From 85674de74598a61991045c1ac36af551029b89c8 Mon Sep 17 00:00:00 2001
From: easy <g-easy@users.noreply.github.com>
Date: Fri, 1 Mar 2019 14:22:02 +1100
Subject: [PATCH] Constant sampler: add option to always follow the parent's
 decision. (#182)

Fixes #180.
---
 src/opencensus/proto/trace/v1/trace_config.proto | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/opencensus/proto/trace/v1/trace_config.proto b/src/opencensus/proto/trace/v1/trace_config.proto
index 07645de..0f9b5f3 100644
--- a/src/opencensus/proto/trace/v1/trace_config.proto
+++ b/src/opencensus/proto/trace/v1/trace_config.proto
@@ -56,12 +56,19 @@ message ProbabilitySampler {
   double samplingProbability = 1;
 }
 
-// Sampler that makes a constant decision (either always "yes" or always "no")
-// on span sampling.
+// Sampler that always makes a constant decision on span sampling.
 message ConstantSampler {
 
-  // Whether spans should be always sampled, or never sampled.
-  bool decision = 1;
+  // How spans should be sampled:
+  // - Always off
+  // - Always on
+  // - Always follow the parent Span's decision (off if no parent).
+  enum ConstantDecision {
+    ALWAYS_OFF = 0;
+    ALWAYS_ON = 1;
+    ALWAYS_PARENT = 2;
+  }
+  ConstantDecision decision = 1;
 }
 
 // Sampler that tries to sample with a rate per time window.