The blocking API

drasi.sync for scripts, notebooks and anywhere async would be awkward.

  2 minute read  

drasi.sync.Drasi mirrors the async API method for method, minus the await. It suits scripts, notebooks, test fixtures and existing synchronous code that has no event loop to hand.

import time

from drasi.sync import Drasi

OPEN_ORDERS = """
MATCH (o:Order)
WHERE o.status = 'open'
RETURN o.id AS id, o.total AS total
"""

with Drasi.create("script") as drasi:
    drasi.start()
    drasi.add_python_source("orders")
    drasi.add_query("open", OPEN_ORDERS, ["orders"])
    drasi.wait_for_query("open")

    drasi.push_change(
        "orders",
        {
            "op": "insert",
            "id": "o1",
            "labels": ["Order"],
            "properties": {"id": "o1", "status": "open", "total": 42},
        },
    )

    # A query processes changes asynchronously, so give it a moment before
    # reading the result set. `query_results` is the alternative: it yields each
    # change as it lands rather than making you guess how long to wait.
    time.sleep(1)
    print(drasi.get_query_results("open"))

Note with, not async with, and Drasi.create(...) returning the engine directly rather than an awaitable.

Streams become ordinary iterators

for event in drasi.query_results("open"):
    for diff in event["results"]:
        print(diff["type"])

Callbacks work unchanged, and are invoked from the background loop:

drasi.on_query_results("open", lambda event: print(event))

How it works

The engine is inherently asynchronous, so the sync facade runs an asyncio loop on a background thread and submits work to it. That thread is shared by every sync engine in the process, so creating several is cheap.

Do not use drasi.sync from inside a running event loop. Blocking the loop to wait on the background thread can deadlock. In async code, use drasi.Drasi directly.

Choosing between them

UseWhen
drasi.DrasiYour code is already async, or you need concurrency
drasi.sync.DrasiA script, a notebook, a synchronous service, or a quick experiment

Both drive the same engine, so neither is a reduced version of the other.

Next