Mattermost Common Shared Configuration Module

The Mattermost Common module defines the Mattermost team messaging platform configuration for the RAD Modules ecosystem. It is a pure configuration module — it creates no GCP resources and produces a config output consumed by platform-specific wrapper modules (Mattermost CloudRun and Mattermost GKE).

1. Overview

Purpose: To centralise all Mattermost-specific configuration (custom container image, PostgreSQL 15 database setup, environment variable mapping, health probes, and initialization job) in a single module shared by both Cloud Run and GKE deployments.

Architecture:

Layer 3: Application Wrappers
├── Mattermost_CloudRun  ──┐
└── Mattermost_GKE       ──┤── instantiate Mattermost_Common
                           ↓
              Mattermost_Common (this module)
              Creates: (no GCP resources)
              Produces: config, secret_ids, storage_buckets, path
                           ↓
Layer 2: Platform Modules
├── App_CloudRun  (serverless deployment)
└── App_GKE       (Kubernetes deployment)
                           ↓
Layer 1: App_Common (networking, database, storage, secrets, IAM)

Key characteristics:

• Uses PostgreSQL 15 — Mattermost requires PostgreSQL 13 or later and does not support MySQL.
• Creates no GCP resources — no secrets, no IAM bindings. Mattermost generates its own internal signing keys, session secrets, and encryption keys at first startup and persists them in the PostgreSQL database.
• Exposes a dedicated health endpoint at /api/v4/system/ping — used by both startup and liveness probes for precise health signalling. This is distinct from most other modules that probe the application root path (/).
• container_image is hardcoded to mattermost/mattermost-team-edition — Mattermost_Common itself has no edition variable. Edition-aware image selection (edition = "enterprise" → mattermost/mattermost-enterprise-edition) is implemented by the wrapper modules (Mattermost_CloudRun, Mattermost_GKE), which override container_image in their own application_config merge when var.edition == "enterprise".
• Redis-aware configuration: when enable_redis = true, injects MM_CACHEBACKEND=redis, MM_REDIS_ADDRESS, and MM_REDIS_PASSWORD environment variables automatically.

---

2. Outputs

config

The application configuration object passed to the platform module via application_config.

Field	Value / Description
app_name	"mattermost"
application_version	Version tag (default: "9.11.2")
container_image	"mattermost/mattermost-team-edition" (hardcoded; wrapper modules override this to the enterprise image when edition = "enterprise")
image_source	"custom" — a custom wrapper image is built from the Common module Dockerfile
enable_image_mirroring	var.enable_image_mirroring (default true) — mirrors the Mattermost Docker Hub image to Artifact Registry before deployment
container_build_config	dockerfile_path = "Dockerfile", context_path = ".", build_args = { MM_VERSION = <version, "latest" mapped to "9.11.2"> } (an app-specific arg name so the Foundation's generic APP_VERSION injection cannot override it)
container_port	8065
database_type	"POSTGRES_15"
db_name	Database name (default: "mattermost")
db_user	Database user (default: "mattermost")
enable_cloudsql_volume	Whether to mount the Cloud SQL Auth Proxy sidecar (default: true)
cloudsql_volume_mount_path	"/cloudsql"
gcs_volumes	List of GCS Fuse volume mounts passed through from var.gcs_volumes
container_resources	CPU: 2000m, Memory: 2Gi (default; higher values recommended for active teams)
environment_variables	Core Mattermost environment variables (see §4) merged with var.environment_variables
secret_environment_variables	var.secret_environment_variables — secret env vars passed to the container; managed externally by default
initialization_jobs	Default db-init job or custom override — see §5
startup_probe	HTTP GET /api/v4/system/ping, 30s initial delay, 10s timeout, 10s period, 30 failure threshold
liveness_probe	HTTP GET /api/v4/system/ping, 30s initial delay, 5s timeout, 30s period, 3 failure threshold

secret_ids

An empty map ({}). Mattermost Common does not auto-generate application secrets. Mattermost generates its own internal keys at first startup and stores them in PostgreSQL. The wrapper modules' module_secret_env_vars is set to this empty map.

storage_buckets

A single-element list declaring one data bucket (name_suffix = "data", STANDARD class, force_destroy = true, versioning off, public_access_prevention = "enforced"). The wrapper modules forward this output verbatim as module_storage_buckets, so the bucket is actually provisioned — despite this, the module's primary file-storage path is gcs_volumes (mounted at /mattermost/data), not this bucket.

path

The absolute path to the module directory, used by wrapper modules to locate the scripts/ directory.

---

3. Input Variables

Application

Variable	Type	Default	Description
application_name	string	"mattermost"	Application name — used as base name for resources.
application_version	string	"9.11.2"	Mattermost Docker image tag. Increment to deploy a new release.
description	string	"Initialize Mattermost database schema"	Description used in the default db-init job.
db_name	string	"mattermost"	PostgreSQL database name.
db_user	string	"mattermost"	PostgreSQL application user.
cpu_limit	string	"2000m"	CPU limit for the Mattermost container.
memory_limit	string	"2Gi"	Memory limit for the Mattermost container.
environment_variables	map(string)	{}	Extra environment variables merged into the core Mattermost configuration.
initialization_jobs	list(object)	[]	Custom init jobs. Empty list triggers the default db-init job.
startup_probe	object	see §6	Startup health probe configuration.
liveness_probe	object	see §6	Liveness health probe configuration.
enable_image_mirroring	bool	true	Mirror the container image to Artifact Registry before deployment.
min_instance_count	number	1	Minimum number of running instances. Default 1 prevents scale-to-zero in Cloud Run.
max_instance_count	number	3	Maximum number of running instances.
region	string	"us-central1"	GCP region for resource deployment.
site_url	string	""	The public URL where Mattermost is accessible. Sets MM_SERVICESETTINGS_SITEURL.

edition is not a Mattermost_Common variable — it is declared on the wrapper modules (Mattermost_CloudRun, Mattermost_GKE) and used there to select the container image. See §9.

Storage & Volumes

Variable	Type	Default	Description
enable_cloudsql_volume	bool	true	Mount Cloud SQL Auth Proxy sidecar socket.
gcs_volumes	list(object)	[]	GCS Fuse volume mounts. Each entry: name, bucket_name, mount_path, readonly, mount_options. Mount at /mattermost/data for persistent file uploads.

Redis Integration

Variable	Type	Default	Description
enable_redis	bool	false	Enable Redis for Mattermost caching and session storage. When true, injects Redis-specific environment variables automatically.
redis_host	string	""	Redis hostname or IP address. Required when enable_redis = true.
redis_port	string	"6379"	Redis server TCP port.
redis_auth	string	""	Redis AUTH password. Marked sensitive in Terraform, but injected as a plain MM_REDIS_PASSWORD environment variable (not a Secret Manager reference) when non-empty — secret_environment_variables is always {} from this module.

---

4. Environment Variables

Mattermost Common injects a set of core environment variables into every deployment. All Mattermost configuration uses the MM_ prefix with double-underscore path notation for nested settings.

Core Service Settings

Variable	Value / Source	Purpose
MM_SERVICESETTINGS_LISTENADDRESS	:8065	Binds Mattermost's HTTP server to all interfaces on port 8065.
MM_METRICSSETTINGS_LISTENADDRESS	:8067	Prometheus-format metrics endpoint. Integrate with Cloud Monitoring via remote write.
MM_SERVICESETTINGS_SITEURL	var.site_url (when non-empty)	The public URL for link generation in emails, webhooks, and OAuth callbacks.
MM_SERVICESETTINGS_TRUSTEDPROXYIPHEADER	X-Forwarded-For	Tells Mattermost to trust the X-Forwarded-For header from Cloud Run's and the load balancer's proxy layer for correct client IP extraction.

File Storage

Variable	Value	Purpose
MM_FILESETTINGS_DRIVERTYPE	local	Instructs Mattermost to use local filesystem storage. When a GCS FUSE volume is mounted at /mattermost/data, this resolves to durable object storage transparently.
MM_FILESETTINGS_DIRECTORY	/mattermost/data/	File storage path — must match the GCS FUSE or NFS mount point.

Logging

Variable	Value	Purpose
MM_LOGSETTINGS_CONSOLELEVEL	INFO	Log level written to stdout. Cloud Run and GKE capture stdout to Cloud Logging automatically.
MM_LOGSETTINGS_ENABLEFILE	false	Disables file-based logging. File logs are not appropriate for containerised deployments — all log output goes to stdout and is captured by Cloud Logging.

Email Batching

Variable	Value	Purpose
MM_EMAILSETTINGS_ENABLEEMAILBATCHING	false	Disabled for Cloud Run compatibility. Email batching requires an in-memory queue that does not survive container restarts or scale-to-zero events.

Redis Cache (injected when enable_redis = true)

Variable	Value / Source	Purpose
MM_CACHEBACKEND	redis	Switches Mattermost's cache backend from in-process memory to the external Redis instance.
MM_REDIS_ADDRESS	<redis_host>:<redis_port>	Connection string for the Redis server.
MM_REDIS_PASSWORD	var.redis_auth (when non-empty)	Redis AUTH password, injected as a secret env var when set.

When enable_redis = false, MM_CACHEBACKEND is set to memory and no Redis connection variables are injected.

---

5. Initialization Job

One db-init job runs by default (when initialization_jobs = []):

Field	Value
Image	postgres:15-alpine
Script	scripts/db-init.sh
Secrets required	DB_PASSWORD (application user password), ROOT_PASSWORD (PostgreSQL superuser, optional)
execute_on_apply	true
CPU / Memory	1000m / 512Mi
Timeout	600s, 1 retry

db-init.sh behaviour:

1. Connects to Cloud SQL PostgreSQL via the Auth Proxy Unix socket or TCP.
2. Creates the mattermost user with the password from Secret Manager if it does not exist.
3. Creates the mattermost database if it does not exist.
4. Grants the mattermost user full privileges on the database.
5. Verifies connectivity by running a simple SELECT 1 query as the application user.

Mattermost then runs its own schema migrations on startup — the db-init job only creates the empty database and user; it does not initialise the Mattermost schema. This is by design: Mattermost's built-in migration system handles schema setup and version upgrades automatically.

Override initialization_jobs with a non-empty list to replace this default job entirely.

---

6. Health Probes

Mattermost Common configures startup and liveness probes targeting the /api/v4/system/ping endpoint. This endpoint is part of Mattermost's REST API and returns HTTP 200 when the server is fully initialised, database-connected, and ready to serve requests.

This is a more precise health signal than probing the root path (/): the ping endpoint validates that Mattermost has successfully connected to PostgreSQL and completed any pending schema migrations.

Probe	Path	Initial Delay	Timeout	Period	Failure Threshold	Purpose
Startup	/api/v4/system/ping	30s	10s	10s	30	Allows up to 330 seconds total for Mattermost to complete database migration and initialise. Generous threshold accommodates first-run schema creation on a fresh database.
Liveness	/api/v4/system/ping	30s	5s	30s	3	Restarts the container if Mattermost becomes unresponsive or loses its database connection.

The GKE module (Mattermost_GKE) uses the same probe paths and defaults. The Cloud Run module (Mattermost_CloudRun) also includes startup_probe_config and health_check_config variables that configure the service-level probes independently — these default to the same paths.

---

7. Scripts and Container Image

All supporting files are in scripts/. The scripts/ directory is used as the Docker build context.

Dockerfile

Wraps the official mattermost/mattermost-team-edition:${MM_VERSION} image:

• Accepts only MM_VERSION as a Docker build argument (default 9.11.2); there is no EDITION build arg, and the FROM line is always mattermost-team-edition regardless of the wrapper module's edition variable.
• Switches to root only to install the entrypoint wrapper, then drops back to the image's built-in mattermost uid (2000).
• Copies entrypoint.sh to /usr/local/bin/mm-entrypoint.sh and uses it as the ENTRYPOINT — this wrapper maps the Foundation's DB_* variables into MM_SQLSETTINGS_DATASOURCE before starting the server; all other MM_* settings are injected directly as environment variables.
• Exposes port 8065 (HTTP).

db-init.sh

Creates the PostgreSQL database and user before Mattermost's first startup:

1. Resolves the PostgreSQL connection from DB_HOST (Unix socket path for Auth Proxy, or TCP hostname).
2. Connects using ROOT_PASSWORD or falls back to peer authentication if the root password is not available.
3. Creates the application user with DB_PASSWORD from Secret Manager.
4. Creates the mattermost database owned by the application user.
5. Verifies connectivity as the application user.
6. Signals the Cloud SQL Proxy to shut down cleanly.

---

8. Platform-Specific Differences

Aspect	Mattermost CloudRun	Mattermost GKE
Default min_instance_count	1 — prevents scale-to-zero from disconnecting WebSocket sessions.	1 — always at least one pod running.
Default max_instance_count	5	5
Health probe path	/ (Cloud Run module default); override to /api/v4/system/ping for precise signalling.	/api/v4/system/ping — GKE module uses the precise Mattermost health endpoint by default.
Cloud SQL connectivity	Auth Proxy Unix socket via enable_cloudsql_volume = true (default).	enable_cloudsql_volume = true by default in GKE too — but this injects a cloud-sql-proxy sidecar listening on TCP 127.0.0.1, not a Unix socket; entrypoint.sh connects over that loopback TCP address.
File storage	GCS FUSE volumes (gcs_volumes) or NFS. GCS FUSE is preferred for Cloud Run.	GCS FUSE volumes via CSI driver (gcs_volumes) or NFS. GCS FUSE or StatefulSet PVC for GKE.
WebSocket timeout	Cloud Run's 60-min max request timeout limits WebSocket lifetime. Set timeout_seconds = 3600.	No timeout constraint — GKE connections persist indefinitely. Better choice for production.
Session affinity	Not applicable to Cloud Run (serverless).	session_affinity = "ClientIP" default — required for consistent Mattermost admin sessions across pod replicas.
site_url	Set after first deploy once the Cloud Run *.run.app URL is known.	Set to the load balancer IP or custom domain after first deploy.

---

9. Edition Selection

The edition variable is declared on the wrapper modules (Mattermost_CloudRun, Mattermost_GKE), not on Mattermost_Common — see §3. When edition = "enterprise", the wrapper overrides the merged container_image field to mattermost/mattermost-enterprise-edition. Note this does not change what Mattermost_Common's static Dockerfile builds FROM (see §7) — that file always pulls mattermost-team-edition:${MM_VERSION} regardless of edition, since it has no EDITION build argument.

edition	Image	Notes
"team" (default)	mattermost/mattermost-team-edition:<version>	Free. Supports up to unlimited users with standard messaging, channels, integrations, and webhooks.
"enterprise"	mattermost/mattermost-enterprise-edition:<version>	Requires a paid licence key. Unlocks LDAP/AD sync, SAML SSO, advanced compliance controls, custom retention, multi-region HA clustering, and enterprise security features.

To activate Enterprise features, set edition = "enterprise" and provide the licence key via environment_variables:

edition = "enterprise"

environment_variables = {
  MM_LicenseKey = "your-enterprise-licence-key"
}

Or use secret_environment_variables to avoid storing the licence key in plaintext:

secret_environment_variables = {
  MM_LicenseKey = "mattermost-licence-key"
}

---

10. Implementation Pattern

The following example illustrates how Mattermost_CloudRun instantiates Mattermost_Common:

module "mattermost_app" {
  source = "../Mattermost_Common"

  application_version    = var.application_version
  db_name                = var.db_name
  db_user                = var.db_user
  cpu_limit              = var.cpu_limit
  memory_limit           = var.memory_limit
  description            = var.description
  startup_probe          = var.startup_probe
  liveness_probe         = var.liveness_probe
  enable_cloudsql_volume = var.enable_cloudsql_volume
  gcs_volumes            = var.gcs_volumes
  site_url               = var.site_url
  enable_redis           = var.enable_redis
  redis_host             = var.redis_host
  redis_port             = var.redis_port
  redis_auth             = var.redis_auth
  environment_variables  = var.environment_variables
  initialization_jobs    = var.initialization_jobs
}

locals {
  mattermost_module = merge(
    module.mattermost_app.config,
    var.edition == "enterprise" ? { container_image = "mattermost/mattermost-enterprise-edition" } : {},
    # ... other container_image/container_port/container_resources overrides
  )
  application_modules    = { mattermost = local.mattermost_module }
  module_env_vars        = {}
  module_secret_env_vars = module.mattermost_app.secret_ids  # {}
  module_storage_buckets = module.mattermost_app.storage_buckets  # [{ name_suffix = "data" }]
  scripts_dir            = abspath("${module.mattermost_app.path}/scripts")
}

module "app_cloudrun" {
  source = "../App_CloudRun"

  application_config     = local.application_modules
  module_storage_buckets = local.module_storage_buckets
  scripts_dir            = local.scripts_dir
  # ... other inputs
}

Key differences from Ghost Common's pattern:

• module_secret_env_vars is always empty ({}) — Mattermost manages its own secrets internally.
• module_storage_buckets is a single data bucket, forwarded verbatim from Mattermost_Common's output — unlike most Common modules, the bucket is declared in Common rather than the wrapper.
• edition is not passed into module "mattermost_app" at all — it exists only on the wrapper module and is consumed locally to override container_image in the merge shown above. Redis variables, by contrast, genuinely are forwarded into Mattermost_Common.