feat: specify different lockfile directory (#238)

Author: AlCalzone

README.md

@@ -82,6 +82,14 @@ The following options exist:
 
 To create a compressed copy of the database in `/path/to/file.dump`, use the `dump()` method. If any data is written to the db during the dump, it is appended to the dump but most likely compressed.
 
+### Changing where the lockfile is created
+
+Normally, the lockfile to avoid concurrent access to the DB file is created right next to the DB file. You can change this, e.g. to put the lockfile into a `tmpfs`:
+```ts
+const db = new DB("/path/to/file", { lockfileDirectory: "/var/tmp" });
+```
+If the directory does not exist, it will be created when opening the DB.
+
 ### Copying and compressing the database
 
 ```ts
@@ -133,6 +141,9 @@ The file will be overwritten if it exists. The 2nd options argument can be used
 	Placeholder for next release:
 	### __WORK IN PROGRESS__
 -->
+### __WORK IN PROGRESS__
+* Add the ability to specify where the lockfile is created
+
 ### 2.1.0 (2021-06-22)
 * When opening the DB, recover from crashes that happened while compressing the DB
 * Ensure that the DB files are flushed to disk when closing or renaming files

src/lib/db.test.ts

@@ -182,6 +182,20 @@ describe("lib/db", () => {
 			await db.close();
 		});
 
+		it("also creates leading directories for the lockfiles if they don't exist", async () => {
+			const lockfileDirectory = path.join(
+				testFSRoot,
+				"this/path/does/not/exist/either",
+			);
+			const db = new JsonlDB(path.join(testFSRoot, "lockfile"), {
+				lockfileDirectory,
+			});
+			await db.open();
+			await db.close();
+
+			await expect(fs.pathExists(lockfileDirectory)).resolves.toBeTrue();
+		});
+
 		it("reads the file if it exists", async () => {
 			const db = new JsonlDB(path.join(testFSRoot, "yes"));
 			await db.open();
@@ -196,7 +210,7 @@ describe("lib/db", () => {
 			try {
 				await db2.open();
 				throw new Error("it did not throw");
-			} catch (e) {
+			} catch (e: any) {
 				expect(e.message).toMatch(/Failed to lock/i);
 			}
 
@@ -240,7 +254,7 @@ describe("lib/db", () => {
 			try {
 				await db.open();
 				throw new Error("it did not throw");
-			} catch (e) {
+			} catch (e: any) {
 				expect(e.message).toMatch(/invalid data/i);
 				expect(e.message).toMatch("line 2");
 			}
@@ -251,7 +265,7 @@ describe("lib/db", () => {
 			try {
 				await db.open();
 				throw new Error("it did not throw");
-			} catch (e) {
+			} catch (e: any) {
 				expect(e.message).toMatch(/invalid data/i);
 				expect(e.message).toMatch("line 2");
 			}
@@ -262,7 +276,7 @@ describe("lib/db", () => {
 			try {
 				await db.open();
 				throw new Error("it did not throw");
-			} catch (e) {
+			} catch (e: any) {
 				expect(e.message).toMatch(/invalid data/i);
 				expect(e.message).toMatch("line 1");
 			}

src/lib/db.ts

@@ -67,6 +67,12 @@ export interface JsonlDBOptions<V> {
 		 */
 		maxBufferedCommands?: number;
 	};
+
+	/**
+	 * Override in which directory the lockfile is created.
+	 * Defaults to the directory in which the DB file is located.
+	 */
+	lockfileDirectory?: string;
 }
 
 /** This is the same as `fs-extra`'s WriteOptions */
@@ -102,6 +108,9 @@ export class JsonlDB<V extends unknown = unknown> {
 		this.filename = filename;
 		this.dumpFilename = this.filename + ".dump";
 		this.backupFilename = this.filename + ".bak";
+		this.lockfileName = options.lockfileDirectory
+			? path.join(options.lockfileDirectory, path.basename(this.filename))
+			: this.filename;
 
 		this.options = options;
 		// Bind all map properties we can use directly
@@ -152,6 +161,7 @@ export class JsonlDB<V extends unknown = unknown> {
 	public readonly filename: string;
 	public readonly dumpFilename: string;
 	public readonly backupFilename: string;
+	private readonly lockfileName: string;
 
 	private options: JsonlDBOptions<V>;
 
@@ -200,7 +210,8 @@ export class JsonlDB<V extends unknown = unknown> {
 		await fs.ensureDir(path.dirname(this.filename));
 
 		try {
-			await lockfile.lock(this.filename, {
+			await fs.ensureDir(path.dirname(this.lockfileName));
+			await lockfile.lock(this.lockfileName, {
 				// We cannot be sure that the file exists before acquiring the lock
 				realpath: false,
 
@@ -215,7 +226,7 @@ export class JsonlDB<V extends unknown = unknown> {
 				},
 			});
 		} catch (e) {
-			throw new Error(`Failed to lock DB file "${this.filename}"!`);
+			throw new Error(`Failed to lock DB file "${this.lockfileName}"!`);
 		}
 
 		// If the application crashed previously, try to recover from it
@@ -784,8 +795,8 @@ export class JsonlDB<V extends unknown = unknown> {
 
 		// Free the lock
 		try {
-			if (await lockfile.check(this.filename, { realpath: false }))
-				await lockfile.unlock(this.filename, { realpath: false });
+			if (await lockfile.check(this.lockfileName, { realpath: false }))
+				await lockfile.unlock(this.lockfileName, { realpath: false });
 		} catch {
 			// whatever - just don't crash
 		}