## Why
The mirrorlist (PR #121) always load-balances round-robin. Round-robin is oblivious to how busy each mirror is, so a slow or saturated mirror keeps getting its fair share of new requests. This adds an opt-in **least-connections** strategy that favors the mirror currently handling the fewest in-flight requests, steering new work toward idle mirrors. Round-robin stays the default, so existing remotes are unchanged.
## How
- **Model**: `models.Remote` gains `mirror_strategy` (`round_robin` default/empty, or `least_conn`). `ValidateMirrorStrategy` checks the enum and requires a non-empty mirrorlist for `least_conn`. Empty behaves as `round_robin` for back-compat.
- **DB**: additive `mirror_strategy TEXT NOT NULL DEFAULT 'round_robin'` column (CREATE TABLE + `ADD COLUMN IF NOT EXISTS`), wired through remoteCols/scanRemote/CreateRemote/UpdateRemote; empty normalized to `round_robin` on write.
- **Engine**: a per-remote, per-pool-URL atomic in-flight gauge is incremented around each upstream call (head/fetch/checkUpstream). For a `least_conn` remote the attempt order starts with the least-loaded pool URL (ties broken by the existing round-robin rotation). Round-robin path and failover order are unchanged; single-URL pools are a no-op.
- **Tests**: unit tests for least-loaded selection, round-robin default, gauge inc/dec, single-URL no-op, and validation; DB round-trip covers the new column; docker e2e adds a `least_conn` distribution test plus a real `dnf` install through a `least_conn` remote.
Back-compat: unset/empty `mirror_strategy` is `round_robin`, so all existing remotes keep their current behavior.
Reviewed-on: #122
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>
## Why
OS package remotes (rpm/deb/apk) fetch many small files and benefit from spreading upstream load across mirrors and surviving a mirror outage. A remote may now set a **`mirrorlist`** of additional upstream base URLs. The effective upstream pool is **`[base_url] + mirrorlist`**, which the shared proxy engine load-balances **round-robin** and, on a network error/timeout/5xx, **fails over** to the next mirror before returning an error. Selection happens in the engine, so it works for every provider that reaches upstream.
**Backward compatible:** `base_url` stays a plain string (providers read it unchanged), and a remote with **no mirrorlist behaves exactly as today** (single attempt, same error path).
## How
- `models.Remote.Mirrorlist` (`[]string`, `json:"mirrorlist,omitempty"`) + `UpstreamPool()` = `[base_url] + mirrorlist`.
- `ValidateMirrorlist`: a non-empty mirrorlist is allowed **only** when `repo_type==remote` **and** `package_type ∈ {rpm, deb, alpine}`; each entry must be an http/https URL. Enforced in the v2 create/update handlers (400 otherwise); `base_url` stays required for remotes.
- Persist the mirrorlist in a new additive `mirrorlist TEXT[]` column (`remoteCols`/`scanRemote`/`CreateRemote`/`UpdateRemote`); the `base_url` column is unchanged.
- Engine keeps a per-remote round-robin cursor over the pool; the fetch/head/revalidate upstream calls run in a failover loop that narrows the remote to one selected mirror per attempt. Only network errors and 5xx fail over (404/403/… return as-is). The circuit breaker stays keyed per remote and trips only after all mirrors fail.
## Scope
Round-robin + failover only, restricted to **remote rpm/deb/apk** repos. Least-connections and a per-remote strategy selector are a **follow-up PR**.
## Tests
- Unit: model JSON round-trip + validation gating (rejected on non-rpm/deb/apk and on local, accepted on rpm/deb/apk, bad URL rejected), engine round-robin/failover/no-mirrorlist-unchanged, DB mirrorlist round-trip. `make test` (`go test -race`) green.
- Docker acceptance (`e2e-docker`, `dockere2e` tag, wired into `docker-e2e.sh`): round-robin distribution across two mock upstreams, failover past a dead primary, no-mirrorlist regression, and a **real `dnf` makecache + install** through a two-mirror rpm remote whose `base_url` is dead. All four pass locally.
Reviewed-on: #121
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>
Adds a black-box e2e suite that runs against the **built container image** via docker-compose (complementing the in-process `e2e/` testcontainers suite).
## What it does
`make docker-e2e` → `scripts/docker-e2e.sh`: builds the image, brings up the full stack (postgres, redis, minio, artifactapi) plus a static nginx **mock upstream** for hermetic caching, waits for `/health`, runs `go test -tags=dockere2e ./e2e-docker/...`, and tears everything down.
## Coverage
- **Repository lifecycle** — add / change / delete for remote, local and virtual repos.
- **Caching** — one immutable artifact for **each of the 10 remote package types** (generic, docker, helm, pypi, npm, rpm, alpine, puppet, terraform, goproxy) proxied through the mock upstream: first fetch `X-Artifact-Source: remote`, second `cache`, bytes verified against the origin fixture.
- **Local uploads** — generic (upload/download), pypi (wheel + generated `simple/` index), rpm (real package + **automatic repodata** generation).
- **Virtual repositories** — pypi simple-index merge and helm `index.yaml` merge across two members.
## Notes
- The artifactapi host port is parameterised (`ARTIFACTAPI_PORT`, default `8000`; the e2e run uses `8001`) so it does not collide with a locally-running instance. This is the only change to the production `docker-compose.yml`.
- Fixtures under `e2e-docker/fixtures/` are real package files (incl. a real RPM so repodata parsing works); a `.gitignore` negation tracks them over the global ignore of those extensions.
## Validation
Ran `make docker-e2e` locally: **all suites pass** against the containerised product.
---------
Co-authored-by: BenVincent <benvin@main.unkin.net>
Reviewed-on: #97
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>
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