LimeSurvey Common — Shared Application Configuration

LimeSurvey_Common is the shared application layer for LimeSurvey. It is not deployed on its own; instead it supplies the LimeSurvey-specific configuration that both LimeSurvey_GKE and LimeSurvey_CloudRun build on, so the two platform variants behave identically where it matters. End users never configure this layer directly — it has no deployment UI inputs of its own — but understanding what it provides explains the defaults you see in the platform docs.

For the infrastructure that actually provisions and runs LimeSurvey, see the platform guides (LimeSurvey_GKE, LimeSurvey_CloudRun) and the foundation guides (App_GKE, App_CloudRun, App_Common).

1. What this layer provides

Area	Provided by LimeSurvey_Common	Where it surfaces
Admin credential	Generates the super-administrator password (20-char) and stores it in Secret Manager; injects it as the `ADMIN_PASSWORD` secret env	Retrieve via Secret Manager (see below)
Container image	Wraps the upstream `martialblog/limesurvey` (Apache) image with a thin cloud entrypoint; builds via Cloud Build and mirrors the base into Artifact Registry	`container_image` output of the platform deployment
Database engine	Fixes Cloud SQL for MySQL 8.0 as the engine and forces the InnoDB storage engine	§Database in the platform guides
Database bootstrap	Defines the first-deploy job (`db-init`) that creates the database, user, and grants	`initialization_jobs` output
Object storage	Declares the Cloud Storage `limesurvey-uploads` bucket	`storage_buckets` output
Core settings	Sets the baseline LimeSurvey environment: `DB_TYPE`, `DB_PORT`, storage engine, `URL_FORMAT`, admin identity, `PUBLIC_URL`	Application behaviour in the platform guides
Health checks	Supplies the default TCP startup probe and HTTP liveness probe targeting the root `/` landing endpoint	§Observability in the platform guides

2. Admin credential in Secret Manager

The upstream martialblog/limesurvey entrypoint requires ADMIN_PASSWORD — it exits with code 1 if the variable is missing — and seeds the initial super-admin account with it on first boot. LimeSurvey_Common generates a 20-character password once and stores it in Secret Manager so it is stable across restarts and never lands in plaintext config:

ADMIN_PASSWORD — the super-administrator password for the admin account. Stored as secret-<resource_prefix>-<application_name>-admin-password. It is exposed to the running container as the ADMIN_PASSWORD secret env via the secret_ids output. The account identity itself is fixed by static env in this layer: ADMIN_USER = admin, ADMIN_NAME = Administrator, ADMIN_EMAIL = admin@techequity.cloud.

The database password is generated and managed separately by the foundation; its secret name is reported in the platform deployment outputs (database_password_secret).

Retrieve the admin password after deployment:

# Find the secret for this deployment (name includes the resource prefix):
gcloud secrets list --project "$PROJECT" --filter="name~admin-password"

# Read the current value:
gcloud secrets versions access latest --secret=<secret-name> --project "$PROJECT"

Once you have logged in and (optionally) created additional accounts, you may rotate the value in Secret Manager and redeploy — the entrypoint re-applies whatever ADMIN_PASSWORD is present. See App_Common for the shared secret and Workload Identity model.

3. Database engine and bootstrap

LimeSurvey requires MySQL 8.0; the engine is fixed to MYSQL_8_0 and other engines are not supported by this module. On the first deployment a one-shot job (db-init) runs using mysql:8.0-debian and idempotently:

Locates the Cloud SQL connection — the Cloud SQL Auth Proxy Unix socket under /cloudsql when a socket volume is mounted, otherwise a TCP connection via the instance private IP (DB_IP),
Waits for MySQL port 3306 to be reachable (TCP path),
Creates (or updates) the application user with the generated password (CREATE USER IF NOT EXISTS … / ALTER USER …),
Creates the application database (CREATE DATABASE IF NOT EXISTS),
Grants all privileges on that database to the application user,
Verifies the application user can actually connect — failing the job early on a password or grant mismatch, and warming the caching_sha2_password server-side auth cache,
Signals the Cloud SQL Auth Proxy sidecar to shut down gracefully (via quitquitquit) so the job container exits cleanly.

The job is safe to re-run. Note that MySQL 8.0 uses caching_sha2_password by default; over plain TCP the script adds --get-server-public-key for RSA key exchange when the client supports it.

No separate migration job exists. The actual LimeSurvey schema (the settings_global, surveys, users, … tables) is created on container start by the upstream martialblog/limesurvey entrypoint, which runs the LimeSurvey console installer / updatedb once db-init has provisioned an empty database and user.

Why InnoDB is forced. Cloud SQL MySQL 8.0 disables the MyISAM storage engine (disabled_storage_engines=MyISAM). The martialblog/limesurvey entrypoint defaults its engine to MyISAM and writes it into config.php, so the console installer would try CREATE TABLE … ENGINE=MyISAM and Cloud SQL rejects it (3161 Storage engine MyISAM is disabled). This layer therefore sets both DB_MYSQL_ENGINE = InnoDB and DBENGINE = InnoDB so table creation succeeds on first boot.

Inspect the database directly with:

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

The instance, database, and user names are in the platform deployment outputs.

4. Container image and entrypoint

The custom image is a thin wrapper FROM martialblog/limesurvey:<tag> (Apache, running on port 8080 as www-data with WORKDIR /var/www/html). The base tag is keyed on an app-specific build arg LIMESURVEY_VERSION — not the generic APP_VERSION, which the foundation injects into build_args and would clobber to latest. LimeSurvey_Common maps application_version == "latest" onto a known-good pinned tag (6-apache) and passes it as LIMESURVEY_VERSION. The image is built via Cloud Build; enable_image_mirroring = true mirrors the public Docker Hub base into Artifact Registry.

The wrapper drops in a cloud-entrypoint.sh that runs before the upstream entrypoint and keeps its work minimal:

Defaults the database backend — DB_TYPE = mysql, DB_PORT = 3306.
Aliases the tenant-scoped DB names — defensively maps DB_USER → DB_USERNAME and DB_DATABASE → DB_NAME if a name is missing (the variant main.tf already renames the foundation-injected values onto DB_USERNAME / DB_NAME / DB_PASSWORD).
Sets PUBLIC_URL — from the foundation-exported service URL (CLOUDRUN_SERVICE_URL / GKE_SERVICE_URL) when unset, so generated links and assets resolve on the real host.
Hands off to the upstream /usr/local/bin/entrypoint.sh, which generates application/config/config.php from the environment, provisions/updates the schema, and finally execs apache2-foreground.

5. Core application settings

LimeSurvey_Common establishes the baseline LimeSurvey environment so the application comes up correctly on first boot:

Database — DB_TYPE = mysql, DB_PORT = 3306, DB_MYSQL_ENGINE = InnoDB, DBENGINE = InnoDB. DB_HOST, DB_USERNAME, DB_NAME, and DB_PASSWORD are injected by the foundation (renamed onto LimeSurvey's native names via db_*_env_var_name).
URL format — URL_FORMAT = path for clean, path-based survey URLs.
Admin identity — ADMIN_USER = admin, ADMIN_NAME = Administrator, ADMIN_EMAIL = admin@techequity.cloud; ADMIN_PASSWORD from Secret Manager.
Public URL — PUBLIC_URL from the predicted/actual service URL so links and assets resolve on the real host.
Port — the container listens on 8080 (Apache).

Platform-specific adjustment handled here:

GKE overrides DB_HOST = 127.0.0.1 because the Cloud SQL Auth Proxy runs as a sidecar bound to loopback. On Cloud Run the app dials the Cloud SQL private IP over TCP (MySQL over private-IP TCP needs no SSL).

6. Health probe behaviour

LimeSurvey serves an unauthenticated HTTP 200 at the root (/) landing endpoint, so the probes target /:

Startup probe — TCP against the container port, 30-second initial delay, 15-second period, 20 failures allowed — a generous window for the first-boot console installer that provisions the schema.
Liveness probe — HTTP GET /, 300-second initial delay, 60-second period, 3 failures allowed.

7. Object storage and file persistence

A dedicated Cloud Storage bucket (limesurvey-uploads) is declared here and provisioned by the foundation, which also grants the workload service account access:

gcloud storage buckets list --project "$PROJECT"

Note that persistence of LimeSurvey's runtime upload directory (/var/www/html/upload — uploaded asset images, signatures, barcodes) across container restarts is provided by the NFS (Cloud Filestore) mount, which both platform variants enable by default (enable_nfs = true). The limesurvey-uploads GCS bucket is provisioned for additional object storage but is not FUSE-mounted by default.

For the LimeSurvey-specific, user-facing configuration (variables by group, outputs, and how to explore each service from the Console and CLI), see the platform guides: LimeSurvey_GKE and LimeSurvey_CloudRun.

By Dr Shiyghan Emmanuel Navti · Google Cloud certified: ACE · PCA · PCD · PDE · PSE · CDL

1. What this layer provides​

2. Admin credential in Secret Manager​

3. Database engine and bootstrap​

4. Container image and entrypoint​

5. Core application settings​

6. Health probe behaviour​

7. Object storage and file persistence​