buzz/docs/push-gateway-deployment.md

Buzz Push Gateway deployment

buzz-push-gateway is the standalone public APNs last hop intended for push.buzz.xyz. Build it with Dockerfile.push-gateway; do not run it in the relay image or give relays APNs credentials.

Network and health

• Public listener: BUZZ_PUSH_BIND_ADDR (default 0.0.0.0:8080). Route https://push.buzz.xyz to this port.
• Private health listener: BUZZ_PUSH_HEALTH_ADDR (default 0.0.0.0:8081). Probe /_liveness and /_readiness; do not expose this port publicly. The chart has no pod-ingress allowance for 8081; Kubernetes node/kubelet-origin probe traffic is exempt from NetworkPolicy. Add a narrowly selected monitoring source only if the target CNI requires pod-origin health scraping.
• Readiness fails when PostgreSQL authority is unavailable. Graceful shutdown stops accepting new requests before draining in-flight APNs calls.

Required configuration

Variable	Purpose
DATABASE_URL	PostgreSQL authority/admission store. Runtime credentials need DML on the six gateway tables, not DDL.
BUZZ_PUSH_PUBLIC_DELIVERY_URL	Exact externally signed URL, normally https://push.buzz.xyz/v1/deliveries/apns.
BUZZ_PUSH_MAX_GRANT_LIFETIME_SECONDS	Maximum delegation capability lifetime (1..=31536000).
BUZZ_PUSH_MAX_INSTALLATION_LIFETIME_SECONDS	Maximum encrypted-token installation lifetime (default 90 days, max one year). Clients must renew before expiry.
BUZZ_PUSH_ENABLED_PROFILES	Comma-separated buzz-ios-production and/or buzz-ios-sandbox.
BUZZ_PUSH_APP_ATTEST_APP_ID	Exact Apple App Attest application identifier (TEAMID.bundle-id).
BUZZ_PUSH_APP_ATTEST_ROOT_CERT_PATH	Read-only mounted Apple App Attest root certificate PEM.
BUZZ_PUSH_APNS_KEY_PATH	Read-only mounted Apple APNs .p8 provider key.
BUZZ_PUSH_APNS_KEY_ID	APNs provider key id.
BUZZ_PUSH_APNS_TEAM_ID	Apple developer team id.
BUZZ_PUSH_APNS_TOPIC	Buzz iOS bundle id.
BUZZ_PUSH_GRANT_KEYS	Capability AEAD keyring, id:base64-32-bytes[,predecessor...]; current key first.
BUZZ_PUSH_TOKEN_KEYS	Independent token-custody AEAD keyring in the same format. Never reuse grant keys.

Optional endpoint quota policy variables are BUZZ_PUSH_ENDPOINT_QUOTA_WINDOW_SECONDS (default 10, max 86400) and BUZZ_PUSH_ENDPOINT_QUOTA_MAX_DELIVERIES (default 10, max 10000). These are Buzz policy hypotheses, not Apple-published limits; tune under load while retaining a hard ceiling.

Secret and key rotation rules

Mount the App Attest root read-only and startup will reject any byte mismatch. The sole accepted artifact is Apple’s Apple App Attestation Root CA from https://www.apple.com/certificateauthority/Apple_App_Attestation_Root_CA.pem: certificate SHA-256 fingerprint 1C:B9:82:3B:A2:8B:A6:AD:2D:33:A0:06:94:1D:E2:AE:4F:51:3E:F1:D4:E8:31:B9:F7:E0:FA:7B:62:42:C9:32; exact PEM-file SHA-256 c778d09ac341f7fd9f8f3b19e2b815af6aed4ad4490e1e92c05cb355212a5013. Treat an Apple root rotation as a reviewed code/config rollout, not an unpinned mount replacement. Mount the APNs key and both AEAD keyrings from a secret manager; never place values in an image, manifest, log, or metrics label. Keep the current AEAD key first and retain decrypt-only predecessors until every capability/token encrypted under them has expired or been re-encrypted. Grant and token key ids and bytes must be distinct. Rotation is an operator rollout: add the new current key while retaining predecessors, deploy, wait through the retention window, then remove the old key.

The gateway stores APNs tokens encrypted in PostgreSQL. Database backups therefore contain ciphertext plus authority metadata and must receive the same access controls and retention treatment as the service secrets.

PostgreSQL and replicas

All replicas must share one PostgreSQL database. Delivery authority, replay admission, and endpoint quota reservation are transactional there, so replica count does not multiply the abuse ceiling. The gateway owns a scoped migration history under crates/buzz-push-gateway/migrations; it creates only the six push_gateway_* authority tables plus SQLx's migration-history table and never runs relay migrations.

The Helm chart runs a single pre-install/pre-upgrade migration Job using migration.existingSecret; that secret contains a DDL-capable DATABASE_URL. The URL MUST name a dedicated gateway database, not the relay database: SQLx stores its _sqlx_migrations history in public, so sharing a database would collide with another application's migration history. migration.runtimeDatabaseRole names an existing LOGIN role (the default is buzz_push_gateway_runtime) used by runtime DATABASE_URL. After scoped migrations, the Job revokes database CREATE from that role and schema CREATE from both PUBLIC and the role, then grants only database CONNECT, schema USAGE, and SELECT, INSERT, UPDATE, DELETE on the six gateway tables. The migration role must own the database/schema objects or otherwise be allowed to issue those grants; it is never provided to runtime replicas. Readiness rejects an empty/partial schema, missing DML, or a runtime role that retains database/schema CREATE. Helm waits for the migration hook before updating replicas, so rolling deployments never race unconditional startup migration. Readiness must be removed from load-balancer service endpoints before terminating a pod.

The service reaps expired challenges and replay rows, idle quota rows, expired/revoked delegations, and retention-eligible installations (including their encrypted token ciphertext) at startup and every five minutes. Monitor reaper failures and table growth; retention does not depend on process restarts.

Metrics and alerting

The gateway serves Prometheus metrics at GET /metrics on the private health listener (BUZZ_PUSH_HEALTH_ADDR, default 0.0.0.0:8081) — the same port as the probes, never on the public 8080. All series are sanitized and bounded-cardinality: label values are drawn only from closed sets (the six APNs outcome classes, the fixed admission results, the static error codes already returned to callers, and the readiness causes). No endpoint, device token, relay pubkey, request id, or any request-scoped identifier is ever used as a label.

Metric	Type	Labels	Meaning
push_gateway_apns_deliveries_total	counter	outcome = accepted | invalid_endpoint | retry | refresh_credential | configuration_fault | permanent_request_fault	Terminal APNs send outcomes.
push_gateway_apns_delivery_seconds	histogram	—	APNs send round-trip latency (seconds).
push_gateway_apns_credential_refreshes_total	counter	—	Provider JWT refreshed after APNs reported expiry.
push_gateway_admissions_total	counter	result = admitted | rejected | unavailable	Outcome at the authorize_delivery replay/quota fence.
push_gateway_delivery_errors_total	counter	class (static)	Selected delivery-handler exit classes only (see note).
push_gateway_reaper_failures_total	counter	—	Retention reaper sweep failures.
push_gateway_readiness_failures_total	counter	cause = not_accepting | authority	Readiness probe failures by cause.

push_gateway_delivery_errors_total is intentionally narrow: it counts only selected exit classes of the /v1/deliveries/apns handler — class ∈ invalid_grant (grant rejected at the admission seam, before a permit is issued), temporarily_unavailable (authority unavailable at the admission seam), profile_mismatch, token_custody (endpoint-token open failure), finish_failed (detached disposition/join failure returned as 503). Request/auth/attestation/grant validation on the enrollment, delegation, rotation, and revocation handlers is not counted by this metric; it is a delivery-hot-path signal, not a total error rate across the API.

Scraping is opt-in and off by default, so the default chart render is unchanged and 8081 keeps no pod ingress. To enable it, set podMonitor.enabled=true (renders a prometheus-operator PodMonitor scraping the health port /metrics) and networkPolicy.monitoring.enabled=true with networkPolicy.monitoring.namespaceSelector / podSelector naming your scraper — this adds a single 8081 ingress rule scoped to that source, never a blanket allowance. Node/kubelet-origin probe traffic remains exempt from NetworkPolicy regardless.

Alerting rules ship as an opt-in prometheus-operator PrometheusRule (prometheusRule.enabled=true). Thresholds and operator actions:

Alert	Fires when	Severity	Action
PushGatewayConfigurationFault	any configuration_fault outcomes for 10m	critical	APNs provider token/topic is unhealthy. Check the .p8 key, BUZZ_PUSH_APNS_KEY_ID, ..._TEAM_ID, and ..._TOPIC. No endpoints are being invalidated, but nothing is delivering.
PushGatewayAdmissionUnavailable	any admission unavailable for 5m	critical	PostgreSQL authority store is unreachable. Check DB connectivity and the pod's postgresEgressCidrs NetworkPolicy.
PushGatewayReadinessAuthorityFailing	readiness authority failures for 5m	warning	Replicas are being pulled from the Service on DB check failure. Fix DB health before capacity drops below the PodDisruptionBudget.
PushGatewayReaperFailing	reaper failed ≥2 times within 30m (runs every 5m)	warning	Expired reservations aren't being swept, growing the bounded-until-expiry window. Check DB write availability.
PushGatewayHighApnsRetryRate	retryable fraction > prometheusRule.apnsRetryRatioThreshold (default 0.25) over a 10m window, above apnsRetryMinSamples (default 20) attempts, held true for 15m	warning	APNs is throttling or degraded (429/500/503). Deliveries are delayed, not lost.

Relay configuration

Relays default BUZZ_PUSH_GATEWAY_DELIVERY_URL to the exact public delivery URL https://push.buzz.xyz/v1/deliveries/apns. Operators can override it with another exact HTTPS /v1/deliveries/apns URL, or explicitly disable NIP-PL push by setting the variable to an empty string. When enabled, the relay advertises its host-scoped NIP-PL descriptor in NIP-11 and starts the matcher and delivery worker. Relays retain lease matching, authorization, coalescing, durable jobs/retries, and generation checks; they receive only opaque capabilities and never APNs tokens or provider credentials.

Relay integration status

The operational relay integration is complete: per-origin event matching with read-authorization checks, durable enqueue, send-time revalidation, and NIP-98 delivery run whenever the gateway URL is enabled. End-to-end use still requires the client App Attest enrollment/delegation flow to place a gateway-issued opaque capability—not a raw APNs token—into the encrypted relay lease.

Helm production inputs

The chart defaults to the main image tag because .github/workflows/docker.yml publishes it from the push-gateway lane. For a production rollout, open that workflow run's Publish public push gateway image job summary and copy its sha256:... digest. Verify the published subject and provenance before injecting it:

gh attestation verify \
  oci://ghcr.io/block/buzz-push-gateway@sha256:<64-lowercase-hex> \
  --owner block

Only after that command succeeds, set the exact digest as image.digest; the chart then renders ghcr.io/block/buzz-push-gateway@sha256:... and ignores the mutable tag. values-production.yaml is an intentionally invalid production-input contract: deployment CI must inject this verified image.digest, the provisioned Apple application identifier, an environment-owned Gateway parent reference, and the actual PostgreSQL network. Schema validation rejects the artifact when any remains empty; the render guard proves both rejection and a fully injected render.

Network policy keeps APNs HTTPS and PostgreSQL egress in separate CIDR lists. APNs currently requires broad TCP/443 reachability; networkPolicy.postgresEgressCidrs must be narrowed to the production database network, and the DNS namespace/pod selectors must match the cluster DNS deployment. The sample private CIDR is not a claim about the production topology.

Kubernetes does not restart pods when referenced Secret bytes change. AEAD or APNs credential rotation therefore requires an explicit rolling restart after the secret manager update (for example, kubectl rollout restart deployment/<release>-buzz-push-gateway) and readiness verification before removing predecessor keys. Service-account token automount is disabled.

Gateway chart release

The gateway chart has a collision-free release lane separate from the main buzz chart. To publish version X.Y.Z, update both version and appVersion in deploy/charts/buzz-push-gateway/Chart.yaml, validate the chart, and open a same-repository PR whose branch is exactly push-chart-release/X.Y.Z:

deploy/charts/buzz-push-gateway/tests/render.sh
git switch -c push-chart-release/X.Y.Z
git add deploy/charts/buzz-push-gateway/Chart.yaml
git commit -m "release: push gateway chart X.Y.Z"
git push -u origin push-chart-release/X.Y.Z

When that PR merges, .github/workflows/auto-tag-on-release-pr-merge.yml creates push-chart-vX.Y.Z and dispatches .github/workflows/push-gateway-helm-chart.yml with that immutable tag and bare version. The publisher verifies the checked-out commit is the tag target and the chart version equals X.Y.Z before pushing oci://ghcr.io/block/buzz/charts/buzz-push-gateway. A manually pushed push-chart-vX.Y.Z tag is the documented rescue path and runs the same checks.