Make kvstore backend in BlueSky asynchronous.

[bluesky.git] / kvstore / kvservice.cc

diff --git a/kvstore/kvservice.cc b/kvstore/kvservice.cc
index e241bc9..59e194a 100644 (file)
--- a/kvstore/kvservice.cc
+++ b/kvstore/kvservice.cc
@@ -1,8 +1,43 @@
 #include "kvservice.h"
 #include <iostream>
 
+extern "C" {
+#include <time.h>
+#include <sys/time.h>
+}
+
 using namespace std;
 
+/* Timing and delay functionality.  We allow the get and put operations to have
+ * a specified minimum latency, and will sleep if the operation would have
+ * completed before that time.  This can be used in benchmarking to see the
+ * effect of increasing latency on an application.
+ *
+ * Call gettimeofday at the start of the operation to get the starting time,
+ * and then use minimum_delay to wait until at least the specified number of
+ * microseconds have elapsed. */
+static void minimum_delay(const struct timeval *tv, unsigned int min_usec)
+{
+    struct timeval now;
+    if (gettimeofday(&now, NULL) < 0)
+        return;
+
+    int64_t t1, t2;             /* Times converted to straight microseconds */
+    t1 = (int64_t)tv->tv_sec * 1000000 + tv->tv_usec;
+    t2 = (int64_t)now.tv_sec * 1000000 + now.tv_usec;
+
+    unsigned int elapsed = t2 - t1;
+    if (elapsed >= min_usec)
+        return;
+
+    struct timespec delay;
+    delay.tv_sec = (min_usec - elapsed) / 1000000;
+    delay.tv_nsec = ((min_usec - elapsed) % 1000000) * 1000;
+
+    while (nanosleep(&delay, &delay) != 0 && errno == EINTR)
+        ;
+}
+
 namespace kvstore
 {
 
@@ -21,6 +56,9 @@ void KeyValueRpcService::PutValue(
                       ::kvrpc::PutReply* response,
                       ::google::protobuf::Closure* done)
 {
+    struct timeval start;
+    gettimeofday(&start, NULL);
+
     if (_backend->Put(request->key(), request->value()))
     {
         response->set_result(kvrpc::SUCCESS);
@@ -30,6 +68,7 @@ void KeyValueRpcService::PutValue(
         response->set_result(kvrpc::FAILURE);
     }
 
+    minimum_delay(&start, 1000000);
     done->Run();
 }
 
@@ -39,6 +78,9 @@ void KeyValueRpcService::GetValue(
                       ::kvrpc::GetReply* response,
                       ::google::protobuf::Closure* done)
 {
+    struct timeval start;
+    gettimeofday(&start, NULL);
+
     string value;
     if (_backend->Get(request->key(), &value))
     {
@@ -49,6 +91,8 @@ void KeyValueRpcService::GetValue(
     {
         response->set_result(kvrpc::FAILURE);
     }
+
+    minimum_delay(&start, 1000000);
     done->Run();
 }