private void ProcessQueueItems()

in src/Elastic.Apm/Report/PayloadSenderV2.cs [358:479]
111 lines of code
16 McCabe index (conditional complexity)

		private void ProcessQueueItems(object[] queueItems)
		{
			// can reuse underlying buffers from a pool in future.
			using var stream = new MemoryStream(1024);

			try
			{
				_cachedMetadataJsonLine ??= _payloadItemSerializer.Serialize(_metadata);

				using (var writer = new StreamWriter(stream, Utf8Encoding, 1024, true))
				{
					writer.Write("{\"metadata\":");
					writer.Write(_cachedMetadataJsonLine);
					writer.Write("}\n");

					foreach (var item in queueItems)
					{
						switch (item)
						{
							case Transaction transaction:
								if (TryExecuteFilter(TransactionFilters, transaction) != null)
									Serialize(item, "transaction", writer);
								break;
							case Span span:
								if (TryExecuteFilter(SpanFilters, span) != null)
									Serialize(item, "span", writer);
								break;
							case Error error:
								if (TryExecuteFilter(ErrorFilters, error) != null)
									Serialize(item, "error", writer);
								break;
							case MetricSet _:
								Serialize(item, "metricset", writer);
								break;
						}
					}
				}

				stream.Position = 0;
				using (var content = new StreamContent(stream))
				{
					content.Headers.ContentType = MediaTypeHeaderValue;

#if NET8_0_OR_GREATER
					HttpResponseMessage response;
					try
					{
						var webRequest = new HttpRequestMessage(HttpMethod.Post, _intakeV2EventsAbsoluteUrl) { Content = content };
						response = HttpClient.Send(webRequest, CancellationTokenSource.Token);
					}
					catch (Exception) //HttpMessageHandler may not support synchronous sending
					{
						response = HttpClient.PostAsync(_intakeV2EventsAbsoluteUrl, content, CancellationTokenSource.Token)
							.ConfigureAwait(false)
							.GetAwaiter()
							.GetResult();
					}
#else
					var response = HttpClient.PostAsync(_intakeV2EventsAbsoluteUrl, content, CancellationTokenSource.Token)
						.ConfigureAwait(false)
						.GetAwaiter()
						.GetResult();
#endif
					// ReSharper disable ConditionIsAlwaysTrueOrFalse
					if (response is null || !response.IsSuccessStatusCode)
					{
						var message = "Unknown 400 Bad Request";
						if (response?.Content != null)
						{
#if NET8_0_OR_GREATER
							var intakeResponse = _payloadItemSerializer.Deserialize<IntakeResponse>(response.Content.ReadAsStream());
#else
							var intakeResponse = _payloadItemSerializer.Deserialize<IntakeResponse>(response.Content.ReadAsStreamAsync().GetAwaiter().GetResult());
#endif
							if (intakeResponse.Errors.Count > 0)
								message = string.Join(", ", intakeResponse.Errors.Select(e => e.Message).Distinct());
						}
						_logger?.Error()
							?.Log("Failed sending event."
								+ " Events intake API absolute URL: {EventsIntakeAbsoluteUrl}."
								+ " APM Server response: status code: {ApmServerResponseStatusCode}"
								+ ", reasons: {ApmServerResponseContent}"
								, _intakeV2EventsAbsoluteUrl.Sanitize()
								, response?.StatusCode,
								message
								);
					}
					// ReSharper enable ConditionIsAlwaysTrueOrFalse
					else
					{
						_logger?.Debug()
							?.Log("Sent items to server:"
								+ $"{Environment.NewLine}{TextUtils.Indentation}{{SerializedItems}}",
								string.Join($",{Environment.NewLine}{TextUtils.Indentation}", queueItems));
					}
				}
			}
			catch (OperationCanceledException)
			{
				// handle cancellation specifically
				_logger?.Warning()
					?.Log(
						"Cancellation requested. Following events were not transferred successfully to the server ({ApmServerUrl}):"
						+ $"{Environment.NewLine}{TextUtils.Indentation}{{SerializedItems}}"
						, HttpClient.BaseAddress.Sanitize()
						, string.Join($",{Environment.NewLine}{TextUtils.Indentation}", queueItems));

				// throw to allow Workloop to handle
				throw;
			}
			catch (Exception e)
			{
				_logger?.Warning()
					?.LogException(
						e,
						"Failed sending events. Following events were not transferred successfully to the server ({ApmServerUrl}):"
						+ $"{Environment.NewLine}{TextUtils.Indentation}{{SerializedItems}}"
						, HttpClient.BaseAddress.Sanitize()
						, string.Join($",{Environment.NewLine}{TextUtils.Indentation}", queueItems)
					);
			}
		}