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RO4R - Remote Objects for Ruby 2.4+

Git export of RO4R, a Ruby RPC library that has been in production use since 2007.

Supported Ruby versions

Supports all Ruby versions from 2.4 above, in all combinations of client and server versions.

For support on older versions, please see below under "Other Ruby versions".

How to see it work

  1. Check out the files:
  git clone git://github.com/crystallabs/RO4R.git
  1. In one terminal, start an example server. It will listen on port 4044, export one Ruby Hash variable, and provide the main loop:
  cd RO4R
  ruby -I. examples/srv.rb
  1. In another terminal, start an example client. It will attach to the server and shared Hash, iterate a counter 10_000 times, and then print the benchmark statistics and the final contents of the Hash:
  cd RO4R
  ruby -I. examples/cli.rb

NOTE: when the client program does its job and disconnects, on the server side you will see the following message which you can safely ignore:

#<NoMethodError: undefined method `length' for nil:NilClass>)

Benchmarks explanation

When you run the above, it will print statistics such as:

0.390000   0.390000   0.780000 (  1.451144)
{:counter=>9999, 1=>A, 2=>#<A:0xb7741e38>}

The first line is the benchmark output, showing user, system, total and real times. (That's benchmark for the 10,000 iterations that the example client does).

The second line are the contents of the shared Hash object. In it you see the :counter that was created on the client side, and two keys that were initialized by the example server.

Testing

To test RO4R, you can create two processes (client and server), and then display and modify variables and invoke remote functions.

  1. To conveniently test modifying data, run the basic benchmark under IRB, then modify some hash keys on the example shared object $r:
$ cd RO4R
$ irb -I. -r examples/cli.rb

# ... statistics will be printed ...

> $r[:counter]
9999
> $r[:test_value]= 717
#-> 717
  1. To run defined functions, simply call them:

On the server side, in the example we have initialized an example method 'm' that returns value of 1; you can run it:

> $r[2].m
#-> 1
  1. Multiple clients:

You can also open a new/third terminal in which you can query all the changes:

$ cd RO4R
$ irb -I. -r examples/cli.rb

> $r
{:counter=>9999, 1=>A, 2=>#<A:0xb7745e34>, :test_value=>717}

Benchmarks

Benchmarks for 10,000 RPC invocations:

Date        Server   Client     Stats
Jun 2018:   2.6.0p2   2.6.0p2   0.192000   0.100000   0.292000 (  0.517264)
Oct 2015:   2.2.3     2.2.3     0.196000   0.076000   0.272000 (  0.481286)

Jun 2018 setup was: i7-4790K CPU @ 4.00GHz on Linux 3.16.0-4-amd64
Oct 2015 setup was: i7-4790K CPU @ 4.00GHz on Linux 4.2.0-040200-lowlatency

Older Benchmarks from 2008:

            Server   Client     Stats
            1.9.2     1.9.2     0.390000   0.390000   0.780000 (  1.451144)
            1.9.2     1.8.7     1.000000   0.280000   1.280000 (  2.009202)
            1.8.7     1.9.2     0.520000   0.300000   0.820000 (  1.914454)
            1.8.7     1.8.7     0.960000   0.260000   1.220000 (  2.472942)

Programming notes

Shared classes

Generally, you will share instances of classes that are known to both the server and the clients.

But it is also possible to share objects that clients know nothing about.

Included in the distribution is rmarshal/, a modification of Ruby marshaller that you need to compile and 'require' into your Ruby app on the server side (the one that exports the object), without any other changes.

With that, the clients will transparently be able to use the remote object even though they don't know its Class.

NOTE: rmarshal.c is currently out of date, and the version included works with Ruby 1.8.

Method return values

When writing methods, you usually don't care about unused return values because Ruby simply discards them.

However, on methods that are invoked remotely, RO4R will pass the return value back to the client, so pay attention to exit a method with an explicit 'nil' if its return value is not needed. This is cleaner and can also save you from errors if the (unnecessary) return value would be a weird object that Ruby marshaller can't serialize and pass back to the client.

Code stability

RO4R has been in production use with Ruby 1.8, 1.9, and later since 2007.

Other Ruby versions

For use with lower versions (Ruby 1.8 to Ruby 2.3) , please either use RO4R release 1.0.0 or edit RO4R.rb to replace "safe= 1" with "safe= 3" and uncomment the line saying "Bignum, Fixnum".

The C marshaller (rmarshall) is operational only for Ruby 1.8 versions.

TODO

  • Add rmarshall for newer Ruby versions