Improved atomicity

src/services/denokv.ts

@@ -14,6 +14,7 @@ interface SerializedFile {
     path: string;
     contentSize: number;
     compression: CompressionAlgorithm;
+    creationTime: number;
 }
 
 interface SerializedFilePathIndex {
@@ -43,8 +44,11 @@ export class DenoKVBlobService implements BlobService {
         }
 
         const blob_id = await this.sha1(content);
-        await this.kv.set(['blob_index', blobIndex, chunckIndex], blob_id);
-        await this.kv.set(['blob', blob_id], content);
+        await this.kv.atomic()
+            .check({key: ['blob_index', blobIndex, chunckIndex], versionstamp: null })
+            .set(['blob_index', blobIndex, chunckIndex], blob_id)
+            .set(['blob', blob_id], content)
+            .commit();
     }
 
     persistBlob(index: string, content: Uint8Array): Promise<number> {
@@ -107,12 +111,12 @@ export class DenoKVFileService implements FileService {
     createFromFullContent(
         path: string,
         content: string | Uint8Array,
-    ): Promise<FileMetaData> {
+    ): Promise<FileMetaData | null> {
         const reader = content instanceof Uint8Array ? new Buffer(content) : new StringReader(content);
         return this.createFromReader(path, reader);
     }
 
-    async createFromReader(path: string, content: Deno.Reader): Promise<FileMetaData> {
+    async createFromReader(path: string, content: Deno.Reader): Promise<FileMetaData | null> {
         const newId = crypto.randomUUID();
 
         const compressedContent = readableStreamFromReader(content).pipeThrough(new CompressionStream(CompressionAlgorithm.GZIP))
@@ -123,12 +127,18 @@ export class DenoKVFileService implements FileService {
             path,
             contentSize: size,
             compression: CompressionAlgorithm.GZIP,
+            creationTime: Date.now()
         };
         const idx: SerializedFilePathIndex = { fileId: newId };
-        await this.kv.set(['file', newId], serializedFile);
-        await this.kv.set(['file_index_path', path], idx);
 
-        return { id: newId, path, contentSize: size };
+        const ret = await this.kv.atomic()
+            .check({key: ['file_index_path', path], versionstamp: null })
+            .set(['file', newId], serializedFile)
+            .set(['file_index_path', path], idx)
+            .commit();
+        
+
+        return ret.ok ? { id: newId, path, contentSize: size } : null;
     }
 
     async *list(): AsyncIterable<FileMetaData> {
@@ -253,10 +263,12 @@ export class DenoKVFileService implements FileService {
             id: fileObject.value.id,
             contentSize: fileObject.value.contentSize,
             compression: fileObject.value.compression,
+            creationTime:  fileObject.value.creationTime,
         };
         await this.kv.atomic()
             .check(fileObject)
             .check(idx)
+            .check({key: ['file_index_path', newPath], versionstamp: null })
             .delete(idx.key)
             .set(['file_index_path', newPath], idx.value)
             .set(fileObject.key, newFile)

src/services/interfaces.ts

@@ -10,9 +10,9 @@ export interface FileService {
     createFromFullContent(
         path: string,
         content: string | Uint8Array,
-    ): Promise<FileMetaData>;
+    ): Promise<FileMetaData | null>;
 
-    createFromReader(path: string, content: Deno.Reader): Promise<FileMetaData>;
+    createFromReader(path: string, content: Deno.Reader): Promise<FileMetaData | null>;
 
     getRawContentByPath(path: string): Promise<Uint8Array | null>;