core asyncstorage and community version

[rogueturnip]

I'm hoping someone could answer my question about a problem I'm seeing.

I'm using aws-amplify which is still using the old react-native core version of asyncstorage. I've moved my app over to using the react-native-community version. When I look at the storage while the app is running both are populating the asyncstorage correctly but when I restart the app only the data from my app using the react-native-community version is still there.

I've tried many things to try to fix this but to no luck. What I'm wondering is if there is a chance of conflict between the two if a module is still using the old version.

Thanks!

[krizzu]

Hi @rogueturnip,

Thanks for bringing this up. Could you provide a repo where the issue is reproducible? Would be helpful in further debugging.

Also, what platform are you seeing this?

thanks

[rogueturnip]

Sorry I don't actually have this in a public repo. The app is private so I can't open it up. The problem only occurs with ios and only with the aws amplify asyncstorage. Android everything works fine.I

Tomorrow I will try adding in the old asyncstorage in my code to add something and see if I get the same issue.

[rogueturnip]

I did a simple test this morning. In my main app code I set up the old AsyncStorage from react-native core along with the new AsyncStorage from react-community. The core one did not persist through an IOS app restart but the react-community one did.

I don't have a repo for you to see this but it's a very simple set up, 2 lines of code with each writing something different to asyncstorage. Still no issues on Android.

[krizzu]

@rogueturnip right. Can you provide some code samples? It's important how you call those two "writings" to AS.

thanks

[rogueturnip]

Hi!

So obviously my code has a bunch more in it but basically I'm calling it like below. My real concern is that is if there is a special way to make these work correctly together that the library "aws-amplify" which uses the old asyncstorage won't work right.

Thanks!

import React, { Component } from 'react';
import { AsyncStorage as oldAS } from 'react-native';
import AsyncStorage from '@react-native-community/async-storage';

class TestApp extends Component {
    constructor(props) {
        super(props);
        oldAS.setItem('oldtest','testing old');
        AsyncStorage.setItem('newtest', 'testing new');
    }

    render() {
        return null;
    }
}

[krizzu]

@rogueturnip .setItem is a asynchronous function. Without waiting for it to finish, you expose yourself for unexpected behavior (such as one you have now).

Try out making those calls wait for results, before going further.

class TestApp extends Component {
    constructor(props) {
        super(props);
		this.saveIt()
    }

	saveIt = async () => {
	    await oldAS.setItem('oldtest','testing old');
        await AsyncStorage.setItem('newtest', 'testing new');
	}
    render() {
        return null;
    }
}

[rogueturnip]

Thanks for that. I tried it with await and it's giving me the same results on ios.

[krizzu]

@rogueturnip you mean it's still an issue for you?

[rogueturnip]

Yes, I'm still having the original AsyncStorage not saving across reloads of the iOS app. it's only iOS. I wanted to point that out in case it's something related to the linking that's causing the issue.

[krizzu]

The implementation of Async Storage (both Comms and core one) for iOS is based on writing/reading from a file. This is the same file for both versions (so during the transition from the core to Community's AS, you won't lose data).

There's this comment left from original authors. This tiny detail is the key to understand the problem.

Each time your app restarts (or you reload the bundle), storage's file is read to the _manifest variable. Each data save/read (setItem/getItem) is done on the _manifest, but once the mutation has finished, its content is saved to the file.

This is a condition race. The last call to setItem will dump the content to the storage file, overriding what another previous one has saved.

My advice here:

• If your dependencies do not use Async Storage, use Community's
• If you're not able to control your dependencies (you cannot change which Async Storage version they use), use Core's Async Storage. Otherwise, swap their version of AS to Community.

There's Async Storage v2 coming, with a different approach for storage capabilities, making it more transparent and less error-prone in the future. Please look forward to it.

thanks.

[rogueturnip]

Brilliant! Thanks so much. I thought this might be an issue at the lower levels. I'm going to post this over to the AWS Amplify team so they can see the potential issue and then go back to using just core.

Do you think it's safe to leave the community version linked so it's ready to go later?

[krizzu]

@rogueturnip Yeah, it would be fine.

Please close the issue if you think that the case is solved.

thanks.

[rogueturnip]

I don't have my iOS environment available until monday (unless I get time to go in and use it) so I'll test on Monday and close then.

Thanks again for your help.

[rogueturnip]

Looks all good using the old core. Thanks!