change_stream
– Watch changes on a collection, database, or cluster¶
Watch changes on a collection, a database, or the entire cluster.
- class pymongo.change_stream.ChangeStream(target, pipeline, full_document, resume_after, max_await_time_ms, batch_size, collation, start_at_operation_time, session, start_after, comment=None, full_document_before_change=None, show_expanded_events=None)¶
The internal abstract base class for change stream cursors.
Should not be called directly by application developers. Use
pymongo.collection.Collection.watch()
,pymongo.database.Database.watch()
, orpymongo.mongo_client.MongoClient.watch()
instead.Added in version 3.6.
See also
The MongoDB documentation on changeStreams.
- Parameters:
target (Union[MongoClient[_DocumentType], Database[_DocumentType], Collection[_DocumentType]])
pipeline (Optional[_Pipeline])
full_document (Optional[str])
resume_after (Optional[Mapping[str, Any]])
max_await_time_ms (Optional[int])
batch_size (Optional[int])
collation (Optional[_CollationIn])
start_at_operation_time (Optional[Timestamp])
session (Optional[ClientSession])
start_after (Optional[Mapping[str, Any]])
comment (Optional[Any])
full_document_before_change (Optional[str])
show_expanded_events (Optional[bool])
- property alive: bool¶
Does this cursor have the potential to return more data?
Note
Even if
alive
isTrue
,next()
can raiseStopIteration
andtry_next()
can returnNone
.Added in version 3.8.
- close()¶
Close this ChangeStream.
- Return type:
None
- next()¶
Advance the cursor.
This method blocks until the next change document is returned or an unrecoverable error is raised. This method is used when iterating over all changes in the cursor. For example:
try: resume_token = None pipeline = [{'$match': {'operationType': 'insert'}}] with db.collection.watch(pipeline) as stream: for insert_change in stream: print(insert_change) resume_token = stream.resume_token except pymongo.errors.PyMongoError: # The ChangeStream encountered an unrecoverable error or the # resume attempt failed to recreate the cursor. if resume_token is None: # There is no usable resume token because there was a # failure during ChangeStream initialization. logging.error('...') else: # Use the interrupted ChangeStream's resume token to create # a new ChangeStream. The new stream will continue from the # last seen insert change without missing any events. with db.collection.watch( pipeline, resume_after=resume_token) as stream: for insert_change in stream: print(insert_change)
Raises
StopIteration
if this ChangeStream is closed.- Return type:
_DocumentType
- property resume_token: Mapping[str, Any] | None¶
The cached resume token that will be used to resume after the most recently returned change.
Added in version 3.9.
- try_next()¶
Advance the cursor without blocking indefinitely.
This method returns the next change document without waiting indefinitely for the next change. For example:
with db.collection.watch() as stream: while stream.alive: change = stream.try_next() # Note that the ChangeStream's resume token may be updated # even when no changes are returned. print("Current resume token: %r" % (stream.resume_token,)) if change is not None: print("Change document: %r" % (change,)) continue # We end up here when there are no recent changes. # Sleep for a while before trying again to avoid flooding # the server with getMore requests when no changes are # available. time.sleep(10)
If no change document is cached locally then this method runs a single getMore command. If the getMore yields any documents, the next document is returned, otherwise, if the getMore returns no documents (because there have been no changes) then
None
is returned.- Returns:
The next change document or
None
when no document is available after running a single getMore or when the cursor is closed.- Return type:
_DocumentType | None
Added in version 3.8.
- class pymongo.change_stream.ClusterChangeStream(target, pipeline, full_document, resume_after, max_await_time_ms, batch_size, collation, start_at_operation_time, session, start_after, comment=None, full_document_before_change=None, show_expanded_events=None)¶
A change stream that watches changes on all collections in the cluster.
Should not be called directly by application developers. Use helper method
pymongo.mongo_client.MongoClient.watch()
instead.Added in version 3.7.
- Parameters:
target (Union[MongoClient[_DocumentType], Database[_DocumentType], Collection[_DocumentType]])
pipeline (Optional[_Pipeline])
full_document (Optional[str])
resume_after (Optional[Mapping[str, Any]])
max_await_time_ms (Optional[int])
batch_size (Optional[int])
collation (Optional[_CollationIn])
start_at_operation_time (Optional[Timestamp])
session (Optional[ClientSession])
start_after (Optional[Mapping[str, Any]])
comment (Optional[Any])
full_document_before_change (Optional[str])
show_expanded_events (Optional[bool])
- class pymongo.change_stream.CollectionChangeStream(target, pipeline, full_document, resume_after, max_await_time_ms, batch_size, collation, start_at_operation_time, session, start_after, comment=None, full_document_before_change=None, show_expanded_events=None)¶
A change stream that watches changes on a single collection.
Should not be called directly by application developers. Use helper method
pymongo.collection.Collection.watch()
instead.Added in version 3.7.
- Parameters:
target (Union[MongoClient[_DocumentType], Database[_DocumentType], Collection[_DocumentType]])
pipeline (Optional[_Pipeline])
full_document (Optional[str])
resume_after (Optional[Mapping[str, Any]])
max_await_time_ms (Optional[int])
batch_size (Optional[int])
collation (Optional[_CollationIn])
start_at_operation_time (Optional[Timestamp])
session (Optional[ClientSession])
start_after (Optional[Mapping[str, Any]])
comment (Optional[Any])
full_document_before_change (Optional[str])
show_expanded_events (Optional[bool])
- class pymongo.change_stream.DatabaseChangeStream(target, pipeline, full_document, resume_after, max_await_time_ms, batch_size, collation, start_at_operation_time, session, start_after, comment=None, full_document_before_change=None, show_expanded_events=None)¶
A change stream that watches changes on all collections in a database.
Should not be called directly by application developers. Use helper method
pymongo.database.Database.watch()
instead.Added in version 3.7.
- Parameters:
target (Union[MongoClient[_DocumentType], Database[_DocumentType], Collection[_DocumentType]])
pipeline (Optional[_Pipeline])
full_document (Optional[str])
resume_after (Optional[Mapping[str, Any]])
max_await_time_ms (Optional[int])
batch_size (Optional[int])
collation (Optional[_CollationIn])
start_at_operation_time (Optional[Timestamp])
session (Optional[ClientSession])
start_after (Optional[Mapping[str, Any]])
comment (Optional[Any])
full_document_before_change (Optional[str])
show_expanded_events (Optional[bool])