[BUG] Random 502 errors when registering push tokens

[Tommigun1980]

Describe the bug Sometimes when my ASP.NET Core server is calling the Azure Notification Hub to register or update a push token the notification hub server returns a 502/bad gateway error. This happens quite frequently.

Exception or Stack Trace AppInsights's error information for a call that returns 502 (with ids blanked out):

Code Snippet

public Task CreateOrUpdateInstallation(string installationId, string deviceToken, SharedConstants.PushPlatform pushPlatform, string[] additionalTags = null)
{
    var platform =
        pushPlatform == SharedConstants.PushPlatform.Apns ? NotificationPlatform.Apns :
        (pushPlatform == SharedConstants.PushPlatform.Fcm ? NotificationPlatform.Fcm : throw new UserArgumentException("Invalid push platform"));

    var tags = new List<string>()
    {
        installationId
    };
    if (additionalTags != null)
        tags.AddRange(additionalTags);

    var templates = new Dictionary<string, InstallationTemplate>(Templates.Count);
    foreach (var kvp in Templates)
        templates.Add(kvp.Key, kvp.Value[platform]);

    var installation = new Installation()
    {
        InstallationId = installationId,
        PushChannel = deviceToken,
        Platform = platform,
        Tags = tags,
        Templates = templates
    };

    // TODO: segment based on LoginSession.NotificationNamespaceIndex. must segment every 10M to a new notification hub namespace
    return this.Hub()?.CreateOrUpdateInstallationAsync(installation) ?? Task.CompletedTask; // error: this call will often return status code 502!!
}

Expected behavior CreateOrUpdateInstallationAsync should return status code 200. Instead, 502/bad gateway is often returned.

Setup (please complete the following information):

• OS: Azure App Service/Windows
• IDE : VS For Mac 8.10
• Version of the Library used: 4.1.0
• ASP.NET Core project, target framework: .NET 5.0

Additional context If I retry the call (i.e. run the above CreateOrUpdateInstallation(...) -> this.Hub()?.CreateOrUpdateInstallationAsync(...)) again, it seems to always succeed on the second try.

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This is hurting me quite badly, so a quick resolution would be greatly appreciated! Thank you.

[Tommigun1980]

On a second thought, this is probably better served by Azure support. Thank you.