concurrency: Add parent's name to new thread's name

[YuvalEvron]

Fixes #174

[idanarye]

This can easily explode:

In [1]: import threading

In [2]: from easypy.concurrency import concurrent, MultiObject

In [3]: def recurse(depth):
   ...:     print('%s remain, I am %r' % (depth, threading.current_thread().name))
   ...:     if 0 < depth:
   ...:         with concurrent(recurse, depth - 1):
   ...:             pass
   ...:

In [4]: recurse(3)
3 remain, I am 'MainThread'
2 remain, I am 'MainThread::7F867069D5F8'
1 remain, I am 'MainThread::7F867069D5F8::7F867069DEF0'
0 remain, I am 'MainThread::7F867069D5F8::7F867069DEF0::7F8670842208'

We usually want only the first (context) and last (actual thread to filter on) parts.

[idanarye]

Also, this doesn't work for MultiObject:

In [6]: MultiObject(range(5)).call(lambda n: print(n, threading.current_thread().name))
0 ThreadPoolExecutor-1_0
1 ThreadPoolExecutor-1_0
2 ThreadPoolExecutor-1_0
3 ThreadPoolExecutor-1_1
4 ThreadPoolExecutor-1_0
Out[6]: <MultiObject[NoneType] (x5/None)>

[YuvalEvron]

Also, this doesn't work for MultiObject:

In [6]: MultiObject(range(5)).call(lambda n: print(n, threading.current_thread().name))
0 ThreadPoolExecutor-1_0
1 ThreadPoolExecutor-1_0
2 ThreadPoolExecutor-1_0
3 ThreadPoolExecutor-1_1
4 ThreadPoolExecutor-1_0
Out[6]: <MultiObject[NoneType] (x5/None)>

This looks like a problem on MultiObject's side. We need to find out why there is not thread name, but this should be a different PR.

[koreno]

Also, this doesn't work for MultiObject:

In [6]: MultiObject(range(5)).call(lambda n: print(n, threading.current_thread().name))
0 ThreadPoolExecutor-1_0
1 ThreadPoolExecutor-1_0
2 ThreadPoolExecutor-1_0
3 ThreadPoolExecutor-1_1
4 ThreadPoolExecutor-1_0
Out[6]: <MultiObject[NoneType] (x5/None)>

This looks like a problem on MultiObject's side. We need to find out why there is not thread name, but this should be a different PR.

MultiObject uses python's thread-pool framework, which controls the name. We could do that as long as we don't need to monkey-patch anything - I don't want to deal with more breakages due to python version differences.

[koreno]

is there a thread that doesn't have a name?
I think every concurrent call is going to have a MainThread:: prefix...

[YuvalEvron]

Don't remember seeing something like this, but wanted to be on the safe side.

[koreno]

Well I think the MainThread:: prefix is redundant and shouldn't be there. A concurrent thread spawned by the main thread should just have its anon-xxx name with no prefix.
would you fix that for us?