python_api.md

Python API

MCAS supports a Python-based client access. This can be accessed through the 'mcas-shell' program or included directly in a Python program.

Note: make sure dist/lib is added to the library path (LD_LIBRARY_PATH)

Run shell (e.g.):

./dist/bin/mcas-shell

Open session to remote MCAS server/shard

session = mcas.Session(ip="10.0.0.21", port=11911)

Create pool

pool = session.create_pool("myPool",int(2e6),100)

Open pool

pool = session.open_pool("myPool")

Put key-value pair

Key parameter is a string. Value parameter is a string or a byte array.

pool.put('key9','The Cute Little Dog')

Put direct

Direct, zero-copy put can be applied to byte arrays

pickled_item = pickle.dumps(item)
pool.put_direct(keyname, bytearray(pickled_item))

Get key-value pair

myval = pool.get('key9')

Direct get:

bytearray_item = pool.get_direct(keyname)
return pickle.loads(bytes(bytearray_item))

Key scanning

If the index component is loaded, then keys can be 'searched':

print(get_keys(pool, "regex:.*"))
print(get_keys(pool, "next:"))
print(get_keys(pool, "prefix:tre"))

In find_key the offset variable is the position to start searching from, the returned out position plus one in the pair should be used to continue the search

(k, offset) = pool.find_key("prefix:tre"), offset)

Example function to get list of keys:

def get_keys(pool, expr):
    result = []
    offset=0
    print(expr)
    (k,offset)=pool.find_key(expr, offset)
    while k != None:
        result.append(k)
        offset += 1
        (k, offset) = pool.find_key(expr, offset)
    return result

Value Attributes

Length and crc32 attributes can be fetched:

print('Len: %d' % pool.get_attribute('array0','length'))
print('Crc: %x' % pool.get_attribute('array0','crc32'))

Pool Attributes

print('Size enquiry:%d' % pool.get_size('array0'))

Get number of objects in a pool:

print(pool.count())

Close pool

pool.close()