Using executeQuery/executeQueryLocally as intermediary between web service and cache

Question

I'm new to breeze.js and I'm having a little trouble coming up with a good way to combine executeQuery and executeQueryLocally.

The use case is this: I want to use breeze data caching to hide the flakiness of a 3rd party web service. I'd like to come up with a pattern that queries the service and falls back to the cache if the service is unavailable when called.

I've been chewing on this for a couple of days now - any suggestions or advice would be appreciated!

Answer 1

I think that this solution can be a good way:

executeQuery= function(query){
    operating(true);
    return manager.executeQuery(query).fail(fail);

    function fail(error){
        //You can decide if you want to query locally depending on the type of error
        //Example: if(error.status===404) ;
        return executeQueryLocally(query);
    }

}

executeQueryLocally= function(query){

    return manager.executeQuery(query).using(FetchStrategy.FromLocalCache).fail(fail);

    function fail(error){
        //You can't get the information, so you can throw an error
        //Or that you want

        throw Error('Impossible to get the requested data');
    }
}

//Example calling this methods
var getCustomers= function(resultArrayObservable,inlineCountObservable){
        var query = new breeze.EntityQuery("Customers").inlineCount(true);
        return executeQuery(query).then(success);

        function success(data){
            inlineCountObservable(data.inlineCount);
            resultArrayObservable(standarizeCustomerDtos(mapCustomerDtosToKos(data.results)));
        }

};

With this solution I have tried to to do easy to check in every query if it is something that is going wrong and not to repeat code.

I hope this can help you.