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performance.md

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Public performance checks

SLO

The public read path is considered safe for the current single-web-process SQLite architecture when the same profile passes on the target host:

  • p95 latency: <= 500 ms
  • p99 latency: <= 1500 ms
  • 5xx rate: <= 0.1%
  • rate limited responses during the test: 0
  • CPU: sustained web container CPU below 80%
  • memory: sustained web container memory below 80%

Use scripts/server-health-snapshot.sh immediately before and after a run to keep CPU and memory evidence next to the latency report.

Load Profile

Run the public profile against staging or production:

BASE_URL=https://polish-open-source.pl \
  CONCURRENCY=4 \
  DURATION=60 \
  scripts/public_load_test.rb > log/public-load-after.json

The profile covers /latest, detailed rankings, profiles, organizations, languages, packages, and a user badge. It does not send authenticated requests and it fails if any 429 is returned. That keeps the scenario from silently training operators to raise crawler-visible rate limits or bypass them with fake client addresses.

If wrk is available, the equivalent request mix is:

wrk -t2 -c4 -d60s -s scripts/public-wrk.lua https://polish-open-source.pl

Use the Ruby runner for the pass/fail SLO gate because it reports p95, p99, 5xx, and 429 counts as structured JSON.

For a before/after comparison, run the same command with the same BASE_URL, CONCURRENCY, DURATION, source IP, and published snapshot before and after a change. Compare requests_per_second, p95_ms, p99_ms, server_error_rate, and rate_limited_responses.

The conservative safe level for this milestone is the default profile above: 4 concurrent anonymous clients for 60 seconds with all SLO checks passing. Raise the profile only after the same report and server health snapshot stay inside the budgets.

Query Plans

Collect representative public SQLite query plans from the public read database:

PUBLIC_DATABASE_URL=sqlite://db/public.sqlite3 scripts/public_query_plans.rb > log/public-query-plans.md

For the default database:

scripts/public_query_plans.rb --database db/polish_open_source_rank.sqlite3 > log/public-query-plans.md

The report covers latest period resolution, people, repository and organization rankings, profile/badge lookups, language index, and package ranking. Add an index only when this report shows a full scan on a production-sized database for a path that is slow in the load report.

Local smoke output for the current schema showed index-backed lookups for the representative ranking, profile, badge, language, and package queries. Temporary B-trees remain for group/order tie-breakers; those are expected until a production-sized report shows they dominate latency. No new index was added in this milestone because the available plans did not prove one was needed.

Gzip Decision

Rack::Deflater stays enabled for now. It is already covered by request tests and reduces public HTML/SVG transfer without changing cache keys. Move gzip to nginx/CDN only if the load report plus server health snapshot show web CPU as the bottleneck while SQLite query plans remain index-backed.

Negative Cache Decision

Only stable public 404s are short-cached for 30 seconds: unknown location slugs that match ranking routes and unsupported package metric/ecosystem combinations. Data-dependent misses such as missing profiles, repositories, organizations, languages, package ecosystem pages, and badges are not negative-cached because a user action or the next published snapshot can make them valid.

Production Limits

The current production shape stays intentionally conservative:

  • one host;
  • one web container behind nginx;
  • one shared SQLite database for web, monthly, packages, and user actions;
  • cache in front of the app, keyed by URL rather than locale cookie.

Do not add systemd socket activation, blue-green deploys, or a second web worker until the read-only public snapshot path is stable in production. With the current shared SQLite write path, more parallel web capacity can increase lock contention instead of reducing user-visible downtime.

Spike Response

When public traffic spikes, use this order:

  1. Keep indexed public PL and EN pages cacheable by URL; do not add a global noindex.
  2. Verify Cloudflare is respecting origin cache headers for anonymous public HTML and badges, including stale-if-error.
  3. Increase CDN or nginx cache aggressiveness for /latest, /en/latest, rankings, profiles, languages, packages, and badges.
  4. Tighten temporary rate limits on /auth/*, /internal/*, and other expensive non-indexed paths before indexed ranking pages.
  5. If the app still needs protection, publish a static status page on a separate non-indexed operational path instead of replacing indexed public pages.