From d6ef707422c8afba5046f395419a2a524a248472 Mon Sep 17 00:00:00 2001
From: yang-g <yangg@google.com>
Date: Wed, 1 Aug 2018 11:22:32 -0700
Subject: Add more filter priority levels

---
 src/cpp/common/channel_filter.cc          | 9 +++++++--
 src/cpp/common/channel_filter.h           | 7 ++++++-
 src/cpp/ext/filters/census/grpc_plugin.cc | 6 ++++--
 3 files changed, 17 insertions(+), 5 deletions(-)

(limited to 'src/cpp')

diff --git a/src/cpp/common/channel_filter.cc b/src/cpp/common/channel_filter.cc
index 422e7bb65e..0634b0416f 100644
--- a/src/cpp/common/channel_filter.cc
+++ b/src/cpp/common/channel_filter.cc
@@ -78,8 +78,13 @@ bool MaybeAddFilter(grpc_channel_stack_builder* builder, void* arg) {
         grpc_channel_stack_builder_get_channel_arguments(builder);
     if (!filter.include_filter(*args)) return true;
   }
-  return grpc_channel_stack_builder_prepend_filter(builder, &filter.filter,
-                                                   nullptr, nullptr);
+  if (filter.prepend) {
+    return grpc_channel_stack_builder_prepend_filter(builder, &filter.filter,
+                                                     nullptr, nullptr);
+  } else {
+    return grpc_channel_stack_builder_append_filter(builder, &filter.filter,
+                                                    nullptr, nullptr);
+  }
 }
 
 }  // namespace
diff --git a/src/cpp/common/channel_filter.h b/src/cpp/common/channel_filter.h
index 5e569c97e6..359c72737c 100644
--- a/src/cpp/common/channel_filter.h
+++ b/src/cpp/common/channel_filter.h
@@ -36,7 +36,8 @@
 /// \c ChannelData. Then register the filter using something like this:
 /// \code{.cpp}
 ///   RegisterChannelFilter<MyChannelDataSubclass, MyCallDataSubclass>(
-///       "name-of-filter", GRPC_SERVER_CHANNEL, INT_MAX, nullptr);
+///       "name-of-filter", GRPC_SERVER_CHANNEL, GRPC_CHANNEL_INIT_PRIORITY_LOW,
+///       true, nullptr);
 /// \endcode
 
 namespace grpc {
@@ -351,6 +352,7 @@ class ChannelFilter final {
 struct FilterRecord {
   grpc_channel_stack_type stack_type;
   int priority;
+  bool prepend;
   std::function<bool(const grpc_channel_args&)> include_filter;
   grpc_channel_filter filter;
 };
@@ -363,12 +365,14 @@ void ChannelFilterPluginShutdown();
 
 /// Registers a new filter.
 /// Must be called by only one thread at a time.
+/// The \a prepend argument decides whether to prepend or append the filter.
 /// The \a include_filter argument specifies a function that will be called
 /// to determine at run-time whether or not to add the filter. If the
 /// value is nullptr, the filter will be added unconditionally.
 template <typename ChannelDataType, typename CallDataType>
 void RegisterChannelFilter(
     const char* name, grpc_channel_stack_type stack_type, int priority,
+    bool prepend,
     std::function<bool(const grpc_channel_args&)> include_filter) {
   // If we haven't been called before, initialize channel_filters and
   // call grpc_register_plugin().
@@ -383,6 +387,7 @@ void RegisterChannelFilter(
   internal::FilterRecord filter_record = {
       stack_type,
       priority,
+      prepend,
       include_filter,
       {FilterType::StartTransportStreamOpBatch, FilterType::StartTransportOp,
        FilterType::call_data_size, FilterType::InitCallElement,
diff --git a/src/cpp/ext/filters/census/grpc_plugin.cc b/src/cpp/ext/filters/census/grpc_plugin.cc
index f978ed3bf5..f79e0e0e96 100644
--- a/src/cpp/ext/filters/census/grpc_plugin.cc
+++ b/src/cpp/ext/filters/census/grpc_plugin.cc
@@ -32,10 +32,12 @@ namespace grpc {
 
 void RegisterOpenCensusPlugin() {
   RegisterChannelFilter<CensusChannelData, CensusClientCallData>(
-      "opencensus_client", GRPC_CLIENT_CHANNEL, INT_MAX /* priority */,
+      "opencensus_client", GRPC_CLIENT_CHANNEL,
+      GRPC_CHANNEL_INIT_PRIORITY_VERY_HIGH, true /* prepend */,
       nullptr /* condition function */);
   RegisterChannelFilter<CensusChannelData, CensusServerCallData>(
-      "opencensus_server", GRPC_SERVER_CHANNEL, INT_MAX /* priority */,
+      "opencensus_server", GRPC_SERVER_CHANNEL,
+      GRPC_CHANNEL_INIT_PRIORITY_VERY_HIGH, true /* prepend */,
       nullptr /* condition function */);
 
   // Access measures to ensure they are initialized. Otherwise, creating a view
-- 
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