Roundcube on Google Cloud Run

Roundcube is a free, open-source, browser-based IMAP webmail client. It gives users a desktop-like mail experience — folders, address book, search and message composition — against an IMAP and SMTP mail server that already exists. Roundcube is a mail client: this module deploys no mail server. It deploys Roundcube on Cloud Run v2 on top of the App_CloudRun foundation, which provisions and manages the shared Google Cloud infrastructure.

This guide focuses on the cloud services Roundcube uses and how to explore and operate them from the Google Cloud Console and the command line. For the mechanics common to every Cloud Run application — service identity, ingress and load balancing, scaling and concurrency, CI/CD, Cloud Armor, IAP, Binary Authorization, VPC Service Controls, backups, and the deployment lifecycle — refer to the App_CloudRun foundation guide rather than repeating them here.

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1. Overview

Roundcube runs as a PHP container (the official roundcube/roundcubemail -apache image, wrapped by a thin custom entrypoint) on Cloud Run v2. The deployment wires together a focused set of Google Cloud services:

Capability	Google Cloud service	Notes
Compute	Cloud Run v2	PHP/Apache service, 1 vCPU / 2 GiB by default, serverless autoscaling; scale-to-zero by default
Database	Cloud SQL for MySQL 8.0	Roundcube's own data — preferences, contacts, session data. Mail itself stays on the IMAP server
Object storage	Cloud Storage	A generic data bucket is provisioned, but Roundcube does not read or write it
Secrets	Secret Manager	Auto-generated des_key (ROUNDCUBEMAIL_DES_KEY); database password
Ingress	Cloud Run URL / Cloud Load Balancing	Default run.app URL; optional external HTTPS load balancer + custom domain
Mail	(none — external)	You supply the IMAP and SMTP servers

Sensible defaults worth knowing up front:

• No IMAP or SMTP server is configured. The module sets ROUNDCUBEMAIL_DEFAULT_HOST and ROUNDCUBEMAIL_SMTP_SERVER to empty values, and this wrapper exposes no input for them. Set them in environment_variables (Group 6) before anyone can sign in — see §3.
• No local accounts. Users sign in with their IMAP username and password. There is no administrator account and no admin-password secret.
• MySQL 8.0 only. The wrapper entrypoint always composes a mysql:// DSN.
• enable_cloudsql_volume = false. The DSN uses DB_IP, the Cloud SQL private IP, so Cloud Run connects over private-IP TCP, not the Auth Proxy Unix socket.
• Scale-to-zero is enabled by default (min_instance_count = 0, max_instance_count = 1). Cold starts add latency to the first request after idle; set min_instance_count = 1 to avoid this.
• No separate schema job. The image runs bin/installto.sh -y on every start, which creates and upgrades the schema idempotently. Only db-init runs as a Cloud Run job.
• Pinned image tag. application_version = "1.6.19-apache". Keep it an exact tag — a rolling tag rebuilds without producing a new revision.

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2. Google Cloud Services & How to Explore Them

All commands assume PROJECT and REGION are set. Service and resource names are reported in the deployment Outputs.

A. Cloud Run — the Roundcube service

Roundcube runs as a Cloud Run v2 service that autoscales by request load between the minimum and maximum instance counts. Each deployment creates an immutable revision; traffic can be split across revisions for safe rollouts.

• Console: Cloud Run → select the service for revisions, traffic, logs, and metrics.
• CLI:

  gcloud run services list --project "$PROJECT" --region "$REGION"
  gcloud run services describe <service-name> --project "$PROJECT" --region "$REGION"
  gcloud run revisions list --service <service-name> --project "$PROJECT" --region "$REGION"

See App_CloudRun for scaling, concurrency, execution environment, and traffic splitting.

B. Cloud SQL for MySQL 8.0

Roundcube stores its own data — user preferences, address-book contacts and session data — in a managed Cloud SQL for MySQL 8.0 instance. Mail is never stored here; it stays on the IMAP server. The service connects over the instance's private IP via TCP. On first deploy, the db-init job creates the application database and user; the schema is then created by Roundcube itself (bin/installto.sh -y) when the container starts.

• Console: SQL → select the instance for connections, backups, flags, metrics.
• CLI:

  gcloud sql instances list --project "$PROJECT"
  gcloud sql instances describe <instance-name> --project "$PROJECT"
  gcloud sql connect <instance-name> --user=<db-user> --database=<db-name> --project "$PROJECT"

The instance name, database, user, and password secret are in the Outputs. See App_CloudRun for the connection model, backups, and password rotation.

C. Cloud Storage

A generic data bucket is provisioned by default (via the Foundation's storage_buckets input), but Roundcube never reads or writes it: gcs_volumes is empty, so no bucket is mounted into the container. Attachments in flight are written to container-local scratch (ROUNDCUBEMAIL_TEMP_DIR = /tmp/roundcube-temp), which is safe to lose on a cold start.

• Console: Cloud Storage → Buckets.
• CLI:

  gcloud storage buckets list --project "$PROJECT"

D. Secret Manager

One application secret is generated automatically: the 24-character des_key, stored as secret-<prefix>-roundcube-des-key and injected as ROUNDCUBEMAIL_DES_KEY. Roundcube uses it to encrypt session data and the IMAP password it holds on each signed-in user's behalf. The database password is managed separately by the foundation.

• Console: Security → Secret Manager.
• CLI:

  gcloud secrets list --project "$PROJECT" --filter="name~des-key"
  gcloud secrets versions access latest --secret=<secret-name> --project "$PROJECT"

See App_CloudRun for injection and rotation details.

E. Networking & ingress

The service is reachable at its run.app URL by default. An external HTTPS load balancer with a custom domain, Cloud CDN, and Cloud Armor can be layered on. Roundcube also makes outbound connections to your IMAP and SMTP servers; with the default vpc_egress_setting = PRIVATE_RANGES_ONLY, traffic to a public mail server leaves directly rather than through the VPC.

• Console: Cloud Run (service URL); Network services → Load balancing.
• CLI:

  gcloud run services describe <service-name> --region "$REGION" --format='value(status.url)'
  gcloud compute addresses list --project "$PROJECT"

See App_CloudRun.

F. Cloud Logging & Monitoring

Container logs flow to Cloud Logging; Cloud Run and Cloud SQL metrics flow to Cloud Monitoring. The uptime check is off by default (uptime_check_config.enabled = false); alert policies are optional.

• Console: Logging → Logs Explorer; Monitoring → Dashboards / Alerting.
• CLI:

  gcloud run services logs read <service-name> --project "$PROJECT" --region "$REGION" --limit 50

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3. Roundcube Application Behaviour

• Pointing Roundcube at a mail server. Roundcube_Common sets these environment variables, and environment_variables (Group 6) is merged over them, so that is where you configure the mail server:

  Variable	Default	Meaning
  ROUNDCUBEMAIL_DEFAULT_HOST	""	IMAP server users sign in against. ssl://host for implicit TLS, tls://host for STARTTLS; a bare host name is cleartext.
  ROUNDCUBEMAIL_DEFAULT_PORT	993	IMAP port — 993 for implicit TLS, 143 for STARTTLS.
  ROUNDCUBEMAIL_SMTP_SERVER	""	SMTP server used for sending.
  ROUNDCUBEMAIL_SMTP_PORT	587	Submission port — 587 or 465. Never 25: Google Cloud blocks outbound port 25.
  ROUNDCUBEMAIL_SKIN	elastic	Roundcube skin.

  Roundcube_Common has imap_host/imap_port/smtp_host/smtp_port/skin inputs that feed these values, but Roundcube_CloudRun does not declare or forward them, so on this wrapper environment_variables is the only way in.

• Sign-in. Open the service URL and sign in with an account on the IMAP server. Roundcube has no local or administrator accounts.

• Database DSN. The wrapper entrypoint composes ROUNDCUBEMAIL_DSNW=mysql://DB_USER:<password>@DB_IP:DB_PORT/DB_NAME with the password URL-encoded by PHP's rawurlencode, sets ROUNDCUBEMAIL_DSNR to the same value, and hands off to the image's own /docker-entrypoint.sh. The vendor entrypoint would otherwise interpolate the password raw, which fails on the @ : / ? # % & + characters Cloud SQL passwords contain.

• Schema. There is no schema job: the image runs bin/installto.sh -y on every start, creating the schema on first boot and upgrading it after a version change.

• PHP memory limit. php_memory_limit reaches the container as PHP_MEMORY_LIMIT; the entrypoint writes it into /usr/local/etc/php/conf.d/zz-rad-overrides.ini, overriding the image's own memory_limit=64M. The container log confirms it at start: [startup] PHP memory_limit set to 512M via ....

• Health check behaviour. Both probes are HTTP GET /, where Roundcube serves its login form. The startup probe allows a 30 s delay plus 20 × 15 s attempts, because the image runs installto.sh and waits for the database before Apache starts.

  curl -s -o /dev/null -w "%{http_code}\n" "$SERVICE_URL/"   # expect 200

• Inspect job execution:

  gcloud run jobs list --project "$PROJECT" --region "$REGION"
  gcloud run jobs executions list --job <job-name> --project "$PROJECT" --region "$REGION"

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4. Configuration Variables

Variables are grouped exactly as they appear on the deployment platform. Only settings specific to or notable for Roundcube are listed; every other input is inherited from App_CloudRun with its standard behaviour.

Group 1 — Project & Identity

Variable	Default	Description
project_id	(required)	Target Google Cloud project.
tenant_id	demo	Short suffix (1–7 lowercase alphanumeric characters) that makes resource names unique per environment.
region	us-central1	Region for the service and regional resources.

Group 2 — Deployment Environment

Variable	Default	Description
support_users	[]	Emails granted project access and monitoring alerts.
resource_labels	{}	Labels applied to all resources.

Group 3 — Application Identity

Variable	Default	Description
application_name	roundcube	Base name for resources. Do not change after first deploy.
display_name	Roundcube	Human-readable name shown in the Console.
application_version	1.6.19-apache	roundcube/roundcubemail tag, passed as the ROUNDCUBE_VERSION build ARG. This wrapper's value is the one that wins. Pin an exact -apache tag.
php_memory_limit	512M	PHP memory_limit, applied through conf.d/zz-rad-overrides.ini.
admin_email	admin@example.com	No effect — Roundcube creates no accounts.
enable_gcs_storage_volume	true	No effect — Roundcube_Common declares it but never uses it; nothing is mounted.

Group 4 — Runtime & Scaling

Variable	Default	Description
deploy_application	true	Set false to provision infrastructure only.
container_image_source	custom	Builds the wrapper image via Cloud Build. "prebuilt" skips the wrapper entrypoint, so the DSN is no longer URL-encoded and php_memory_limit stops working.
cpu_limit	1000m	CPU per instance.
memory_limit	2Gi	Memory per instance.
min_instance_count	0	0 enables scale-to-zero.
max_instance_count	1	Autoscaling upper bound.
container_port	80	Apache listens on port 80.
execution_environment	gen2	Gen2 required for GCS Fuse mounts.
timeout_seconds	300	Max request duration.
enable_cloudsql_volume	false	The DSN uses DB_IP over TCP; the socket is not used.
enable_image_mirroring	true	Mirror the image into Artifact Registry.
container_protocol	http1	HTTP/1.1.

Group 5 — Access & Ingress Control

Variable	Default	Description
ingress_settings	all	Public ingress by default.
vpc_egress_setting	PRIVATE_RANGES_ONLY	Route only RFC 1918 traffic via VPC. Use ALL_TRAFFIC only if the IMAP/SMTP servers must be reached through the VPC.
enable_iap	false	Require Google sign-in in front of the Roundcube login.
iap_authorized_users / iap_authorized_groups	[]	Who may access through IAP.

Group 6 — Environment Variables & Secrets

Variable	Default	Description
environment_variables	{}	Extra non-secret settings, merged over the module defaults. Set ROUNDCUBEMAIL_DEFAULT_HOST, ROUNDCUBEMAIL_DEFAULT_PORT, ROUNDCUBEMAIL_SMTP_SERVER, ROUNDCUBEMAIL_SMTP_PORT and, optionally, ROUNDCUBEMAIL_SKIN here.
secret_environment_variables	{}	Map of env var → Secret Manager secret name.
protect_sensitive_environment_variables	true	Credential-named keys typed into environment_variables are moved into Secret Manager automatically.
secret_propagation_delay	30	Seconds to wait after secret creation before proceeding.
secret_rotation_period	2592000s	Secret Manager rotation notification frequency.

Group 7 — Backup & Restore

Variable	Default	Description
backup_schedule	0 2 * * *	Automated backup cron (UTC).
backup_retention_days	7	Retention; raise for production.
enable_backup_import / backup_source / backup_uri / backup_format	restore options	Restore from a backup on deploy.

Group 8 — CI/CD & Binary Authorization

Standard App_CloudRun Cloud Build / Cloud Deploy integration — see App_CloudRun. Key inputs: enable_cicd_trigger, github_repository_url, github_token, enable_cloud_deploy, enable_binary_authorization.

Group 9 — Custom SQL Scripts & NFS server

enable_custom_sql_scripts, custom_sql_scripts_bucket, custom_sql_scripts_path, custom_sql_scripts_use_root — run SQL from a GCS bucket after provisioning. nfs_instance_name / nfs_instance_base_name select or name an NFS VM, and only matter if enable_nfs is turned on. See App_CloudRun.

Group 10 — Load Balancer, CDN & Image Retention

Variable	Default	Description
enable_cloud_armor	false	Provision Global HTTPS LB + Cloud Armor WAF.
admin_ip_ranges	[]	CIDR allowlist for privileged access.
application_domains	[]	Custom domain names for the HTTPS LB.
enable_cdn	false	Enable Cloud CDN on the HTTPS LB backend.
max_images_to_retain / delete_untagged_images / image_retention_days	7 / true / 30	Artifact Registry cleanup policy.

Group 11 — Storage & Filesystem

Variable	Default	Description
create_cloud_storage	true	Create the generic data GCS bucket. Not read or written by Roundcube.
enable_nfs	false	Not needed — the image declares no volumes and keeps no state on disk that must survive a restart.
nfs_mount_path	/var/lib/roundcube	Mount path, only used when enable_nfs = true.
gcs_volumes	[]	GCS Fuse volume mounts (requires gen2). Empty — nothing is mounted.
manage_storage_kms_iam / enable_artifact_registry_cmek	false	CMEK options.

Group 12 — Database Backend

Variable	Default	Description
database_type	MYSQL_8_0	Must stay MySQL — the entrypoint composes a mysql:// DSN. The picker also offers POSTGRES and NONE; neither works.
db_name / db_user	roundcube	Tenant-prefixed at deploy time. Immutable after first deploy.
database_password_length	32	Generated password length (16–64). Set once — changing it on a running deployment breaks database authentication.
enable_auto_password_rotation	false	Automated database password rotation.
rotation_propagation_delay_sec	90	Wait after rotation before restarting the service.
db_host_env_var_name	DB_IP	Additional name for the DB host IP. The Foundation already injects DB_IP, which is what the entrypoint reads, so the default only duplicates it.

Group 13 — Jobs & Scheduled Tasks

Variable	Default	Description
initialization_jobs	[]	Leave empty to use the built-in db-init job. Supplying any list replaces it.
cron_jobs	[]	No platform-scheduled recurring tasks by default.

Group 14 — Observability & Health

Variable	Default	Description
startup_probe	HTTP GET /, 30s delay, 10s timeout, 15s period, 20 retries	Waits for installto.sh and the database before Apache starts.
liveness_probe	HTTP GET /, 60s delay, 10s timeout, 30s period, 3 retries	The login form at the document root.
uptime_check_config	{ enabled = false, path = "/" }	Cloud Monitoring uptime check — off by default.
alert_policies	[]	Metric alert policies.

Group 21 — Redis

Variable	Default	Description
enable_redis	false	This module wires no Redis integration into Roundcube.
redis_host	""	Redis endpoint.
redis_port	6379	Redis port.

Group 22 — VPC Service Controls & Audit Logging

Variable	Default	Description
enable_vpc_sc	false	Enforce a VPC-SC perimeter (requires organization_id).
enable_audit_logging	false	Detailed Cloud Audit Logs.

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5. Outputs

Returned on a successful deployment — the quickest way to locate and explore the running resources.

Output	Description
service_name	Cloud Run service name.
service_url	Default run.app URL of the service.
service_location	Region the service runs in.
stage_services	Cloud Deploy stage services (when enabled).
load_balancer_ip / load_balancer_url	External HTTPS load balancer IP / URL (when enabled).
database_instance_name	Cloud SQL instance name.
database_name / database_user	Application database name / user.
database_password_secret	Secret Manager secret holding the DB password.
database_host / database_port	DB endpoint / port.
storage_buckets	Created Cloud Storage buckets.
network_name / network_exists / regions	VPC network, presence, regions.
container_image / container_registry	Deployed image and Artifact Registry repo.
monitoring_enabled / monitoring_notification_channels / uptime_check_names	Monitoring status, channels, uptime checks.
initialization_jobs	Names of the setup jobs (db-init).
deployment_id / tenant_id / resource_prefix	Naming identifiers.
project_id / project_number	Project identifiers.
cicd_enabled / github_repository_url / github_repository_owner / github_repository_name / cicd_configuration	CI/CD status and details.
artifact_registry_repository / cloudbuild_trigger_name / cloudbuild_trigger_id	Registry and build trigger.
vpc_sc_enabled / vpc_sc_perimeter_name / vpc_sc_dry_run_mode	VPC-SC status.
audit_logging_enabled / artifact_registry_cmek_enabled	Audit logging and CMEK status.

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6. Configuration Pitfalls & Sensible Defaults

Risk: Critical (data loss / outage / security) — High (service degraded) — Medium (cost or partial degradation) — Low (minor).

Inherited plan-time validation. This module passes its configuration through the App_CloudRun foundation engine, which validates values and combinations at plan time. Invalid configuration fails the plan with a clear, named error before any resource is created, so most mistakes below are caught up front rather than at apply or runtime.

Setting	Sensible value	Risk	Consequence if wrong
ROUNDCUBEMAIL_DEFAULT_HOST / ROUNDCUBEMAIL_SMTP_SERVER (via environment_variables)	Your IMAP and SMTP servers	High	Left empty by default. The service is healthy and serves its login form, but no user can sign in or send mail. A green health check is not evidence that mail works.
ROUNDCUBEMAIL_SMTP_PORT	587 or 465	High	Google Cloud blocks outbound port 25 for all egress; sending through port 25 never succeeds.
ROUNDCUBEMAIL_DEFAULT_HOST scheme	ssl://host or tls://host	High	A bare host name connects in cleartext, sending users' IMAP passwords unencrypted. Use a bare host only for a server inside the VPC.
ROUNDCUBEMAIL_DES_KEY (auto-generated)	Never hand-edit in Secret Manager	High	It encrypts session data and the stored IMAP passwords. Changing it signs every user out; removing it makes the vendor image mint a different key per container, logging users out at random across instances and cold starts with nothing in the logs.
container_image_source	custom	Critical	prebuilt deploys an image without the wrapper entrypoint — the database password is no longer URL-encoded into the DSN, so the connection fails on the punctuation Cloud SQL passwords contain.
database_type	MYSQL_8_0	Critical	The entrypoint always builds a mysql:// DSN. Any other engine (or NONE) leaves Roundcube without a usable database.
application_version	An exact -apache tag	Medium	latest or a rolling 1.6.x-apache tag can change content under the same tag string, which produces no Terraform diff and no new revision — the running container silently keeps the old image. The -fpm variants have no web server.
db_name / db_user	Set once	Critical	Immutable after first deploy; renaming recreates the DB/user and loses stored preferences and contacts.
database_password_length	Set once, at first deploy	High	Changing it on a running deployment writes a new password the database does not hold, and every connection fails until the database job is re-run.
php_memory_limit	512M or higher	Medium	The image's own default is 64M; large messages and attachments are where a small PHP heap runs out.
admin_email, enable_gcs_storage_volume	Leave as-is	Low	Neither has any effect on this module, whatever their descriptions say.
min_instance_count	1 for production	Medium	Scale-to-zero (0) adds cold-start latency, including the installto.sh run, to the first request after idle.
enable_cloud_armor	enable for production	Medium	The login form is publicly reachable without WAF protection by default.

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For the foundation behaviour referenced throughout — service identity, scaling and concurrency, ingress and load balancing, CI/CD, Cloud Armor, IAP, Binary Authorization, VPC-SC, backups, and image mirroring — see App_CloudRun. Roundcube-specific application configuration is described in Roundcube_Common.

Related guides

• Hands-on lab: Roundcube on Cloud Run — deploy it step by step, with the console screens and commands at each stage.
• Roundcube Common — Shared Application Configuration — the application layer this module builds on.