erlang_v8_vm_sup + hash_ring
erlang_v8_vm
PROC1 -> OS1
PROC2 -> OS2
{ok, Context} = create_context().
{ok, Value} = eval(Context, Source).
{ok, Value} = call(Context, Fun, Args).
ok = destroy_context(Context).
- Send timeouts to os proc
- Report invalid contexts
- Collect "dead" contexts
- Create base-context pre-initialized with code from erlang
Requires libtinfo.
Run JavaScript from Erlang in an external OS process.
This is just an experiment to see if embedding v8 in an actual OS process is more predictable than using a port driver or NIF. I will give the project proper attention if the experiment works out.
The most notable features:
- You can
eval/3
things like "while (true) {}" with a timeout and have the v8 VM actually terminate when it times out (the OS process is killed and restarted). - The context of the VM can then be reset (the current implementation is pretty naive; I'm working on a more elegant solution). This is useful when you want multiple parties to share the same VM(s).
- A VM can be initialized with pre-defined source that's loaded into the OS process and automatically evaluated when the VM is reset or restarted.
I'm also planning two-way communication (i.e. passing messages back to the controlling process from JS) and a few other things.
Subversion, and Python 2.6-2.7 (needed by GYP) are required to build v8.
Build using make:
make
GYP is not compatible with Python3. If python3
is the default, you can
symlink python2
to ~/bin
and set your path temporarily before compiling:
ln -s /usr/bin/python2 ~/bin/python
PATH=$HOME/bin:$PATH make
You can run a few tests to verify basic functionality:
make tests
Start a VM:
{ok, VM} = erlang_v8:start_vm().
Define a function:
{ok, undefined} =
erlang_v8:eval(VM, <<"function sum(a, b) { return a + b }">>).
Call the function:
{ok, 2} = erlang_v8:call(VM, <<"sum">>, [1, 1]).
You can reset the VM:
ok = erlang_v8:reset_vm(VM).
{error, <<"ReferenceError: sum is not defined">>} =
erlang_v8:call(VM, <<"sum">>, [1, 1]).
Stop the VM:
ok = erlang_v8:stop_vm(VM).
VMs can be initialized with code that is automatically reloaded when the VM is reset or restarted:
{ok, VM} = erlang_v8:start_vm([{source, <<"var x = 1;">>}]).
{ok, 1} = erlang_v8:eval(VM, <<"x;">>).
ok = erlang_v8:reset_vm(VM).
{ok, 1} = erlang_v8:eval(VM, <<"x;">>).
{ok, 2} = erlang_v8:eval(VM, <<"x = 2;">>).
{ok, 2} = erlang_v8:eval(VM, <<"x;">>).
ok = erlang_v8:reset_vm(VM).
{ok, 1} = erlang_v8:eval(VM, <<"x;">>).
ok = erlang_v8:stop_vm(VM).
You can also initialize the VMs using paths to source files:
{ok, VM} = erlang_v8:start_vm([{file, "a.js"}, {file, "b.js"}]).
Set a custom timeout (defaults to 5000
):
{error, timeout} = erlang_v8:eval(VM, <<"while (true) {}">>, 500).
You might want to use some kind of pooling mechanism as the VMs are real OS processes. I've had much success using devinus/poolboy for this purpose in the past (I considered including the application, but decided against it as it might not always be desirable to have a pool. Besides, poolboy is easy to set up).
I'm also working on strange/erlang-v8-lib, a little framework that, among other things, implements a pool.
- Use custom protocol to support more data types (binary, dates etc
- Refactor the API
- Experiment with calling Erlang from v8 synchronously