Streamo!

streamo.py

#!/usr/bin/env python

import os
import subprocess
import shutil
import hashlib
import time
from string import Template

STREAMS = [
    {
        'path': '/home/corpix/Code/streamo/streams/test',
        'cmds': {
            'create': 'mkdir $path; echo `date` > $path/date', # Will run in streams directory
            'update': 'echo `date` > $path/date' # Will run inside concrete stream
        }
    }
]

INDEX_ROOT = '/home/corpix/Code/streamo/index'
ctr = 0

def run(cmd, cwd=None):
    print('Running', cmd, 'in', cwd)
    if subprocess.call(cmd, shell=True, cwd=cwd) is not 0:
        raise RuntimeError('Non zero exit code')

def sha1(s):
    m = hashlib.sha1()
    m.update(s)
    return m.hexdigest()

def get_sipath(stream_path):
    global ctr
    ctr += 1
    ts = '%s-%s-%s' % (int(time.time()), os.getpid(), ctr)
    path_hash = sha1(stream_path)
    return os.path.join(INDEX_ROOT, '%s-%s' % (ts, path_hash))

def get_sipaths(stream_path):
    path_hash = sha1(stream_path)
    lst = [ f for f in os.listdir(INDEX_ROOT) if f.endswith(path_hash) ]
    lst.sort()
    return lst

def create_stream(stream):
    sipath = get_sipath(stream['path'])
    createCmd = Template(stream['cmds']['create']).substitute(dict(path=sipath))

    try:
        run(createCmd, os.path.dirname(INDEX_ROOT))
    except Exception as e:
        return None, e

    return sipath, None

def get_stream_revs(stream):
    h = sha1(stream['path'])
    lst = [ f for f in os.listdir(INDEX_ROOT) if f.endswith(h) ]
    lst.sort()
    return lst

def prune_stream(stream):
    lst = get_stream_revs(stream)
    if len(lst) > 1:
        for d in lst[:-1]:
            print('Removing', d)
            shutil.rmtree(os.path.join(INDEX_ROOT, d))

def create_link(target, lnk_path):
    if os.path.islink(lnk_path):
        print('Removing symlink', lnk_path, 'pointing to', os.readlink(lnk_path))
        os.unlink(lnk_path)

    print('Creating symlink to', target, 'pointing to', lnk_path)
    os.symlink(target, lnk_path)

def update_stream(stream):
    sipath, err = create_stream(stream)
    if err:
        return None, err

    if 'update' in stream['cmds']:
        updateCmd = Template(stream['cmds']['update']).substitute(dict(path=sipath))
        run(updateCmd, sipath)

    create_link(sipath, stream['path'])

    return sipath, None

for stream in STREAMS:
    prune_stream(stream)

    if not os.path.exists(stream['path']):
        sipath, err = create_stream(stream)
        if err:
            raise err

        create_link(sipath, stream['path'])
    else:
        _, err = update_stream(stream)
        if err:
            raise err

        prune_stream(stream)