Langfuse on Google Cloud Run

Langfuse is an open-source, MIT-licensed LLM engineering and observability platform — tracing, prompt management, evaluations, and metrics for applications built on large language models. This module deploys Langfuse 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 Langfuse 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

Langfuse runs as a Next.js container on Cloud Run v2. This module deploys the v2 line (Postgres-only); Langfuse v3 additionally requires ClickHouse, Redis, and S3 and is out of scope. The deployment wires together a focused set of Google Cloud services:

Capability	Google Cloud service	Notes
Compute	Cloud Run v2	Next.js service, 2 vCPU / 4 GiB by default, serverless autoscaling
Database	Cloud SQL for PostgreSQL 15	Required — Langfuse v2 does not support MySQL or other engines
Object storage	Cloud Storage	A dedicated bucket provisioned automatically; optional NFS share for exports
Secrets	Secret Manager	Auto-generated NEXTAUTH_SECRET and SALT; database password
Ingress	Cloud Run URL / Cloud Load Balancing	Default run.app URL; optional external HTTPS load balancer + custom domain

Sensible defaults worth knowing up front:

• Langfuse v2 (Postgres-only) is pinned. The image is built FROM langfuse/langfuse:2 via the LANGFUSE_VERSION build ARG. Even application_version = "latest" resolves to 2. Deploying v3 would require ClickHouse + Redis + S3 that this module does not provision.
• PostgreSQL 15 is mandatory. The database engine is fixed by the shared application layer; selecting any other engine breaks startup.
• NEXTAUTH_SECRET and SALT are generated automatically and stored in Secret Manager. Langfuse's zod env validation refuses to boot without both — NEXTAUTH_SECRET signs the session JWTs and SALT hashes API keys. Rotating them invalidates sessions / stored API keys.
• Prisma migrations run on every start. The cloud entrypoint composes DATABASE_URL from the injected DB_* vars, then hands off to Langfuse's own startup, which runs prisma migrate deploy. The db-init job only creates the role and database.
• The first user to sign up becomes the owner. AUTH_DISABLE_SIGNUP = "false" is injected; there is no pre-seeded admin credential. Disable sign-up after onboarding.
• min_instance_count = 1 with cpu_always_allocated = true. One instance stays warm so Langfuse's background processing (batched ingestion, scheduled work) keeps running between requests; CPU is not throttled to zero while idle.
• Public ingress is the default. ingress_settings = "all" so the UI and the ingestion/API endpoints are reachable by your LLM app's SDK clients. Enabling IAP will block unauthenticated SDK traffic.
• No Redis. Langfuse v2 uses a PostgreSQL-backed queue and cache; enable_redis stays false.

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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 Langfuse service

Langfuse 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 PostgreSQL 15

Langfuse stores all application data (traces, observations, scores, prompts, users, projects, API keys) in a managed Cloud SQL for PostgreSQL 15 instance. The service connects privately through the Cloud SQL Auth Proxy over a Unix socket; no public IP is exposed. On first deploy an initialization Job creates the application role and database; Langfuse then applies its schema via prisma migrate deploy on start.

• 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=langfuse --database=langfuse --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 dedicated Cloud Storage bucket is provisioned automatically. Langfuse v2 keeps all trace and observability data in PostgreSQL; the bucket (and the optionally-mounted NFS share) are available for exports and media rather than primary state.

• Console: Cloud Storage → Buckets.
• CLI:

  gcloud storage buckets list --project "$PROJECT"
  gcloud storage ls gs://<bucket>/        # bucket name is in the Outputs

See App_CloudRun for GCS Fuse and CMEK options.

D. Secret Manager

Two cryptographic secrets are generated automatically and stored in Secret Manager: NEXTAUTH_SECRET (signs the auth session JWTs) and SALT (hashes API keys). Both are injected as secret env vars and are required at boot. The database password is managed separately by the foundation.

• Console: Security → Secret Manager.
• CLI:

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

See App_CloudRun for injection and rotation details.

E. Networking & ingress

The service is reachable at its run.app URL by default, which allows the public access your LLM app's SDK clients need to POST traces to the ingestion API. An external HTTPS load balancer with a custom domain, Cloud CDN, and Cloud Armor can be layered on; ingress settings and VPC egress control connectivity.

• 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, with optional uptime checks and alert policies.

• 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. Langfuse Application Behaviour

• First-deploy database setup. An initialization Job runs db-init.sh using postgres:15-alpine. It connects through the Cloud SQL Auth Proxy and idempotently creates the application role and database and grants privileges. It does not create tables — the job is safe to re-run.
• Prisma migrations on start. The cloud entrypoint composes DATABASE_URL and then delegates to Langfuse's own startup, which runs prisma migrate deploy before launching the server. Upgrading the application version therefore applies schema changes without a separate migration step — allow extra time on the first boot after an upgrade.
• NEXTAUTH_SECRET and SALT are immutable after first boot. They are generated once and written to Secret Manager. Changing NEXTAUTH_SECRET invalidates all active sessions; changing SALT permanently invalidates all existing API keys (SDK clients then get 401). Only rotate during a planned maintenance window.
• First user is the owner. On first visit, the Langfuse sign-up page creates the initial account, which becomes the instance owner (no seeded credential). After onboarding, set AUTH_DISABLE_SIGNUP = "true" in environment_variables and apply via Update to prevent further self-service registration.
• Ingestion endpoints. The default ingress_settings = "all" lets your LLM app's SDK clients POST traces to the public ingestion API. Enabling IAP blocks these unauthenticated calls — keep IAP off if SDKs must reach the service, or authorize the callers explicitly.
• Health path. Startup and liveness probes default to / in variables.tf — not the app's dedicated /api/public/health endpoint, which is not wired in as the default. Allow a generous window on first boot (the startup probe uses a wide failure threshold and a 60s initial delay) so Prisma migrations finish; consider overriding path to /api/public/health for a more precise readiness signal.
• 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 Langfuse 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.
region	us-central1	Region for the service and regional resources.

Group 2 — Deployment Environment

Variable	Default	Description
tenant_deployment_id	demo	Short suffix that makes resource names unique per environment.
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	langfuse	Base name for resources. Do not change after first deploy.
display_name	Langfuse Helpdesk	Human-readable name shown in the Console. Leftover clone-rot text in variables.tf (Langfuse is an LLM observability platform, not a helpdesk) — override with e.g. "Langfuse" for an accurate display name.
description	Langfuse - Open-source helpdesk and customer support platform	Service description. Same clone-rot leftover as display_name — override for an accurate description.
application_version	2	Langfuse image tag. Pinned to the v2 (Postgres-only) line.

Group 4 — Runtime & Scaling

Variable	Default	Description
deploy_application	true	Set false to provision infrastructure only.
container_image_source	custom	Langfuse builds a thin wrapper image from langfuse/langfuse:2.
cpu_limit	2000m	CPU per instance; 2 vCPU recommended.
memory_limit	4Gi	Memory per instance; minimum 2 GiB.
cpu_always_allocated	true	Keep CPU allocated so background processing runs between requests.
min_instance_count	1	Keeps one instance warm for background processing.
max_instance_count	5	Autoscaling upper bound.
container_port	3000	Langfuse (Next.js) listens on port 3000.
execution_environment	gen2	Gen2 required for NFS and GCS Fuse mounts.
timeout_seconds	300	Maximum request duration (0–3600 seconds).
enable_cloudsql_volume	true	Cloud SQL Auth Proxy for socket connections.
enable_image_mirroring	true	Mirror the Langfuse image into Artifact Registry.
traffic_split	[]	Split traffic across revisions for staged rollouts.
max_revisions_to_retain	7	How many old revisions to keep.

Group 5 — Access & Ingress Control

Variable	Default	Description
ingress_settings	all	all is required for public SDK ingestion endpoints.
vpc_egress_setting	PRIVATE_RANGES_ONLY	Route only RFC 1918 traffic via VPC.
enable_iap	false	Require Google sign-in. Blocks unauthenticated SDK ingestion.
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. Do not set NEXTAUTH_SECRET, SALT, or DATABASE_URL here — they are managed by the module. Set AUTH_DISABLE_SIGNUP = "true" here after onboarding.
secret_environment_variables	{}	Map of env var → Secret Manager secret name.
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/compliance.
enable_backup_import / backup_source / backup_file / 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 — Load Balancer, CDN & Image Retention

Variable	Default	Description
enable_cloud_armor	false	Provision Global HTTPS LB + Cloud Armor WAF.
admin_ip_ranges	[]	CIDR ranges exempted from WAF rules.
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	(set)	Artifact Registry cleanup policy.

Group 10 — Storage & Filesystem

Variable	Default	Description
create_cloud_storage	true	Create GCS buckets defined in storage_buckets.
storage_buckets	[{ name_suffix = "data" }]	Buckets to provision.
enable_nfs	true	Mount an NFS share at /opt/langfuse/storage for optional exports/media.
nfs_mount_path	/opt/langfuse/storage	Mount path inside the container.
gcs_volumes	[]	GCS Fuse volume mounts (requires gen2).
manage_storage_kms_iam / enable_artifact_registry_cmek	false	CMEK options.

Group 11 — Custom SQL Scripts

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. See App_CloudRun.

Group 12 — Database Backend

Variable	Default	Description
database_type	POSTGRES_15	Fixed — Langfuse requires PostgreSQL.
db_name	langfuse	PostgreSQL database name. Immutable after first deploy.
db_user	langfuse	Application database user. Password auto-generated in Secret Manager.
database_password_length	32	Generated password length (16–64).
enable_auto_password_rotation / rotation_propagation_delay_sec	off	DB password rotation.

Group 13 — Jobs & Scheduled Tasks

Variable	Default	Description
initialization_jobs	[]	Leave empty to use the built-in db-init job.
cron_jobs	[]	Scheduled Cloud Scheduler + Cloud Run Jobs.

Group 14 — Observability & Health

Variable	Default	Description
startup_probe	HTTP /, 60s delay, wide failure threshold	Startup probe. Allow generous time for first-boot Prisma migrations.
liveness_probe	HTTP /, 60s delay	Liveness probe.
startup_probe_config / health_check_config	HTTP /	Alternative structured probes.
uptime_check_config	{ enabled=false }	Cloud Monitoring uptime check.
alert_policies	[]	Metric alert policies.

Group 21 — Redis Cache & Queue

Variable	Default	Description
enable_redis	false	Langfuse v2 uses a PostgreSQL-backed queue and cache — leave false.
redis_host / redis_port / redis_auth	"" / 6379 / ""	Only used if externalizing to Redis.

Group 22 — VPC Service Controls & Audit Logging

Variable	Default	Description
enable_vpc_sc	false	Enforce a VPC-SC perimeter (requires organization_id).
vpc_cidr_ranges / vpc_sc_dry_run	(set)	Access level CIDRs / dry-run mode.
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	Stage-specific service URLs (Cloud Deploy).
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.
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 — a read replica without its primary, IAP with no authorized identities, a gen1 runtime with NFS/GCS mounts, a database_type that does not match an enabled extension, an out-of-range redis_port/backup_retention_days. 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
NEXTAUTH_SECRET (auto-generated)	Never rotate after first boot	Critical	Rotating it invalidates all active sessions, forcing immediate re-login for everyone.
SALT (auto-generated)	Never rotate after first boot	Critical	Rotating it permanently invalidates all existing API keys — every SDK client using them gets 401 until re-keyed.
db_name / db_user	Set once	Critical	Immutable after first deploy; renaming recreates the DB/user and destroys all trace data.
application_version	2 (v2 line)	Critical	Setting a v3 tag points the build at an image needing ClickHouse + Redis + S3 that this module does not provision — the service fails to start.
enable_backup_import	false unless restoring	Critical	Enabling without a valid backup fails the import job.
memory_limit	4Gi (≥ 2Gi)	High	Below 2 GiB, Langfuse's Next.js server OOM-kills during first-boot migrations or under ingestion load.
ingress_settings	all	High	Setting to internal blocks all external SDK ingestion calls.
enable_iap	only when SDK ingestion not needed	High	IAP blocks all unauthenticated requests, including SDK trace ingestion.
AUTH_DISABLE_SIGNUP (auto-injected "false")	Disable after first owner	High	Leaving sign-up open lets anyone with the URL create an account.
min_instance_count	1	Medium	Scale-to-zero (0) stops background processing and adds cold-start latency to the first request after idle.
cpu_always_allocated	true	Medium	Request-based billing throttles background processing to ~0 CPU between requests.
backup_retention_days	7 (raise for prod)	Medium	Too short for compliance retention.
enable_cloud_armor	enable for production	Medium	The UI and ingestion endpoints are publicly reachable without WAF protection.

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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. Langfuse-specific application configuration shared with the GKE variant is described in Langfuse_Common.