feat: ability to specify cache-control headers for v2 proxied paths

Author: zone117x

.proxy-cache-control.json

@@ -0,0 +1,11 @@
+{
+  "paths": {
+    // Examples of common paths -- default is to not set a cache-control value (null).
+    // They can be set to cache with a lifetime e.g. "public, max-age=150"
+    "^/v2/info(.*)": null,
+    "^/v2/pox(.*)": null,
+    "^/v2/contracts/call-read(.*)": null,
+    "^/v2/map_entry(.*)": null,
+    "^/v2(.*)": null
+  }
+}

package-lock.json

@@ -106,6 +106,7 @@
     "bluebird": "^3.7.2",
     "bn.js": "^4.11.8",
     "c32check": "^1.1.2",
+    "chokidar": "^3.5.1",
     "coinselect": "^3.1.12",
     "compression": "^1.7.4",
     "cors": "^2.8.5",
@@ -117,6 +118,7 @@
     "express-list-endpoints": "^5.0.0",
     "express-winston": "^4.0.3",
     "http-proxy-middleware": "^1.0.6",
+    "jsonc-parser": "^3.0.0",
     "jsonrpc-lite": "^2.1.0",
     "node-fetch": "^2.6.0",
     "node-pg-migrate": "^4.2.3",

package.json

@@ -2,8 +2,11 @@ import * as express from 'express';
 import * as cors from 'cors';
 import { createProxyMiddleware, Options } from 'http-proxy-middleware';
 import { logger, parsePort } from '../../helpers';
-import { Agent, IncomingMessage } from 'http';
+import { Agent } from 'http';
+import * as fs from 'fs';
 import { addAsync } from '@awaitjs/express';
+import * as chokidar from 'chokidar';
+import * as jsoncParser from 'jsonc-parser';
 
 export const V2_POX_MIN_AMOUNT_USTX_ENV_VAR = 'V2_POX_MIN_AMOUNT_USTX';
 
@@ -40,6 +43,40 @@ export function createCoreNodeRpcProxyRouter(): express.Router {
     maxTotalSockets: 400,
   });
 
+  const PROXY_CACHE_CONTROL_FILE = '.proxy-cache-control.json';
+  const cacheControlFileWatcher = chokidar.watch(PROXY_CACHE_CONTROL_FILE);
+  let pathCacheOptions = new Map<RegExp, string | null>();
+
+  const updatePathCacheOptions = () => {
+    try {
+      const configContent: { paths: Record<string, string> } = jsoncParser.parse(
+        fs.readFileSync(PROXY_CACHE_CONTROL_FILE, 'utf8')
+      );
+      pathCacheOptions = new Map(
+        Object.entries(configContent.paths).map(([k, v]) => [RegExp(k), v])
+      );
+    } catch (error) {
+      pathCacheOptions.clear();
+      logger.error(`Error reading changes from ${PROXY_CACHE_CONTROL_FILE}`, error);
+    }
+  };
+  updatePathCacheOptions();
+  cacheControlFileWatcher.on('all', (eventName, path, stats) => {
+    updatePathCacheOptions();
+  });
+
+  const getCacheControlHeader = (statusCode: number, url: string): string | null => {
+    if (statusCode < 200 || statusCode > 299) {
+      return null;
+    }
+    for (const [regexp, cacheControl] of pathCacheOptions.entries()) {
+      if (cacheControl && regexp.test(url)) {
+        return cacheControl;
+      }
+    }
+    return null;
+  };
+
   router.getAsync('/pox', async (req, res, next) => {
     const overrideVal = getPoxOverride();
     if (!overrideVal) {
@@ -48,12 +85,16 @@ export function createCoreNodeRpcProxyRouter(): express.Router {
     }
     logger.info(`Overriding /v2/pox 'min_amount_ustx' with ${overrideVal}`);
     const poxRes = await fetch(`http://${stacksNodeRpcEndpoint}${req.originalUrl}`);
-    res.setHeader('content-type', poxRes.headers.get('content-type') as string);
+    res.header('content-type', poxRes.headers.get('content-type') as string);
     res.status(poxRes.status);
     const poxResString = await poxRes.text();
     try {
       const resJson: { min_amount_ustx: number } = JSON.parse(poxResString);
       resJson.min_amount_ustx = overrideVal;
+      const header = getCacheControlHeader(res.statusCode, req.originalUrl);
+      if (header) {
+        res.header('Cache-Control', header);
+      }
       res.json(resJson);
     } catch (error) {
       res.send(poxResString);
@@ -64,6 +105,12 @@ export function createCoreNodeRpcProxyRouter(): express.Router {
     agent: httpAgent,
     target: `http://${stacksNodeRpcEndpoint}`,
     changeOrigin: true,
+    onProxyRes: (proxyRes, req, res) => {
+      const header = getCacheControlHeader(res.statusCode, req.url);
+      if (header) {
+        proxyRes.headers['Cache-Control'] = header;
+      }
+    },
     onError: (error, req, res) => {
       const msg =
         (error as any).code === 'ECONNREFUSED'