Can’t get it to work

[gr2m]

Hey @nolanlawson, it took a while, but finally got around to give this a try. Unfortunately something’s not quite working:

const PouchDB = require('pouchdb-core').plugin(require('pouchdb-adapter-fs'))
const db = new PouchDB('test')

db.put({_id: 'test'})

This creates a test.json file withe the content of undefined in it. I guess the problem is in fsdown.

I’m pretty sure the adapter worked when I tested it right after you created it, something must get broken since then. Do you have an idea? Or could you give me pointers for what to look for?

[nolanlawson]

hmmmm sorry I'm not sure off the top of my head why that would happen 😞 . it is very likely a bug in fsdown, yes. the way to know would be to try some alternative *down adapter (e.g. pouchdb-adapter-memory) and see if you get the same problem.

[gr2m]

No worries I’ll look into it :)

[janl]

I did a quick look through things. I think this never worked 😅

I think this was always in-memory, and the tests don’t account for “server restarts”, e.g. reading from the file system again (unless I missed something, it was a quick look).

This should address the issue:

commit f8060022ee1cb5e2ae2063fb4cab34eeea12fa2e
Author: Jan Lehnardt <jan@apache.org>
Date:   Thu Jan 19 17:40:55 2017 +0100

    fix: make data actually persist to disk
    
    Adds `LocalStorageCore.export()` and `import(data)` for loading
    data from a file into memory or dumping the current memory
    contents to a file.
    
    I will need help with tests.

diff --git a/lib/localstorage-core.js b/lib/localstorage-core.js
index d5697a4..e9e213c 100644
--- a/lib/localstorage-core.js
+++ b/lib/localstorage-core.js
@@ -37,7 +37,7 @@ function LocalStorageCore(dbname) {
     dbs.set(dbname, self._db);
     // Read from disk once at startup.
     try {
-      self._db.store = JSON.parse(fs.readFileSync(filename, 'utf-8'));
+      self.import(JSON.parse(fs.readFileSync(filename, 'utf-8')));
     } catch (e) { /* ignore if the file isn't there */ }
     mkdirp.sync(path.dirname(filename));
   }
@@ -45,7 +45,7 @@ function LocalStorageCore(dbname) {
   // Periodically write to disk. Yes this is prone to failure, but this module isn't
   // designed to be bullet-proof.
   self._scheduleWrite = debounce(function () {
-    var json = JSON.stringify(self._db.store);
+    var json = JSON.stringify(self.export());
     fs.writeFile(filename, json, 'utf-8', function (error) {
       if (error) {
         console.log('ERROR: ' + filename + ' could not be written');
@@ -90,6 +90,22 @@ LocalStorageCore.prototype.remove = function (key, callback) {
   });
 };
 
+LocalStorageCore.prototype.import = function (data) {
+  // assert object
+  Object.keys(data).forEach(function (key) {
+    this._db.set(key, data[key]);
+  })
+  return true;
+};
+
+LocalStorageCore.prototype.export = function () {
+  var result = {};
+  this._db.forEach(function (key, value) {
+    result[key] = value;
+  });
+  return result;
+};
+
 LocalStorageCore.destroy = function (dbname, callback) {
   var db = dbs.get(dbname);
   callbackify(callback, function () {

I have a full commit too, just wanna get a +1 on the approach. And I’ll need help with tests.

[gr2m]

Code looks good to me! Could you start a pull request and we discuss there? I’ll do some testing locally

[janl]

@gr2m nolanlawson/fsdown#12

[nolanlawson]

lol, "it never works" is quite possible... 😅 I think I hacked this up on a Saturday when @gr2m and @boennemann were in town.

Good catch, and thanks for the PR!

[gr2m]

@nolanlawson I just found https://github.com/voltraco/level-fsdown – any reason you didn’t use that for the fs adapter for PouchDB?

[nolanlawson]

I didn't know it existed! :/