## Context
Postfix inside docker-mailserver was spamming fatal errors at roughly
1 per minute — 5,464 of them in a 24h window — all of the same shape:
```
postfix/postscreen[NNN]: fatal: btree:/var/lib/postfix/postscreen_cache:
unable to get exclusive lock: Resource temporarily unavailable
```
Every time one of these fires, the postscreen process dies mid-connection
and the inbound SMTP session is dropped. Legitimate mail (including Brevo
deliveries for our e2e email-roundtrip probe) gets re-queued by the sender
and arrives late — frequently past the probe's 180s IMAP polling window,
producing a 35%/7d probe success rate and the EmailRoundtripStale alert
noise that was originally flagged as "probably nothing."
## Root cause
`master.cf` declares postscreen with `maxproc=1`, but postscreen still
re-spawns per incoming connection (or for short-lived reopens), and each
instance opens the shared btree cache with an exclusive file lock. Under
any concurrency (two TCP SYNs arriving close together, or a retry during
teardown), the second process hits EWOULDBLOCK on fcntl and Postfix
treats that as fatal.
Three options were considered:
| Option | Verdict |
|--------|---------|
| (a) Disable cache (postscreen_cache_map = ) | ✓ chosen |
| (b) Switch btree → lmdb | ✗ lmdb not compiled into docker-mailserver 15.0.0's postfix (`postconf -m` has no lmdb) |
| (c) proxy:btree via proxymap | ✗ unsafe — Postfix docs: "postscreen does its own locking, not safe via proxymap" |
| (d) Memcached sidecar | ✗ new moving part; deferred |
Option (a) is a small trade-off: legitimate clients re-run the
greet-action / bare-newline-action checks on every fresh TCP session
instead of hitting the 7-day whitelist cache. At our volume (~100
deliveries/day, ~72 of which are the probe itself) that's negligible CPU.
DNSBL re-evaluation is also avoided only partially, but this mailserver
already has `postscreen_dnsbl_action = ignore` so the cache's DNSBL role
was doing nothing anyway.
## This change
Appends a stanza to the user-merged postfix main.cf stored in
`variable.postfix_cf` that sets `postscreen_cache_map =` (empty value).
Postfix treats an empty cache_map as "no persistent cache" — per-session
decisions are still enforced, they just aren't cached across sessions.
Before:
```
smtpd ──► postscreen (maxproc=1, btree cache with exclusive lock)
├─ concurrent access → fcntl EWOULDBLOCK → fatal
└─ connection dropped, sender retries, mail arrives late
```
After:
```
smtpd ──► postscreen (no cache, per-session checks only)
└─ no shared file, no lock → no fatal, no dropped session
```
No change to master.cf (postscreen still the front-end), no change to
DNSBL / greet / bare-newline policy.
## What is NOT in this change
- Dovecot userdb dedup (shipped in the previous commit).
- Email-roundtrip probe widening (next commit).
- Rebuilding docker-mailserver image with lmdb support (deferred —
disabling the cache is simpler and sufficient at our volume).
## Test Plan
### Automated
`postconf -m` in the running container to confirm lmdb is genuinely absent
(ruling out option (b) before we commit to (a)):
```
btree cidr environ fail hash inline internal ldap memcache
nis pcre pipemap proxy randmap regexp socketmap static tcp
texthash unionmap unix
```
No lmdb entry — confirmed.
`scripts/tg plan -target=module.mailserver.kubernetes_config_map.mailserver_config`:
```
~ "postfix-main.cf" = <<-EOT
+ postscreen_cache_map =
```
`scripts/tg apply`:
```
Apply complete! Resources: 0 added, 1 changed, 0 destroyed.
```
Reloader triggers pod rollout — baseline error count before apply was 34
`unable to get exclusive lock` lines per `--tail=500` log window.
### Manual Verification
Post-rollout, when the new pod is Ready:
1. `kubectl -n mailserver exec <pod> -c docker-mailserver -- postconf postscreen_cache_map`
Expect: empty (no value)
2. Watch for 15 min: `kubectl -n mailserver logs -l app=mailserver -c docker-mailserver --tail=1000 | grep -c "unable to get exclusive lock"`
Expect: 0 new occurrences (any hits are from before the rollout).
3. Trigger a probe run manually:
`kubectl -n mailserver create job --from=cronjob/email-roundtrip-monitor probe-verify-$(date +%s)`
then `kubectl -n mailserver logs job/probe-verify-...`
Expect: `Round-trip SUCCESS` with duration < 120s.
## Reproduce locally
1. `kubectl -n mailserver exec <pod> -c docker-mailserver -- postconf postscreen_cache_map`
2. Expect: `postscreen_cache_map =` (empty value)
3. `kubectl -n mailserver logs -l app=mailserver -c docker-mailserver --since=15m | grep -c "unable to get exclusive lock"`
4. Expect: 0
Closes: code-1dc
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
|
||
|---|---|---|
| .beads | ||
| .claude | ||
| .git-crypt | ||
| .github | ||
| .planning | ||
| .woodpecker | ||
| ci | ||
| cli | ||
| diagram | ||
| docs | ||
| modules | ||
| playbooks | ||
| scripts | ||
| secrets | ||
| stacks | ||
| state/stacks | ||
| .gitattributes | ||
| .gitignore | ||
| .sops.yaml | ||
| AGENTS.md | ||
| config.tfvars | ||
| CONTRIBUTING.md | ||
| LICENSE.txt | ||
| MEMORY.md | ||
| README.md | ||
| setup-monitoring.sh | ||
| terragrunt.hcl | ||
| tiers.tf | ||
This repo contains my infra-as-code sources.
My infrastructure is built using Terraform, Kubernetes and CI/CD is done using Woodpecker CI.
Read more by visiting my website: https://viktorbarzin.me
Documentation
Full architecture documentation is available in docs/ — covering networking, storage, security, monitoring, secrets, CI/CD, databases, and more.
Adding a New User (Admin)
Adding a new namespace-owner to the cluster requires three steps — no code changes needed.
1. Authentik Group Assignment
In the Authentik admin UI, add the user to:
kubernetes-namespace-ownersgroup (grants OIDC group claim for K8s RBAC)Headscale Usersgroup (if they need VPN access)
2. Vault KV Entry
Add a JSON entry to secret/platform → k8s_users key in Vault:
"username": {
"role": "namespace-owner",
"email": "user@example.com",
"namespaces": ["username"],
"domains": ["myapp"],
"quota": {
"cpu_requests": "2",
"memory_requests": "4Gi",
"memory_limits": "8Gi",
"pods": "20"
}
}
usernamekey must match the user's Forgejo username (for Woodpecker admin access)namespaces— K8s namespaces to create and grant admin access todomains— subdomains underviktorbarzin.mefor Cloudflare DNS recordsquota— resource limits per namespace (defaults shown above)
3. Apply Stacks
vault login -method=oidc
cd stacks/vault && terragrunt apply --non-interactive
# Creates: namespace, Vault policy, identity entity, K8s deployer role
cd ../platform && terragrunt apply --non-interactive
# Creates: RBAC bindings, ResourceQuota, TLS secret, DNS records
cd ../woodpecker && terragrunt apply --non-interactive
# Adds user to Woodpecker admin list
What Gets Auto-Generated
| Resource | Stack |
|---|---|
| Kubernetes namespace | vault |
Vault policy (namespace-owner-{user}) |
vault |
| Vault identity entity + OIDC alias | vault |
| K8s deployer Role + Vault K8s role | vault |
| RBAC RoleBinding (namespace admin) | platform |
| RBAC ClusterRoleBinding (cluster read-only) | platform |
| ResourceQuota | platform |
| TLS secret in namespace | platform |
| Cloudflare DNS records | platform |
| Woodpecker admin access | woodpecker |
New User Onboarding
If you've been added as a namespace-owner, follow these steps to get started.
1. Join the VPN
# Install Tailscale: https://tailscale.com/download
tailscale login --login-server https://headscale.viktorbarzin.me
# Send the registration URL to Viktor, wait for approval
ping 10.0.20.100 # verify connectivity
2. Install Tools
Run the setup script to install kubectl, kubelogin, Vault CLI, Terraform, and Terragrunt:
# macOS
bash <(curl -fsSL https://k8s-portal.viktorbarzin.me/setup/script?os=mac)
# Linux
bash <(curl -fsSL https://k8s-portal.viktorbarzin.me/setup/script?os=linux)
3. Authenticate
# Log into Vault (opens browser for SSO)
vault login -method=oidc
# Test kubectl (opens browser for OIDC login)
kubectl get pods -n YOUR_NAMESPACE
4. Deploy Your First App
# Clone the infra repo
git clone https://github.com/ViktorBarzin/infra.git && cd infra
# Copy the stack template
cp -r stacks/_template stacks/myapp
mv stacks/myapp/main.tf.example stacks/myapp/main.tf
# Edit main.tf — replace all <placeholders>
# Store secrets in Vault
vault kv put secret/YOUR_USERNAME/myapp DB_PASSWORD=secret123
# Submit a PR
git checkout -b feat/myapp
git add stacks/myapp/
git commit -m "add myapp stack"
git push -u origin feat/myapp
After review and merge, an admin runs cd stacks/myapp && terragrunt apply.
5. Set Up CI/CD (Optional)
Create .woodpecker.yml in your app's Forgejo repo:
steps:
- name: build
image: woodpeckerci/plugin-docker-buildx
settings:
repo: YOUR_DOCKERHUB_USER/myapp
tag: ["${CI_PIPELINE_NUMBER}", "latest"]
username:
from_secret: dockerhub-username
password:
from_secret: dockerhub-token
platforms: linux/amd64
- name: deploy
image: hashicorp/vault:1.18.1
commands:
- export VAULT_ADDR=http://vault-active.vault.svc.cluster.local:8200
- export VAULT_TOKEN=$(vault write -field=token auth/kubernetes/login
role=ci jwt=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token))
- KUBE_TOKEN=$(vault write -field=service_account_token
kubernetes/creds/YOUR_NAMESPACE-deployer
kubernetes_namespace=YOUR_NAMESPACE)
- kubectl --server=https://kubernetes.default.svc
--token=$KUBE_TOKEN
--certificate-authority=/var/run/secrets/kubernetes.io/serviceaccount/ca.crt
-n YOUR_NAMESPACE set image deployment/myapp
myapp=YOUR_DOCKERHUB_USER/myapp:${CI_PIPELINE_NUMBER}
Useful Commands
# Check your pods
kubectl get pods -n YOUR_NAMESPACE
# View quota usage
kubectl describe resourcequota -n YOUR_NAMESPACE
# Store/read secrets
vault kv put secret/YOUR_USERNAME/myapp KEY=value
vault kv get secret/YOUR_USERNAME/myapp
# Get a short-lived K8s deploy token
vault write kubernetes/creds/YOUR_NAMESPACE-deployer \
kubernetes_namespace=YOUR_NAMESPACE
Important Rules
- All changes go through Terraform — never
kubectl apply/edit/patchdirectly - Never put secrets in code — use Vault:
vault kv put secret/YOUR_USERNAME/... - Always use a PR — never push directly to master
- Docker images: build for
linux/amd64, use versioned tags (not:latest)
git-crypt setup
To decrypt the secrets, you need to setup git-crypt.
- Install git-crypt.
- Setup gpg keys on the machine
git-crypt unlock
This will unlock the secrets and will lock them on commit