This applicatiuon when launched can be used to fetch the TOP N ranked news stories using the Hacker news URL https://hacker-news.firebaseio.com/v0. The top ID list is resolved along with all stories returned within that list. These fetches are cached to prevent overloading the Hacker data source.
Note the author is an experienced C# server developer but not in ASP Net.
It has been assumed that the kids returned from a given story are all comments, no filter is applied which would require recursively resolving the graph to resolve type.
There has been around 20-25 hrs of development time to build this applicaton. It was based on the skeleton VS core ASP service using VS2022.
Once built, should be possible to launch in usual way (e.g. F5) from Visual Studio - A console is expected hosting the service and in debug a Swagger web page http://localhost:5110/swagger/index.html should be launched.
the console will show output such as below :-
info: Microsoft.Hosting.Lifetime[14]
Now listening on: http://localhost:5110
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: C:\Users\me\dev\cs\HackerTopNews\HackerTopNewsuse the Swagger page for example HackerApi->Get->Execute
should see a JSON ID list of 200 IDs.
[
38655066,
38647484,
38657126,
38657577,
38673292,
38677124,
38675616,
38666032,
38652619,
38653456
]the console is expected to show output resolving the ID list
info: HackerNewsWebService[0]
rootUrl = https://hacker-news.firebaseio.com/v0, getTopStoriesUrl = https://hacker-news.firebaseio.com/v0/beststories.json
info: HackerTopNews.Services.Cache.NewsStoryCache[0]
TopStoryCache expiry lifetime = 00:00:20
info: HackerNewsWebService[0]
rootUrl = https://hacker-news.firebaseio.com/v0, getTopStoriesUrl = https://hacker-news.firebaseio.com/v0/beststories.json
info: HackerTopNews.Services.Cache.NewsStoryCache[0]
NewsStoryCache expiry lifetime = 00:01:20
info: HackerTopNews.Controllers.HackerTopNewsController[0]
Get all ids
info: HackerNewsWebService[0]
GetTopStoryID [https://hacker-news.firebaseio.com/v0/beststories.json]
info: HackerNewsWebService[0]
GetResponse url = https://hacker-news.firebaseio.com/v0/beststories.json?print=pretty
info: System.Net.Http.HttpClient.IHackerNewsService.LogicalHandler[100]
Start processing HTTP request GET https://hacker-news.firebaseio.com/v0/beststories.json?print=pretty
info: System.Net.Http.HttpClient.IHackerNewsService.ClientHandler[100]
Sending HTTP request GET https://hacker-news.firebaseio.com/v0/beststories.json?print=pretty
info: System.Net.Http.HttpClient.IHackerNewsService.ClientHandler[101]
Received HTTP response headers after 358.0862ms - 200
info: System.Net.Http.HttpClient.IHackerNewsService.LogicalHandler[101]
End processing HTTP request after 381.3149ms - 200
info: HackerNewsWebService[0]
GetTopStories url = https://hacker-news.firebaseio.com/v0/beststories.json?print=pretty, response len = 2003, list len = 200Note that the cache used within this application can be configured with setttings in appsettings.json
"NewsCache": {
"TopNewsExpireSeconds": 20,
"NewsStoryExpireSeconds": 80,
"CullFrequency": 5
}The first call made when resolving top ranked score stories is to fetch the list of IDs. This cache is currently configured to expire at a faster rate than the stories resolved from it. Hence new IDs will be resolved and added into the story cache which expires at 4 x age by default. Over time, old stories will expire and at all times all stories making up the top score will be cached however some may be out of date until they also expire and are re-fetched.
This is done to limit the number of calls made to the Hacker API - there is a deep discussion to be made on how such a cache is best implemented and indeed the integrity of the data as one may find a cache story receives a lot of comments whilst cached which would mean its score is not reflected when invoking the service. However, given an upper limit on how long an item lives in the cache means this would eventually resolve.
a very simple cache implementation is used AgedCache see Services/Cache
There are 2 REST each of which is described below.
This is a simple wrapper around the Hacker API returning the raw data as returned by their API - this allows the service to be visualised. Note that the service is also using the cache so repeatedly pressing the Swagger Execute button will fetch cached results. Eventually the service goes back to fetch again from Hacker API.
The first top call returns a JSON list of IDs, one of these can be copied onto the second call which takes that ID and returns the story it belongs too. Note that theses stories are all cached based on json settings.
the second should return JSON such as below
{
"url": "https://minnesotareformer.com/2022/12/15/toxic-3m-knew-its-chemicals-were-harmful-decades-ago-but-didnt-tell-the-public-government/",
"type": "story",
"title": "3M knew its chemicals were harmful decades ago, but didn't tell the public",
"time": 1702841447,
"score": 432,
"id": 38675616,
"by": "Jimmc414",
"kids": [
38675761,
38676586,
38675804,
38675835,
38676398,
38676345,
38676117,
38676619,
38676549,
38677423
}GET /HackerApi
GET /HackerApi/{id}
This is main service making use of the above service to resolve the top N ranked by score stories based on RankedNewsStory definition shown below. Note this service is using the above described caches and hence is not aware from where the data is being sourced
- if the execute button is pressed, after the expiry period the rankings are re-resolved and re-ordered. enter say 2 into parameter for top 2 news stories from Swagger and hit Execute. Press execute repeatedly
GET /HackerTopNews/{n}
we expect JSON such as the following
[
{
"title": "Database Fundamentals",
"uri": "https://tontinton.com/posts/database-fundementals/",
"postedBy": "tontinton",
"time": "2023-12-15T15:28:30",
"score": 735,
"commentCount": 29
},
{
"title": "Mitchell reflects as he departs HashiCorp",
"uri": "https://www.hashicorp.com/blog/mitchell-reflects-as-he-departs-hashicorp",
"postedBy": "manojlds",
"time": "2023-12-14T21:27:17",
"score": 716,
"commentCount": 39
}
] public class RankedNewsStory
{
public string Title { get; }
public string Uri { get; }
public string PostedBy { get; }
public DateTime Time { get; }
public int Score { get; }
public int CommentCount { get; }
}| name | summary |
|---|---|
| AppBuilder | set up the DI container with services for this application |
| AgedCache | abstract class used to cache and expire items which when not present are asynchrnously resolved |
| HackerTopNewsController | the entry REST point for resolving stories |
| HackerNewsWebService | service used to fetch from HackerNews API. Note root url in config |
| TopStoryCache | aged cache of all IDs of top stories |
| NewsStoryCache | aged cache indexed by ID of story |
| ScoreRankedNews | resolve and compute top N stories by score making use of caches |
There are some unit tests which can be run, these include a test time service so the time can be eplicitely set rather than using system time. There is also a Moq using real life data of the Hacker API. This is done with DI, see TestNews/Support/TestAppBuilder.
Using R# (which was only used for this purpose), coverage stats show ~80% coverage of the application