Terraform
Reliability and Availability
This section covers details relating to the reliability and availability of Terraform Enterprise installations. This documentation may be useful to customers evaluating Terraform Enterprise or operators responsible for installing and maintaining Terraform Enterprise.
Components
Terraform Enterprise consists of several distinct components that each play a role when considering the reliability of the overall system:
Application Layer
TFE Core - A Rails application at the center of Terraform Enterprise; consists of web frontends and background workers
TFE Services - A set of Go services that provide various pieces of key functionality for Terraform Enterprise
Terraform Workers - A fleet of isolated execution environments that perform Terraform Runs on behalf of Terraform Enterprise users
Coordination Layer
- Redis - Used for Rails caching and coordination between Terraform Enterprise Core's web and background workers
Storage Layer
PostgreSQL Database - Serves as the primary store of Terraform Enterprise's application data such as workspace settings and user settings
Blob Storage - Used for storage of Terraform state files, plan files, configuration, and output logs
HashiCorp Vault - Used for encryption of sensitive data. There are two types of Vault data in Terraform Enterprise - key material and storage backend data.
Configuration Data - The information provided and/or generated at install-time (e.g. database credentials, hostname, etc.)
Operation Modes
This section describes how to set up your Terraform Enterprise deployment to recover from failures in the various operational modes (Mounted Disk, External Services). The operational mode is selected at install time and can not be changed once the install is running.
The below tables explain where each data type in the Storage Layer is stored and the corresponding snapshot and restore procedure. For the data types that use Terraform Enterprise's built-in snapshot and restore function, follow these instructions. For the data types that do not use the built-in functionality, backup and restore is the responsibility of the user.
Data Location
| Configuration | Vault | PostgreSQL | Blob Storage | |
|---|---|---|---|---|
| Mounted Disk | Stored in Docker volumes on instance | Key material on host in /var/lib/tfe-vault, storage backend is mounted disk PostgreSQL | Stored in mounted disks | Stored in mounted disks |
| External Services | Stored in Docker volumes on instance | Key material on host in /var/lib/tfe-vault, storage backend is external PostgreSQL | Stored in external service | Stored in external service |
| External Vault | - | Key material in external Vault with user-defined storage backend | - | - |
Backup and Restore Responsibility
| Configuration | Vault | PostgreSQL | Blob Storage | |
|---|---|---|---|---|
| Mounted Disk | Terraform Enterprise | Terraform Enterprise | User | User |
| External Services | Terraform Enterprise | Terraform Enterprise | User | User |
| External Vault | - | User | - | - |
Mounted Disk
PostgreSQL Database and Blob Storage use mounted disks for their data. Backup and restore of those volumes is the responsibility of the user, and is not managed by Terraform Enterprise's built-in systems.
Vault Data is stored in PostgreSQL and accordingly lives on the mounted disk. As long as the user has restored the mounted disk successfully, the built-in restore mechanism will restore Vault operations in the event of a failure.
Configuration Data for the installation is stored in Docker volumes on the instance. The built-in snapshot mechanism can package up the Configuration data and store it off the instance, and the built-in restore mechanism can recover the configuration data and restore operation in the event of a failure. Configure snapshot and restore by following the automated recovery instructions.
If the instance running Terraform Enterprise is lost, the use of mounted disks means no state data is lost.
External Services
In the External Services operation mode, the Application Layer and Coordination Layer execute on a Linux instance, but the Storage Layer is configured to use external services in the form of a PostgreSQL server and an S3-compatible Blob Storage.
The maintenance of PostgreSQL and Blob Storage are handled by the user, which includes backing up and restoring if necessary.
Vault Data is stored in PostgreSQL. As long as PostgreSQL has been restored successfully by the user, the built-in restore mechanism will restore Vault operations in the event of a failure.
Configuration Data for the installation is stored in Docker volumes on the instance. The built-in snapshot mechanism can package up the data and store it off the instance, and the built-in restore mechanism can recover the data and restore operation in the event of a failure. Configure snapshot and restore by following the automated recovery instructions.
If the instance running Terraform Enterprise is lost, the use of external services means no state data is lost.
NOTE: Customers running an optional external Vault cluster are responsible for backing up the Vault data and restoring it if necessary.
Availability During Upgrades
Upgrades use the installer dashboard. Once an upgrade has been been detected (either online or airgap), the new code is imported. Once ready, all services on the instance are restarted running the new code. The expected downtime is between 30 seconds and 5 minutes, depending on whether database updates have to be applied.
Only application services are changed during the upgrade; data is not backed up or restored. The only data changes that may occur during upgrade are the application of migrations the new version might apply to the PostgreSQL Database.
When an upgrade is ready to start the new code, the system waits for all Terraform runs to finish before continuing. Once the new code has started, the queue of runs is continued in the same order.