ApolloNetworkException sometime on Apollo Mutation on Android

Question

I am using ApolloClient for Android. Sometime one mutation api failed with ApolloNetworkException. Problem is i can't generate in debugging. This exception occurs sometime in live version as i got some firebase non fatal log for this. And the message i got for this exception is

Failed to execute http call

As ApolloNetworkException don't have any code so i got confused that is it server side issue of application side issue?

When Failed to execute http call exception message is thrown?

I only get exception message so i can't figure out whats going wrong.

I am using Apollo version 1.3.2 with apollo-rx2-support.

My api call code snippet is like

val mutation = ....
ApolloProvider.getApolloNetworkClient(...url...)
                .rxMutate(mutation)
                .map{

                }

Please help me to find out the cause.

Thanks in advance.