Before we would delve into the process of obtaining and refreshing the actual access_token and refresh_token it is recommended to check the overall setup of authorisation procedure in the integration component:

  1. Here is how the OAuth2 authorization process works at elastic.io.
  2. Prepare and check your component.json. Here are the instructions and suggestions.
  3. Prepare the verifyCredentials.js. Here is what can be done for that.
  4. The stored credentials can be accessed following this example.

Refreshing the tokens

The very definition of an access_token within the scope of OAuth2 is that it will expire sooner or later. If any system is accepting the same access_token for long period then it is prone to a potential security breach. Dependent on a system the access_token is valid only for several hours. Some systems require it to be updated every hour and this is regarded as a standard practice.

The process of refreshing the access_token is initiated when the API responds with an access error 401 UNAUTHORIZED. The methods of encountering and coding might vary from component to component due to different requirements from different API providers, however, the logic is the same, Service responds with the message: Give me the refresh_token and I will give you the new access_token to continue accessing the protected data.

It is the job of the component creator to make sure that there is a routine in place to refresh the access_token according to the requirements of external API provider to which the component connects.

Method of refreshing token during each access

This method is perhaps too overzealous but works quite well while in ensuring to have an up-to-date. This method is not waiting for the above mentioned 401 error from the server but simply requests the refresh_token along with the access_token every time. Some API providers might discourage this but there is nothing technically wrong to do this. Here is an example of implementation:

return co(function* mainLoop() {
        console.log('Refreshing an OAuth Token');
        const newToken = yield rp({
            method: 'POST',
            uri: 'https://login.microsoftonline.com/common/oauth2/v2.0/token',
            json: true,
            form: {
                refresh_token: cfg.oauth.refresh_token,
                scope: cfg.oauth.scope,
                grant_type: 'refresh_token',
                client_id: process.env.MSAPP_CLIENT_ID,
                client_secret: process.env.MSAPP_CLIENT_SECRET
            }
        });
        console.log('Updating token');
        this.emit('updateKeys', {
            oauth: newToken
        });

        const client = MicrosoftGraph.init({
            defaultVersion: 'v1.0',
            debugLogging: true,
            authProvider: (done) => {
                done(null, newToken.access_token);
            }
        });
...

}

In this example, which is taken from the Microsoft Outlook component, the whole procedure includes refreshing first the refresh_token then using the first to refresh the access_token.

Notice how the refresh token is emitted via updateKeys event (on line 15 in the above example).

This solution was chosen since Microsoft requires the refresh_token to be updated regularly as well. This is rather an exception than a rule. Normally API providers do not require the refresh_token to be updated regularly or they are just updated and sent along with the access_token from time to time.

It is important to get familiarised in advance with the requirements of the API provider in order to know when and how to initiate the refresh token procedure.

Refreshing the tokens when it is required

This is the more standard implementation of the token refresh procedure. The tokens are being refreshed only when the API provider rejects with 401 UNAUTHORIZED error. The following is an example taken from the Salesforce Java component by elastic.io:

private String sendRequestAndRefreshTokensIfRequired(
            final HttpRequestBase request, final JsonObject configuration) {

        try {
            return HttpClientUtils.sendRequest(request);
        } catch (AuthorizationException e) {

            HttpClientUtils.refreshTokens(configuration);

            logger.info("Emitting updated keys");

            getEventEmitter().emitUpdateKeys(configuration);

            HttpClientUtils.authorizeRequest(request, configuration);

            logger.info("Sending the original request width refreshed access_token");
            try {
                return HttpClientUtils.sendRequest(request);
            } catch (AuthorizationException e1) {
                throw new RuntimeException(e1);
            }

        }
    }

The procedure presented in the example ensures the proper execution of these steps:

  • Sends a request to the API using the access_token from the component's configuration
  • If the request succeeds, the data from the response are emitted
  • If the API response with 401 UNAUTHORIZED, the access_token is updated using the refresh_token.
  • The response of the refresh token request is emitted using the updateKeys event. It is important to note here that the entire response must be emitted since some OAuth2 API providers also refresh the refresh_token from time to time or repeatedly.
  • Finally the system sends the original request one more time, now using the new access_token.

In the above example HttpClientUtils.refreshTokens(configuration) is defined separately like this:

public static final void refreshTokens(final JsonObject configuration) {

        logger.info("About to refresh tokens");

        final JsonObject oauth = configuration.get(Constants.CONFIGURATION_OAUTH).getAsJsonObject();

        if (oauth == null) {
            throw new RuntimeException("Please authenticate with Salesforce");
        }

        final String refreshToken = getRequiredConfigurationParameter(
                oauth, Constants.CONFIGURATION_REFRESH_TOKEN);

        final List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("grant_type", "refresh_token"));
        params.add(new BasicNameValuePair("client_id", System.getenv("SALESFORCE_KEY")));
        params.add(new BasicNameValuePair("client_secret", System.getenv("SALESFORCE_SECRET")));
        params.add(new BasicNameValuePair("refresh_token", refreshToken));
        params.add(new BasicNameValuePair("format", "json"));

        final String url = "https://login.salesforce.com/services/oauth2/token";

        final HttpPost httpPost = new HttpPost(url);
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }


        final String content;
        try {
            content = HttpClientUtils.sendRequest(httpPost);
        } catch (AuthorizationException e) {
            throw new RuntimeException(e);
        }

        logger.info("Refresh token response: {}", content);

        final JsonObject newOauth = new JsonParser().parse(content).getAsJsonObject();

        configuration.add(Constants.CONFIGURATION_OAUTH, newOauth);
    }