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Postgres

Since testcontainers-go v0.20.0

Introduction

The Testcontainers module for Postgres.

Adding this module to your project dependencies

Please run the following command to add the Postgres module to your Go dependencies:

go get github.com/testcontainers/testcontainers-go/modules/postgres

Usage example

ctx := context.Background()

dbName := "users"
dbUser := "user"
dbPassword := "password"

postgresContainer, err := postgres.RunContainer(ctx,
    testcontainers.WithImage("docker.io/postgres:15.2-alpine"),
    postgres.WithInitScripts(filepath.Join("testdata", "init-user-db.sh")),
    postgres.WithConfigFile(filepath.Join("testdata", "my-postgres.conf")),
    postgres.WithDatabase(dbName),
    postgres.WithUsername(dbUser),
    postgres.WithPassword(dbPassword),
    testcontainers.WithWaitStrategy(
        wait.ForLog("database system is ready to accept connections").
            WithOccurrence(2).
            WithStartupTimeout(5*time.Second)),
)
if err != nil {
    panic(err)
}

// Clean up the container
defer func() {
    if err := postgresContainer.Terminate(ctx); err != nil {
        panic(err)
    }
}()

Module reference

The Postgres module exposes one entrypoint function to create the Postgres container, and this function receives two parameters:

func RunContainer(ctx context.Context, opts ...testcontainers.ContainerCustomizer) (*PostgresContainer, error)
  • context.Context, the Go context.
  • testcontainers.ContainerCustomizer, a variadic argument for passing options.

Container Options

When starting the Postgres container, you can pass options in a variadic way to configure it.

Tip

You can find all the available configuration and environment variables for the Postgres Docker image on Docker Hub.

Image

If you need to set a different Postgres Docker image, you can use testcontainers.WithImage with a valid Docker image for Postgres. E.g. testcontainers.WithImage("docker.io/postgres:9.6").

Image Substitutions

In more locked down / secured environments, it can be problematic to pull images from Docker Hub and run them without additional precautions.

An image name substitutor converts a Docker image name, as may be specified in code, to an alternative name. This is intended to provide a way to override image names, for example to enforce pulling of images from a private registry.

Testcontainers for Go exposes an interface to perform this operations: ImageSubstitutor, and a No-operation implementation to be used as reference for custom implementations:

// ImageSubstitutor represents a way to substitute container image names
type ImageSubstitutor interface {
    // Description returns the name of the type and a short description of how it modifies the image.
    // Useful to be printed in logs
    Description() string
    Substitute(image string) (string, error)
}

type NoopImageSubstitutor struct{}

// Description returns a description of what is expected from this Substitutor,
// which is used in logs.
func (s NoopImageSubstitutor) Description() string {
    return "NoopImageSubstitutor (noop)"
}

// Substitute returns the original image, without any change
func (s NoopImageSubstitutor) Substitute(image string) (string, error) {
    return image, nil
}

Using the WithImageSubstitutors options, you could define your own substitutions to the container images. E.g. adding a prefix to the images so that they can be pulled from a Docker registry other than Docker Hub. This is the usual mechanism for using Docker image proxies, caches, etc.

Wait Strategies

If you need to set a different wait strategy for the container, you can use testcontainers.WithWaitStrategy with a valid wait strategy.

Info

The default deadline for the wait strategy is 60 seconds.

At the same time, it's possible to set a wait strategy and a custom deadline with testcontainers.WithWaitStrategyAndDeadline.

Startup Commands

Testcontainers exposes the WithStartupCommand(e ...Executable) option to run arbitrary commands in the container right after it's started.

Info

To better understand how this feature works, please read the Create containers: Lifecycle Hooks documentation.

It also exports an Executable interface, defining one single method: AsCommand(), which returns a slice of strings to represent the command and positional arguments to be executed in the container.

You could use this feature to run a custom script, or to run a command that is not supported by the module right after the container is started.

Docker type modifiers

If you need an advanced configuration for the container, you can leverage the following Docker type modifiers:

  • testcontainers.WithConfigModifier
  • testcontainers.WithHostConfigModifier
  • testcontainers.WithEndpointSettingsModifier

Please read the Create containers: Advanced Settings documentation for more information.

Initial Database

If you need to set a different database, and its credentials, you can use the WithDatabase(db string), WithUsername(user string) and WithPassword(pwd string) options.

Init Scripts

If you would like to do additional initialization in the Postgres container, add one or more *.sql, *.sql.gz, or *.sh scripts to the container request with the WithInitScripts function. Those files will be copied after the container is created but before it's started under /docker-entrypoint-initdb.d. According to Postgres Docker image, it will run any *.sql files, run any executable *.sh scripts, and source any non-executable *.sh scripts found in that directory to do further initialization before starting the service.

An example of a *.sh script that creates a user and database is shown below:

#!/bin/bash
set -e

psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
    CREATE USER docker;
    CREATE DATABASE docker;
    GRANT ALL PRIVILEGES ON DATABASE docker TO docker;
    CREATE TABLE IF NOT EXISTS testdb (id int, name varchar(255));
    INSERT INTO testdb (id, name) VALUES (1, 'test')
EOSQL

Database configuration

In the case you have a custom config file for Postgres, it's possible to copy that file into the container before it's started, using the WithConfigFile(cfgPath string) function.

Tip

For information on what is available to configure, see the PostgreSQL docs for the specific version of PostgreSQL that you are running.

Container Methods

ConnectionString

This method returns the connection string to connect to the Postgres container, using the default 5432 port. It's possible to pass extra parameters to the connection string, e.g. sslmode=disable or application_name=myapp, in a variadic way.

// explicitly set sslmode=disable because the container is not configured to use TLS
connStr, err := container.ConnectionString(ctx, "sslmode=disable", "application_name=test")

Postgres variants

It's possible to use the Postgres container with Timescale or Postgis, to name a few. You simply need to update the image name and the wait strategy.

image: "docker.io/timescale/timescaledb:2.1.0-pg11",
wait:  wait.ForLog("database system is ready to accept connections").WithOccurrence(2).WithStartupTimeout(5 * time.Second),

image: "docker.io/postgis/postgis:12-3.0",
wait:  wait.ForLog("database system is ready to accept connections").WithOccurrence(2).WithStartupTimeout(30 * time.Second),