New argument --csv-append

Adds --csv-append flag to enable appending of the metrics CSV log.
This allows for tracking changes in response times over the course of long test runs.

locust/main.py

@@ -45,14 +45,14 @@ def parse_options():
         default="",
         help="Host to bind the web interface to. Defaults to '' (all interfaces)"
     )
-    
+
     parser.add_argument(
         '-P', '--port', '--web-port',
         type=int,
         default=8089,
         help="Port on which to run web host"
     )
-    
+
     parser.add_argument(
         '-f', '--locustfile',
         default='locustfile',
@@ -66,6 +66,15 @@ def parse_options():
         help="Store current request stats to files in CSV format.",
     )
 
+    # if locust should append the CSV file instead of replacing it.
+    parser.add_argument(
+        '--csv-append',
+        action='store_true',
+        dest='csvappend',
+        default=False,
+        help="Set locust to append CSV file at set interval instead of replacing.",
+    )
+
     # if locust should be run in distributed mode as master
     parser.add_argument(
         '--master',
@@ -79,14 +88,14 @@ def parse_options():
         action='store_true',
         help="Set locust to run in distributed mode with this process as slave"
     )
-    
+
     # master host options
     parser.add_argument(
         '--master-host',
         default="127.0.0.1",
         help="Host or IP address of locust master for distributed load testing. Only used when running with --slave. Defaults to 127.0.0.1."
     )
-    
+
     parser.add_argument(
         '--master-port',
         type=int,
@@ -99,7 +108,7 @@ def parse_options():
         default="*",
         help="Interfaces (hostname, ip) that locust master should bind to. Only used when running with --master. Defaults to * (all available interfaces)."
     )
-    
+
     parser.add_argument(
         '--master-bind-port',
         type=int,
@@ -491,15 +500,15 @@ def timelimit_stop():
         except socket.error as e:
             logger.error("Failed to connect to the Locust master: %s", e)
             sys.exit(-1)
-    
+
     if not options.only_summary and (options.print_stats or (options.no_web and not options.slave)):
         # spawn stats printing greenlet
         gevent.spawn(stats_printer)
 
     if options.csvfilebase:
-        gevent.spawn(stats_writer, options.csvfilebase)
+        gevent.spawn(stats_writer, options.csvfilebase, options.csvappend)
+
 
-
     def shutdown(code=0):
         """
         Shut down locust by firing quitting event, printing/writing stats and exiting
@@ -514,16 +523,16 @@ def shutdown(code=0):
         print_stats(runners.locust_runner.stats)
         print_percentile_stats(runners.locust_runner.stats)
         if options.csvfilebase:
-            write_stat_csvs(options.csvfilebase)
+            write_stat_csvs(options.csvfilebase, options.csvappend)
         print_error_report()
         sys.exit(code)
-    
+
     # install SIGTERM handler
     def sig_term_handler():
         logger.info("Got SIGTERM signal")
         shutdown(0)
     gevent.signal(signal.SIGTERM, sig_term_handler)
-    
+
     try:
         logger.info("Starting Locust %s" % version)
         main_greenlet.join()

locust/stats.py

@@ -712,32 +712,39 @@ def stats_printer():
         print_stats(runners.locust_runner.stats)
         gevent.sleep(CONSOLE_STATS_INTERVAL_SEC)
 
-def stats_writer(base_filepath):
+def stats_writer(base_filepath, append_file=False):
     """Writes the csv files for the locust run."""
+    write_stat_csvs(base_filepath, include_totals=(not append_file))
     while True:
-        write_stat_csvs(base_filepath)
         gevent.sleep(CSV_STATS_INTERVAL_SEC)
+        write_stat_csvs(base_filepath, append_file, include_totals=(not append_file))
 
+def write_stat_csvs(base_filepath, append_file=False, include_totals=True):
+    """
+    Writes the requests and distribution CSV files.
+    By default overwrites the existing file,
+    optionally appends the existing file
+    """
+    file_mode = "a" if append_file else "w"
 
-def write_stat_csvs(base_filepath):
-    """Writes the requests and distribution csvs."""
-    with open(base_filepath + '_requests.csv', "w") as f:
-        f.write(requests_csv())
+    with open(base_filepath + '_requests.csv', file_mode) as f:
+        f.write(requests_csv(append_file, include_totals) + "\n")
 
-    with open(base_filepath + '_distribution.csv', 'w') as f:
-        f.write(distribution_csv())
+    with open(base_filepath + '_distribution.csv', file_mode) as f:
+        f.write(distribution_csv(append_file, include_totals) + "\n")
 
 
 def sort_stats(stats):
     return [stats[key] for key in sorted(six.iterkeys(stats))]
 
 
-def requests_csv():
+def requests_csv(append_file=False, include_totals=True):
     from . import runners
 
     """Returns the contents of the 'requests' tab as CSV."""
-    rows = [
-        ",".join([
+    rows = []
+    if not append_file:
+        rows.append(",".join([
             '"Method"',
             '"Name"',
             '"# requests"',
@@ -748,10 +755,14 @@ def requests_csv():
             '"Max response time"',
             '"Average Content Size"',
             '"Requests/s"',
-        ])
-    ]
+        ]))
+
+    maybe_agg_stats = []
 
-    for s in chain(sort_stats(runners.locust_runner.request_stats), [runners.locust_runner.stats.total]):
+    if include_totals:
+        maybe_agg_stats = [runners.locust_runner.stats.total]
+
+    for s in chain(sort_stats(runners.locust_runner.request_stats), maybe_agg_stats):
         rows.append('"%s","%s",%i,%i,%i,%i,%i,%i,%i,%.2f' % (
             s.method,
             s.name,
@@ -766,30 +777,36 @@ def requests_csv():
         ))
     return "\n".join(rows)
 
-def distribution_csv():
+def distribution_csv(append_file=False, include_totals=True):
     """Returns the contents of the 'distribution' tab as CSV."""
     from . import runners
 
-    rows = [",".join((
-        '"Name"',
-        '"# requests"',
-        '"50%"',
-        '"66%"',
-        '"75%"',
-        '"80%"',
-        '"90%"',
-        '"95%"',
-        '"98%"',
-        '"99%"',
-        '"99.9%"',
-        '"99.99%"',
-        '"100%"',
-    ))]
-    for s in chain(sort_stats(runners.locust_runner.request_stats), [runners.locust_runner.stats.total]):
-        if s.num_requests:
-            rows.append(s.percentile(tpl='"%s",%i,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i'))
-        else:
-            rows.append('"%s",0,"N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A"' % s.name)
+    rows = []
+    if not append_file:
+        rows.append(",".join((
+            '"Name"',
+            '"# requests"',
+            '"50%"',
+            '"66%"',
+            '"75%"',
+            '"80%"',
+            '"90%"',
+            '"95%"',
+            '"98%"',
+            '"99%"',
+            '"99.9%"',
+            '"99.99%"',
+            '"100%"',
+        )))
+
+    maybe_agg_stats = []
+    if include_totals:
+        maybe_agg_stats = [runners.locust_runner.stats.total]
+        for s in chain(sort_stats(runners.locust_runner.request_stats), maybe_agg_stats):
+            if s.num_requests:
+                rows.append(s.percentile(tpl='"%s",%i,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i'))
+            else:
+                rows.append('"%s",0,"N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A","N/A"' % s.name)
 
     return "\n".join(rows)