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Writing Custom Deployment Automation

Redpanda supports several deployment tools for setting up a cluster:

  • Ansible Playbook

  • Helm Chart

  • Kubernetes Operator

Redpanda strongly recommends using one of these supported deployment tools.

This page provides information for anyone creating their own automation for deploying Redpanda clusters; that is, anyone not using one of these supported tools.

Configure bootstrapping

Redpanda cluster configuration is written with the Admin API and the rpk cluster config CLIs.

In the special case where you want to provide configuration to Redpanda before it starts for the first time, you can write a .bootstrap.yaml file in the same directory as redpanda.yaml.

This file is only read on the first startup of the cluster. Any subsequent changes to .bootstrap.yaml are ignored, so changes to cluster configuration must be done with the Admin API.

The content format is a YAML dictionary of cluster configuration properties. For example, to initialize a cluster with Admin API authentication enabled and a single superuser, the .bootstrap.yaml file would contain the following:

admin_api_require_auth: true
superusers:
- alice

With this configuration, the Admin API is not accessible until you bootstrap a user account.

Bootstrap a user account

When using username/password authentication, it’s helpful to be able to create one user before the cluster starts for the first time.

Do this by setting the RP_BOOTSTRAP_USER environment variable when starting Redpanda for the first time. The value has the format <username>:<password>. For example, you could set RP_BOOTSTRAP_USER to alice:letmein.

RP_BOOTSTRAP_USER only creates a user account. You must still set up authentication using cluster configuration.

Secure the Admin API

The Admin API is used to create SASL user accounts and ACLs, so it’s important to think about how you secure it when creating a cluster.

There are three ways to authenticate the Admin API:

  • No authentication, but listening only on 127.0.0.1: This may be appropriate if your Redpanda processes are running in an environment where only administrators can access the host.

  • mTLS authentication: You can generate client and server x509 certificates before starting Redpanda for the first time, refer to them in redpanda.yaml, and use the client certificate when accessing the Admin API.

  • Username/password authentication: Use the combination of admin_api_require_auth, superusers, and RP_BOOTSTRAP_USER to access the Admin API username/password authentication. You probably still want to enable TLS on the Admin API endpoint to protect credentials in flight.

Configure seed_servers list

The seed_servers node configuration property controls how Redpanda finds its peers when initially forming a cluster. Redpanda clusters form with these guidelines:

  • When a node starts with an empty seed_servers list, it creates a single node cluster with itself as the only member.

  • When a node starts with a non-empty seed_servers list, it sends requests to the nodes in that list to join the cluster.

Therefore, it’s essential that only one node has an empty seed_servers list.

Redpanda expects its storage to be persistent, and it’s an error to erase a node’s drive and restart it. However, in some environments (like when migrating to a different node pool on Kubernetes), truly persistent storage is unavailable, and nodes may find their data volumes erased. In this situation, the node should not have an empty seed_servers list. If it does, then when it starts with an empty data volume, it tries to initialize a new Redpanda cluster and write new content to its controller log unrelated to the previous state of the cluster. This can result in undefined behavior when the node later rejoins its peers and tries to reconcile its local controller log with the controller log from peers.

Configure strict data volumes

When Redpanda starts, by default it looks for its data volume and initializes it if it’s empty. However, there can be cases when a node’s drive is accidentally erased or an incorrect drive is mounted to the data volume. Redpanda has no way to distinguish whether or not the data volume is incorrect upon start; consequently, there is no way for it to avoid this type of error. You can avoid such errors by setting the configuration option storage_strict_data_init, which enables Redpanda to distinguish between a purposefully empty data volume and an inadvertently empty one.

When storage_strict_data_init is set to true on a node, Redpanda looks in the root of its data volume for an empty file named .redpanda_data_dir. If the file is not there Redpanda will not start. You must create this file manually when the data volume is created. Its existence enables Redpanda to distinguish whether or not the data volume it’s reading from is correct.

Use new node ID

Redpanda recommends using a fresh node_id each time you add a node to the cluster.

In general, it is not safe to reuse a node ID (for example, when adding a new node after decommissioning the node with that node ID). While it’s convenient to have low, consecutive node IDs, it’s not necessary. Node IDs can take any value in the 32-bit space.

Upgrade considerations

Deployment automation should place each node into maintenance mode and wait for it to drain leaderships before restarting it with a newer version of Redpanda. For information about how to drive a rolling upgrade of a Redpanda cluster, see Node Maintenance Mode.

Rolling restarts preserve high availability and reduce risk during upgrades. Check the cluster’s health after upgrading each node. Rolling back an upgrade to an earlier feature release is only supported until the last node has been updated, so it’s important to identify any issues before that point.