KUDU-1684 - [python] Add Scan Resource Metrics Capabilities

Currently, the python client doesn't expose scanner resource metrics.
This patch enables this ability and includes tests.

Change-Id: Ib6c4057bd2644e46bdbf8bae0d4a768306e2dbd9
Reviewed-on: http://gerrit.cloudera.org:8080/4675
Tested-by: Kudu Jenkins
Reviewed-by: Todd Lipcon <[email protected]>

python/kudu/client.pyx

@@ -20,6 +20,7 @@
 
 from libcpp.string cimport string
 from libcpp cimport bool as c_bool
+from libcpp.map cimport map
 
 cimport cpython
 from cython.operator cimport dereference as deref
@@ -1453,6 +1454,22 @@ cdef class Scanner:
         result.schema = schema
         return result
 
+    def get_resource_metrics(self):
+        """
+        Return the cumulative resource metrics since the scan was started.
+
+        Returns
+        -------
+        metrics : Dictionary
+        """
+        _map = self.scanner.GetResourceMetrics().Get()
+
+        # Convert map to python dictionary
+        result = {}
+        for it in _map:
+            result[frombytes(it.first)] = it.second
+        return result
+
     def open(self):
         """
         Returns a reference to itself to facilitate chaining

python/kudu/libkudu_client.pxd

@@ -21,6 +21,7 @@ from libc.stdint cimport *
 from libcpp cimport bool as c_bool
 from libcpp.string cimport string
 from libcpp.vector cimport vector
+from libcpp.map cimport map
 
 # This must be included for cerr and other things to work
 cdef extern from "<iostream>":
@@ -631,6 +632,7 @@ cdef extern from "kudu/client/client.h" namespace "kudu::client" nogil:
         Status AddExclusiveUpperBound(const KuduPartialRow& key)
 
         KuduSchema GetProjectionSchema()
+        const ResourceMetrics& GetResourceMetrics()
         string ToString()
 
     cdef cppclass KuduScanToken:
@@ -681,3 +683,11 @@ cdef extern from "kudu/client/client.h" namespace "kudu::client" nogil:
         KuduWriteOperation* release_failed_op()
 
         c_bool was_possibly_successful()
+
+cdef extern from "kudu/client/resource_metrics.h" namespace "kudu::client" nogil:
+
+    cdef cppclass ResourceMetrics:
+        ResourceMetrics()
+
+        map[string, int64_t] Get()
+        int64_t GetMetric(const string& name)

python/kudu/tests/test_scanner.py

@@ -215,6 +215,21 @@ def test_read_mode(self):
             # Avoid tight looping
             time.sleep(0.05)
 
+    def test_resource_metrics(self):
+        """
+        Test getting the resource metrics after scanning.
+        """
+
+        # Build scanner and read through all batches and retrieve metrics.
+        scanner = self.table.scanner()
+        scanner.set_fault_tolerant().open()
+        scanner.read_all_tuples()
+        metrics = scanner.get_resource_metrics()
+
+        # Confirm that the scanner returned cache hit and miss values.
+        self.assertTrue('cfile_cache_hit_bytes' in metrics)
+        self.assertTrue('cfile_cache_miss_bytes' in metrics)
+
     def verify_pred_type_scans(self, preds, row_indexes, count_only=False):
         # Using the incoming list of predicates, verify that the row returned
         # matches the inserted tuple at the row indexes specified in a