I am learning about microservices and I get very confused when it comes to data duplication. From different sources on the internet I get very different opinions on the subject, but the main conclusion that I got is that it depends if it's good on your use case or application.
Now I am struggling because I am trying to make a very simple microservice where I think data duplication is not necessary, but can't seem to think of a good alternative to it.
My Application
I am basically making a Twitter clone to understand the basics of microservices using AWS. To start I have 3 services:
Timeline Service
Post (or tweet) Service
Follow Service
Timeline service
The timeline service should return the timeline of the user that asked it. It should check who the user is, that requests his/her timeline is following, get the 100 most recent posts from those users and return it to the user (that requested his/her timeline)
Posts/tweet Service
When a user is posting a new tweet/post, the post timeline should save the post in the post database to keep track of who posts what.
Follow Service
When a user wants to follow another user the follow service should keep track of that.
If I put it into an image it would look like this:
The problem
My question is about the timeline service. Should the timeline
Have two (in memory) databases that also keep track of who follows who and who posts which tweets to give the user quickly their timeline back
Or should the timeline service call the different services to get that information?
The 'bad' thing from the last option would be that if my posts service is failing and can't send or receive requests, my timeline service also does not work and you create dependency which goes against microservice principles.
Since the last option seems the worst one to me, I would say data duplication is the better option because of response time and to keep the different services from relying on each other.
Can anyone help me to get on the right track with this problem?
Related
I am new to web development. I have few requirements for a web application.
I have two Qualtrics surveys and the flow of the application is that a user lands on the first survey and upon completing it gets redirected to a chat room and then to the second and final Qualtrics survey. The whole flow is also created as a task for workers on the Amazon Mechanical Turk.
When a user refresh the first survey(in any of the 4 pages of the first survey), it maintains the current state as well as the selected answers and it doesn't navigate back to the Introduction page of the first survey. But when a user refreshes from the final survey, it lands the user on the Introduction page of the first survey. It only happens when I deploy the whole flow into Amazon Mechanical Turk. When I test the whole flow without deploying on Mechanical Turk, it doesn't redirect the user to the first survey upon refresh and behaves as intended.
As far as I can understand Mechanical Turk must be overriding the Qualtrics way of maintaining the page state. Now I am unable to figure out how to solve this. I can only use Qualtrics JS API to solve this but if MTurk is causing the issue, it won't do any good. Any suggestions on what might be the issue and how to solve this?
Take a breath... it's a very specific question, not directly a bug.
(But I can't get an answer from Facebook, after thousands of FAQ pages I somehow landed in a chat with Facebook Advertisers Support, they told me to come here.)
Description of my app
I have a Facebook Page, on which I'm sharing events from some other Facebook Pages I'm cooperating with. Kind of an event aggregator. The main goal is to help people who are new in town to find all that interesting events and the groups and pages they are organized by.
As you can imagine, it's based on a server-side application, that collects the upcoming events through Graph API and posts on my own Facebook Page the day before the event.
Of course I had to give the server-side application the manage_pages and publish_pages right. This Facebook App will never be used by an end-user, I'm the only user and I'm only posting to my own Facebook Page.
The server-side application worked fine for more than a year.
I just started a Facebook Ad Campaign and poster and flyers are currently being printed. And now...
What broke
You all heard of Cambridge Analytica. Due to these bad guys Facebook is currently changing a lot. One change was this:
As we begin enhancing our new app review process and make changes to our platform, the Events, Groups, Pages and Instagram APIs will no longer be available to new developers. Testing of our more robust process starts today and the new process should resume in a few weeks, but apps currently accessing Events and Groups APIs will lose access today. Going forward, access to these APIs will require a formal app review and for apps using the Pages API, submission is required within 90 days once app review resumes or access will be removed.
(See https://developers.facebook.com/blog/post/2018/04/04/facebook-api-platform-product-changes)
Since nearly two weeks my server-application can't fetch events. Graph API is always returning an empty array data: [].
I have full understanding for this. Now I tried to follow these new requirements and had a look on how to submit my App for review. But that's where my struggles began:
The specific problem
The whole form for applying for review is aimed to Apps for end-users, not server-side bots.
I should provide details on why I'm using manage_pages or publish_pages. Well okay...
When selecting "automated posting" there immediatly a message pops up, telling me, that this is not allowed. Of course it is not - for applications that post in the name of persons without their knowing and aggreement. But my App is posting in the name of my own Facebook Page and I'm the only user and I'm knowing what's going to be posted. So I have to select "Other" and enter a custom description. No problem.
But at the end of the form there's asked for a Screencast! What should I make a movie of? Should I make a slideshow of my code? I can't save this form without that Screencast.
I want to be conform to the new Facebook processes, but I simply don't know how to become approved nor at least fill out for review...
I know this is not a programming question but Facebook directed me here.
So I hope I find a Facebook official or Facebook developer here. Thank you so far!
I want to build a dashboard that returns more customized insights from the insights generated by app.
The app is a facebook connect website that users visit and view a list of products. They can post to facebook about that particular product by sharing a custom story that incorporates that product on their timeline.
When I go to the insights for my app, it does a great job of showing me all social impressions for all custom stories that were generated on my site.
I'd like to narrow that down even more for specific products.
My plan is to record the object ids that are generated by these actions and link them to a partucular product in my database.
I'd then like to create a new dashboard page that will allow me to login, request read_insights permission from me and then use that object_id:product mapping from my database to show how many social impressions where recorded for a given product's object_ids.
Is this possible? I've read alot about it but still haven't found the most elegant way to get a segmented report of social impressions per type of content that was posted.
Thanks for your time.
The implementation all depends on which platform you want your app to run on.
The first major component is you must have a Facebook developers account which is easy to signup for. Just go to developers.facebook.com and register. Takes like 2 mins. After that you will need to create your first app and add the correct domain name where your app will be hosted and what platform it will run on. (iOS, Android, Web, ect.) Once that is finished you can make your app public so you can use the Facebook API in your code.
For the app creation itself. The first thing you need to do is import the correct API for your platform. Which you can find a walk through at https://developers.facebook.com/docs/. Once the API is imported you must build a Facebook object which contains your app id and possibly app secret. If you're using JavaScript you don't want to use the app secret because it will be visible to the public.
Now that you have your Facebook object you must require the app users to log in and grant permission to your app. You can add extended permissions to your log in process by adding a scope value to the log in button generated by Facebook. Here is an example.
<fb:login-button id="loginBtn" max_rows="1" scope="basic_info,read_insights,manage_pages" size="medium" show_faces="false" auto_logout_link="true"></fb:login-button>
After the user is logged in you can now query information from the users account using Facebook Api calls to Social Graph. Facebook also provides a tool to help you figure out what information you can query. https://developers.facebook.com/tools/explorer
Everything else you want to do with the app can be done by Facebook API calls. You just need to insure you grant the user the correct permissions before making the API calls.
API calls are a little different depending on which language syntax you are using but they all follow the same data model and return some array of responses which can be parsed using JSON or the standard array format. The Graph Explorer tool listed above will show you the output for your queries so you can handle them accordingly.
I hope this helps gets you started.
EDITED
Here's the implementation in JavaScript
function getMetric(){
// make the API call
FB.api(
"/{app-id}/insights/application_opengraph_story_impressions",
function (response) {
if (response && !response.error) {
/* handle the result */
}
}
);
}
Here's the reference now that Facebook docs are back up https://developers.facebook.com/docs/graph-api/reference/insights
application_opengraph_story_impressions will probably give you the total impression of all stories made by your app. I ran it against my Facebook app and it came back empty but I don't have any stories so it might work with your's. Also to note in the documentation there is an * by this metric and I could't find what that means.
I'm pretty sure that right now Facebook don't give developers ability to get insights about app custom stories.
Currently Facebook documentation has the following Graph APIs for Insights data:
/{page-id}/insights
/{app-id}/insights
/{domain-id}/insights
/{post-id}/insights (where this is a Page post)
So /{post-id}/insights won't work because custom story is actually user's post and others endpoints don't apply to your case.
As far as I know the only other option to access Insights is FQL. For that you'd use insights table in a manner similar to this:
SELECT ... FROM insights WHERE object_id = ... AND metric = ... AND end_time = ... AND period = ...
Now most likely this also won't work with your custom story posts (I don't have posts which I could try it on right now, so I can't tell) but at least it is not explicitly stated so in the documentation, so you should probably try it out.
UPDATE:
I wasn't able to get any insights data via FQL, although as far as I understand the following code should have gave me at least something (object id is for my page):
SELECT breakdown, end_time, event, metric, object_id, period, value FROM insights WHERE object_id = 224981264214413 and metric = 'page_fans' and period = period('lifetime') and end_time = 1395597892
But it results just in
{
"data": []
}
Facebook also has some pretty old bug report about similar topic: https://developers.facebook.com/x/bugs/508088155954330/ where they confirmed the issue, assigned it, and... did nothing to fix it for 6 months.
In case FQL doesn't work, my suggestion to you is - use your own analytics code to track the creation of custom stories and get the friend count of the users. It won't show you the real exposure of the posts but at least you will see some data on which types of custom stories where posted more often and what was the maximum potential friend count that could have seen them. By the way - to make charting easier, you could use Google Analytics events for that.
I made a Django online-store site and I need to include paypal checkout system for the cart, but solutions I found online either just for one item only(Buy Now buttons) or something like django-paypal-cart, which is not well-documented and I can't figure out how to make it to the checkout.
Please, give me some hint, maybe good article about how to make your cart items go to the checkout, anything will be highly appreciated, I don't know what else to google now
There are numerous options for tying PayPal into your website or app. Depending on exactly what you're doing or how good you are with web service API's you may choose one or another.
If you want to keep things simple, you can stick with Payments Standard. This is basically what you're referring to about the one item only buy now button, but you can use the cart upload command method to build a form that includes multiple items and pass it all over to PayPal at once.
If you prefer web service API's I'd recommend using Express Checkout. This consists of SetExpressCheckout, GetExpressCheckoutDetails, and DoExpressCheckoutPayment. Read through that general EC documentation to get familiar with the calls and how it all flows.
Another thing I would highly recommend utilizing is Instant Payment Notification (IPN). This is a feature where PayPal will POST transaction data to a listener script that you have sitting on your server any time a transaction occurs on your PayPal account. This includes payments, refunds, disputes, cleared payments that were pending, etc. This allows you to automate tasks like updating your database, sending out custom email notifications, hitting 3rd party web services, etc. and it happens in real-time, so it's very powerful.
I'm trying to make a site where users can create accounts then chat with each other in real time using Django, Orbited, and Twisted. I want it so that two users individual chats are private and only they can see it.
Based on my knowledge of Orbited(which is limited since it seems like the site is down, so I've just been going off of blog posts and whatnot), there are channels that basically anyone can subscribe to and get the messages sent to it. Since the subscribing is done through Javascript, it would be easy for someone to just change what channel they're subscribed to and subscribe to someone else's private chat and see what they're saying.
So how would you get around this and have some kind of authentication in Orbited's channels? I've been looking around and most people cite Hotdot as an example, but it's not extremely documented so it's hard to understand. It also seems like it just checks for authentication before allowing you to subscribe to anything, but once you're logged in you'd still be able to subscribe to any channel you want.
a dirty way is to do this:
since sessionids are unique to each logged in user, you can create a unique id for each chatsession and attach the sessionids of the users to that.
then let your channel-name be /messages/{sessionid} or something similar and your users subscribe to that channel
whenever you want to push messages, just push to all /messages/{sessionids} attached to that chatsession
for a better solution, you should try the orbited discussion group: http://groups.google.com/group/orbited-users
it is still alive ;-)