fix: ensure MFS is continually preloaded

License: MIT
Signed-off-by: Alan Shaw <alan@tableflip.io>

src/core/mfs-preload.js

@@ -22,12 +22,14 @@ module.exports = (self, options) => {
       if (rootCid !== stats.hash) {
         log(`preloading updated MFS root ${rootCid} -> ${stats.hash}`)
 
-        self._preload(stats.hash, (err) => {
+        return self._preload(stats.hash, (err) => {
           timeoutId = setTimeout(preloadMfs, options.interval)
           if (err) return log.error(`failed to preload MFS root ${stats.hash}`, err)
           rootCid = stats.hash
         })
       }
+
+      timeoutId = setTimeout(preloadMfs, options.interval)
     })
   }
 

test/core/mfs-preload.spec.js

@@ -0,0 +1,54 @@
+/* eslint max-nested-callbacks: ["error", 8] */
+/* eslint-env mocha */
+'use strict'
+
+const chai = require('chai')
+const dirtyChai = require('dirty-chai')
+const expect = chai.expect
+chai.use(dirtyChai)
+
+const mfsPreload = require('../../src/core/mfs-preload')
+
+const createMockFilesStat = (cids = []) => {
+  let n = 0
+  return (path, cb) => cb(null, { hash: cids[n++] || 'QmHash' })
+}
+
+const createMockPreload = () => {
+  return function preload (cid, cb) {
+    preload.cids = preload.cids || []
+    preload.cids.push(cid)
+    cb()
+  }
+}
+
+describe('MFS preload', () => {
+  it('should preload MFS root periodically', (done) => {
+    // CIDs returned from our mock files.stat function
+    const statCids = ['QmInitial', 'QmSame', 'QmSame', 'QmUpdated']
+    // The CIDs we expect to have been preloaded
+    const expectedPreloadCids = ['QmSame', 'QmUpdated']
+
+    const mockPreload = createMockPreload()
+    const mockFilesStat = createMockFilesStat(statCids)
+    const mockIpfs = { files: { stat: mockFilesStat }, _preload: mockPreload }
+
+    const interval = 10
+    const preloader = mfsPreload(mockIpfs, { interval })
+
+    preloader.start((err) => {
+      expect(err).to.not.exist()
+
+      setTimeout(() => {
+        preloader.stop((err) => {
+          expect(err).to.not.exist()
+          expect(
+            // Slice off any extra CIDs it processed
+            mockPreload.cids.slice(0, expectedPreloadCids.length)
+          ).to.deep.equal(expectedPreloadCids)
+          done()
+        })
+      }, statCids.length * (interval + 5))
+    })
+  })
+})