feat: predownload geo CSVs at local build time (M4)

Local (non-Docker) runs had no geodb/ and resolved every peer to
region="unknown". Add a FetchGeoDb MSBuild target that caches the two
CSVs in packages/geodb and copies them next to the build output. Docker
builds/containers (FetchGeoDb=false) and CI (CI=true) skip it, so the
images' build-time ADD stays authoritative.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: mikhail-dcl

Dockerfile.debug

@@ -9,5 +9,8 @@ COPY . .
 ADD https://cdn.jsdelivr.net/npm/@ip-location-db/geo-whois-asn-country/geo-whois-asn-country-ipv4-num.csv \
     https://cdn.jsdelivr.net/npm/@ip-location-db/geo-whois-asn-country/geo-whois-asn-country-ipv6-num.csv \
     /app/geodb/
+# The image already has fresh geo CSVs from the ADD above; the entrypoint's `dotnet run`
+# would otherwise trigger the csproj predownload at container start, so disable it.
+ENV FetchGeoDb=false
 EXPOSE 7777/udp
 ENTRYPOINT ["dotnet", "run", "--project", "src/DCLPulse/DCLPulse.csproj", "--configuration", "Debug", "--property:GenerateProto=false"]

docs/metrics.md

@@ -281,7 +281,12 @@ histogram_quantile(0.5, sum by (le) (rate(dcl_pulse_peer_rtt_ms_bucket{region="a
 | `unknown` dominating with a real player population | Geo database missing from the image, or peers behind private/CGNAT egress the DB can't place |
 | Everything near 500 ms right after a connect burst | The ENet seed showing through before ACK samples arrive — transient, ignore |
 
-**Data source**: [geo-whois-asn-country](https://github.com/sapics/ip-location-db) (CC0, public domain), the `-num` CSV variants. Each of the three Dockerfiles fetches the IPv4 and IPv6 CSVs into the image's `geodb/` directory at build time via a single `ADD` — no runtime download. `ContinentResolver` loads them once at startup from `Transport:GeoDbDirectory` (default `geodb`, resolved against the app base directory; absolute paths are used as-is). Missing files are tolerated — every peer then reports under `region="unknown"`.
+**Data source**: [geo-whois-asn-country](https://github.com/sapics/ip-location-db) (CC0, public domain), the `-num` CSV variants. `ContinentResolver` loads them once at startup from `Transport:GeoDbDirectory` (default `geodb`, resolved against the app base directory; absolute paths are used as-is). Missing files are tolerated — every peer then reports under `region="unknown"`.
+
+Two ways the CSVs get to that directory:
+
+- **Docker**: each of the three Dockerfiles fetches fresh IPv4 and IPv6 CSVs into the image's `geodb/` directory at build time via a single `ADD` — no runtime download. These freshly-fetched copies are authoritative for images.
+- **Local (non-Docker) builds**: the `DCLPulse.csproj` `FetchGeoDb` target predownloads the two CSVs into the gitignored `packages/geodb/` cache (once) and copies them next to the build output, so local runs resolve regions without a Docker image. Delete `packages/geodb` to force a refresh. Offline builds warn and continue — the app then degrades to `region="unknown"`. The download is skipped in Docker builds and containers (`FetchGeoDb=false`) and on CI (`CI=true`), so it never runs where the `ADD`-provided or in-memory test copies already apply.
 
 ---
 

src/DCLPulse/DCLPulse.csproj

@@ -49,4 +49,29 @@
             <TargetPath>libenet.dylib</TargetPath>
         </None>
     </ItemGroup>
+
+    <!-- Geo database predownload for local runs. Docker images fetch their own fresh
+         copies via ADD (which take precedence at runtime); Docker builds and CI set
+         FetchGeoDb=false / CI=true so this never runs there. Delete packages/geodb
+         to force a re-download. -->
+    <PropertyGroup>
+        <GeoDbCacheDir>$(MSBuildThisFileDirectory)..\..\packages\geodb\</GeoDbCacheDir>
+    </PropertyGroup>
+
+    <Target Name="FetchGeoDb" BeforeTargets="Build"
+            Condition="'$(FetchGeoDb)' != 'false' and '$(CI)' == ''">
+        <DownloadFile SourceUrl="https://cdn.jsdelivr.net/npm/@ip-location-db/geo-whois-asn-country/geo-whois-asn-country-ipv4-num.csv"
+                      DestinationFolder="$(GeoDbCacheDir)"
+                      Condition="!Exists('$(GeoDbCacheDir)geo-whois-asn-country-ipv4-num.csv')"
+                      ContinueOnError="WarnAndContinue" />
+        <DownloadFile SourceUrl="https://cdn.jsdelivr.net/npm/@ip-location-db/geo-whois-asn-country/geo-whois-asn-country-ipv6-num.csv"
+                      DestinationFolder="$(GeoDbCacheDir)"
+                      Condition="!Exists('$(GeoDbCacheDir)geo-whois-asn-country-ipv6-num.csv')"
+                      ContinueOnError="WarnAndContinue" />
+        <ItemGroup>
+            <GeoDbFiles Include="$(GeoDbCacheDir)*.csv" />
+        </ItemGroup>
+        <Copy SourceFiles="@(GeoDbFiles)" DestinationFolder="$(OutDir)geodb"
+              SkipUnchangedFiles="true" Condition="'@(GeoDbFiles)' != ''" />
+    </Target>
 </Project>

src/DCLPulse/Dockerfile

@@ -1,5 +1,8 @@
 FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
 ARG BUILD_CONFIGURATION=Release
+# The image fetches its own fresh geo CSVs via ADD in the final stage; disable the
+# csproj's local predownload so the build/publish steps never hit the network for them.
+ENV FetchGeoDb=false
 WORKDIR /build
 COPY ["src/DCLPulse/DCLPulse.csproj", "src/DCLPulse/"]
 COPY ["src/DCLPulse/global.json", "src/DCLPulse/"]

src/DCLPulse/Dockerfile.dev-debug

@@ -1,4 +1,7 @@
 FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+# The image fetches its own fresh geo CSVs via ADD in the final stage; disable the
+# csproj's local predownload so the build/publish steps never hit the network for them.
+ENV FetchGeoDb=false
 WORKDIR /build
 COPY ["src/DCLPulse/DCLPulse.csproj", "src/DCLPulse/"]
 COPY ["src/DCLPulse/global.json", "src/DCLPulse/"]