X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Scheduler%2FClockService.hh;h=8fb1341a12d8d56bd24d20c7a205135b782dcbc8;hb=81f84badf27b66dbadec9890646ca1193e998505;hp=da50573e35b335826ffc321999c7f0ba94fb4655;hpb=c6811d4b2fdd60eb33af627ae287dd228f435d14;p=senf.git diff --git a/Scheduler/ClockService.hh b/Scheduler/ClockService.hh index da50573..8fb1341 100644 --- a/Scheduler/ClockService.hh +++ b/Scheduler/ClockService.hh @@ -23,8 +23,8 @@ /** \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 @@ -32,7 +32,9 @@ #include #include #include +#include "../config.hh" #include "../Utils/singleton.hh" +#include "../Utils/Console/Parse.hh" //#include "ClockService.mpp" ///////////////////////////////hh.p//////////////////////////////////////// @@ -43,55 +45,21 @@ namespace senf { 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 @@ -105,7 +73,12 @@ namespace senf { 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 @@ -114,6 +87,12 @@ namespace senf { */ 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 @@ -126,6 +105,12 @@ namespace senf { 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. @@ -157,7 +142,10 @@ namespace senf { 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(); @@ -176,6 +164,43 @@ namespace senf { #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: + + + + + + +
\c ddays
\c hhours
\c mminutes
\c sseconds
+ + Additionally, the unit may be prefixed by an SI scale: + + + + + +
\c mmilli
\c umicro
\c nnano
+ + An optional decimal point is also supported. A single timer interval may combine any number + of these specifications. The following are all valid intervals: + + + + + + + + + +
10d10 days
5d5d10 days
1d2h100m3.5s27 hours, 30 minutes and 3.5 seconds
1s100ms1.1 seconds
1.1s1.1 seconds
123.456us123.456 microseconds
2md(very unusual) 2 milli-days
+ */ + void parseClockServiceInterval(console::ParseCommandInfo::TokensRange const & tokens, + ClockService::clock_type & out); + + void formatClockServiceInterval(ClockService::clock_type interval, std::ostream & os); } ///////////////////////////////hh.e////////////////////////////////////////