.NET Core high memory usage in Docker (AWS ECS Fargate)

Question

Here is a description of the application. I have a console application that runs Hangfire. There are several jobs that are recurring. One job, in particular, parses several large XML files. I deploy this console app as an AWS ECS Fargate ontainer.

Every time the recurring job runs, the container memory usage keeps rising and rising until either the application becomes unresponsive or AWS kills the container. This is a 16GB container on ECS (big) and so it should be able to handle anything I throw at it. I can tell as soon as the memory usage gets up toward ~13GB it is doomed.

The kicker is that I run this application locally and it never gets very high in memory usage. I will post a couple of example logs from both my workstation and on the container below.

THANKS FOR ANY INSIGHT!

Parsing the XML:

• Use XmlSerializer to drop into a JSON formatted object
• Use XDocument to just go through the document
• Use XSD file to generate classes, and then XmlSerializer to populate

All three work locally, but use a ton of memory on the server. These are unchanging XML files, and I run the exact same files on both local and in the container.

FYI: I have turned off server garbage collection on the container. That didn't work.

EDIT 3/5/2019

The logs below are from the following code. It doesn't have the full breath of the application which is quite complex. This code is in a method registered with Hangfire to run once per day. It pulls XML files from an FTP site, and then runs essentially the code below to process those files. Each file is at most 10 MB in size.

XmlSerializer serializer = new XmlSerializer(Model);
foreach (var file in files)
{
    Console.WriteLine($"Processing file: {file.Name}");
    Model model;
    using (XmlReader reader = XmlReader.Create(file.FullName, new XmlReaderSettings { CheckCharacters = false }))
    {
        model = (Model)serializer.Deserialize(reader);
    }
    SaveToDatabase(model);
    Console.WriteLine($"Application Memory Usage - Working: {Process.GetCurrentProcess()?.WorkingSet64 ?? 0}, Private: {Process.GetCurrentProcess()?.PrivateMemorySize64 ?? 0}");
}

Workstation log:

[13:52:58 INF] Processing file: price_feed_supplemental_002981.xml
[13:52:58 INF] Application Memory Usage - Working: 1.4 GB, Private: 1.6 GB
[13:52:58 INF] Processing file: price_feed_002982.xml
[13:53:01 INF] Application Memory Usage - Working: 1.4 GB, Private: 1.6 GB
[13:53:01 INF] Processing file: price_feed_supplemental_002982.xml
[13:53:01 INF] Application Memory Usage - Working: 1.4 GB, Private: 1.6 GB
[13:53:01 INF] Processing file: price_feed_002983.xml
[13:53:01 INF] Application Memory Usage - Working: 1.4 GB, Private: 1.6 GB
[13:53:01 INF] Processing file: price_feed_supplemental_002983.xml
[13:53:02 INF] Application Memory Usage - Working: 1.4 GB, Private: 1.6 GB
[13:53:02 INF] Processing file: price_feed_002984.xml

Container log:

[19:05:35 INF] Application Memory Usage - Working: 1.9 GB, Private: 0.0 bytes
[19:05:35 INF] Processing file: price_feed_supplemental_002987.xml
[19:05:35 INF] Application Memory Usage - Working: 1.9 GB, Private: 0.0 bytes
[19:05:35 INF] Processing file: price_feed_supplemental_002988.xml
[19:05:35 INF] Application Memory Usage - Working: 1.9 GB, Private: 0.0 bytes
[19:05:35 INF] Processing file: price_feed_002988.xml
[19:05:40 INF] Application Memory Usage - Working: 1.9 GB, Private: 0.0 bytes
[19:05:40 INF] Processing file: price_feed_002989.xml
[19:05:43 INF] Application Memory Usage - Working: 2.1 GB, Private: 0.0 bytes
[19:05:43 INF] Processing file: price_feed_supplemental_002989.xml
[19:05:43 INF] Application Memory Usage - Working: 2.1 GB, Private: 0.0 bytes
[19:05:43 INF] Processing file: price_feed_supplemental_002990.xml
[19:05:43 INF] Application Memory Usage - Working: 2.1 GB, Private: 0.0 bytes
[19:05:43 INF] Processing file: price_feed_002990.xml
[19:05:51 INF] Application Memory Usage - Working: 2.6 GB, Private: 0.0 bytes
[19:05:51 INF] Processing file: price_feed_002991.xml
[19:05:57 INF] Application Memory Usage - Working: 2.2 GB, Private: 0.0 bytes
[19:05:57 INF] Processing file: price_feed_supplemental_002991.xml
[19:06:00 INF] Application Memory Usage - Working: 2.2 GB, Private: 0.0 bytes
[19:06:00 INF] Processing file: price_feed_002992.xml
[19:06:19 INF] Application Memory Usage - Working: 2.1 GB, Private: 0.0 bytes
[19:06:19 INF] Processing file: price_feed_supplemental_002992.xml
[19:06:21 INF] Application Memory Usage - Working: 2.3 GB, Private: 0.0 bytes
[19:06:21 INF] Uncompressing file: usa_LTSF_20190228_002993_001_INC.zip
[19:06:22 INF] Source file: price_feed_002993_1.xml
[19:06:22 INF] Source file: price_feed_supplemental_002993_8.xml
[19:06:23 INF] Source file: price_feed_supplemental_002993_11.xml
[19:06:23 INF] Source file: price_feed_002993_2.xml
[19:06:23 INF] Source file: price_feed_supplemental_002993_5.xml
[19:06:23 INF] Source file: price_feed_supplemental_002993_4.xml
[19:06:24 INF] Source file: price_feed_supplemental_002993_17.xml
[19:06:24 INF] Source file: price_feed_supplemental_002993_15.xml
[19:06:24 INF] Source file: price_feed_supplemental_002993_3.xml
[19:06:25 INF] Source file: price_feed_supplemental_002993_1.xml
[19:06:25 INF] Source file: price_feed_supplemental_002993_9.xml
[19:06:25 INF] Source file: price_feed_supplemental_002993_7.xml
[19:06:26 INF] Source file: price_feed_supplemental_002993_6.xml
[19:06:26 INF] Source file: price_feed_supplemental_002993_14.xml
[19:06:26 INF] Source file: price_feed_supplemental_002993_13.xml
[19:06:27 INF] Source file: price_feed_supplemental_002993_16.xml
[19:06:27 INF] Source file: price_feed_supplemental_002993_12.xml
[19:06:27 INF] Source file: price_feed_supplemental_002993_2.xml
[19:06:28 INF] Source file: price_feed_supplemental_002993_10.xml
[19:06:28 INF] Processing file: price_feed_002984.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_supplemental_002984.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_supplemental_002985.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_002985.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_supplemental_002986.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_002986.xml
[19:06:28 INF] Application Memory Usage - Working: 2.5 GB, Private: 0.0 bytes
[19:06:28 INF] Processing file: price_feed_002987.xml
[19:06:30 INF] Application Memory Usage - Working: 2.6 GB, Private: 0.0 bytes
[19:06:30 INF] Processing file: price_feed_supplemental_002987.xml
[19:06:30 INF] Application Memory Usage - Working: 2.6 GB, Private: 0.0 bytes
[19:06:30 INF] Processing file: price_feed_supplemental_002988.xml
[19:06:30 INF] Application Memory Usage - Working: 2.6 GB, Private: 0.0 bytes
[19:06:30 INF] Processing file: price_feed_002988.xml
[19:06:35 INF] Application Memory Usage - Working: 2.9 GB, Private: 0.0 bytes
[19:06:35 INF] Processing file: price_feed_002989.xml
[19:06:38 INF] Application Memory Usage - Working: 3.1 GB, Private: 0.0 bytes
[19:06:38 INF] Processing file: price_feed_supplemental_002989.xml
[19:06:38 INF] Application Memory Usage - Working: 3.1 GB, Private: 0.0 bytes
[19:06:38 INF] Processing file: price_feed_supplemental_002990.xml
[19:06:38 INF] Application Memory Usage - Working: 3.1 GB, Private: 0.0 bytes
[19:06:38 INF] Processing file: price_feed_002990.xml
[19:06:47 INF] Application Memory Usage - Working: 3.7 GB, Private: 0.0 bytes
[19:06:47 INF] Processing file: price_feed_002991.xml
[19:06:53 INF] Application Memory Usage - Working: 4.1 GB, Private: 0.0 bytes
[19:06:53 INF] Processing file: price_feed_supplemental_002991.xml
[19:06:55 INF] Application Memory Usage - Working: 4.3 GB, Private: 0.0 bytes
[19:06:55 INF] Processing file: price_feed_002992.xml
[19:07:05 INF] Application Memory Usage - Working: 4.9 GB, Private: 0.0 bytes
[19:07:05 INF] Processing file: price_feed_supplemental_002992.xml
[19:07:07 INF] Application Memory Usage - Working: 5.0 GB, Private: 0.0 bytes
[19:07:07 INF] Processing file: price_feed_002993_1.xml
[19:09:40 INF] 1 servers were removed due to timeout
[19:10:49 INF] Application Memory Usage - Working: 10.0 GB, Private: 0.0 bytes
[19:10:49 INF] Processing file: price_feed_supplemental_002993_8.xml
[19:12:10 INF] Application Memory Usage - Working: 12.5 GB, Private: 0.0 bytes
[19:12:10 INF] Processing file: price_feed_supplemental_002993_11.xml
[19:13:08 INF] Application Memory Usage - Working: 13.5 GB, Private: 0.0 bytes
[19:13:08 INF] Processing file: price_feed_002993_2.xml
[19:14:06 INF] Application Memory Usage - Working: 13.8 GB, Private: 0.0 bytes
[19:14:06 INF] Processing file: price_feed_supplemental_002993_5.xml

Answer 1

Disabling Server Garbage Collection (forcing Workstation Garbage Collection) by adding <ServerGarbageCollection>false</ServerGarbageCollection> to the web app's csproj file seemed to make the GC more eager and so that helped keep the heap small, but unmanaged memory was still creeping up slowly. It ended up being a memory leak- a static method was passing one of its arguments by reference back to the caller, static methods aren't managed by GC sooo each time this method was called and given more strings to enumerate, that objected passed by reference got larger and larger.

I removed the pass-by-reference and the method is now returning the object normally (via return ) but I still had to call GC.Collect() in this static method to prevent momentary spikes of around 500MB-1GB. Normally this might be alright even in a production environment because GC does quickly bring memory usage back down to normal levels, however just one of these memory spikes will kill the ECS instance if it causes the .NET app to exceed the memory quota.

Needless to say, we are working with some large strings in O(N^2) enumerations and I suspect the call to GC.Collect() can be removed after a good rewrite of this method. In your case, you might be missing a using somewhere, or you're using events (unlikely), or maybe like me you have a static method passing something by reference- or not- and that static method, exempt from GC, is slowly leaking.

As for disabled "Server" garbage collection, this seems to be effective only because the Fargate/ECS task is running on one vCPU only. See here for more info on Server vs Workstation GC.

Visual Studio 2022's built-in performance measurement tools are okay, but VS would occasionally crash (my work computer is also weak as hell) so I ended up using Jetbrains' dotMemory, which has a nicer interface and better snapshot comparison functionality.