Nest fails to write to ES while executed from Azure functions - elasticsearch

Question

I do have azure function which listens to events and write data to ES, but randomly it fails.
Exception while executing function: ElasticSearchIndexer Invalid NEST response built from a unsuccessful low level call on POST: /_bulk
# Invalid Bulk items:
# Audit trail of this API call:
- [1] AllNodesDead: Took: 00:00:00
- [2] Resurrection: Node: http://ip:9200/ Took: 00:00:00
- [3] PingFailure: Node: http://ip:9200/ Exception: PipelineException Took: 00:00:02.0095670
# OriginalException: Elasticsearch.Net.ElasticsearchClientException: Failed to ping the specified node.. Call: Status code unknown from: HEAD / ---> Elasticsearch.Net.PipelineException: Failed to ping the specified node. ---> Elasticsearch.Net.PipelineException: An error occurred trying to read the response from the specified node. ---> System.Net.WebException: The request was aborted: The request was canceled.
at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Elasticsearch.Net.HttpWebRequestConnection.<RequestAsync>d__5`1.MoveNext()
--- End of inner exception stack trace ---
at Elasticsearch.Net.RequestPipeline.<PingAsync>d__65.MoveNext()
--- End of inner exception stack trace ---
at Elasticsearch.Net.RequestPipeline.<PingAsync>d__65.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Elasticsearch.Net.Transport`1.<PingAsync>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Elasticsearch.Net.Transport`1.<PingAsync>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Elasticsearch.Net.Transport`1.<RequestAsync>d__15`1.MoveNext()
--- End of inner exception stack trace ---
# Audit exception in step 3 PingFailure:
Elasticsearch.Net.PipelineException: An error occurred trying to read the response from the specified node. ---> System.Net.WebException: The request was aborted: The request was canceled.
at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Elasticsearch.Net.HttpWebRequestConnection.<RequestAsync>d__5`1.MoveNext()
--- End of inner exception stack trace ---
at Elasticsearch.Net.RequestPipeline.<PingAsync>d__65.MoveNext()
# Request:
<Request stream not captured or already read to completion by serializer. Set DisableDirectStreaming() on ConnectionSettings to force it to be set on the response.>
# Response:
<Response stream not captured or already read to completion by serializer. Set DisableDirectStreaming() on ConnectionSettings to force it to be set on the response.>
I am registering in DI .
var uris = FlymarkAppSettings.Instance.ElasticServerConnection.Split(';').Select(url => new Uri(url));
var settings = new ConnectionSettings(new StaticConnectionPool(uris));
#if DEBUG
settings.EnableDebugMode();
#endif
builder.Register(c => new ElasticClient(settings))
.As<IElasticClient>()
.SingleInstance();