Merge pull request #2669 from a-veitch/init_api_fix

Enrich census initialization and feature code

include/grpc/census.h

@@ -44,26 +44,30 @@
 extern "C" {
 #endif
 
-/* Identify census functionality that can be enabled via census_initialize(). */
-enum census_functions {
-  CENSUS_NONE = 0,    /* Do not enable census. */
-  CENSUS_TRACING = 1, /* Enable census tracing. */
-  CENSUS_STATS = 2,   /* Enable Census stats collection. */
-  CENSUS_CPU = 4,     /* Enable Census CPU usage collection. */
-  CENSUS_ALL = CENSUS_TRACING | CENSUS_STATS | CENSUS_CPU
+/* Identify census features that can be enabled via census_initialize(). */
+enum census_features {
+  CENSUS_FEATURE_NONE = 0,    /* Do not enable census. */
+  CENSUS_FEATURE_TRACING = 1, /* Enable census tracing. */
+  CENSUS_FEATURE_STATS = 2,   /* Enable Census stats collection. */
+  CENSUS_FEATURE_CPU = 4,     /* Enable Census CPU usage collection. */
+  CENSUS_FEATURE_ALL =
+      CENSUS_FEATURE_TRACING | CENSUS_FEATURE_STATS | CENSUS_FEATURE_CPU
 };
 
-/* Shutdown and startup census subsystem. The 'functions' argument should be
- * the OR (|) of census_functions values. If census fails to initialize, then
+/** Shutdown and startup census subsystem. The 'features' argument should be
+ * the OR (|) of census_features values. If census fails to initialize, then
  * census_initialize() will return a non-zero value. It is an error to call
  * census_initialize() more than once (without an intervening
  * census_shutdown()). */
-int census_initialize(int functions);
-void census_shutdown();
+int census_initialize(int features);
+void census_shutdown(void);
 
-/* If any census feature has been initialized, this funtion will return a
- * non-zero value. */
-int census_available();
+/** Return the features supported by the current census implementation (not all
+ * features will be available on all platforms). */
+int census_supported(void);
+
+/** Return the census features currently enabled. */
+int census_enabled(void);
 
 /* Internally, Census relies on a context, which should be propagated across
  * RPC's. From the RPC subsystems viewpoint, this is an opaque data structure.

src/core/census/grpc_context.c

@@ -39,7 +39,7 @@ static void grpc_census_context_destroy(void *context) {
 }
 
 void grpc_census_call_set_context(grpc_call *call, census_context *context) {
-  if (!census_available()) {
+  if (census_enabled() == CENSUS_FEATURE_NONE) {
     return;
   }
   if (context == NULL) {

src/core/census/initialize.c

@@ -33,20 +33,25 @@
 
 #include <grpc/census.h>
 
-static int census_fns_enabled = CENSUS_NONE;
+static int features_enabled = CENSUS_FEATURE_NONE;
 
-int census_initialize(int functions) {
-  if (census_fns_enabled != CENSUS_NONE) {
+int census_initialize(int features) {
+  if (features_enabled != CENSUS_FEATURE_NONE) {
     return 1;
   }
-  if (functions != CENSUS_NONE) {
+  if (features != CENSUS_FEATURE_NONE) {
     return 1;
   } else {
-    census_fns_enabled = functions;
+    features_enabled = features;
     return 0;
   }
 }
 
-void census_shutdown() { census_fns_enabled = CENSUS_NONE; }
+void census_shutdown(void) { features_enabled = CENSUS_FEATURE_NONE; }
 
-int census_available() { return (census_fns_enabled != CENSUS_NONE); }
+int census_supported(void) {
+  /* TODO(aveitch): improve this as we implement features... */
+  return CENSUS_FEATURE_NONE;
+}
+
+int census_enabled(void) { return features_enabled; }

src/core/surface/init.c

@@ -80,8 +80,11 @@ void grpc_init(void) {
     grpc_security_pre_init();
     grpc_iomgr_init();
     grpc_tracer_init("GRPC_TRACE");
-    if (census_initialize(CENSUS_NONE)) {
-      gpr_log(GPR_ERROR, "Could not initialize census.");
+    /* Only initialize census if noone else has. */
+    if (census_enabled() == CENSUS_FEATURE_NONE) {
+      if (census_initialize(census_supported())) { /* enable all features. */
+        gpr_log(GPR_ERROR, "Could not initialize census.");
+      }
     }
     grpc_timers_global_init();
   }