CODEWITHSUNDEEP
c#memorymemory-managementmemory-leaksdotnet-httpclient
Matt
Matt

Reputation: 105

HttpClient seems to be causing my app to slowdown every ~3 minutes while freeing up a ton of memory

So basically I am running a program which is able to send up to 7,000 HTTP requests every second in average, 24/7, in order to detect last changes on a website as quickly as possible.

However, every 2.5 to 3 minutes in average, my program slowdowns for around 10-15 seconds and goes from ~7K rq/s to less than 1000.

Here are logs from my program, where you can see the amount of requests it sends every second: https://pastebin.com/029VLxZG

When scrolling down through the logs, you can see it goes slower every ~3 minutes. Example: https://i.sstatic.net/bUqmr.jpg

At first I thought it was my server's ethernet connection going in a temporary "restricted" mode, and I even tried contacting my host about it. But then I ran 2 instances of my program simulteanously just to see what would happen and I noticed that, even though the issue (downtime) was happening on both, it wasn't always happening at the same time (depending on when the program was started, if you get what I mean), which meant the problem wasn't coming from the internet connection, but my program itself.

I investigated a little bit more, and found out that as soon as my program goes from ~7K rq/s to ~700, a lot of RAM is being freed up on my server.

I have taken 2 screenshots of the consecutive seconds before and once the downtime occurs (including RAM metrics), to compare, and you can view them here: https://i.sstatic.net/l9BWB.jpg (please note that I was using less threads here, which is why the average "normal" speed is ~2K rq/s instead of ~7K as mentioned before)

If you'd like to see more of it, here is the full record of the issue, in a video which lasts about 40 seconds: https://i.imgur.com/z27FlVP.mp4 - As you can see, after the RAM is freed up, its usage slowly goes up again, before the same process repeats every ~3 minutes.

For more context, here is the method I am using to send the HTTP requests (it is being called from a lot of threads concurrently, as my app is multi-threaded in order to be super fast):

public static async Task<bool> HasChangedAsync(string endpoint, HttpClient httpClient)
{
    const string baseAddress = "https://example.com/";

    string response = await httpClient.GetStringAsync(baseAddress + endpoint);

    return response.Contains("example");
}

One thing I did is I tried replacing the whole method by await Task.Delay(25) then return false, and that fixed the issue, RAM usage was barely increasing.

This lead me to believe the issue is HttpClient / my HTTP requests, and even though I tried replacing the GetStringAsync method by GetAsync using both a HttpRequestMessage and HttpResponseMessage (and disposing them with using), the behavior ended up being the exact same.

So here I am, desperate for a fix, and without enough knowledge about memory, garbage collector etc (if that's even needed here) to be able to fix this myself.

Please, Stack Overflow, do you have any idea?

Thanks a lot.

Upvotes: 0

Views: 555

Answers (1)

JohanP
JohanP

Reputation: 5472

Your best bet would be to stream the response and then use chunks of it to find what your are looking for. An example implementation could be something as follows:

using var response = await Client.GetAsync(BaseUrl, HttpCompletionOption.ResponseHeadersRead);
await using var stream = await response.Content.ReadAsStreamAsync();
using var reader = new StreamReader(stream);
string line = null;
while ((line = await reader.ReadLineAsync()) != null)
{
    if(line.Contains("example"))// do whatever
}

Upvotes: 1

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