Merge pull request #70 from CodeForPhilly/feat/hot-reload-webhook

feat(api): hot-reload webhook for the public data branch

Author: themightychris

apps/api/src/app.ts

@@ -53,6 +53,7 @@ import { helpWantedRoutes } from './routes/projects-help-wanted.js';
 import { projectMembershipRoutes } from './routes/projects-members.js';
 import { previewRoutes } from './routes/preview.js';
 import { samlRoutes } from './routes/saml.js';
+import { internalRoutes } from './routes/internal.js';
 
 declare module 'fastify' {
   interface FastifyInstance {
@@ -174,6 +175,7 @@ export async function buildApp(opts: BuildAppOptions = {}): Promise<FastifyInsta
   await fastify.register(projectMembershipRoutes);
   await fastify.register(previewRoutes);
   await fastify.register(samlRoutes);
+  await fastify.register(internalRoutes);
 
   // Serve the OpenAPI JSON at the spec-mandated path /api/_openapi.json
   // (swagger-ui also exposes it at /api/_docs/json, but the spec names this path)

apps/api/src/env.ts

@@ -17,6 +17,13 @@ export const EnvSchema = z.object({
   CFP_DATA_REMOTE: z.string().optional(),
   /** Branch the push daemon pushes to. Defaults to the repo's current HEAD. */
   CFP_DATA_BRANCH: z.string().optional(),
+  /**
+   * Shared bearer-token secret for the `POST /api/_internal/reload-data`
+   * webhook (see specs/behaviors/storage.md#hot-reload). When unset, the
+   * route is still registered but responds 503 — hot-reload is opt-in per
+   * environment via the sealed Secret in the GitOps repo.
+   */
+  CFP_DATA_RELOAD_SECRET: z.string().min(32).optional(),
   /** Which private-storage backend to use. */
   STORAGE_BACKEND: z.enum(['s3', 'filesystem']),
   /** Filesystem backend: absolute path to the private-storage directory. */
@@ -73,6 +80,7 @@ export const envJsonSchema = {
     CFP_DATA_REPO_PATH: { type: 'string' },
     CFP_DATA_REMOTE: { type: 'string' },
     CFP_DATA_BRANCH: { type: 'string' },
+    CFP_DATA_RELOAD_SECRET: { type: 'string', minLength: 32 },
     STORAGE_BACKEND: { type: 'string', enum: ['s3', 'filesystem'] },
     CFP_PRIVATE_STORAGE_PATH: { type: 'string' },
     S3_ENDPOINT: { type: 'string' },

apps/api/src/routes/internal.ts

@@ -0,0 +1,262 @@
+/**
+ * Internal-only routes.
+ *
+ * Currently houses the hot-reload webhook documented in
+ * `specs/behaviors/storage.md#hot-reload`:
+ *
+ *   POST /api/_internal/reload-data
+ *     - Hidden from the public OpenAPI doc (`schema.hide: true`)
+ *     - Auth: `Authorization: Bearer <CFP_DATA_RELOAD_SECRET>` —
+ *       constant-time compare, length-checked first to avoid a different
+ *       early-exit timing side channel
+ *     - Body: optional `{ branch?: string, commitHash?: string }`
+ *     - Behavior:
+ *         1. If `commitHash` is given AND already an ancestor of local
+ *            HEAD, return 200 noChanges without touching the lock or
+ *            the network (handles self-trigger from push-daemon pushes).
+ *         2. Otherwise call `fastify.reconcileDataRepo({ branch })`
+ *            under the data-repo lock.
+ *         3. If outcome === 'in-sync', skip the rebuild and return
+ *            200 noChanges.
+ *         4. Otherwise rebuild the in-memory state + FTS index in place,
+ *            invalidate the facet cache, and return 200 with
+ *            `rebuilt: true`.
+ *
+ * The route is registered unconditionally — when `CFP_DATA_RELOAD_SECRET`
+ * is unset, requests get a 503 at request time. This keeps the
+ * deployment surface stable across environments that haven't been
+ * configured for hot reloads yet.
+ */
+import { execFile } from 'node:child_process';
+import { timingSafeEqual } from 'node:crypto';
+import { promisify } from 'node:util';
+
+import type { FastifyInstance } from 'fastify';
+
+import { errorResponse, ok } from '../lib/response.js';
+import { reloadInMemoryStateAndFts } from '../store/memory/reload.js';
+import type { ReconcileOutcome } from '../store/reconcile.js';
+
+const exec = promisify(execFile);
+
+/** Bearer-token regex — case-insensitive, single whitespace separator. */
+const BEARER_RE = /^Bearer\s+(\S+)$/i;
+
+/**
+ * Constant-time comparison of two strings. Returns false (without
+ * decoding) when the lengths differ — comparing length is its own early
+ * exit, but a length mismatch tells the attacker only the secret's
+ * length, which we accept as a cheaper-than-real-world side channel.
+ */
+function safeEqualStrings(a: string, b: string): boolean {
+  if (a.length !== b.length) return false;
+  const ab = Buffer.from(a, 'utf8');
+  const bb = Buffer.from(b, 'utf8');
+  // Buffer.from('utf8') for ASCII tokens has length === string length,
+  // so the lengths still match; defensive guard anyway.
+  if (ab.length !== bb.length) return false;
+  return timingSafeEqual(ab, bb);
+}
+
+interface ReloadBody {
+  readonly branch?: string;
+  readonly commitHash?: string;
+}
+
+const reloadBodySchema = {
+  type: 'object',
+  additionalProperties: false,
+  properties: {
+    branch: { type: 'string', minLength: 1, maxLength: 200 },
+    commitHash: {
+      type: 'string',
+      // git supports abbreviated SHAs; allow 4-40 hex chars
+      pattern: '^[0-9a-fA-F]{4,40}$',
+    },
+  },
+} as const;
+
+export async function internalRoutes(fastify: FastifyInstance): Promise<void> {
+  fastify.post<{ Body: ReloadBody | undefined }>(
+    '/api/_internal/reload-data',
+    {
+      schema: {
+        hide: true,
+        body: reloadBodySchema,
+      },
+    },
+    async (request, reply) => {
+      const traceId = (request as typeof request & { traceId?: string }).traceId;
+      const expected = fastify.config.CFP_DATA_RELOAD_SECRET;
+
+      // ---- Bearer auth (route refuses to do anything before this passes) ----
+      const headerValue = request.headers['authorization'];
+      const headerStr = Array.isArray(headerValue) ? headerValue[0] : headerValue;
+      const match = typeof headerStr === 'string' ? BEARER_RE.exec(headerStr) : null;
+      const provided = match?.[1];
+
+      if (!provided) {
+        return reply
+          .code(401)
+          .send(errorResponse('unauthorized', 'Authentication required', traceId));
+      }
+
+      // 503 takes precedence over a token-match check ONLY when the
+      // operator hasn't even configured the secret. We still return 401
+      // on a missing/empty header BEFORE checking the secret so that
+      // unauthenticated probes don't get a different status code
+      // depending on whether the env var is set. Order matters: header
+      // present → check secret configured → check token equality.
+      if (!expected) {
+        return reply.code(503).send(
+          errorResponse(
+            'service_unavailable',
+            'hot-reload not configured',
+            traceId,
+          ),
+        );
+      }
+
+      if (!safeEqualStrings(provided, expected)) {
+        return reply
+          .code(401)
+          .send(errorResponse('unauthorized', 'Authentication required', traceId));
+      }
+
+      // ---- Resolve effective branch ----
+      const body: ReloadBody = request.body ?? {};
+      const branch = body.branch ?? fastify.config.CFP_DATA_BRANCH;
+      if (!branch) {
+        return reply
+          .code(400)
+          .send(
+            errorResponse(
+              'bad_request',
+              'branch is required when CFP_DATA_BRANCH is unset',
+              traceId,
+            ),
+          );
+      }
+
+      const startedAt = Date.now();
+      const repoPath = fastify.config.CFP_DATA_REPO_PATH;
+      const commitHash = body.commitHash;
+
+      // ---- Cheap pre-check: is `commitHash` already in local HEAD? ----
+      // No lock acquired here — `merge-base --is-ancestor` only reads
+      // git's object store, which is safe alongside an in-flight
+      // gitsheets transact. Worst case (a transact lands between this
+      // check and the answer being read) we accept a stale "no" and
+      // proceed to the full reconcile.
+      if (commitHash) {
+        try {
+          const head = (
+            await exec('git', ['rev-parse', 'HEAD'], { cwd: repoPath })
+          ).stdout.trim();
+          await exec(
+            'git',
+            ['merge-base', '--is-ancestor', commitHash, head],
+            { cwd: repoPath },
+          );
+          // `git merge-base --is-ancestor` exits 0 = is-ancestor, 1 = not.
+          // Reaching here means exit 0; short-circuit.
+          fastify.log.info(
+            { branch, commitHash, head },
+            'hot-reload short-circuit: commit already in local HEAD',
+          );
+          return reply.send(
+            ok({
+              noChanges: true,
+              outcome: 'in-sync' as ReconcileOutcome,
+              head,
+              durationMs: Date.now() - startedAt,
+            }),
+          );
+        } catch (err) {
+          // exec throws with `code: 1` when not-ancestor (continue to
+          // reconcile) and with other codes when the commit is unknown
+          // or git itself fails. We treat all non-zero as "fall through
+          // to reconcile" — the reconcile will fetch and try again.
+          fastify.log.debug(
+            {
+              err: err instanceof Error ? err.message : String(err),
+              branch,
+              commitHash,
+            },
+            'hot-reload pre-check fell through to full reconcile',
+          );
+        }
+      }
+
+      // ---- Reconcile under the data-repo lock ----
+      const result = await fastify.reconcileDataRepo({ branch });
+
+      if (result.outcome === 'in-sync') {
+        fastify.log.info(
+          { branch, commit: result.newCommit, outcome: result.outcome },
+          'hot-reload: nothing to do (in-sync after fetch)',
+        );
+        return reply.send(
+          ok({
+            noChanges: true,
+            outcome: result.outcome,
+            oldCommit: result.oldCommit,
+            newCommit: result.newCommit,
+            durationMs: Date.now() - startedAt,
+          }),
+        );
+      }
+
+      // ---- Rebuild ----
+      try {
+        await reloadInMemoryStateAndFts(fastify);
+      } catch (err) {
+        // The in-memory state + FTS index may be partially mutated.
+        // Log loudly so the operator knows a pod restart is warranted,
+        // then 500 the request.
+        fastify.log.error(
+          {
+            err: err instanceof Error ? err.message : String(err),
+            branch,
+            outcome: result.outcome,
+            oldCommit: result.oldCommit,
+            newCommit: result.newCommit,
+          },
+          'hot-reload: in-memory rebuild failed AFTER reconcile — pod is in an undefined state, restart required',
+        );
+        return reply.code(500).send(
+          errorResponse(
+            'internal_error',
+            'Hot-reload rebuild failed — pod restart required',
+            traceId,
+          ),
+        );
+      }
+
+      const durationMs = Date.now() - startedAt;
+      fastify.log.info(
+        {
+          branch,
+          outcome: result.outcome,
+          oldCommit: result.oldCommit,
+          newCommit: result.newCommit,
+          conflictBranch: result.conflictBranch,
+          durationMs,
+        },
+        'hot-reload: in-memory state + FTS rebuilt',
+      );
+
+      return reply.send(
+        ok({
+          noChanges: false,
+          rebuilt: true,
+          outcome: result.outcome,
+          oldCommit: result.oldCommit,
+          newCommit: result.newCommit,
+          ...(result.conflictBranch ? { conflictBranch: result.conflictBranch } : {}),
+          durationMs,
+        }),
+      );
+    },
+  );
+}