Make CAS and AC server not to use the same store

When CAS and AC uses the same store, it might produce unexpected
side-effects and wrong behaviors. To prevent system from such situation,
it currently raises an error when CAS and AC uses the same store.
An integration test is added for this using nix test file and github's
nix workflow.

.github/workflows/nix.yaml

@@ -134,4 +134,5 @@ jobs:
 
       - name: Test nix run
         run: |
+          nix run -L .#nativelink-prevent-store-conflict-test
           nix run -L .#nativelink-is-executable-test

flake.nix

@@ -133,6 +133,8 @@
 
         local-image-test = pkgs.callPackage ./tools/local-image-test.nix {};
 
+        nativelink-prevent-store-conflict-test = pkgs.callPackage ./tools/nativelink-prevent-store-conflict-test.nix {inherit nativelink;};
+
         nativelink-is-executable-test = pkgs.callPackage ./tools/nativelink-is-executable-test.nix {inherit nativelink;};
 
         rbe-configs-gen = pkgs.callPackage ./local-remote-execution/rbe-configs-gen.nix {};
@@ -251,7 +253,7 @@
           };
         };
         packages = rec {
-          inherit publish-ghcr local-image-test nativelink-is-executable-test nativelink nativelink-debug native-cli lre-cc nativelink-worker-init;
+          inherit publish-ghcr local-image-test nativelink-prevent-store-conflict-test nativelink-is-executable-test nativelink nativelink-debug native-cli lre-cc nativelink-worker-init;
           default = nativelink;
 
           rbe-autogen-lre-cc = rbe-autogen lre-cc;

src/bin/nativelink.rs

@@ -243,6 +243,23 @@ async fn inner_main(
         // Currently we only support http as our socket type.
         let ListenerConfig::http(http_config) = server_cfg.listener;
 
+        // Check if CAS and AC use the same store.
+        if let Some(cas_config) = &services.cas {
+            if let Some(ac_config) = &services.ac {
+                for (instance_name, cas_store_config) in cas_config {
+                    if let Some(ac_store_config) = ac_config.get(instance_name) {
+                        if cas_store_config.cas_store == ac_store_config.ac_store {
+                            return Err(make_err!(
+                                Code::InvalidArgument,
+                                "CAS and AC cannot use the same store '{}' in the config",
+                                cas_store_config.cas_store
+                            ))?;
+                        }
+                    }
+                }
+            }
+        }
+
         let tonic_services = TonicServer::builder()
             .add_optional_service(
                 services

tools/nativelink-prevent-store-conflict-test.nix

@@ -0,0 +1,72 @@
+{
+  nativelink,
+  writeShellScriptBin,
+}:
+writeShellScriptBin "prevent-store-conflict-test" ''
+  set -xuo pipefail
+
+  cat > store_conflict_test.json <<EOF
+  {
+    "stores": {
+      "FILESYSTEM_STORE": {
+        "compression": {
+          "compression_algorithm": {
+            "lz4": {}
+          },
+          "backend": {
+            "filesystem": {
+              "content_path": "~/.cache/nativelink/content_path-cas",
+              "temp_path": "~/.cache/nativelink/tmp_path-cas",
+              "eviction_policy": {
+                // 10gb.
+                "max_bytes": 10000000000,
+              }
+            }
+          }
+        }
+      }
+    },
+    "servers": [{
+      "listener": {
+        "http": {
+          "socket_address": "0.0.0.0:50053"
+        }
+      },
+      "services": {
+        "cas": {
+          "main": {
+            "cas_store": "FILESYSTEM_STORE"
+          }
+        },
+        "ac": {
+          "main": {
+            "ac_store": "FILESYSTEM_STORE"
+          }
+        },
+        "capabilities": {},
+        "bytestream": {
+          "cas_stores": {
+            "main": "FILESYSTEM_STORE",
+          }
+        }
+      }
+    }]
+  }
+  EOF
+
+  nativelink_output="$(${nativelink}/bin/nativelink ./store_conflict_test.json 2>&1)"
+
+  rm ./store_conflict_test.json
+
+  print_error_output=$(cat <<EOF
+  Error: Error { code: InvalidArgument, messages: ["CAS and AC cannot use the same store 'FILESYSTEM_STORE' in the config"] }
+  EOF)
+
+  if [ "$nativelink_output" = "$print_error_output" ]; then
+    echo "The output of nativelink matches the print_error output."
+  else
+    echo 'The output of nativelink does not match the print_error output:'
+    diff <(echo "$nativelink_output") <(echo "$print_error_output") >&2
+    exit 1
+  fi
+''