/** \file
\brief ClockService public header */
-#ifndef HH_ClockService_
-#define HH_ClockService_ 1
+#ifndef HH_SENF_Scheduler_ClockService_
+#define HH_SENF_Scheduler_ClockService_ 1
// Custom includes
#include <sys/time.h>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/scoped_ptr.hpp>
#include <boost/cstdint.hpp>
+#include "../config.hh"
#include "../Utils/singleton.hh"
+#include "../Utils/Console/Parse.hh"
//#include "ClockService.mpp"
///////////////////////////////hh.p////////////////////////////////////////
namespace detail { class ClockServiceTest; }
#endif
- // Implementation note:
+ // Implementation note: The clock value is represented as a 64bit unsigned integer number of
+ // nanosecods based on the CLOCK_MONOTONIC POSIX clock.
//
- // The clock value is represented as a 64bit unsigned integer number of nanosecods elapsed since
- // the construction of the ClockService object.
- //
- // The implementation must provide two features:
- // a) It must reliably detect clock changes
- // b) In case of a clock change a reasonably accurate fallback clock value must be provided
- //
- // We do this using setitimer/getitimer. We setup an interval timer sending SIGALRM whenever
- // CheckInverval seconds have elapsed.
- //
- // On every SIGALRM signal we save the current value of gettimeofday(). If this new value is
- // substantially different from the currently saved value + CheckInterval, the clock has been
- // changed.
- //
- // Whenever the current clock value is requested using now(), the current gettimeofday() value
- // is compared with the saved value. If the difference is substantially more than CheckInterval,
- // the clock has been changed.
- //
- // This provides clock skew detection. If clock skew is detected, we need to move base_ by the
- // amount the time has been changed. To do this we need an as accurate as possible approximation
- // of the expected current time value. We need to differentiate two cases:
- //
- // a) Clock skew detected within now()
- //
- // In this case, we use getitimer() to find the time remaining in the timer. Using this value
- // and the saved gettimeofday() value we can adjust base_ accordingly.
- //
- // b) Clock skew detected in the signal handler
- //
- // In this case we use the saved gettimeofday() value + CheckInterval to adjust base_.
+ // To allow conversion between clock value and absolute time, the ClockService samples the
+ // absolute current time and the clock value when the conversion is performed. This is done at
+ // most once per second on a if-needed basis.
/** \brief Reliable high precision monotonous clock source
The ClockService provides a highly accurate monotonous clock source based on
gettimeofday(). However, it takes additional precautions to detect clock skew.
- \implementation We use a mix of static and non-static members to achieve high performance
- in the normal case (no clock skew) and still encapsulate the dependency on legacy C
- headers. Using the senf::singleton mixin ensures, that the instance is constructed
- before main even when instance() is not called.
-
- \bug There is a deadlock condition between ClockService and the streaming of Boost.DateTime
- values: Boost.DateTime seems to call tzset() whenever writing a date/time value (ugh)
- and since tzset changes basic date/time values, it seems to block gettimeofday() which
- leads to the SIGLARM handler blocking indefinitely. Resolution either a) find out, why
- tzset() of all functions is called or b) move the ClockService heartbeat functionality
- into the Scheduler.
+ \implementation The funny mixture of static and non-static members stems from the old
+ implementation based on interval timers and gettimeofday(). The current implementation
+ usses POSIX clocks and is much simpler and more precise.
*/
class ClockService
: singleton<ClockService>
Unsigned integer type representing scheduler time. Scheduler time is measured in
nanoseconds relative to some implementation defined reference time.
*/
- typedef boost::int_fast64_t clock_type;
+ typedef config::time_type clock_type;
+
+ /** \brief Supplementary integer type
+
+ This type is used to represent varies supplementary values (e.g. number of microseconds)
+ */
typedef boost::int_fast64_t int64_type;
/** \brief Absolute time data type
*/
typedef boost::posix_time::ptime abstime_type;
+ /** \brief Relative time data type
+
+ Boost.DateTime datatype used to represent time intervals
+ */
+ typedef boost::posix_time::time_duration reltime_type;
+
///////////////////////////////////////////////////////////////////////////
static clock_type now(); ///< Return current clock value
monotonous, absolute time may be non-monotonous if
the system date/time is changed. */
+ static reltime_type reltime(clock_type clock); ///< Convert clock to relative time
+ /**< This member converts a clock value into a relative
+ Boost.DateTime time interval
+ \note The resolution of reltime_type might be smaller
+ than the clock_type resolution */
+
static clock_type clock(abstime_type time); ///< Convert absolute time to clock value
/**< This member converst an absolute time value into the
corresponding clock value.
static int64_type in_hours(clock_type v); ///< Convert \a v to hours
static int64_type in_days(clock_type v); ///< Convert \a v to days
- static void restart();
+ static void restart(); ///< Force re-syncronisation of abstime and clock
+ /**< Calling the member should never be necessary since
+ abstime() / clock() automatically call restart() if
+ needed */
private:
ClockService();
#endif
};
+ /** \brief Console argument parser to parse value as time interval
+
+ This parser will parse a time interval specification into a ClockService::clock_type
+ value. The following units are supported:
+
+ <table class="senf fixedcolumn">
+ <tr><td>\c d</td><td>days</td></tr>
+ <tr><td>\c h</td><td>hours</td></tr>
+ <tr><td>\c m</td><td>minutes</td></tr>
+ <tr><td>\c s</td><td>seconds</td></tr>
+ </table>
+
+ Additionally, the unit may be prefixed by an SI scale:
+
+ <table class="senf fixedcolumn">
+ <tr><td>\c m</td><td>milli</td></tr>
+ <tr><td>\c u</td><td>micro</td></tr>
+ <tr><td>\c n</td><td>nano</td></tr>
+ </table>
+
+ An optional decimal point is also supported. A single timer interval may combine any number
+ of these specifications. The following are all valid intervals:
+
+ <table class="senf fixedcolumn">
+ <tr><td><code>10d</code></td><td>10 days</td></tr>
+ <tr><td><code>5d5d</code></td><td>10 days</td></tr>
+ <tr><td><code>1d2h100m3.5s</code></td><td>27 hours, 30 minutes and 3.5 seconds</td></tr>
+ <tr><td><code>1s100ms</code></td><td>1.1 seconds</td></tr>
+ <tr><td><code>1.1s</code></td><td>1.1 seconds</td></tr>
+ <tr><td><code>123.456us</code></td><td>123.456 microseconds</td></tr>
+ <tr><td><code>2md</code></td><td>(very unusual) 2 milli-days</td></tr>
+ </table>
+ */
+ void parseClockServiceInterval(console::ParseCommandInfo::TokensRange const & tokens,
+ ClockService::clock_type & out);
}
///////////////////////////////hh.e////////////////////////////////////////
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