fix: avoid to generate an empty write batch

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 1.7.0 [unreleased]
 
+### Bug Fixes
+1. [#85](https://github.com/influxdata/influxdb-client-python/issues/85): Fixed a possibility to generate empty write batch
+
 ## 1.6.0 [2020-04-17]
 
 ### Documentation

influxdb_client/client/write_api.py

@@ -1,13 +1,12 @@
 # coding: utf-8
 import logging
+import os
 from datetime import timedelta
 from enum import Enum
 from random import random
 from time import sleep
 from typing import Union, List
 
-import os
-
 import rx
 from rx import operators as ops, Observable
 from rx.scheduler import ThreadPoolScheduler
@@ -172,8 +171,9 @@ def __init__(self, influxdb_client, write_options: WriteOptions = WriteOptions()
                         ops.map(lambda xs: _BatchItem(key=group.key, data=_body_reduce(xs), size=len(xs))))),
                     ops.merge_all())),
                 # Write data into InfluxDB (possibility to retry if its fail)
-                ops.map(mapper=lambda batch: self._retryable(data=batch, delay=self._jitter_delay())),  #
-                ops.merge_all())\
+                ops.filter(lambda batch: batch.size > 0),
+                ops.map(mapper=lambda batch: self._retryable(data=batch, delay=self._jitter_delay())),
+                ops.merge_all()) \
                 .subscribe(self._on_next, self._on_error, self._on_complete)
 
         else:

tests/test_WriteApiBatching.py

@@ -378,6 +378,35 @@ def test_user_agent_header(self):
         self.assertEqual(1, len(requests))
         self.assertEqual(f'influxdb-client-python/{influxdb_client.__version__}', requests[0].headers['User-Agent'])
 
+    def test_to_low_flush_interval(self):
+
+        self._write_client.__del__()
+        self._write_client = WriteApi(influxdb_client=self.influxdb_client,
+                                      write_options=WriteOptions(batch_size=8,
+                                                                 flush_interval=1,
+                                                                 jitter_interval=1000))
+
+        httpretty.register_uri(httpretty.POST, uri="http://localhost/api/v2/write", status=204)
+
+        for i in range(50):
+            val_one = float(i)
+            val_two = float(i) + 0.5
+            point_one = Point("OneMillis").tag("sensor", "sensor1").field("PSI", val_one).time(time=i)
+            point_two = Point("OneMillis").tag("sensor", "sensor2").field("PSI", val_two).time(time=i)
+
+            self._write_client.write("my-bucket", "my-org", [point_one, point_two])
+            time.sleep(0.1)
+
+        self._write_client.__del__()
+
+        _requests = httpretty.httpretty.latest_requests
+
+        for _request in _requests:
+            body = _request.parsed_body
+            self.assertTrue(body, msg="Parsed body should be not empty " + str(_request))
+
+        httpretty.reset()
+
 
 if __name__ == '__main__':
     unittest.main()