feat: prometheus metrics for time_since_last_pending_block_proposal_ms

src/api/routes/prom-metrics.ts

@@ -16,6 +16,19 @@ export const SignerPromMetricsRoutes: FastifyPluginAsync<
 
   const signerRegistry = new Registry();
 
+  new Gauge({
+    name: 'time_since_last_pending_block_proposal_ms',
+    help: 'Time in milliseconds since the oldest pending block proposal',
+    registers: [signerRegistry],
+    async collect() {
+      const dbResult = await db.sqlTransaction(async sql => {
+        return await db.getLastPendingProposalDate({ sql });
+      });
+      this.reset();
+      this.set(dbResult ? Date.now() - dbResult.getTime() : 0);
+    },
+  });
+
   new Gauge({
     name: 'avg_block_push_time_ms',
     help: 'Average time (in milliseconds) taken for block proposals to be accepted and pushed over different block periods',

src/pg/pg-store.ts

@@ -1059,4 +1059,33 @@ export class PgStore extends BasePgStore {
     `;
     return result;
   }
+
+  async getLastPendingProposalDate(args: { sql: PgSqlClient }) {
+    const result = await args.sql<
+      {
+        received_at: Date | null;
+      }[]
+    >`
+      WITH last_confirmed_height AS (
+        SELECT GREATEST(
+          COALESCE(MAX(b.block_height), 0),
+          COALESCE(MAX(bp.block_height), 0)
+        ) AS height
+        FROM blocks b
+        LEFT JOIN block_pushes bp ON true
+      ),
+      oldest_pending_proposal AS (
+        SELECT received_at
+        FROM block_proposals bp
+        WHERE bp.block_height > (SELECT height FROM last_confirmed_height)
+        ORDER BY received_at ASC
+        LIMIT 1
+      )
+      SELECT received_at
+      FROM oldest_pending_proposal
+    `;
+
+    // Return the computed value or null if no pending proposals exist
+    return result.length > 0 ? result[0].received_at : null;
+  }
 }

tests/db/endpoints.test.ts

@@ -95,6 +95,17 @@ describe('Endpoint tests', () => {
     ENV.reload();
     const blockRanges = ENV[bucketsEnvName].split(',').map(Number);
 
+    // Delete from confirmed blocks tables to ensure there is a pending block_proposal
+    const [{ block_height }] = await db.sql<
+      { block_height: number }[]
+    >`SELECT block_height FROM block_proposals ORDER BY block_height DESC LIMIT 1`;
+    await db.sql`DELETE FROM blocks WHERE block_height >= ${block_height}`;
+    await db.sql`DELETE FROM block_pushes WHERE block_height >= ${block_height}`;
+
+    const pendingProposalDate = await db.getLastPendingProposalDate({ sql: db.sql });
+    expect(pendingProposalDate).toBeInstanceOf(Date);
+    expect(new Date().getTime() - pendingProposalDate!.getTime()).toBeGreaterThan(0);
+
     const dbPushMetricsResult = await db.getRecentBlockPushMetrics({ sql: db.sql, blockRanges });
     expect(dbPushMetricsResult).toEqual([
       { block_range: 1, avg_push_time_ms: 27262 },
@@ -143,6 +154,10 @@ describe('Endpoint tests', () => {
       .expect(200);
     const receivedLines = responseTest.text.split('\n');
 
+    const expectedPendingProposalLineRegex =
+      /# TYPE time_since_last_pending_block_proposal_ms gauge\ntime_since_last_pending_block_proposal_ms [1-9]\d*/;
+    expect(responseTest.text).toMatch(expectedPendingProposalLineRegex);
+
     const expectedPushTimeLines = `# TYPE avg_block_push_time_ms gauge
 avg_block_push_time_ms{period="1"} 27262
 avg_block_push_time_ms{period="2"} 30435.5