Running Postgres

Kwil is built on PostgreSQL, and requires an external PostgreSQL host running and configured for kwild. kwild currently requires PostgreSQL 16, from at least v16.1. Future major versions will require an update to Kwil.

Quickstart PostgreSQL

For quick usage, Kwil provides a Docker image with a properly configured PostgreSQL instance. This is convenient for quick setup of a Kwil node, but is less configurable than a system service. The following command will pull and start a new container:

docker run -p 5432:5432 --name kwil-postgres -e "POSTGRES_HOST_AUTH_METHOD=trust" \
    --shm-size 256m kwildb/postgres:latest

Be sure to disable any OS unattended upgrades to prevent "docker", "containerd", and "postgresql" packages from being updated while the node is running.

PostgreSQL Installation

Standard PostgreSQL installers and operating system packages are supported. We also provide Docker images and Compose service definitions with the required settings, roles, and databases pre-configured for ease of deployment and evaluation.

The recommended options are:

• System installation of postgres. This requires some manual configuration.
• The kwildb/postgres Docker image on Docker Hub. It is pre-configured for kwild and is convenient for quick setup, but may be less reliable or secure than a manually configured postgres instance.

info

If a user-provided installation of PostgreSQL, such as an operating system postgres package, is used, the configuration must be changed as described in PostgreSQL Configuration.

See the README for other convenient methods for developers to start test nodes or networks.

System Install

An operator may use a system installation of postgres from one of the official PostgreSQL installers or operating system packages managers.

Be sure to install version-specific packages, such as postgresql-16, rather than a metapackage that will automatically install the latest major version, which may not be supported by Kwil.

tip

It is recommended to use a postgresql.org repository, such as the "pgdg" Ubuntu Apt Repository rather than the operating system's own packages.

Also, be sure any unattended upgrades exclude the PostgreSQL package to prevent it from restarting while in used. For instance, on Debian-based systems, configure Unattended-Upgrade::Package-Blacklist. with an entry for "postgresql-*".

Finally, a system install of postgres requires making some configuration changes to support kwild. These are described in the PostgreSQL Configuration section.

Docker Image

The kwildb/postgres Docker image is available on Docker Hub. This is convenient for quick setup of a Kwil node, but is less configurable than a system service. The following command will pull and start a new container:

docker run -p 5432:5432 -v kwil-pgdata:/var/lib/postgresql/data --shm-size 256m \
    -e "POSTGRES_HOST_AUTH_METHOD=trust" kwildb/postgres:latest

The above will start a pre-configured postgres in a Docker container, using a persistent Docker volume named kwil-pgdata. To require authentication, use "POSTGRES_PASSWORD=mypass" to set the postgres superuser password instead of "POSTGRES_HOST_AUTH_METHOD=trust".

This service automatically creates a "kwild" database owned by a "kwild" role. The password for this user is initially "kwild", which would be specified with the kwild flag --app.pg-db-pass flag if not using "trust" authentication. Use psql if you wish to change it.

info

This service exposes postgres on port 5432 of the host machine so that it may be accessed for administrative purposes from the host machine via psql. This means that it will fail to start if there is a process on the host machine already listening on port 5432.

If resetting kwild's data folders, it is also necessary to delete the kwil-pgdata Docker volume, or whatever named volume was used in the docker run command. Ensure that the Docker Daemon is running and configured so that the postgres service has sufficient disk, CPU, and memory resources for demand of your application.

tip

If using Docker Daemon directly rather than Docker Desktop, such as would be the case on a headless server, it is recommended to modify the Docker configuration to disable the "userland proxy" for performance reasons.

Also, if the system disk partition has limited free space or uses a slow block device, as is common on certain cloud providers, either change the "data-root" Docker setting or use a suitable host file system path rather than a named volume.

Modify the docker configuration as follows, setting "userland-proxy" to false, and "data-root" to the location of a directory on a file system with sufficient free disk space and performance characteristics:

/etc/docker/daemon.json

{
  "userland-proxy": false,
  "data-root": "/mnt/suitable_drive/docker"
}

If changing "data-root", be sure to copy the previous Docker folder, which is typically /var/lib/docker.

PostgreSQL Configuration

When using Kwil's Postgres Docker image (kwildb/postgres) or one of the Docker Compose service definitions described in the previous section, no changes to the postgres process configuration are required, skip this section and proceed to Running kwild.

If using any other installation of PostgreSQL such as from an operating system package manager, it is necessary to change a few settings in the postgresql.conf file. Once reconfigured, it may also be necessary to create a new database and "role" to match kwild's configuration.

PostgreSQL Settings

kwild requires some changes to the default postgres configuration:

• wal_level set to "logical" to enable logical replication functionality
• max_wal_senders at least 10
• max_replication_slots at least 10
• max_prepared_transactions at least 2 for two-phase commit capability

In addition to the above non-default settings, kwild will also verify the following settings, which are satisfied by postgres defaults:

• synchronous_commit = on
• fsync = on
• max_connections at least 50 (the default is usually 100)

tip

It is recommended to enable data checksums on the database cluster. See the documentation for more information. The provided Docker Compose services do this automatically.

PostgreSQL Initialization

Depending on kwild configuration, is may be necessary to create a postgres role and database.

The relevant kwild settings are:

• app.pg-db-host is the host name for the postgres server. Default is 127.0.0.1, but may also be a path to a UNIX socket such as /var/run/postgresql. Most PostgreSQL packages are configured to listen on both by default.
• app.pg-db-port is the TCP port for the postgres server. Default is 5432. This setting is ignored if a UNIX socket is used for app.pg-db-host.
• app.pg-db-user is the name of the role (like a user). Default is kwild.
• app.pg-db-pass is the password for the role specified by app.pg-db-user. Default is unset. Required if a password is set for the role, and not using "trust" authentication.

Use the psql command to connect to postgres and create the specified role and database. For example, to create a "superuser" role named "kwild" with the password "kwild", and a database called "kwild" owned by that role:

CREATE USER kwild WITH PASSWORD 'kwild' SUPERUSER REPLICATION;
CREATE DATABASE kwild OWNER kwild;

danger

kwild currently requires a "superuser" role to perform various tasks that require elevated privileges, such as creating triggers and publications for logical replication. The postgres database cluster should be dedicated to kwild, and should not be used for any other purpose.

For more information about authentication configuration please see the official PostgreSQL documentation.

Running kwild

Continue to the Using kwild page for running Kwil node.