indexer-service: Add /subgraphs/health/:deployment route

packages/indexer-service/src/server/deployment-health.ts

@@ -0,0 +1,89 @@
+import fetch from 'cross-fetch'
+import { Router } from 'express'
+
+export interface DeploymentHealthServerOptions {
+  graphNodeStatusEndpoint: string
+}
+
+export const createDeploymentHealthServer = ({
+  graphNodeStatusEndpoint,
+}: DeploymentHealthServerOptions): Router => {
+  const router = Router()
+
+  // This route returns an HTTP 200 response if the deployment in question
+  // has not failed and is caught up with the chain head; otherwise an
+  // HTTP 500 is returned
+  router.get('/:deployment', async (req, res) => {
+    // Query indexing status for this particular deployment
+    const response = await fetch(graphNodeStatusEndpoint, {
+      method: 'POST',
+      headers: {
+        'content-type': 'application/json',
+      },
+      body: JSON.stringify({
+        query: `query indexingStatus($subgraphs: [String!]!) {
+{
+  indexingStatuses(subgraphs: $subgraphs) {
+    health
+    chains {
+      network
+      ... on EthereumIndexingStatus {
+        latestBlock { number hash }
+        chainHeadBlock { number hash }
+      }
+    }
+  }
+}`,
+        variables: {
+          subgraphs: [req.params.deployment],
+        },
+      }),
+    })
+
+    // We couldn't get a good HTTP response from Graph Node
+    if (!response.ok) {
+      return res.status(500).send('Unknown error')
+    }
+
+    // Assert that we got JSON back
+    let data
+    try {
+      data = await response.json()
+    } catch (err) {
+      return res.status(500).send('Malformatted indexing status')
+    }
+
+    // Assert that we got a valid indexing status back
+    if (
+      !data.data ||
+      data.errors ||
+      !data.data.indexingStatuses ||
+      !Array.isArray(data.data.indexingStatuses) ||
+      data.data.indexingStatuses.length < 1
+    ) {
+      return res.status(500).send('Invalid indexing status')
+    }
+
+    // We can safely access this, thanks to the previous check
+    const status = data.data.indexingStatuses[0]
+
+    if (status.health === 'failed') {
+      return res.status(500).send('Subgraph deployment has failed')
+    }
+
+    const latestBlock = status.chains[0]?.latestBlock
+    const headBlock = status.chains[0]?.chainHeadBlock
+
+    // Check whether the subgraph is caught up with the chain head
+    if (
+      latestBlock?.number === headBlock?.number &&
+      latestBlock?.hash === headBlock?.hash
+    ) {
+      return res.status(200).send('Subgraph deployment is up to date')
+    } else {
+      return res.status(500).send('Subgraph deployment is lagging behind')
+    }
+  })
+
+  return router
+}

packages/indexer-service/src/server/index.ts

@@ -5,6 +5,7 @@ import morgan from 'morgan'
 import { Stream } from 'stream'
 import { QueryProcessor } from '../types'
 import { createStatusServer } from './status'
+import { createDeploymentHealthServer } from './deployment-health'
 import {
   Logger,
   Metrics,
@@ -178,6 +179,13 @@ export const createApp = async ({
     await createStatusServer({ graphNodeStatusEndpoint }),
   )
 
+  // Endpoint for subgraph health checks
+  app.use(
+    '/subgraphs/health',
+    slowLimiter,
+    createDeploymentHealthServer({ graphNodeStatusEndpoint }),
+  )
+
   // Endpoint for the public cost API
   app.use(
     '/cost',