Direct TCP: Add metrics, address back pressure issue, and eliminate some resource leaks

[David-Noble-at-work]

In addition to resolving issue #228 and adding back stack traces to DocumentClientException this PR

1. Addresses three specific resource leaks:

   • Inactive RntbdServiceEndpoint instances are now closed and do not accumulate over time
   • RntbdContext instances no longer hold on to pooled byte buffers
   • RntbdResponse.decode now releases the byte buffers associated with partially decoded responses.

2. Adds RntbdTransportClient and RntbdServiceEndpoint metrics using micrometer.

   • Metrics are encapsulated by the RntbdMetrics class and an instance of this class is instantiated by each RntbdServiceEndpoint. Console logging can be turned on/or using this Java property: cosmos.monitoring.consoleLogging.step Reporting frequency in seconds. Use a value less than or equal to zero to explicitly disable console logging.
   • Customers can collect metrics using the MetricsRegistry of their choosing using (the new) AsyncDocumentClient.monitor method
   • The benchmark app enables monitoring using Application Insights by way of these Java properties: cosmos.monitoring.azureMonitor.instrumentationKey An Azure Application Insights instrumentation key cosmos.monitoring.azureMonitor.step Reporting frequency in seconds cosmos.monitoring.azureMonitor.disabled A value of true disables monitoring (useful during development/testing)
   • The benchmark app enables monitoring using Graphite by way of these Java properties: cosmos.monitoring.graphite.serviceAddress Graphite pickle (not plaintext) endpoint address (e.g., cosmos-sdk.eastus.cloudapp.azure.com:2004) cosmos.monitoring.graphite.step Reporting frequency in seconds cosmos.monitoring.graphite.disabled A value of true disables monitoring (useful during development/testing)

E2E test results

e2e.log

Read/write latency performance numbers (complete performance test results attached)

• benchmark-appserver-lin-1-WriteLatency-2019-08-01T18.25.26+00.00.log
• benchmark-appserver-lin-1-ReadLatency-2019-08-01T18.22.30+00.00.log