cairnobs/docs/architecture.md

Sentry Architecture

Status: Updated through Phase 4. The component map/diagram below is still the Phase 0 request path (agent → ingest → ClickHouse → api → web) — it was never redrawn for the full-text search, dashboards/ alerting, or enterprise/ additions; see each phase's runbook (/docs/phase-N-runbook.md) for what was actually verified when it shipped. The component responsibilities table and the sections below the diagram are kept current. Phase 0's original framing ("draft, correct as needed") still applies to anything not yet built.

Mission

Open-core, Kubernetes-native centralized logging platform. Compete with Splunk on features; win on cost-per-GB, a modern language stack, and multi-tenant RBAC that's actually honest about its guarantees.

Component map

┌──────────┐   gRPC/mTLS   ┌──────────┐   produce   ┌───────────┐  consume  ┌────────────┐
│  agent   │ ────────────▶ │  ingest  │ ──────────▶ │ Redpanda  │ ────────▶ │  ingest     │
│ (Rust)   │                │ (Go)     │             │ (Kafka API)│           │  consumer   │
└──────────┘                └──────────┘             └───────────┘           │  (Go)       │
                                                                              └──────┬─────┘
                                                                                     │ batch INSERT
                                                                                     ▼
                                                                              ┌────────────┐
                                                                              │ ClickHouse │
                                                                              └─────┬──────┘
                                                                                    │ SQL
                                                                        ┌───────────▼───────────┐
                                                                        │ api (Go: gRPC+REST)    │
                                                                        └───────────┬───────────┘
                                                                                    │ REST
                                                                        ┌───────────▼───────────┐
                                                                        │ web (SvelteKit)        │
                                                                        └────────────────────────┘

Decision (confirmed 2026-08-12): Redpanda stays in the Phase 0 path. The ingest service's gRPC front end produces to Redpanda rather than writing ClickHouse directly; a separate consumer path reads from Redpanda and batches inserts into ClickHouse. This exercises the real transport layer from day one instead of deferring it, and keeps Kafka credentials off the edge agent.

Storage / query split

• ClickHouse is the analytical store of record for structured log data: timestamp, host, service, severity, message, plus a Map(String,String) for arbitrary structured fields. Partitioned by day, ordered by (service, timestamp).
• Tantivy (Phase 1) will provide full-text indexing over the message field and unstructured payloads, queried out-of-band from ClickHouse and joined by a log identifier. Not built in Phase 0.
• Schema-on-write using OTel semantic conventions as the default log schema; schema-on-read fallback for unstructured/raw text that doesn't fit the structured columns (captured via the Map column and/or a raw passthrough field).
• Postgres (Phase 3) holds control-plane config only — dashboards, panels, notification targets, alert rules/state, delivery log, and (Phase 4) tenants/users/tenant_memberships/audit_log. Never log data; ClickHouse/Tantivy stay the only place a log record itself lives. See /docs/phase-3-dashboard-design.md for why ClickHouse's MergeTree family isn't a fit for this (no real row-level locking/transactional read-modify-write).

This split is not to be changed without discussion — see CLAUDE.md.

Component responsibilities

Component	Responsibility
agent (Rust, musl)	Tail a log file or read journald; parse RFC 5424 syslog with raw passthrough fallback; batch; ship via gRPC/mTLS to ingest. Windows (ETW/Event Log) code exists but is unverified on real Windows hardware — see /agent/README.md.
proto	Shared .proto contracts for agent↔ingest and api↔search gRPC, versioned independently of either side.
transport	Redpanda docker-compose + topic provisioning scripts. No application code.
ingest (Go)	gRPC server accepting agent connections; produces normalized OTel-log-like records to Redpanda; separate consumer reads from Redpanda and batch-writes to ClickHouse. No tenant concept — every record lands in the one shared logs table regardless of source (see "Tenant isolation" below).
storage	ClickHouse schema migrations + docker-compose for local/homelab.
search (Rust, Phase 1)	Consumes the same Redpanda topic ingest does (own offset tracking), builds a Tantivy full-text index over message, serves matches over gRPC. Writes always go to one shared (default) index (ingest isn't tenant-aware); reads can be scoped per-tenant via SearchRequest.tenant_id and src/registry.rs's IndexRegistry (Phase 4) — see "Tenant isolation" below.
api (Go)	gRPC + REST gateway. POST /query compiles pipe-syntax or raw SQL to one IR, executed across ClickHouse/Tantivy (/docs/query-language-design.md). internal/dashboards is CRUD only — panel query execution happens client-side, reusing /query. internal/authz (Phase 4) enforces RBAC via a network call to enterprise-auth, never an import.
alerting (Go, Phase 3)	Evaluates alert rules on an interval, calls api's POST /query (via a RoleService credential once Phase 4 auth is configured — see /docs/phase-4-isolation-design.md's alerting↔api gap), delivers firing/resolved notifications (webhook/Slack/PagerDuty).
enterprise (Go, commercial license, Phase 4)	OIDC login (internal/loginhandler's /auth/oidc/login+/auth/oidc/callback, real IdP round trip, verified with a fake IdP but not a real external one), RBAC storage (internal/rbacstore), session/service-token issuance (internal/session), the append-only audit log (internal/audit), enterprise-auth's HTTP surface (/internal/authorize, /auth/features), per-tenant ClickHouse provisioning (internal/tenantprovision) and query routing (internal/chrunner), and cmd/enterprise-api — a second binary combining core's api/queryapi/api/dashboards handlers with these tenant-aware implementations. Never imported by core — see "Licensing boundary" below. Also internal/searchclient (per-tenant Tantivy routing, wired the same way into search). Does not yet include SAML's login ACS handler (protocol mechanics only) — see /docs/security/threat-model.md.
web (SvelteKit, static build)	Query bar, dashboards, alerts, and (Phase 4) a settings page that renders SSO status via a runtime capability check (GET /auth/features) rather than bundling enterprise-licensed components.
cli (sentryctl)	ping, query, dashboards (list/get/apply), alerts (list/get/apply). $SENTRYCTL_TOKEN, if set, is forwarded as a Bearer credential (Phase 4).
deploy	A Helm chart covering every docker-compose.yml service, plus (Phase 4) a small Go Operator managing one CRD (Tenant) that provisions a per-tenant ClickHouse credential Secret. Never applied to a live cluster in the environment this was built in — see /deploy/README.md's verification section before trusting it.

Tenant isolation model (Phase 4)

Full design rationale: /docs/phase-4-isolation-design.md. Full honest accounting of what's actually enforced vs. designed-only: /docs/security/threat-model.md — read that before assuming any claim below holds for log data specifically.

As designed: one dedicated ClickHouse database + narrowly-granted user per tenant (never the shared default/admin credential), one dedicated Tantivy index directory per tenant, system.* access revoked per tenant, connections resolved from an immutable per-tenant map (never a shared pool with session-level USE). Isolation lives at the connection layer — every query, compiled or raw SQL, is forced through a tenant-scoped connection the database's own access control enforces — not at the query-compiler layer, since Phase 2's raw-SQL escape hatch is opaque to any compiler-injected filter.

As built, currently:

• Role-based access control (api/authz) is live on /query and /dashboards, resolved via enterprise-auth over HTTP.
• Control-plane tenant scoping is live for dashboards (api/dashboards's store filters every query by the authenticated identity's tenant, never a client-supplied field).
• The alerting↔api service-identity gap (task 2's finding) is closed: a RoleService credential, distinct from every human role.
• ClickHouse connection-layer isolation is built, but lives in a second binary: enterprise/internal/tenantprovision (real CREATE DATABASE/CREATE USER/GRANT against ClickHouse) and enterprise/internal/chrunner (a per-tenant connection registry implementing api/querylang/executor.SQLRunner, resolving the right tenant's connection from the authenticated identity in request context) are wired into enterprise/cmd/enterprise-api — a binary that imports both api's handler packages and enterprise's tenant-aware implementations (the allowed enterprise → api import direction; core still never imports enterprise/). Real integration tests assert a tenant cannot read another tenant's database by fully-qualified name, and that system.query_log/system.tables/ SHOW DATABASES don't leak across tenants either — written but not yet run against a live ClickHouse in this environment, see /docs/security/threat-model.md and /docs/phase-4-runbook.md's verification-status sections. Plain api/cmd/api still exists, unchanged, with its single shared connection — nothing forces a deployment to run enterprise-api instead, and nothing flags it if it doesn't.
• Tantivy index-layer isolation is built, and verified. search/src/registry.rs's IndexRegistry resolves SearchRequest.tenant_id (added to proto/sentry/search/v1/ search.proto) to its own on-disk index, opened on demand; enterprise/internal/searchclient sets that field from the authenticated request identity, the same "read from ctx, fail closed" shape chrunner uses. Unlike the ClickHouse pieces, this one actually ran in the environment it was built in — Tantivy is an embedded library, so the cross-tenant isolation probe needed no live database or Docker to execute for real, and it passed.
• Neither storage engine's isolation extends to ingest: every record ingest produces lands in the one shared ClickHouse database and the one shared (default) Tantivy index regardless of tenant. A newly-provisioned tenant's database/index are real and isolated at query time — and permanently empty until something upstream of chrunner/searchclient becomes tenant-aware on the write side, which is undesigned, not merely unbuilt.
• deploy/operator's Tenant CRD still manages only the K8s-side artifact (a credential Secret); it doesn't call enterprise-api -provision-tenant or otherwise trigger ClickHouse-side provisioning. The two mechanisms are independent today, not reconciled into one state machine.

The deployment-topology gap is closed for the Helm chart: deploy/ helm/sentry/templates/api.yaml/enterprise-api.yaml are mutually exclusive on enterprise.enabled, rendering to the same Service name and port either way, so a Helm-deployed cluster can't accidentally run the wrong binary — the same flag that turns on RBAC/audit/SSO now also chooses the query binary. docker-compose.yml still runs plain api unconditionally, so this enforcement doesn't yet extend to local/dev. With both storage engines' connection/index-layer mechanisms built and deployment topology enforced at the Helm layer, the largest remaining gaps are ingest's lack of tenant-awareness (undesigned) and unifying the Tenant CRD with -provision-tenant into one provisioning flow.

Licensing boundary

AGPLv3 for core + agents. Enterprise features (SSO, RBAC storage, audit logging) live under enterprise/ (commercial license stub, added Phase 4). AGPL code must never import from enterprise/ — enforced in CI by hack/check-tenant-boundary.sh, which greps every build for the import edge. Where core needs a decision only enterprise/ can make (is this request authorized, what SSO is configured), it calls enterprise-auth over plain HTTP instead (api/authz.HTTPAuthorizer, web's GET /auth/features) — the same "network boundary, not import boundary" shape /alerting↔api already used before enterprise/ existed.

Non-negotiables carried from CLAUDE.md

• Rust agent: statically linked musl, x86_64-unknown-linux-musl and aarch64-unknown-linux-musl, no glibc runtime deps.
• Windows support via native ETW/Event Log API, not WSL — designed (Phase 1) but still unverified on real Windows hardware.
• Every UI action maps to a documented REST/gRPC call — no UI-only logic.
• Pinned stack (see CLAUDE.md table) — no substitutions without discussion.

Explicitly out of scope (current, Phase 4)

Per /CLAUDE.md's Phase 4 non-goals and /docs/security/threat-model.md: deny-override permission grants, a data retention/deletion policy for deprovisioned tenants, general multi-cluster orchestration in /deploy, and any defense against a privileged ClickHouse/Postgres administrator — every isolation and audit-integrity guarantee here is a structural defense against application-layer bugs, not an operational control.

Open questions for you to resolve

• Retention/TTL policy for the ClickHouse logs table — not specified yet, deferred until storage sizing is a real concern.
• Exact OTel log schema field mapping (which OTel resource/log attributes map to which ClickHouse columns) — Phase 0 uses a minimal subset (timestamp, host, service, severity, message, attributes map); full mapping deferred.
• mTLS certificate provisioning/rotation story for agents — Phase 0 will use a static dev CA and manually issued certs; production PKI design is out of scope here.