When the database is empty, using the ‘createReadStream’ method, no event is triggered

[xupengkun]

db.createReadStream()
  .on('data', function (data) {
    console.log(data.key, '=', data.value)
  })
  .on('error', function (err) {
    console.log('Oh my!', err)
  })
  .on('close', function () {
    console.log('Stream closed')
  })
  .on('end', function () {
    console.log('Stream ended')
  })

tip: db database is empty

  .on('end', function () {
    console.log('Stream ended')
  })

event is not trigger

[vweevers]

Can you post a full example, including require statements and creating the db?

Because with the following code I cannot replicate:

const level = require('level')
const db = level('test')

db.createReadStream()
  .resume()
  .on('end', function () {
    console.log('ok')
  })

[xupengkun]

@vweevers Thanks

const level = electron.remote.require('level');
const DB = level('./myDB');

DB.createValueStream({})
          .on('data', function (data) {
            console.log('level-data----------');
          })
          .on('end', function () {
            console.log('level-end----------');
          })
          .on('error', function (err) {
            console.error(err, '----------get-level-err');
          })
          .on('close', function () {
            console.error('level-close----------');
          });

maybe because I did not use .resume() ?

[vweevers]

Attaching a data event listener has the same effect as .resume(), so that's not it.

What does electron.remote.require() do? Where is this code running?

[xupengkun]

I started a local service in electron, so I will use this method to introduce the library

"electron": "^5.0.4",
 "level": "^6.0.0",

Insert can be used normally, and ‘createValueStream’ method can be used normally when there is data in the database

[vweevers]

Could you share a repository or gist that I can clone + install + run, to replicate?

[xupengkun]

Sorry, this is an internal project, but I can give you the code related to the warehouse

[xupengkun]

const electron = require('electron'); const level = electron.remote.require('level');

const path = electron.remote.require('path'); const userData = electron.remote.app.getPath('userData'); export default class Tool { constructor() { this.SetStaticDBPath(); };

USERPATH = ''; DBPATH = ''; DBDIR = ''; DBPath = '';

DBMap = {};

SetStaticDBPath = (pathName = 'default') => { this.USERPATH = pathName; this.DBPATH = 'DBDIR' + '/' + this.USERPATH; this.DBDIR = path.join(userData, this.DBPATH); this.DBPath = path.join(this.DBDIR, './defaultDB'); this.setDBPath(); this.CheckDBState(); }; setDBPath = () => { $BG.pathMap.setPath('DBDIR', this.DBDIR); }; CreateDB = (DBName) => { let DB; try { DB = level(path.join(this.DBDIR, './', DBName)); } catch (e) { console.log(e); } this.DBMap[DBName] = DB; window.onbeforeunload = () => { Object.keys(this.DBMap).map((item) => { this.DBMap[item].close(); }); }; return DB; }; Clear = (DBName) => { if (!this.DBMap.hasOwnProperty(DBName)) this.CreateDB(DBName); return new Promise((resolve, reject) => { this.DBMap[DBName].clear(() => { resolve(); }); }); }; CheckDBState = () => { if (!this.DBMap.hasOwnProperty('MsgDB')) this.CreateDB('MsgDB'); if (!this.DBMap.hasOwnProperty('LinkDB')) this.CreateDB('LinkDB'); }; PutHandle = (chatId, data) => { this.CheckDBState(); const MsgDBKey = data.id; const LinkDBKey = chatId + '' + data.time + '' + MsgDBKey; return Promise.all([ this.HandleMsgDB([{ type: 'put', key: MsgDBKey, value: JSON.stringify(data) }]), this.HandleLinkDB([{ type: 'put', key: LinkDBKey, value: MsgDBKey }]) ]); }; DeleteHandle = (msgId) => { return this.HandleMsgDB([{ type: 'del', key: msgId }]); }; HandleLinkDB = (BatchData) => { return new Promise((resolve, reject) => { this.DBMap['LinkDB'].batch(BatchData, (err) => { try { if (err) { reject(err) } else { resolve(); } } catch (e) { reject(e); } }) }) }; HandleMsgDB = (BatchData) => { return new Promise((resolve, reject) => { this.DBMap['MsgDB'].batch(BatchData, (err) => { try { if (err) { reject(err) } else { resolve(); } } catch (e) { reject(e); } }) }) }; GetHandle = async (chatId, params, onProgress = () => {}) => { this.CheckDBState();

const msgIdList = await this.GetMsgIdList( chatId, params );
const msgDataList = await this.GetMsgDataByMsgId(msgIdList);

return msgDataList;

}; GetMsgIdList = (chatId, params) => { const list = []; return new Promise((resolve, reject) => { const searchParams = { limit: params.limit, reverse: params.reverse, keys: false, values: true }; if (params.startTime) searchParams.lte = chatId + '' + params.startTime; if (params.endTime) searchParams.gte = chatId + '' + params.endTime; try { this.DBMap['LinkDB'].createValueStream(searchParams) .on('data', function (data) { console.log('level-data----------'); list.push(data); }) .on('end', function () { console.log('level-end----------'); resolve(list); }) .on('error', function (err) { console.error(err, '----------get-level-err'); reject(err); }) .on('close', function () { console.error('level-close----------'); reject(); }); } catch (e) { console.log(e); }

})

}; GetMsgDataByMsgId = (msgIdList) => { return Promise.all(msgIdList.map((item) => { return this.GetItemByKey(item); })); }; GetItemByKey = (key = '') => { if (key) { return new Promise((resolve, reject) => { this.DBMap['MsgDB'].get(key, { asBuffer: false }, (err, val) => { try { if (err) { reject(err); } else { resolve(val && JSON.parse(val)); } } catch (e) { reject(e); } }); }); } else { return Promise.resolve(); } } }

[xupengkun]

This is my tool class

[vweevers]

That's not enough to work with, could you please put it in a new repository (or gist) including a package.json and instructions on how to run? You don't have to share private code, just a stripped down version that demonstrates the problem.

[xupengkun]

mmmmmmm When I put it in an empty project, it works again

[xupengkun]

I'm sorry, but I don't know exactly what happened in my code

[vweevers]

If I had to guess, it's something to do with remote.require. I don't know how that works exactly, it somehow makes a module from the main process available to renderer processes?

[xupengkun]

such: The main rendering process of electron renders a webpack service. I write these codes in the webpack folder and then call the method of the main process to get the level.

[xupengkun]

Is it because the code is parsed by webpack?

[vweevers]

Maybe, if webpack is configured to resolve the browser field of package.json in which case level does not use LevelDB as the underlying store, but IndexedDB.

Do you see your db folder (path.join(this.DBDIR, './', DBName)) getting created on disk?

[xupengkun]

yes

[xupengkun]

At the same time, the folder http_localhost_9080.indexeddb.leveldb was added to my disk.

[vweevers]

That suggests it's somehow using both LevelDB and IndexedDB.

At this point though, unless you manage to replicate the issue outside of your project, I'm afraid I can't help any further. We can conclude there's no bug in level.

[xupengkun]

Yes, this is not a bug. This should be my problem. I will close this problem until I can reproduce it in an empty project. All in all, thanks for reminding

[vweevers]

Good luck!