TargetCache: Use StorageConfig instance for sharding

Instead of computing the shard based on the RemoteExecutionConfig
singleton, use the already computed hash stored in the passed
StorageConfig instance, which now needs to be set up separately
if bootstrapping in order to avoid unwanted includes.

Storing the backend description to CAS and corresponding audit
checks now take place in main.

1 files changed, 3 insertions, 17 deletions

diff --git a/src/buildtool/storage/target_cache.hpp b/src/buildtool/storage/target_cache.hpp
index e5a64737..2f52e100 100644
--- a/src/buildtool/storage/target_cache.hpp
+++ b/src/buildtool/storage/target_cache.hpp
@@ -27,7 +27,6 @@
 #include "src/buildtool/build_engine/base_maps/entity_name_data.hpp"
 #include "src/buildtool/build_engine/expression/configuration.hpp"
 #include "src/buildtool/common/artifact.hpp"
-#include "src/buildtool/execution_api/remote/config.hpp"
 #include "src/buildtool/file_system/file_storage.hpp"
 #include "src/buildtool/file_system/object_type.hpp"
 #include "src/buildtool/logging/logger.hpp"
@@ -36,7 +35,6 @@
 #include "src/buildtool/storage/target_cache_entry.hpp"
 #include "src/buildtool/storage/target_cache_key.hpp"
 #include "src/buildtool/storage/uplinker.hpp"
-#include "src/utils/cpp/gsl.hpp"
 
 /// \brief The high-level target cache for storing export target's data.
 /// Supports global uplinking across all generations. The uplink is
@@ -58,16 +56,10 @@ class TargetCache {
         GenerationConfig const& config,
         gsl::not_null<Uplinker<kDoGlobalUplink> const*> const& uplinker)
         : cas_{*cas},
-          file_store_{config.target_cache / ComputeShard()},
+          file_store_{config.target_cache /
+                      config.storage_config->backend_description_id},
           uplinker_{*uplinker},
-          explicit_shard_{std::nullopt} {
-        if constexpr (kDoGlobalUplink) {
-            // write backend description (shard) to CAS
-            [[maybe_unused]] auto id =
-                cas_.StoreBlob(RemoteExecutionConfig::DescribeBackend());
-            EnsuresAudit(id and ArtifactDigest{*id}.hash() == ComputeShard());
-        }
-    }
+          explicit_shard_{std::nullopt} {}
 
     /// \brief Returns a new TargetCache backed by the same CAS, but the
     /// FileStorage uses the given \p shard. This is particularly useful for the
@@ -152,12 +144,6 @@ class TargetCache {
         LocalGenerationTC const& latest,
         std::string const& key_digest) const noexcept -> bool;
 
-    [[nodiscard]] static auto ComputeShard() noexcept -> std::string {
-        return ArtifactDigest::Create<ObjectType::File>(
-                   RemoteExecutionConfig::DescribeBackend())
-            .hash();
-    }
-
     [[nodiscard]] auto DownloadKnownArtifacts(
         TargetCacheEntry const& value,
         ArtifactDownloader const& downloader) const noexcept -> bool;