Merge pull request #14 from xapi-project/private/asultanov/monotonic-timestamp

librrd: Get timestamp at a higher precision

Author: last-genius

README.md

@@ -107,9 +107,8 @@ considered private to the library.
 
 The name of the plugin is descriptive, as whether it reports data
 for a single machine (`RRD_LOCAL_DOMAIN`) or multiple
-(`RRD_INTER_DOMAIN`). The second parameter of `rrd_sample` is typically
-NULL. If it isn't, it us used to obtain a timestamp instead of using
-time(3).
+(`RRD_INTER_DOMAIN`). The second parameter of `rrd_sample` is deprecated
+and will be ignored (and should be NULL).
 
 When a plugin is opened, the file at `path` is being created and it is
 removed when the plugin is closed.

librrd.c

@@ -218,6 +218,14 @@ json_for_plugin(RRD_PLUGIN * plugin)
     }
     return root_json;
 }
+
+double get_timestamp()
+{
+    struct timeval tp;
+    gettimeofday(&tp, NULL);
+    return (double) tp.tv_sec + (double) tp.tv_usec / 1e6;
+}
+
 /*
  * initialise the buffer that we update and write out to a file. Once
  * initialised, it is kept up to date by sample().
@@ -263,7 +271,7 @@ initialise(RRD_PLUGIN * plugin)
     memcpy(&header->rrd_magic, MAGIC, MAGIC_SIZE);
     header->rrd_checksum_value = htonl(0x01234567);
     header->rrd_header_datasources = htonl(plugin->n);
-    header->rrd_timestamp = htonll((uint64_t) time(NULL));
+    header->rrd_timestamp = htonll(get_timestamp());
     if (header->rrd_timestamp == -1) {
         free(plugin->buf);
         plugin->buf_size = 0;
@@ -450,7 +458,7 @@ rrd_sample(RRD_PLUGIN * plugin, time_t(*t) (time_t *))
      * update timestamp, calculate crc
      */
 
-    header->rrd_timestamp = htonll((uint64_t) (t ? t(NULL) : time(NULL)));
+    header->rrd_timestamp = htonll(get_timestamp());
     uint32_t        crc = crc32(0L, Z_NULL, 0);
     crc = crc32(crc,
                 (unsigned char *)&header->rrd_timestamp,

librrd.h

@@ -23,7 +23,7 @@
 
 
 #include <stdint.h>
-#include <time.h>
+#include <sys/time.h>
 
 #define RRD_MAX_SOURCES         16
 
@@ -131,8 +131,6 @@ int             rrd_del_src(RRD_PLUGIN * plugin, RRD_SOURCE * source);
  * calling rrd_sample(plugin) triggers that all data sources are sampled
  * and the results are reported to the RRD daemon. This function needs
  * to be called every 5 seconds by the client. The second parameter is
- * typically NULL. If it isn't, it will be used instead of time(3) to
- * obtain the time stamp that is written to the RRD file. This can be
- * used to create RRD files that don't depend on the current time.
+ * deprecated and will be ignored (and should be NULL).
  */
 int             rrd_sample(RRD_PLUGIN * plugin, time_t (*t)(time_t*));