allow providing stream start ts (#162)

Co-authored-by: Lucas Pedroza <lucas.pedroza@fauna.com>

fauna/client/client.py

@@ -56,13 +56,16 @@ class StreamOptions:
 
     * max_attempts - The maximum number of times to attempt a stream query when a retryable exception is thrown.
     * max_backoff - The maximum backoff in seconds for an individual retry.
+    * start_ts - The starting timestamp of the stream, exclusive. If set, Fauna will return events starting after
+    the timestamp.
     * status_events - Indicates if stream should include status events. Status events are periodic events that
-    * update the client with the latest valid timestamp (in the event of a dropped connection) as well as metrics
-    * about about the cost of maintaining the stream other than the cost of the received events.
+    update the client with the latest valid timestamp (in the event of a dropped connection) as well as metrics
+    about the cost of maintaining the stream other than the cost of the received events.
     """
 
   max_attempts: Optional[int] = None
   max_backoff: Optional[int] = None
+  start_ts: Optional[int] = None
   status_events: bool = False
 
 
@@ -550,6 +553,8 @@ def _create_stream(self):
     data: Dict[str, Any] = {"token": self._token.token}
     if self.last_ts is not None:
       data["start_ts"] = self.last_ts
+    elif self._opts.start_ts is not None:
+      data["start_ts"] = self._opts.start_ts
 
     return self._http_client.stream(
         url=self._endpoint, headers=self._headers, data=data)

tests/integration/test_stream.py

@@ -1,11 +1,8 @@
 import threading
 import time
-from datetime import timedelta
-
 import pytest
 import httpx
 import fauna
-
 from fauna import fql
 from fauna.client import Client, StreamOptions
 from fauna.http.httpx_client import HTTPXClient
@@ -77,8 +74,6 @@ def thread_fn():
 def test_error_on_stream(scoped_client):
   scoped_client.query(fql("Collection.create({name: 'Product'})"))
 
-  events = []
-
   def thread_fn():
     stream = scoped_client.stream(fql("Product.all().map(.foo / 0).toStream()"))
 
@@ -171,6 +166,41 @@ def thread_fn():
   assert events == ["add", "add", "add"]
 
 
+def test_providing_start_ts(scoped_client):
+  scoped_client.query(fql("Collection.create({name: 'Product'})"))
+
+  stream_token = scoped_client.query(fql("Product.all().toStream()")).data
+
+  createOne = scoped_client.query(fql("Product.create({})"))
+  createTwo = scoped_client.query(fql("Product.create({})"))
+  createThree = scoped_client.query(fql("Product.create({})"))
+
+  events = []
+
+  def thread_fn():
+    # replay excludes the ts that was passed in, it provides events for all ts after the one provided
+    stream = scoped_client.stream(stream_token,
+                                  StreamOptions(start_ts=createOne.txn_ts))
+    with stream as iter:
+      for event in iter:
+        events.append(event)
+        if (len(events) == 3):
+          iter.close()
+
+  stream_thread = threading.Thread(target=thread_fn)
+  stream_thread.start()
+
+  # adds a delay so the thread can open the stream,
+  # otherwise we could miss some events
+  time.sleep(0.5)
+
+  createFour = scoped_client.query(fql("Product.create({})"))
+  stream_thread.join()
+  assert events[0]["txn_ts"] == createTwo.txn_ts
+  assert events[1]["txn_ts"] == createThree.txn_ts
+  assert events[2]["txn_ts"] == createFour.txn_ts
+
+
 @pytest.mark.xfail(reason="not currently supported by core")
 def test_handle_status_events(scoped_client):
   scoped_client.query(fql("Collection.create({name: 'Product'})"))