fix: instrument the number of open outgoing connections (#155)

* fix: instrument the number of open outgoing connections

* fix: add `finally` block to trigger instrumentation on promise settle

src/metrics.ts

@@ -47,6 +47,18 @@ export const ipfsGatewaysReturnCount = new client.Counter({
   labelNames: ['name']
 });
 
+export const countOpenProvidersRequest = new client.Gauge({
+  name: 'providers_open_connections_count',
+  help: 'Number of open connections to providers',
+  labelNames: ['name']
+});
+
+export const countOpenGatewaysRequest = new client.Gauge({
+  name: 'ipfs_gateways_open_connections_count',
+  help: 'Number of open connections to gateways',
+  labelNames: ['name']
+});
+
 export const providersInstrumentation = (req, res, next) => {
   const oldJson = res.json;
   res.json = body => {

src/providers/index.ts

@@ -1,9 +1,9 @@
+import { timeProvidersUpload, providersUploadSize, countOpenProvidersRequest } from '../metrics';
 import * as fleek from './fleek';
 import * as infura from './infura';
 import * as pinata from './pinata';
 import * as web3Storage from './web3storage';
 import * as fourEverland from './4everland';
-import { timeProvidersUpload, providersUploadSize } from '../metrics';
 
 // List of providers used for pinning images
 export const IMAGE_PROVIDERS = ['fleek', 'infura', 'pinata', '4everland'];
@@ -21,12 +21,20 @@ export default function uploadToProviders(providers: string[], params: any) {
   return Promise.any(
     providers.map(async name => {
       const end = timeProvidersUpload.startTimer({ name });
-      const result = await providersMap[name].set(params);
-      end();
 
-      const size = (params instanceof Buffer ? params : Buffer.from(JSON.stringify(params))).length;
-      providersUploadSize.inc({ name }, size);
-      return result;
+      try {
+        countOpenProvidersRequest.inc({ name });
+
+        const result = await providersMap[name].set(params);
+        const size = (params instanceof Buffer ? params : Buffer.from(JSON.stringify(params)))
+          .length;
+        providersUploadSize.inc({ name }, size);
+
+        return result;
+      } finally {
+        end();
+        countOpenProvidersRequest.dec({ name });
+      }
     })
   );
 }

src/proxy.ts

@@ -5,7 +5,11 @@ import { capture } from '@snapshot-labs/snapshot-sentry';
 import gateways from './gateways.json';
 import { set, get } from './aws';
 import { MAX, sha256 } from './utils';
-import { ipfsGatewaysReturnCount, timeIpfsGatewaysResponse } from './metrics';
+import {
+  ipfsGatewaysReturnCount,
+  timeIpfsGatewaysResponse,
+  countOpenGatewaysRequest
+} from './metrics';
 
 const router = express.Router();
 
@@ -18,10 +22,18 @@ router.get('/ipfs/*', async (req, res) => {
     const result = await Promise.any(
       gateways.map(async gateway => {
         const end = timeIpfsGatewaysResponse.startTimer({ name: gateway });
-        const url = `https://${gateway}${req.originalUrl}`;
-        const response = await fetch(url);
-        end();
-        return { gateway, json: await response.json() };
+
+        try {
+          countOpenGatewaysRequest.inc({ name: gateway });
+
+          const url = `https://${gateway}${req.originalUrl}`;
+          const response = await fetch(url);
+
+          return { gateway, json: await response.json() };
+        } finally {
+          end();
+          countOpenGatewaysRequest.dec({ name: gateway });
+        }
       })
     );
     ipfsGatewaysReturnCount.inc({ name: result.gateway });