fix: nginx — re-resolve upstream hostname via Docker DNS

Mirror of wowcheckout e0c349a. Same bug would bite xmrcheckout after any api container rebuild — nginx caches IP at startup and never re-resolves, so a rebuild that gives the api container a new IP leaves nginx 502'ing until manually restarted. Use 'resolver 127.0.0.11 valid=10s' + variable-based proxy_pass so nginx re-resolves every ~10s via Docker's internal DNS.

TODO.md

@@ -0,0 +1,85 @@
+# xmrcheckout — Local TODO / Followups
+
+Notes for ourselves. Not committed (see .gitignore or just left untracked).
+Kept here so context survives a terminal restart.
+
+## Reconciler wallet handling
+
+### Understanding (not a bug — design)
+
+- Each merchant has their own Monero view-only wallet (`user-<uuid>-<fingerprint>.keys`).
+- We run 3 `monero-wallet-rpc` containers as a pool. monero-wallet-rpc can hold
+  one wallet open at a time. We hash-shard wallets across the 3 backends
+  (consistent hashing on wallet_name).
+- At any idle moment, 2 out of 3 backends are expected to hold no wallet.
+  That's fine. Wallets open lazily when the reconciler needs to query them
+  (via `_ensure_wallet_open`).
+- `open_wallet` / `close_wallet` on the monero-wallet-rpc process is cheap
+  when the wallet is already open in the wallet-rpc process (the wallet-rpc
+  itself short-circuits), but our Python-side `backend.current_wallet` cache
+  is reset every reconciler loop, so we send redundant RPC calls each loop.
+
+### Medium-priority followups
+
+1. **Make `MoneroWalletService` long-lived across reconciler loops.**
+   Currently `reconciler.main()` constructs `MoneroWalletService()` fresh every
+   iteration, which resets `backend.current_wallet = None`. The actual
+   monero-wallet-rpc process usually still has the wallet open, but our Python
+   code doesn't know that, so it resends `close_wallet` + `open_wallet` on
+   every loop. Harmless but wasteful — ~2 extra RPCs per active invoice per
+   tick. Fix: hoist the service out of the loop, keep it across iterations.
+
+2. **Verify wallet-rpc recovery after wallet-rpc container restart.**
+   When wallet-rpc containers restart, the `_ensure_wallet_open` path should
+   reopen wallets on first use. It appears to work in practice but we haven't
+   written a targeted test. Add a test that simulates wallet-rpc restart
+   between two invoice reconciliation passes for the same tenant.
+
+3. **Dedicated wallet-rpc backend per busy tenant.**
+   The consistent-hash sharding works fine at low tenant count. When one
+   tenant becomes hot (lots of invoices), one backend is hit 100% and the
+   other two sit idle. If we hit scale, think about either pinning hot
+   tenants to dedicated backends, or sharding by invoice rather than tenant.
+
+## Webhook payload: amount propagation
+
+- We now include `amount` (fiat from quote), `currency`, and `amount_crypto`
+  in the BTCPay-compat webhook payload. This was added because Medusa's
+  capture workflow needs the amount to flip `captured_at` — without it, it
+  captures 0 and the payment stays stuck "authorized" even after we fire
+  `InvoiceSettled`/`InvoicePaymentSettled`.
+- Downstream followups:
+  - Consider including `amount_atomic` (integer atomic units) for any
+    processor that prefers integer arithmetic over Decimal strings.
+  - Consider including `exchange_rate` at webhook time so downstream can
+    reproduce the fiat figure if their Decimal precision differs.
+
+## Logging
+
+- Silenced `monero.backends.jsonrpc.wallet` library logger (set to CRITICAL)
+  in `reconciler.py` so the `-13 No wallet file` errors from routine
+  `close_wallet` calls on idle backends stop polluting logs.
+- If we need to debug wallet-rpc issues in the future, temporarily set it
+  back to WARNING and rebuild.
+
+## Upstream PRs
+
+Open PRs we submitted upstream (xmrcheckout/xmrcheckout):
+- Advisory locks, restore_height lookback, transfer-deletion guard,
+  decimal formatting, webhook retries, reconciler error logging.
+
+Followups for upstream:
+- Propose the webhook-amount addition as a PR once we've run it in prod for
+  a week. That's a breaking-ish change for anyone downstream relying on a
+  specific payload shape, so flag it carefully.
+- Propose the `get_status` fix (drop the set_daemon call). Clear win — quiets
+  log noise with no functional change. Low-risk PR.
+
+## Known-unfixed
+
+- We do not yet have a way for a tenant to manually trigger re-send of a
+  webhook delivery (e.g. if Medusa was down when the settle fired). Would
+  be a nice admin UI action.
+- If wallet-rpc runs out of memory handling many simultaneous wallet opens,
+  we have no backpressure — the reconciler will just keep trying. Should
+  add a circuit-breaker / per-backend queue depth limit at some point.

nginx/conf.d/default.conf

@@ -1,5 +1,13 @@
 limit_req_zone $binary_remote_addr zone=global_rate_limit:10m rate=50r/s;
 
+# Docker's embedded DNS (127.0.0.11) lets nginx re-resolve upstream service
+# hostnames. Without `resolver` + a variable-based proxy_pass, nginx resolves
+# `api` / `ui` to an IP once at startup and caches it forever — if the api
+# container is rebuilt and Docker gives it a new IP, nginx keeps hitting the
+# old one and every request returns 502 Bad Gateway until nginx is manually
+# restarted. `valid=10s` bounds the stale window to ~10 seconds.
+resolver 127.0.0.11 valid=10s ipv6=off;
+
 server {
   listen 80;
   server_name xmrcheckout.such.software localhost;
@@ -11,7 +19,8 @@ server {
   }
 
   location /api/ {
-    proxy_pass http://api:8000/api/;
+    set $api_upstream "api";
+    proxy_pass http://$api_upstream:8000/api/;
     proxy_http_version 1.1;
     proxy_set_header Host $host;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
@@ -23,7 +32,8 @@ server {
   }
 
   location = /openapi.json {
-    proxy_pass http://api:8000/openapi.json;
+    set $api_upstream "api";
+    proxy_pass http://$api_upstream:8000/openapi.json;
     proxy_http_version 1.1;
     proxy_set_header Host $host;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
@@ -37,7 +47,8 @@ server {
   }
 
   location / {
-    proxy_pass http://ui:3000/;
+    set $ui_upstream "ui";
+    proxy_pass http://$ui_upstream:3000/;
     proxy_http_version 1.1;
     proxy_set_header Host $host;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;