posthaste

An Erlang/Elixir hooking library.

When to use Posthaste ?

When you want to lookup callbacks of hooks (especially with large numbers of processes at the same time), Posthaste is about 3-5 times faster than Erlang ETS. But in add/delete operations it's too slow (compared with ETS). Then if you have more lookup operation than add/delete operations, use Posthaste.

How to use?

In Posthaste, each hook must be an Erlang atom.

-type hook() :: atom().

Each hook has one or more key.

-type key() :: atom() | binary() | number() | list() | tuple().

Finally each key has its own handlers. handlers is a list which may contain one or more handler. Each handler contains priority which is non negative integer and module and function which are atoms.

-type handlers() :: [] | [handlers()].
-type  handlers() :: {priority(), module(), func()}.
-type   priority() :: non_neg_integer().
-type   func() :: atom().

Posthaste maps each key to its handlers for each hook:

1> Hooks = my_hooks.
my_hooks

%% Starting hook server process:
2> posthaste:start_link(Hooks).
{ok,<0.97.0>}

3> Hook1 = foo.
foo

4> Key1 = bar.
bar

%% Adding a hook with priority 10, module 'module' and function 'function':
5> posthaste:add(Hooks, Hook1, Key1, module, function, 10).
ok

%% Getting handlers of Key1 for Hook1:
6> posthaste:handlers(Hooks, Hook1, Key1).
[{10, module, function}]

7> posthaste:add(Hooks, Hook1, Key1, module, function, 10).
ok
8> posthaste:add(Hooks, Hook1, Key1, module2, function2, 20).
ok
9> posthaste:add(Hooks, Hook1, Key1, module2, function2, 15).
ok

10> posthaste:handlers(Hooks, Hook1, Key1).                  
[{10, module, function},
 {10, module, function},
 {15, module2, function2},
 {20, module2, function2}]

11> Key2 = baz.                                               
baz
12> posthaste:add(Hooks, Hook1, Key2, mod, func, 100).        
ok

13> posthaste:handlers(Hooks, Hook1, Key2).          
[{100,{mod,func}}]

14> posthaste:handlers(Hooks, Hook1, Key1).
[{10, module, function},
 {10, module, function},
 {15, module2, function2},
 {20, module2, function2}]

%% New hook:
15> Hook2 = qux.                                      
qux
16> posthaste:add(Hooks, Hook2, Key1, m, f, 1).        
ok
17> posthaste:handlers(Hooks, Hook2, Key1).   
[{1, m, f}]

%% Deleting a callback:
18> posthaste:delete(Hooks, Hook1, Key1, module2, function2, 15).
ok
19> posthaste:callbacks(Hooks, Hook1, Key1).                     
[{10, module,function},
 {10, module,function},
 {20, module2,function2}]

What is going on? (under the hood)

Let's run above code snippet again:

1> Hooks = my_hooks.        
my_hooks
2> posthaste:start_link(Hooks).
{ok,<0.97.0>}
3> Hook1 = foo.
foo
4> Key1 = bar.
bar
5> posthaste:add(Hooks, Hook1, Key1, module, function, 10).
ok

6> Hooks:Hook1(Key1).
[{10, module, function}]

7> my_hooks:foo(bar).
[{10, module, function}]

Actually each Posthaste server process creates new Erlang module and adds every hook as an Erlang function to it. key is an argument of hook function and finally callbacks are in function body.

Contributing

I love pull requests from everyone. But it's good to explain idea, feautre or bug in issues before.

Author

pouriya.jahanbakhsh@gmail.com

License

BSD 3-Clause

Hex version

18.5.19