fix: prevent creating unnecessary threads repeatedly (#562)

* fix: prevent creating unnecessary threads repeatedly

Use ThreadPoolScheduler for WriteApi batch subject instead of TimeoutScheduler.

Fixes #561

* docs: Update CHANGELOG.md

* docs: update CHANGELOG.md

---------

Co-authored-by: Jakub Bednář <jakub.bednar@gmail.com>

Author: goznauk

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 1.40.0 [unreleased]
 
+### Bug Fixes
+1. [#562](https://github.com/influxdata/influxdb-client-python/pull/562): Use `ThreadPoolScheduler` for `WriteApi`'s batch subject instead of `TimeoutScheduler` to prevent creating unnecessary threads repeatedly
+
 ## 1.39.0 [2023-12-05]
 
 ### Features

influxdb_client/client/write_api.py

@@ -258,7 +258,8 @@ def __init__(self,
             self._disposable = self._subject.pipe(
                 # Split incoming data to windows by batch_size or flush_interval
                 ops.window_with_time_or_count(count=write_options.batch_size,
-                                              timespan=timedelta(milliseconds=write_options.flush_interval)),
+                                              timespan=timedelta(milliseconds=write_options.flush_interval),
+                                              scheduler=ThreadPoolScheduler(1)),
                 # Map  window into groups defined by 'organization', 'bucket' and 'precision'
                 ops.flat_map(lambda window: window.pipe(
                     # Group window by 'organization', 'bucket' and 'precision'