diff options
Diffstat (limited to 'TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp')
| -rw-r--r-- | TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp | 110 |
1 files changed, 100 insertions, 10 deletions
diff --git a/TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp b/TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp index 37f458dd722..9252ffaf438 100644 --- a/TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp +++ b/TAO/orbsvcs/orbsvcs/LoadBalancing/LB_LeastLoaded.cpp @@ -1,5 +1,3 @@ -// -*- C++ -*- - #include "LB_LeastLoaded.h" #include "LB_LoadMap.h" #include "LB_Random.h" @@ -211,6 +209,10 @@ TAO_LB_LeastLoaded::next_member ( if (found_location) { +// ACE_DEBUG ((LM_DEBUG, +// "RETURNING REFERENCE FOR LOCATION \"%s\"\n", +// location[0].id.in ())); + return load_manager->get_member_ref (object_group, location ACE_ENV_ARG_PARAMETER); @@ -340,7 +342,7 @@ TAO_LB_LeastLoaded::get_location ( ACE_ENV_ARG_DECL) { CORBA::Float min_load = FLT_MAX; // Start out with the largest - // possible. + // positive value. CORBA::ULong location_index = 0; CORBA::Boolean found_location = 0; @@ -374,14 +376,16 @@ TAO_LB_LeastLoaded::get_location ( // ACE_DEBUG ((LM_DEBUG, // "LOC = %u" -// "\tCOND = %d" +// "\tC = %d" // "\treject = %f" -// "\tload = %f\n", +// "\tload = %f\n" +// "\tmin_load = %f\n", // i, // (this->reject_threshold_ == 0 // || load.value < this->reject_threshold_), // this->reject_threshold_, -// load.value)); +// load.value, +// min_load)); if ((this->reject_threshold_ == 0 || load.value < this->reject_threshold_) @@ -391,10 +395,94 @@ TAO_LB_LeastLoaded::get_location ( // "**** LOAD == %f\n", // load.value)); - min_load = load.value; - location_index = i; - found_location = 1; + if (i > 0 && load.value != 0) + { + /* + percent difference = + (min_load - load.value) / load.value + == (min_load / load.value) - 1 + + The latter form is used to avoid a potential + arithmetic overflow problem, such as when + (min_load - load.value) > FLT_MAX, assuming that + either load.value is negative and min_load is + positive, or vice versa. + */ + const CORBA::Float percent_diff = + (min_load / load.value) - 1; + + /* + A "thundering herd" phenomenon may occur when + location loads are basically the same (e.g. only + differ by a very small amount), where one object + group member ends up receiving the majority of + requests from different clients. In order to + prevent a single object group member from + receiving such request bursts, one of two equally + loaded locations is chosen at random. Thanks to + Carlos, Marina and Jody at ATD for coming up with + this solution to this form of the thundering herd + problem. + + See the documentation for + TAO_LB::LL_DEFAULT_LOAD_PERCENT_DIFF_CUTOFF in + LB_LeastLoaded.h for additional information. + */ + if (percent_diff <= TAO_LB::LL_DEFAULT_LOAD_PERCENT_DIFF_CUTOFF) + { + // Prevent integer arithmetic overflow. + const CORBA::Float NUM_MEMBERS = 2; + + // n == 0: Use previously selected location. + // n == 1: Use current location. + const CORBA::ULong n = + ACE_static_cast (CORBA::ULong, + NUM_MEMBERS * ACE_OS::rand () + / (RAND_MAX + 1.0)); + + ACE_ASSERT (n == 0 || n == 1); + + if (n == 1) + { + min_load = load.value; + location_index = i; + found_location = 1; + +// ACE_DEBUG ((LM_DEBUG, +// "** NEW MIN_LOAD == %f\n", +// min_load)); + } + +// if (n == 0) +// ACE_DEBUG ((LM_DEBUG, "^^^^^ PREVIOUS LOCATION\n")); +// else +// ACE_DEBUG ((LM_DEBUG, "^^^^^ CURRENT LOCATION\n")); + + } + else + { + min_load = load.value; + location_index = i; + found_location = 1; + +// ACE_DEBUG ((LM_DEBUG, +// "***** NEW MIN_LOAD == %f\n", +// min_load)); + } + } + else + { + min_load = load.value; + location_index = i; + found_location = 1; + +// ACE_DEBUG ((LM_DEBUG, +// "NEW MIN_LOAD == %f\n", +// min_load)); + } } + + // ACE_DEBUG ((LM_DEBUG, "NEW MIN_LOAD == %f\n", min_load)); } ACE_CATCH (CosLoadBalancing::LocationNotFound, ex) { @@ -407,7 +495,7 @@ TAO_LB_LeastLoaded::get_location ( // ACE_DEBUG ((LM_DEBUG, // "FOUND_LOAD == %u\n" -// "FOUND_LOCATION = %u\n", +// "FOUND_LOCATION == %u\n", // found_load, // found_location)); @@ -420,6 +508,8 @@ TAO_LB_LeastLoaded::get_location ( location = locations[location_index]; else if (this->reject_threshold_ != 0) ACE_THROW_RETURN (CORBA::TRANSIENT (), 0); + +// ACE_DEBUG ((LM_DEBUG, "LOCATION ID == %s\n", location[0].id.in ())); } // ACE_DEBUG ((LM_DEBUG, "LOCATED = %u\n", location_index)); |