cairnobs/docs/phase-0-runbook.md

Phase 0 runbook

Walks one log line from a Linux host, through the Rust agent, Redpanda, ingest, and ClickHouse, to a browser table. This is the actual "done" criterion for Phase 0 — if this doesn't work, Phase 0 isn't done, regardless of what any individual component's tests say.

Update: this sequence has since been run for real, more than once, against a live Docker install — not just written and trusted. Two real bugs turned up doing that (ClickHouse's official image silently disabling network access without a password set; rpk's exact flag syntax) and got fixed; see the git history around the "Fix two bugs found by actually running the Phase 0 pipeline end-to-end" commit if you want the details. The steps below reflect what was actually run, not just planned. The "Troubleshooting" section below is still worth reading first if something doesn't work — it's not an exhaustive list, but it does reflect real failures encountered, not hypothetical ones.

Prerequisites

• Docker with Compose v2 (docker compose, not the legacy docker-compose v1 binary) — the compose file uses service_completed_successfully conditions that v1 doesn't support.
• Rust toolchain (cargo) and protoc — to build the agent.
• openssl — to generate dev mTLS certs.
• A systemd-based Linux host to run the agent on (journald is the default source). If you're not on such a host, see /agent/README.md's file-tail feature as an alternative source.

You do not need the musl cross-compilation target for this runbook — that's for producing the distro-agnostic release binary. A native cargo build --release is enough to run the agent on the same machine you're testing on.

1. Generate dev mTLS certs

./hack/dev-certs/generate.sh

Writes a throwaway CA plus a server cert (for ingest) and a client cert (for the agent) to hack/dev-certs/out/. Dev-only — see the script's header comment for why.

2. Bring up the backend stack

docker compose up -d --build

This builds and starts, in dependency order: redpanda → redpanda-provision (creates the sentry.logs.raw topic, then exits) → clickhouse → clickhouse-migrate (applies /storage/migrations, then exits) → ingest and api → web.

Check everything came up:

docker compose ps

redpanda-provision and clickhouse-migrate should show Exited (0) (one-shot jobs, not long-running). Everything else should show Up / healthy.

If ingest or api crash-looped, they likely started before their depends_on conditions were actually satisfied, or the dev certs from step 1 don't exist yet — check docker compose logs ingest.

3. Sanity-check the backend before involving the agent

curl http://localhost:8080/healthz
# -> 200, empty body

curl -X POST http://localhost:8080/query \
  -H 'Content-Type: application/json' \
  -d '{"sql": "SELECT 1"}'
# -> {"columns":["1"],"rows":[[1]]} (exact column name may vary by ClickHouse version)

This confirms api can reach clickhouse before you go looking for bugs anywhere else. It doesn't touch the logs table, so it works even before any agent has sent data.

4. Install the agent's mTLS material

The agent's default config expects certs at /etc/cairnobs-agent/ (see /agent/config/agent.example.toml), which requires root:

sudo mkdir -p /etc/cairnobs-agent
sudo cp hack/dev-certs/out/ca.pem \
        hack/dev-certs/out/client.pem \
        hack/dev-certs/out/client-key.pem \
        /etc/cairnobs-agent/

5. Build and run the agent

cd agent
cargo build --release

The agent's built-in defaults already match this setup with zero config file: journald source (whole journal), service name default, ingest endpoint https://127.0.0.1:4317 (matches the port ingest publishes in docker-compose.yml), and the cert paths from step 4. This is the "no required flags for the common case" design goal from /agent/README.md — if it doesn't just run, that design assumption is wrong somewhere and worth reporting as a bug, not working around.

Reading the system journal generally needs root (or membership in the systemd-journal group with a distro that grants it read access — varies by distro, root is the reliable path for this runbook):

sudo RUST_LOG=info ./target/release/cairnobs-agent

RUST_LOG=info matters: tracing_subscriber's default filter is otherwise strict enough to suppress even the startup log line, and the agent will look like it's silently doing nothing. Leave it running in this terminal — you should see a connected to ingest service log line. If you see a TLS or connection error instead, stop here and check the Troubleshooting section before continuing.

6. Generate a test log line

In another terminal, after the agent is running and connected (journald tailing starts from "now" — anything logged before the agent started won't be picked up):

logger "hello from sentry phase 0"

logger (part of util-linux, present on virtually every Linux distro) writes this to the system log, which journald captures immediately.

Give it a couple of seconds — the agent batches with a 2-second flush interval by default, so the line won't hit ingest instantly.

7. Confirm it's queryable

Via the web UI:

web is already running from step 2 (docker compose up -d --build starts every service in the file). Open http://localhost:3000, run the default query (SELECT * FROM logs ORDER BY timestamp DESC LIMIT 100), and look for a row with message = "hello from sentry phase 0".

Or via curl, if you want to skip the browser:

curl -X POST http://localhost:8080/query \
  -H 'Content-Type: application/json' \
  -d '{"sql": "SELECT * FROM logs ORDER BY timestamp DESC LIMIT 10"}'

Or via sentryctl, just to confirm api is up (doesn't check the data itself):

cd cli && go run ./cmd/sentryctl ping

If you see the row: that's Phase 0 done, end to end. If you don't, see Troubleshooting below.

Tearing down

docker compose down        # stops and removes containers, keeps volumes
docker compose down -v     # also wipes Redpanda/ClickHouse data — start clean next time

Troubleshooting

Agent logs a TLS/certificate error on startup. Check the server cert's SAN actually covers how the agent is connecting (openssl x509 -in hack/dev-certs/out/server.pem -noout -ext subjectAltName — should list DNS:ingest, DNS:localhost, IP:127.0.0.1). If you changed the agent's ingest.endpoint to something not in that list, regenerate certs with an updated SAN in hack/dev-certs/generate.sh, don't disable TLS verification.

Agent connects but no data ever shows up in ClickHouse. Check each hop in order rather than guessing:

1. docker compose logs ingest — look for "batch produced to redpanda" (gRPC front end got the batch) vs. errors.
2. docker compose logs ingest again — look for "batch flushed to clickhouse" from the consumer half. If you see repeated "clickhouse batch write failed... will redeliver" messages, clickhouse-migrate likely hasn't finished (check docker compose ps) — the consumer will keep retrying and self-heal once the table exists, per its at-least-once design (see /ingest/README.md), so this may just need more time rather than intervention.
3. docker compose exec redpanda rpk topic list — confirm sentry.logs.raw exists (if redpanda-provision failed, it won't).

docker compose up fails on service_completed_successfully. You're likely on Compose v1 (docker-compose, hyphenated) rather than v2 (docker compose, space) — see Prerequisites.

Web UI query returns an error instead of rows. Open the browser's network tab — if the request never leaves the page (CORS error in the console), confirm api's CORS_ALLOWED_ORIGIN (defaults to *, should not be the issue) and that VITE_API_BASE_URL was set correctly at web's build time (it's baked in, not read at container start — see /web/README.md).