feat(zbugs-swift): a backend that keeps its database across restarts

server.ts recreates the database on every start and signs tokens with new
keys, so each restart sends every app that synced back to an empty store and
logs it out. With ZBUGS_KEEP=1 it keeps the database (where zero-cache keeps
the client groups), the replica, and the keys in ZBUGS_DIR, and seeds only a
database that doesn't exist yet.

Amp-Thread-ID: https://ampcode.com/threads/T-01a1557f-dff8-761e-ad04-7fc6c1bd83db
Co-authored-by: Amp <amp@ampcode.com>

Author: tmm

apps/zbugs-swift/README.md

@@ -25,6 +25,19 @@ ZBUGS_PG=postgresql://user:password@127.0.0.1:6434/postgres \
 It recreates the `zbugs_swift` database with zbugs' seed data, then prints a
 token for a crew user and `ready <zero-cache> <API>` (ports 4848 and 5173).
 
+Each start makes new signing keys and a new database, so an app that ran
+against the last one needs the new token and starts over from an empty local
+store. To keep both across restarts, set `ZBUGS_KEEP=1` and a directory for
+the replica and the keys:
+
+```sh
+ZBUGS_KEEP=1 ZBUGS_DIR=~/.zbugs-swift ZBUGS_PG=... \
+  node apps/zbugs-swift/server/server.ts
+```
+
+It seeds the database only when it doesn't exist; drop it, or run once
+without `ZBUGS_KEEP`, to start over.
+
 Then generate the Xcode project and run the `ZBugsApp` scheme on a Mac or an
 iOS simulator:
 

apps/zbugs-swift/server/server.ts

@@ -2,7 +2,9 @@
  * Runs zbugs' backend for the Swift app, in development and in the
  * end-to-end tests: a fresh Postgres database with zbugs' migrations and
  * seed data, zbugs' API server (apps/zbugs/api), and zero-cache, all from
- * this repository's sources.
+ * this repository's sources. With `ZBUGS_KEEP=1` it keeps the database, the
+ * replica, and its signing keys from the last run instead, so an app keeps
+ * its local data and its token across restarts.
  *
  *   node apps/zbugs-swift/server/server.ts
  *
@@ -22,9 +24,18 @@
  *   ZBUGS_PORT       zero-cache port (default 4848)
  *   ZBUGS_API_PORT   API server port (default 5173)
  *   ZBUGS_DIR        working directory for the replica (default a temp dir)
+ *   ZBUGS_KEEP       1 to keep the last run's database, and the replica and
+ *                    keys in ZBUGS_DIR, which it needs
  */
 import {execFileSync, spawn} from 'node:child_process';
-import {mkdtempSync, readdirSync} from 'node:fs';
+import {
+  existsSync,
+  mkdtempSync,
+  readFileSync,
+  readdirSync,
+  rmSync,
+  writeFileSync,
+} from 'node:fs';
 import {registerHooks} from 'node:module';
 import {networkInterfaces, tmpdir} from 'node:os';
 import {join} from 'node:path';
@@ -42,6 +53,13 @@ const localHost = everywhere ? '127.0.0.1' : host;
 const port = Number(env['ZBUGS_PORT'] ?? 4848);
 const apiPort = Number(env['ZBUGS_API_PORT'] ?? 5173);
 const workDir = env['ZBUGS_DIR'] ?? mkdtempSync(join(tmpdir(), 'zbugs-swift-'));
+const keep = env['ZBUGS_KEEP'] === '1';
+if (keep && !env['ZBUGS_DIR']) {
+  process.stderr.write(
+    'ZBUGS_KEEP needs ZBUGS_DIR, for the replica and keys\n',
+  );
+  process.exit(2);
+}
 
 const here = (path: string) => fileURLToPath(new URL(path, import.meta.url));
 const zbugs = here('../../zbugs/');
@@ -77,29 +95,43 @@ function psql(url: string, ...args: string[]) {
   });
 }
 
-// The database: zbugs' migrations, then its seed script.
-psql(adminURL, '-c', `DROP DATABASE IF EXISTS ${dbName} WITH (FORCE)`);
-psql(adminURL, '-c', `CREATE DATABASE ${dbName}`);
-const migrations = join(zbugs, 'db/migrations');
-for (const file of readdirSync(migrations)
-  .filter(f => f.endsWith('.sql'))
-  .sort()) {
-  // In a transaction each, as drizzle-kit applies them.
-  psql(upstreamURL, '--single-transaction', '-f', join(migrations, file));
+// The database: zbugs' migrations, then its seed script. Kept, it also
+// holds zero-cache's client groups, which an app's local data belongs to.
+const kept =
+  keep &&
+  execFileSync(
+    'psql',
+    [adminURL, '-tAc', `SELECT 1 FROM pg_database WHERE datname = '${dbName}'`],
+    {encoding: 'utf8'},
+  ).trim() === '1';
+if (!kept) {
+  psql(adminURL, '-c', `DROP DATABASE IF EXISTS ${dbName} WITH (FORCE)`);
+  psql(adminURL, '-c', `CREATE DATABASE ${dbName}`);
+  const migrations = join(zbugs, 'db/migrations');
+  for (const file of readdirSync(migrations)
+    .filter(f => f.endsWith('.sql'))
+    .sort()) {
+    // In a transaction each, as drizzle-kit applies them.
+    psql(upstreamURL, '--single-transaction', '-f', join(migrations, file));
+  }
+  execFileSync(process.execPath, [join(zbugs, 'scripts/seed.ts')], {
+    cwd: zbugs,
+    stdio: ['ignore', 'ignore', 'inherit'],
+    env: {
+      ...env,
+      ['ZERO_UPSTREAM_DB']: upstreamURL,
+      ['ZERO_SEED_DATA_DIR']: join(
+        zbugs,
+        'db/seed-data',
+        env['ZBUGS_SEED'] ?? 'github',
+      ),
+    },
+  });
+  // A replica of an earlier database.
+  for (const file of readdirSync(workDir)) {
+    if (file.startsWith('replica.db')) rmSync(join(workDir, file));
+  }
 }
-execFileSync(process.execPath, [join(zbugs, 'scripts/seed.ts')], {
-  cwd: zbugs,
-  stdio: ['ignore', 'ignore', 'inherit'],
-  env: {
-    ...env,
-    ['ZERO_UPSTREAM_DB']: upstreamURL,
-    ['ZERO_SEED_DATA_DIR']: join(
-      zbugs,
-      'db/seed-data',
-      env['ZBUGS_SEED'] ?? 'github',
-    ),
-  },
-});
 const crewID = execFileSync(
   'psql',
   [
@@ -110,8 +142,18 @@ const crewID = execFileSync(
   {encoding: 'utf8'},
 ).trim();
 
-// The API server, as `pnpm dev` runs it in apps/zbugs, with keys of its own.
-const {privateJwk, publicJwk} = await createJwkPair();
+// The API server, as `pnpm dev` runs it in apps/zbugs, with keys of its own:
+// the last run's, kept, so that the tokens it printed still work.
+const keysFile = join(workDir, 'keys.json');
+const {privateJwk, publicJwk} =
+  keep && existsSync(keysFile)
+    ? (JSON.parse(readFileSync(keysFile, 'utf8')) as Awaited<
+        ReturnType<typeof createJwkPair>
+      >)
+    : await createJwkPair();
+if (keep) {
+  writeFileSync(keysFile, JSON.stringify({privateJwk, publicJwk}));
+}
 env['ZERO_UPSTREAM_DB'] = upstreamURL;
 env['PRIVATE_JWK'] = JSON.stringify(privateJwk);
 env['VITE_PUBLIC_JWK'] = JSON.stringify(publicJwk);