feat: support multiple URLs in sources

apt/private/apt_deb_repository.bzl

@@ -3,7 +3,7 @@
 load(":util.bzl", "util")
 load(":version_constraint.bzl", "version_constraint")
 
-def _fetch_package_index(rctx, url, dist, comp, arch, integrity):
+def _fetch_package_index(rctx, urls, dist, comp, arch, integrity):
     target_triple = "{dist}/{comp}/{arch}".format(dist = dist, comp = comp, arch = arch)
 
     # See https://linux.die.net/man/1/xz , https://linux.die.net/man/1/gzip , and https://linux.die.net/man/1/bzip2
@@ -20,25 +20,29 @@ def _fetch_package_index(rctx, url, dist, comp, arch, integrity):
 
     failed_attempts = []
 
-    for (ext, cmd) in supported_extensions.items():
-        output = "{}/Packages{}".format(target_triple, ext)
-        dist_url = "{}/dists/{}/{}/binary-{}/Packages{}".format(url, dist, comp, arch, ext)
-        download = rctx.download(
-            url = dist_url,
-            output = output,
-            integrity = integrity,
-            allow_fail = True,
-        )
-        decompress_r = None
-        if download.success:
-            decompress_r = rctx.execute(cmd + [output])
-            if decompress_r.return_code == 0:
-                integrity = download.integrity
-                break
+    for url in urls:
+        for (ext, cmd) in supported_extensions.items():
+            output = "{}/Packages{}".format(target_triple, ext)
+            dist_url = "{}/dists/{}/{}/binary-{}/Packages{}".format(url, dist, comp, arch, ext)
+            download = rctx.download(
+                url = dist_url,
+                output = output,
+                integrity = integrity,
+                allow_fail = True,
+            )
+            decompress_r = None
+            if download.success:
+                decompress_r = rctx.execute(cmd + [output])
+                if decompress_r.return_code == 0:
+                    integrity = download.integrity
+                    break
+
+            failed_attempts.append((dist_url, download, decompress_r))
 
-        failed_attempts.append((dist_url, download, decompress_r))
+        if download.success:
+            break
 
-    if len(failed_attempts) == len(supported_extensions):
+    if len(failed_attempts) == len(supported_extensions) * len(urls):
         attempt_messages = []
         for (url, download, decompress) in failed_attempts:
             reason = "unknown"
@@ -55,7 +59,7 @@ def _fetch_package_index(rctx, url, dist, comp, arch, integrity):
 {}
         """.format(len(failed_attempts), "\n".join(attempt_messages)))
 
-    return ("{}/Packages".format(target_triple), integrity)
+    return ("{}/Packages".format(target_triple), url, integrity)
 
 def _parse_repository(state, contents, root):
     last_key = ""
@@ -117,16 +121,16 @@ def _create(rctx, sources, archs):
     )
 
     for arch in archs:
-        for (url, dist, comp) in sources:
+        for (urls, dist, comp) in sources:
             # We assume that `url` does not contain a trailing forward slash when passing to
             # functions below. If one is present, remove it. Some HTTP servers do not handle
             # redirects properly when a path contains "//"
             # (ie. https://mymirror.com/ubuntu//dists/noble/stable/... may return a 404
             # on misconfigured HTTP servers)
-            url = url.rstrip("/")
+            urls = [url.rstrip("/") for url in urls]
 
             rctx.report_progress("Fetching package index: {}/{} for {}".format(dist, comp, arch))
-            (output, _) = _fetch_package_index(rctx, url, dist, comp, arch, "")
+            (output, url, _) = _fetch_package_index(rctx, urls, dist, comp, arch, "")
 
             # TODO: this is expensive to perform.
             rctx.report_progress("Parsing package index: {}/{} for {}".format(dist, comp, arch))

apt/private/deb_resolve.bzl

@@ -44,8 +44,15 @@ def internal_resolve(rctx, yq_toolchain_prefix, manifest, include_transitive):
     for src in manifest["sources"]:
         distr, components = src["channel"].split(" ", 1)
         for comp in components.split(" "):
+            if "urls" in src:
+                urls = src["urls"]
+            elif "url" in src:
+                urls = [src["url"]]
+            else:
+                fail("Source missing 'url' or 'urls' field")
+
             sources.append((
-                src["url"],
+                urls,
                 distr,
                 comp,
             ))