/*---------------------------------------------------------------------------
*
* _make_cursor --
*
* Construct and send the aggregate command and create the resulting
* cursor. On error, stream->cursor remains NULL, otherwise it is
* created and must be destroyed.
*
* Return:
* False on error and sets stream->err.
*
*--------------------------------------------------------------------------
*/
static bool
_make_cursor (mongoc_change_stream_t *stream)
{
mongoc_client_session_t *cs = NULL;
bson_t command_opts;
bson_t command; /* { aggregate: "coll", pipeline: [], ... } */
bson_t reply;
bson_t getmore_opts = BSON_INITIALIZER;
bson_iter_t iter;
mongoc_server_description_t *sd;
uint32_t server_id;
int32_t max_wire_version = -1;
BSON_ASSERT (stream);
BSON_ASSERT (!stream->cursor);
_make_command (stream, &command);
bson_copy_to (&(stream->opts.extra), &command_opts);
sd = mongoc_client_select_server (
stream->client, false /* for_writes */, stream->read_prefs, &stream->err);
if (!sd) {
goto cleanup;
}
server_id = mongoc_server_description_id (sd);
bson_append_int32 (&command_opts, "serverId", 8, server_id);
bson_append_int32 (&getmore_opts, "serverId", 8, server_id);
max_wire_version = sd->max_wire_version;
mongoc_server_description_destroy (sd);
if (bson_iter_init_find (&iter, &command_opts, "sessionId")) {
if (!_mongoc_client_session_from_iter (
stream->client, &iter, &cs, &stream->err)) {
goto cleanup;
}
} else if (stream->implicit_session) {
/* If an implicit session was created before, and this cursor is now
* being recreated after resuming, then use the same session as before. */
cs = stream->implicit_session;
if (!mongoc_client_session_append (cs, &command_opts, &stream->err)) {
goto cleanup;
}
} else {
/* Create an implicit session. This session lsid must be the same for the
* agg command and the subsequent getMores. Thus, this implicit session is
* passed as if it were an explicit session to
* collection_read_command_with_opts and cursor_new_from_reply, but it is
* still implicit and its lifetime is owned by this change_stream_t. */
mongoc_session_opt_t *session_opts;
session_opts = mongoc_session_opts_new ();
mongoc_session_opts_set_causal_consistency (session_opts, false);
/* returns NULL if sessions aren't supported. ignore errors. */
cs = mongoc_client_start_session (stream->client, session_opts, NULL);
stream->implicit_session = cs;
mongoc_session_opts_destroy (session_opts);
if (cs &&
!mongoc_client_session_append (cs, &command_opts, &stream->err)) {
goto cleanup;
}
}
if (cs && !mongoc_client_session_append (cs, &getmore_opts, &stream->err)) {
goto cleanup;
}
if (stream->read_concern && !bson_has_field (&command_opts, "readConcern")) {
mongoc_read_concern_append (stream->read_concern, &command_opts);
}
/* even though serverId has already been set, still pass the read prefs.
* they are necessary for OP_MSG if sending to a secondary. */
if (!mongoc_client_read_command_with_opts (stream->client,
stream->db,
&command,
stream->read_prefs,
&command_opts,
&reply,
&stream->err)) {
bson_destroy (&stream->err_doc);
bson_copy_to (&reply, &stream->err_doc);
bson_destroy (&reply);
goto cleanup;
}
bson_append_bool (
&getmore_opts, MONGOC_CURSOR_TAILABLE, MONGOC_CURSOR_TAILABLE_LEN, true);
bson_append_bool (&getmore_opts,
MONGOC_CURSOR_AWAIT_DATA,
MONGOC_CURSOR_AWAIT_DATA_LEN,
true);
/* maxTimeMS is only appended to getMores if these are set in cursor opts. */
if (stream->max_await_time_ms > 0) {
bson_append_int64 (&getmore_opts,
MONGOC_CURSOR_MAX_AWAIT_TIME_MS,
MONGOC_CURSOR_MAX_AWAIT_TIME_MS_LEN,
stream->max_await_time_ms);
}
if (stream->batch_size > 0) {
bson_append_int32 (&getmore_opts,
MONGOC_CURSOR_BATCH_SIZE,
MONGOC_CURSOR_BATCH_SIZE_LEN,
stream->batch_size);
}
/* Change streams spec: "If neither startAtOperationTime nor resumeAfter are
* specified, and the max wire version is >= 7, and the initial aggregate
* command does not return a resumeToken (indicating no results), the
* ChangeStream MUST save the operationTime from the initial aggregate
* command when it returns." */
if (bson_empty (&stream->resume_token) &&
_mongoc_timestamp_empty (&stream->operation_time) &&
max_wire_version >= 7 &&
bson_iter_init_find (&iter, &reply, "operationTime")) {
_mongoc_timestamp_set_from_bson (&stream->operation_time, &iter);
}
/* steals reply. */
stream->cursor = mongoc_cursor_new_from_command_reply_with_opts (
stream->client, &reply, &getmore_opts);
cleanup:
bson_destroy (&command);
bson_destroy (&command_opts);
bson_destroy (&getmore_opts);
return stream->err.code == 0;
}
/* Construct and send the aggregate command and create the resulting cursor.
* Returns false on error, and sets stream->err. On error, stream->cursor
* remains NULL, otherwise it is created and must be destroyed. */
static bool
_make_cursor (mongoc_change_stream_t *stream)
{
mongoc_client_session_t *cs = NULL;
bson_t command_opts;
bson_t command; /* { aggregate: "coll", pipeline: [], ... } */
bson_t reply;
bson_iter_t iter;
mongoc_server_description_t *sd;
uint32_t server_id;
BSON_ASSERT (stream);
BSON_ASSERT (!stream->cursor);
_make_command (stream, &command);
bson_copy_to (&stream->opts, &command_opts);
sd = mongoc_client_select_server (stream->coll->client,
false /* for_writes */,
stream->coll->read_prefs,
&stream->err);
if (!sd) {
goto cleanup;
}
server_id = mongoc_server_description_id (sd);
bson_append_int32 (&command_opts, "serverId", 8, server_id);
mongoc_server_description_destroy (sd);
if (bson_iter_init_find (&iter, &command_opts, "sessionId")) {
if (!_mongoc_client_session_from_iter (
stream->coll->client, &iter, &cs, &stream->err)) {
goto cleanup;
}
} else if (stream->implicit_session) {
/* If an implicit session was created before, and this cursor is now
* being recreated after resuming, then use the same session as before. */
cs = stream->implicit_session;
if (!mongoc_client_session_append (cs, &command_opts, &stream->err)) {
goto cleanup;
}
} else {
/* Create an implicit session. This session lsid must be the same for the
* agg command and the subsequent getMores. Thus, this implicit session is
* passed as if it were an explicit session to
* collection_read_command_with_opts and cursor_new_from_reply, but it is
* still implicit and its lifetime is owned by this change_stream_t. */
mongoc_session_opt_t *session_opts;
session_opts = mongoc_session_opts_new ();
mongoc_session_opts_set_causal_consistency (session_opts, false);
/* returns NULL if sessions aren't supported. ignore errors. */
cs =
mongoc_client_start_session (stream->coll->client, session_opts, NULL);
stream->implicit_session = cs;
mongoc_session_opts_destroy (session_opts);
if (cs &&
!mongoc_client_session_append (cs, &command_opts, &stream->err)) {
goto cleanup;
}
}
/* use inherited read preference and read concern of the collection */
if (!mongoc_collection_read_command_with_opts (
stream->coll, &command, NULL, &command_opts, &reply, &stream->err)) {
bson_destroy (&stream->err_doc);
bson_copy_to (&reply, &stream->err_doc);
bson_destroy (&reply);
goto cleanup;
}
stream->cursor = mongoc_cursor_new_from_command_reply (
stream->coll->client, &reply, server_id); /* steals reply */
if (cs) {
stream->cursor->client_session = cs;
stream->cursor->explicit_session = true;
}
/* maxTimeMS is only appended to getMores if these are set in cursor opts */
bson_append_bool (&stream->cursor->opts,
MONGOC_CURSOR_TAILABLE,
MONGOC_CURSOR_TAILABLE_LEN,
true);
bson_append_bool (&stream->cursor->opts,
MONGOC_CURSOR_AWAIT_DATA,
MONGOC_CURSOR_AWAIT_DATA_LEN,
true);
if (stream->max_await_time_ms > 0) {
BSON_ASSERT (
_mongoc_cursor_set_opt_int64 (stream->cursor,
MONGOC_CURSOR_MAX_AWAIT_TIME_MS,
stream->max_await_time_ms));
}
if (stream->batch_size > 0) {
mongoc_cursor_set_batch_size (stream->cursor,
(uint32_t) stream->batch_size);
}
cleanup:
bson_destroy (&command);
bson_destroy (&command_opts);
return stream->err.code == 0;
}