Custom Connector Issues and Caching

[rmonfort]

Greetings,

We're using a rest API to get data from our application into Power BI. Our original query would just retrieve a token and use that token to retrieve a dataset.

let
    Source = Json.Document(Web.Contents("http://localhost/crm151/bulkapi/Token", [Headers=[username="myusername", password="mypassword", apikey="myapikey"]])),
    SessionToken = Source[Result][AccessToken],
    ApiUrl = "http://localhost/crm151/Bulkapi/savedviews/24113",
    Options = [Headers =[#"sessiontoken"=SessionToken]],
    Result = Csv.Document(Web.Contents(ApiUrl , Options))
in
    Result

Next we needed to create a custom data connector so that it is much easier for the end user to use, and give them the option to select their dataset by id.

// This file contains Data Connector logic
section DataConnector;

[DataSource.Kind="DataConnector", Publish="DataConnector.Publish"]
shared DataConnector.Contents = (Url as text, SavedviewId as text) =>
	let
	  Credential = Extension.CurrentCredential(),
	  split = Text.Split(Credential[Username],"#"),
	  Username = List.First(split),
	  Api_key = List.Last(split),
	  Source = Json.Document(Web.Contents(Url&"/bulkapi/token", [Headers=[#"username"=Username, #"password"=Extension.CurrentCredential()[Password], #"apikey"=Api_key]])),
	  SessionToken = Source[Result][AccessToken],
	  ApiUrl = Url&"/Bulkapi/savedviews/"&SavedviewId,
	  Options = [Headers =[#"sessiontoken"=SessionToken]],
	  Result = Csv.Document(Web.Contents(ApiUrl , Options))
	in
		Result;

// Data Source Kind description
DataConnector = [
	Authentication = [
		// Key = [],
		UsernamePassword = [
		Label = "Authentication",
		UsernameLabel = "Username#APIKey (Enter Username and APIKey seperated by '#')"
		]
		// Windows = [],
		//Implicit = []
	],
	Label = Extension.LoadString("DataSourceLabel")
];

// Data Source UI publishing description
DataConnector.Publish = [
	Beta = true,
	Category = "Other",
	ButtonText = { Extension.LoadString("ButtonTitle"), Extension.LoadString("ButtonHelp") },
	LearnMoreUrl = "https://powerbi.microsoft.com/",
	SourceImage = DataConnector.Icons,
	SourceTypeImage = DataConnector.Icons
];

DataConnector.Icons = [
	Icon16 = { Extension.Contents("DataConnector16.png"), Extension.Contents("DataConnector20.png"), Extension.Contents("DataConnector24.png"), Extension.Contents("DataConnector32.png") },
	Icon32 = { Extension.Contents("DataConnector32.png"), Extension.Contents("DataConnector40.png"), Extension.Contents("DataConnector48.png"), Extension.Contents("DataConnector64.png") }
];

At first this works perfectly fine. However, after session tokens start expiring we run into issues. When I look at Fiddler, I noticed that it's using an old session token and not retrieving a fresh session token. Just to make sure it's not an issue on my API's end, I ran the original query script and it worked fine. When I clear Power BI's cache, the data connector works again, however, once the session tokens start to expire I run into the same issues. 

Is there a way to make sure the data connector is retrieving a fresh session token each time and not refer to cached information? Any suggestions would be greatly appreciated. 

[Anonymous]

Hi there,

@rmonfort  I am facing the exact same issue, have you been able to solve it? @v-jiascu-msft , we are both using UsernamePassword authentication, is there a similar refresh/logout functionality for this auth?

[v-jiascu-msft]

Hi @rmonfort,

Please refer to docs/m-extensions.md#authentication-kinds. The parameters "Refresh" and "Logout" could help.

Authentication = [
    OAuth = [
        StartLogin = StartLogin,
        FinishLogin = FinishLogin,
        Refresh = Refresh,
        Logout = Logout
    ],
    Key = [],
    UsernamePassword = [],
    Windows = [],
    Implicit = []
]

Best Regards,

Dale