peek at docs without fetching from mongo

services/document-updater/app.js

@@ -53,6 +53,7 @@ app.param('doc_id', (req, res, next, docId) => {
 })
 
 app.get('/project/:project_id/doc/:doc_id', HttpController.getDoc)
+app.get('/project/:project_id/doc/:doc_id/peek', HttpController.peekDoc)
 // temporarily keep the GET method for backwards compatibility
 app.get('/project/:project_id/doc', HttpController.getProjectDocsAndFlushIfOld)
 // will migrate to the POST method of get_and_flush_if_old instead

services/document-updater/app/js/HttpController.js

@@ -1,6 +1,7 @@
 const DocumentManager = require('./DocumentManager')
 const HistoryManager = require('./HistoryManager')
 const ProjectManager = require('./ProjectManager')
+const RedisManager = require('./RedisManager')
 const Errors = require('./Errors')
 const logger = require('logger-sharelatex')
 const Settings = require('@overleaf/settings')
@@ -11,6 +12,7 @@ const async = require('async')
 
 module.exports = {
   getDoc,
+  peekDoc,
   getProjectDocsAndFlushIfOld,
   clearProjectState,
   setDoc,
@@ -65,6 +67,22 @@ function getDoc(req, res, next) {
   )
 }
 
+// return the doc from redis if present, but don't load it from mongo
+function peekDoc(req, res, next) {
+  const docId = req.params.doc_id
+  const projectId = req.params.project_id
+  logger.log({ projectId, docId }, 'peeking at doc via http')
+  RedisManager.getDoc(projectId, docId, function (error, lines, version) {
+    if (error) {
+      return next(error)
+    }
+    if (lines == null || version == null) {
+      return next(new Errors.NotFoundError('document not found'))
+    }
+    res.json({ id: docId, lines, version })
+  })
+}
+
 function _getTotalSizeOfLines(lines) {
   let size = 0
   for (const line of lines) {

services/document-updater/test/unit/js/HttpController/HttpControllerTests.js

@@ -14,6 +14,7 @@ describe('HttpController', function () {
         './ProjectManager': (this.ProjectManager = {}),
         './ProjectFlusher': { flushAllProjects() {} },
         './DeleteQueueManager': (this.DeleteQueueManager = {}),
+        './RedisManager': (this.RedisManager = {}),
         './Metrics': (this.Metrics = {}),
         './Errors': Errors,
       },