probability.rb in opencensus-0.4.0

- old
+ new

@@ -10,22 +10,25 @@
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+
+require "monitor"
+
 module OpenCensus
   module Trace
     module Samplers
       ##
       # The Probability sampler uses a random number generator against a
       # configured rate to determine whether or not to sample.
       #
       class Probability
         ##
-        # The default sampling probability.
+        # The default sampling probability, equal to 1/10000.
         #
-        DEFAULT_RATE = 0.1
+        DEFAULT_RATE = 0.0001
 
         ##
         # Create a sampler for the given probability.
         #
         # @param [Number] rate Probability that we will sample. This value must
@@ -37,30 +40,35 @@
           if rate > 1 || rate < 0
             raise ArgumentError, "Invalid rate - must be between 0 and 1."
           end
           @rate = rate
           @rng = rng || Random.new
+          @lock = Monitor.new
         end
 
         ##
         # Implements the sampler contract. Checks to see whether a sample
         # should be taken at this time.
         #
         # @param [Hash] opts The options to sample with.
         # @option opts [SpanContext] :span_context If provided, the span context
-        #         will be used to generate a deterministic value in place of the
-        #         pseudo-random number generator.        #
+        #         will be checked and the parent's sampling decision will be
+        #         propagated if the parent was sampled. The span context will
+        #         also be used to generate a deterministic value in place of the
+        #         pseudo-random number generator.
         # @return [boolean] Whether to sample at this time.
         #
         def call opts = {}
           span_context = opts[:span_context]
           return true if span_context && span_context.sampled?
           value =
             if span_context
               (span_context.trace_id.to_i(16) % 0x10000000000000000).to_f /
                 0x10000000000000000
             else
-              @rng.rand
+              @lock.synchronize do
+                @rng.rand
+              end
             end
           value <= @rate
         end
       end
     end