Direct TCP: Use transport request id instead of activity id to correlate requests with responses

[David-Noble-at-work]

We now use the transport request id header to track pending requests. See issue #130 which this PR resolves.

Also revised:

• Channel pool management strategy

  These changes address issue #144 and result in smoother startup and reduce the number of retries that may result when many connections are being opened simultaneously. We now allow just one pending request on a channel while awaiting completion of the RNTBD context request. We've also simplified RntbdClientChannelPool.pollChannel quite a bit.

  See changes to RntbdClientChannelPool. Note addition of RntbdRequestManager.isServiceable.

• Error handling

  See changes to RntbdRequestManager.completeAllPendingRequestsExceptionally and a few toString methods. The messages produced when a connection closes with pending requests are now easier to visually parse/understand. Further: with our revised channel pool management strategy many fewer pending request failure messages are produced.

• SslHandler management

  Moved the code which calls SslHandler.closeOutbound from RntbdRequestManager.exceptionCaught to RntbdRequestManager.close so that we know SslHandler.closeOutbound is always called.

• Project dependencies

  Removed dependency on commons-validator (issue #140) to eliminate a security vulnerability reported by Snyk.

• RntbdReporter

  Addressed an issue that manifested on class loader exception on Windows systems. See issue #145.

• RntbdRequestManager

  Addressed a memory leak that occurs when a connection is reset (closed) by the Cosmos server. See issue #163.

Performance Benchmarks

Read latency is improved. Write latency is about the same. Anecdotal evidence that batch write times are improved due to revised channel pool management strategy.

Read Latency

Direct TCP

2019-05-26 18:40:29,690       [main] INFO  com.microsoft.azure.cosmosdb.benchmark.AsyncReadBenchmark - [1000000] operations performed in [159] seconds.
5/26/19 6:40:29 PM =============================================================

-- Meters ----------------------------------------------------------------------
#Successful Operations
             count = 1000000
         mean rate = 6262.27 events/second
     1-minute rate = 6198.53 events/second
     5-minute rate = 5572.52 events/second
    15-minute rate = 5285.01 events/second
#Unsuccessful Operations
             count = 0
         mean rate = 0.00 events/second
     1-minute rate = 0.00 events/second
     5-minute rate = 0.00 events/second
    15-minute rate = 0.00 events/second

-- Timers ----------------------------------------------------------------------
Latency
             count = 1000000
         mean rate = 6262.31 calls/second
     1-minute rate = 6198.69 calls/second
     5-minute rate = 5573.85 calls/second
    15-minute rate = 5286.87 calls/second
               min = 1.26 milliseconds
               max = 4.53 milliseconds
              mean = 1.54 milliseconds
            stddev = 0.15 milliseconds
            median = 1.52 milliseconds
              75% <= 1.60 milliseconds
              95% <= 1.78 milliseconds
              98% <= 1.85 milliseconds
              99% <= 1.91 milliseconds
            99.9% <= 2.55 milliseconds

Direct HTTPS

2019-05-26 18:35:49,081       [main] INFO  com.microsoft.azure.cosmosdb.benchmark.AsyncReadBenchmark - [1000000] operations performed in [175] seconds.
5/26/19 6:35:49 PM =============================================================

-- Meters ----------------------------------------------------------------------
#Successful Operations
             count = 1000000
         mean rate = 5684.83 events/second
     1-minute rate = 5655.35 events/second
     5-minute rate = 5052.53 events/second
    15-minute rate = 4746.05 events/second
#Unsuccessful Operations
             count = 0
         mean rate = 0.00 events/second
     1-minute rate = 0.00 events/second
     5-minute rate = 0.00 events/second
    15-minute rate = 0.00 events/second

-- Timers ----------------------------------------------------------------------
Latency
             count = 1000000
         mean rate = 5684.88 calls/second
     1-minute rate = 5655.57 calls/second
     5-minute rate = 5054.23 calls/second
    15-minute rate = 4748.54 calls/second
               min = 1.40 milliseconds
               max = 9.47 milliseconds
              mean = 1.71 milliseconds
            stddev = 0.39 milliseconds
            median = 1.66 milliseconds
              75% <= 1.75 milliseconds
              95% <= 1.95 milliseconds
              98% <= 2.09 milliseconds
              99% <= 2.75 milliseconds
            99.9% <= 9.47 milliseconds

Write Latency benchmarks

Direct TCP

2019-05-26 17:23:18,382       [main] INFO  com.microsoft.azure.cosmosdb.benchmark.AsyncWriteBenchmark - [1000000] operations performed in [533] seconds.
5/26/19 5:23:18 PM =============================================================

-- Meters ----------------------------------------------------------------------
#Successful Operations
             count = 1000000
         mean rate = 1872.67 events/second
     1-minute rate = 1870.55 events/second
     5-minute rate = 1825.98 events/second
    15-minute rate = 1721.27 events/second
#Unsuccessful Operations
             count = 0
         mean rate = 0.00 events/second
     1-minute rate = 0.00 events/second
     5-minute rate = 0.00 events/second
    15-minute rate = 0.00 events/second

-- Timers ----------------------------------------------------------------------
Latency
             count = 1000000
         mean rate = 1872.68 calls/second
     1-minute rate = 1870.56 calls/second
     5-minute rate = 1826.09 calls/second
    15-minute rate = 1721.61 calls/second
               min = 3.93 milliseconds
               max = 16.32 milliseconds
              mean = 5.33 milliseconds
            stddev = 1.11 milliseconds
            median = 5.11 milliseconds
              75% <= 5.50 milliseconds
              95% <= 7.57 milliseconds
              98% <= 8.55 milliseconds
              99% <= 9.29 milliseconds
            99.9% <= 16.15 milliseconds

Direct HTTPS

2019-05-26 17:46:35,901       [main] INFO  com.microsoft.azure.cosmosdb.benchmark.AsyncWriteBenchmark - [1000000] operations performed in [529] seconds.
5/26/19 5:46:35 PM =============================================================

-- Meters ----------------------------------------------------------------------
#Successful Operations
             count = 1000000
         mean rate = 1890.27 events/second
     1-minute rate = 1895.80 events/second
     5-minute rate = 1837.31 events/second
    15-minute rate = 1716.07 events/second
#Unsuccessful Operations
             count = 0
         mean rate = 0.00 events/second
     1-minute rate = 0.00 events/second
     5-minute rate = 0.00 events/second
    15-minute rate = 0.00 events/second

-- Timers ----------------------------------------------------------------------
Latency
             count = 1000000
         mean rate = 1890.27 calls/second
     1-minute rate = 1895.77 calls/second
     5-minute rate = 1837.38 calls/second
    15-minute rate = 1716.41 calls/second
               min = 4.07 milliseconds
               max = 11.02 milliseconds
              mean = 5.24 milliseconds
            stddev = 0.70 milliseconds
            median = 5.14 milliseconds
              75% <= 5.49 milliseconds
              95% <= 6.10 milliseconds
              98% <= 7.22 milliseconds
              99% <= 8.48 milliseconds
            99.9% <= 11.02 milliseconds

---

This change is 

[moderakh]

I am not sure if the 99 percentile printed by metrics/dropwizard to console is for the whole duration of the run or the last period (1s or 10s). @David-Noble-at-work to get the accurate numbers for the TCP could you check please?