serve service: Use digest when requesting serve to set up a tree

...instead of passing just the Git hash, which imposes the remote
to always be native.

The serve service proto file is updated accordingly.

2 files changed, 37 insertions, 9 deletions

diff --git a/src/other_tools/root_maps/TARGETS b/src/other_tools/root_maps/TARGETS
index 61e16cb7..921dbf80 100644
--- a/src/other_tools/root_maps/TARGETS
+++ b/src/other_tools/root_maps/TARGETS
@@ -209,6 +209,7 @@
     , ["src/buildtool/common", "config"]
     , ["src/buildtool/crypto", "hash_function"]
     , ["src/buildtool/execution_api/serve", "mr_git_api"]
+    , ["src/buildtool/execution_api/serve", "utils"]
     , ["src/buildtool/file_system", "object_type"]
     ]
   }
diff --git a/src/other_tools/root_maps/root_utils.cpp b/src/other_tools/root_maps/root_utils.cpp
index 0e61c548..89e71653 100644
--- a/src/other_tools/root_maps/root_utils.cpp
+++ b/src/other_tools/root_maps/root_utils.cpp
@@ -21,6 +21,7 @@
 #include "src/buildtool/common/repository_config.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
 #include "src/buildtool/execution_api/serve/mr_git_api.hpp"
+#include "src/buildtool/execution_api/serve/utils.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
 
 auto CheckServeHasAbsentRoot(ServeApi const& serve,
@@ -48,6 +49,14 @@ auto EnsureAbsentRootOnServe(
     IExecutionApi const* remote_api,
     AsyncMapConsumerLoggerPtr const& logger,
     bool no_sync_is_fatal) -> bool {
+    auto const native_digest = ArtifactDigestFactory::Create(
+        HashFunction::Type::GitSHA1, tree_id, 0, /*is_tree=*/true);
+    if (not native_digest) {
+        (*logger)(fmt::format("Failed to create digest for {}", tree_id),
+                  /*fatal=*/true);
+        return false;
+    }
+    // check if upload is required
     if (remote_api != nullptr) {
         // upload tree to remote CAS
         auto repo = RepositoryConfig{};
@@ -57,18 +66,15 @@ auto EnsureAbsentRootOnServe(
                 /*fatal=*/true);
             return false;
         }
-        auto const digest = ArtifactDigestFactory::Create(
-            HashFunction::Type::GitSHA1, tree_id, 0, /*is_tree=*/true);
-
         auto git_api = MRGitApi{&repo,
                                 native_storage_config,
                                 compat_storage_config,
                                 compat_storage,
                                 local_api};
-        if (not digest or not git_api.RetrieveToCas(
-                              {Artifact::ObjectInfo{.digest = *digest,
-                                                    .type = ObjectType::Tree}},
-                              *remote_api)) {
+        if (not git_api.RetrieveToCas(
+                {Artifact::ObjectInfo{.digest = *native_digest,
+                                      .type = ObjectType::Tree}},
+                *remote_api)) {
             (*logger)(fmt::format("Failed to sync tree {} from repository {}",
                                   tree_id,
                                   repo_path.string()),
@@ -76,8 +82,29 @@ auto EnsureAbsentRootOnServe(
             return false;
         }
     }
-    // ask serve endpoint to retrieve the uploaded tree
-    if (not serve.GetTreeFromRemote(tree_id)) {
+    // ask serve endpoint to retrieve the uploaded tree; this can only happen if
+    // we have access to a digest that the remote knows
+    ArtifactDigest remote_digest = *native_digest;
+    if (compat_storage_config != nullptr) {
+        // in compatible mode, get compatible digest from mapping, if exists
+        auto cached_obj = MRApiUtils::ReadRehashedDigest(*native_digest,
+                                                         *native_storage_config,
+                                                         *compat_storage_config,
+                                                         /*from_git=*/true);
+        if (not cached_obj) {
+            (*logger)(cached_obj.error(), /*fatal=*/true);
+            return false;
+        }
+        if (not *cached_obj) {
+            // digest is not known; respond based on no_sync_is_fatal flag
+            (*logger)(fmt::format("No digest provided to sync root tree {}.",
+                                  tree_id),
+                      /*fatal=*/no_sync_is_fatal);
+            return not no_sync_is_fatal;
+        }
+        remote_digest = cached_obj->value().digest;
+    }
+    if (not serve.GetTreeFromRemote(remote_digest)) {
         // respond based on no_sync_is_fatal flag
         (*logger)(
             fmt::format("Serve endpoint failed to sync root tree {}.", tree_id),