline.Main$1.lambda$run$0(Main.java:361)
    at liquibase.Scope.lambda$child$0(Scope.java:160)
    at liquibase.Scope.child(Scope.java:169)
    at liquibase.Scope.child(Scope.java:159)
    at liquibase.Scope.child(Scope.java:138)
    at liquibase.Scope.child(Scope.java:222)
    at liquibase.Scope.child(Scope.java:226)
    at liquibase.integration.commandline.Main$1.run(Main.java:360)
    at liquibase.integration.commandline.Main$1.run(Main.java:193)
    at liquibase.Scope.child(Scope.java:169)
    at liquibase.Scope.child(Scope.java:145)
    at liquibase.integration.commandline.Main.run(Main.java:193)
    at liquibase.integration.commandline.Main.main(Main.java:156)
Caused by: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: Connection could not be created to jdbc:postgresql://localhost:5432/sisdb with driver org.postgresql.Driver.  Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at liquibase.database.DatabaseFactory.openConnection(DatabaseFactory.java:216)
    at liquibase.database.DatabaseFactory.openConnection(DatabaseFactory.java:175)
    at liquibase.database.DatabaseFactory.openDatabase(DatabaseFactory.java:140)
    at liquibase.integration.commandline.CommandLineUtils.createDatabaseObject(CommandLineUtils.java:96)
    ... 14 more
Caused by: liquibase.exception.DatabaseException: liquibase.exception.DatabaseException: Connection could not be created to jdbc:postgresql://localhost:5432/sisdb with driver org.postgresql.Driver.  Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at liquibase.database.ConnectionServiceFactory.create(ConnectionServiceFactory.java:36)
    at liquibase.database.DatabaseFactory.openConnection(DatabaseFactory.java:213)
    ... 17 more
Caused by: liquibase.exception.DatabaseException: Connection could not be created to jdbc:postgresql://localhost:5432/sisdb with driver org.postgresql.Driver.  Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at liquibase.database.jvm.JdbcConnection.open(JdbcConnection.java:43)
    at com.datical.liquibase.ext.database.jvm.ProJdbcConnection.open(Unknown Source)
    at liquibase.database.ConnectionServiceFactory.create(ConnectionServiceFactory.java:33)
    ... 18 more

What am I doing wrong? Is the database not yet ready to receive connections at this point? Will I have to run liquibase only after the container is running? If so, is there a best practices guide for such a flow?

Answer 1

Inside a Dockerfile, you can never connect to a database. If you're trying to extend a database image, the database is never running during the docker build sequence; if the database is in a separate container, none of the networking setup for the build to call the database has been done. The standard Docker Hub database images are also configured in a way that prevents creating an image with data preloaded.

For migration tools like Liquibase, they're typically packaged with the application, not the database. If your application is built using Spring Boot, for example, it has support to Execute Liquibase Database Migrations on Startup .

If you need to run migrations using Docker mechanics, one pattern is to use an entrypoint wrapper script to do it when your container starts up. Your application image needs to include Liquibase as you've shown here. Have the script run the liquibase command, then exec "$@" to run the main container application; COPY it into your image and make it be the ENTRYPOINT (must use JSON-array syntax), and leave CMD java -jar... as is. (You might look for similar examples using Python's Django framework.)