Author  : Hakan Mattsson <hakan@cslab.ericsson.se>
Created : 21 Jun 2001 by Hakan Mattsson <hakan@cslab.ericsson.se>

This is an implementation of a real-time database benchmark
(LMC/UU-01:025), defined by Richard Trembley (LMC) and Miroslaw
Zakrzewski (LMC) . The implementation runs the benchmark on the Mnesia
DBMS which is a part of Erlang/OTP (www.erlang.org).

The implementation is organized in the following parts:

  bench.erl          - main API, startup and configuration
  bench.hrl          - record definitions
  bench_populate.erl - create database and populate it with records
  bench_trans.erl    - the actual transactions to be benchmarked
  bench_generate.erl - request generator, statistics computation

Compile the files with:

  make all

and run the benchmarks with:

  make test

================================================================

The benchmark runs on a set of Erlang nodes which should reside on
one processor each.

There are many options when running the benchmark. Benchmark
configuration parameters may either be stated in a configuration file
or as command line arguments in the Erlang shell. Erlang nodes may
either be started manually or automatically by the benchmark program.

In its the most automated usage you only need to provide one or more
configuration files and run the

        bench.sh <ConfigFiles>

script to start all Erlang nodes, populate the database and run the
actual benchmark for each one of the configuration files. The
benchmark results will be displayed at stdout.

In order to be able to automatically start remote Erlang nodes, 
you need to:

 - put the $ERL_TOP/bin directory in your path on all nodes
 - bind IP addresses to hostnames (e.g via DNS or /etc/hosts)
 - enable usage of ssh so it does not prompt for password

If you cannot achieve this, it is possible to run the benchmark
anyway, but it requires more manual work to be done for each
execution of the benchmark.

================================================================

For each configuration file given to the bench.sh script:

  - a brand new Erlang node is started
  - the bench:run(['YourConfigFile']) function is invoked
  - the Erlang node(s) are halted.

Without arguments, the bench.sh simply starts an Erlang shell.
In that shell you have the ability to invoke Erlang functions,
such as bench:run/1. 

The bench:start_all/1 function analyzes the configuration, starts
all Erlang nodes necessary to perform the benchmark and starts
Mnesia on all these nodes.

The bench:populate/1 function populates the database according
to the configuration and assumes that Mnesia is up and running
on all nodes.

The bench:generate/1 function starts the actual benchmark
according to the configuration and assumes that Mnesia is
up and running and that the database is fully populated.
Given some arguments such as

   Args = ['YourConfigFile', {statistics_detail, debug}].

the invocation of

   bench:run(Args).

is equivalent with:

   SlaveNodes = bench:start_all(Args).
   bench:populate(Args).
   bench:generate(Args).
   bench:stop_slave_nodes(SlaveNodes).

In case you cannot get the automatic start of remote Erlang nodes to
work (implied by bench:start_all/1) , you may need to manually start
an Erlang node on each host (e.g. with bench.sh without arguments) and
then invoke bench:run/1 or its equivivalents on one of them.

================================================================

The following configuration parameters are valid:

generator_profile 

  Selects the transaction profile of the benchmark. Must be one
  of the following atoms: t1, t2, t3, t4, t5, ping, random.
  Defaults to random which means that the t1 .. t5 transaction
  types are randomly selected according to the benchmark spec.
  The other choices means disables the random choice and selects
  one particular transaction type to be run over and over again.

generator_warmup

  Defines how long the request generators should "warm up" the
  DBMS before the actual measurements are performed. The unit
  is milliseconds and defaults to 2000 (2 seconds).

generator_duration

  Defines the duration of the actual benchmark measurement activity.
  The unit is milliseconds and defaults to 15000 (15 seconds).

generator_cooldown

  Defines how long the request generators should "cool down" the
  DBMS after the actual measurements has been performed. The unit
  is milliseconds and defaults to 2000 (2 seconds).

generator_nodes

  Defines which Erlang nodes that should host request generators.
  The default is all connected nodes.

n_generators_per_node

  Defines how many generator processes that should be running on
  each generator node. The default is 2.

statistics_detail

  Regulates the detail level of statistics. It must be one of the
  following atoms: normal, debug and debug2. debug enables a
  finer grain of statistics to be reported, but since it requires
  more counters, to be updated by the generator processes it may
  cause slightly worse benchmark performance figures than the brief
  default case, that is normal. debug2 prints out the debug info
  and formats it according to LMC's benchmark program.

storage_type 

  Defines whether the database should be kept solely in primary
  memory (ram_copies), solely on disc (disc_only_copies) or
  in both (disc_copies). The default is ram_copies. Currently
  the other choices requires a little bit of manual preparation.

table_nodes

  Defines which Erlang nodes that should host the tables. 

n_fragments

  Defines how many fragments each table should be divided in.
  Default is 100. The fragments are evenly distributed over
  all table nodes. The group table not divided in fragments.

n_replicas

  Defines how many replicas that should be kept of each fragment.
  The group table is replicated to all table nodes.
  
n_subscribers

  Defines the number of subscriber records. Default 25000.

n_subscribers

  Defines the number of subscriber records. Default 25000.

n_groups

  Defines the number of group records. Default 5.

n_servers

  Defines the number of server records. Default 1.

write_lock_type 

  Defines whether the transactions should use ordinary
  write locks or if they utilize sticky write locks.
  Must be one of the following atoms: write, sticky_write.
  Default is write.
  
use_binary_subscriber_key

  Defines whether the subscriber key should be represented
  as a string (binary) or as an integer. Default is false.

always_try_nearest_node

  The benchmark was initially written to test scalability
  when more nodes were added to the database and when the
  (fragmented) tables were distributed over all nodes. In
  such a system the transactions should be evenly distributed
  over all nodes. When this option is set to true it is possible
  to make fair measurements of master/slave configurations, when
  all transactions are performed on on one node. Default is false.

cookie

  Defines which cookie the Erlang node should use in its
  distribution protocol. Must be an atom, default is 'bench'.
