Source code for locust.web

from __future__ import annotations

import csv
import json
import logging
import os.path
from functools import wraps
from html import escape
from io import StringIO
from itertools import chain
from json import dumps
from time import time
from typing import TYPE_CHECKING, Any

import gevent
from flask import (
from flask_cors import CORS
from flask_login import LoginManager, login_required
from gevent import pywsgi

from . import __version__ as version
from . import argument_parser
from . import stats as stats_module
from .html import BUILD_PATH, ROOT_PATH, STATIC_PATH, get_html_report
from .log import get_logs, greenlet_exception_logger
from .runners import STATE_MISSING, STATE_RUNNING, MasterRunner
from .stats import StatsCSV, StatsCSVFileWriter, StatsErrorDict, sort_stats
from .user.inspectuser import get_ratio
from .util.cache import memoize
from .util.timespan import parse_timespan

    from .env import Environment

logger = logging.getLogger(__name__)
greenlet_exception_handler = greenlet_exception_logger(logger)


[docs] class WebUI: """ Sets up and runs a Flask web app that can start and stop load tests using the :attr:`environment.runner <locust.env.Environment.runner>` as well as show the load test statistics in :attr:`environment.stats <locust.env.Environment.stats>` """ app: Flask | None = None """ Reference to the :class:`flask.Flask` app. Can be used to add additional web routes and customize the Flask app in other various ways. Example:: from flask import request"/my_custom_route") def my_custom_route(): return "your IP is: %s" % request.remote_addr """ greenlet: gevent.Greenlet | None = None """ Greenlet of the running web server """ server: pywsgi.WSGIServer | None = None """Reference to the :class:`pyqsgi.WSGIServer` instance""" template_args: dict[str, Any] """Arguments used to render index.html for the web UI. Must be used with custom templates extending index.html.""" auth_args: dict[str, Any] """Arguments used to render auth.html for the web UI auth page. Must be used when configuring auth""" def __init__( self, environment: Environment, host: str, port: int, web_login: bool = False, tls_cert: str | None = None, tls_key: str | None = None, stats_csv_writer: StatsCSV | None = None, delayed_start=False, userclass_picker_is_active=False, ): """ Create WebUI instance and start running the web server in a separate greenlet (self.greenlet) Arguments: environment: Reference to the current Locust Environment host: Host/interface that the web server should accept connections to port: Port that the web server should listen to web_login: Enables a login page tls_cert: A path to a TLS certificate tls_key: A path to a TLS private key delayed_start: Whether or not to delay starting web UI until `start()` is called. Delaying web UI start allows for adding Flask routes or Blueprints before accepting requests, avoiding errors. """ environment.web_ui = self self.stats_csv_writer = stats_csv_writer or StatsCSV(environment, stats_module.PERCENTILES_TO_REPORT) self.environment = environment = host self.port = port self.tls_cert = tls_cert self.tls_key = tls_key self.userclass_picker_is_active = userclass_picker_is_active self.web_login = web_login app = Flask(__name__) CORS(app) = app app.jinja_env.add_extension("") app.debug = True app.root_path = ROOT_PATH self.webui_build_path = BUILD_PATH self.greenlet: gevent.Greenlet | None = None self._swarm_greenlet: gevent.Greenlet | None = None self.template_args = {} self.auth_args = {} = BUILD_PATH = STATIC_PATH = "/assets/" if self.web_login: self.login_manager = LoginManager() self.login_manager.init_app(app) self.login_manager.login_view = "login" if environment.runner: self.update_template_args() if not delayed_start: self.start() @app.errorhandler(Exception) def handle_exception(error): error_message = str(error) error_code = getattr(error, "code", 500) logger.log( logging.INFO if error_code <= 404 else logging.ERROR, f"UI got request for {request.path}, but it resulted in a {error.code}: {}", ) return make_response(error_message, error_code) @app.route("/assets/<path:path>") def send_assets(path): return send_from_directory(os.path.join(self.webui_build_path, "assets"), path) @app.route("/") @self.auth_required_if_enabled def index() -> str | Response: if not environment.runner: return make_response("Error: Locust Environment does not have any runner", 500) self.update_template_args() return render_template("index.html", template_args=self.template_args) @app.route("/swarm", methods=["POST"]) @self.auth_required_if_enabled def swarm() -> Response: assert request.method == "POST" # Loading UserClasses & ShapeClasses if Locust is running with UserClass Picker if self.userclass_picker_is_active: if not self.environment.available_user_classes: err_msg = "UserClass picker is active but there are no available UserClasses" return jsonify({"success": False, "message": err_msg, "host":}) # Getting Specified User Classes form_data_user_class_names = request.form.getlist("user_classes") # Updating UserClasses if form_data_user_class_names: user_classes = {} for user_class_name, user_class_object in self.environment.available_user_classes.items(): if user_class_name in form_data_user_class_names: user_classes[user_class_name] = user_class_object else: if self.environment.runner and self.environment.runner.state == STATE_RUNNING: # Test is already running # Using the user classes that have already been selected user_classes = { key: value for (key, value) in self.environment.available_user_classes.items() if value in self.environment.user_classes } else: # Starting test with no user class selection # Defaulting to using all available user classes user_classes = self.environment.available_user_classes self._update_user_classes(user_classes) # Updating ShapeClass if specified in WebUI Form form_data_shape_class_name = request.form.get("shape_class", "Default") if form_data_shape_class_name == "Default": self._update_shape_class(None) else: self._update_shape_class(form_data_shape_class_name) parsed_options_dict = vars(environment.parsed_options) if environment.parsed_options else {} run_time = None for key, value in request.form.items(): if key == "user_count": # if we just renamed this field to "users" we wouldn't need this user_count = int(value) parsed_options_dict["users"] = user_count elif key == "spawn_rate": spawn_rate = float(value) parsed_options_dict[key] = spawn_rate elif key == "host": # Replace < > to guard against XSS = str(request.form["host"]).replace("<", "").replace(">", "") parsed_options_dict[key] = elif key == "user_classes": # Set environment.parsed_options.user_classes to the selected user_classes parsed_options_dict[key] = request.form.getlist("user_classes") elif key == "run_time": if not value: continue try: run_time = parse_timespan(value) parsed_options_dict[key] = run_time except ValueError: err_msg = "Valid run_time formats are : 20, 20s, 3m, 2h, 1h20m, 3h30m10s, etc." logger.error(err_msg) return jsonify({"success": False, "message": err_msg, "host":}) elif key in parsed_options_dict: # update the value in environment.parsed_options, but dont change the type. parsed_options_value = parsed_options_dict[key] if isinstance(parsed_options_value, bool): parsed_options_dict[key] = value == "true" elif parsed_options_value is None: parsed_options_dict[key] = parsed_options_value else: parsed_options_dict[key] = type(parsed_options_dict[key])(value) if environment.shape_class and environment.runner is not None: environment.runner.start_shape() return jsonify( { "success": True, "message": f"Swarming started using shape class '{type(environment.shape_class).__name__}'", "host":, } ) if self._swarm_greenlet is not None: self._swarm_greenlet.kill(block=True) self._swarm_greenlet = None if environment.runner is not None: self._swarm_greenlet = gevent.spawn(environment.runner.start, user_count, spawn_rate) self._swarm_greenlet.link_exception(greenlet_exception_handler) response_data = { "success": True, "message": "Swarming started", "host":, } if run_time: gevent.spawn_later(run_time, self._stop_runners).link_exception(greenlet_exception_handler) response_data["run_time"] = run_time if self.userclass_picker_is_active: response_data["user_classes"] = sorted(user_classes.keys()) return jsonify(response_data) else: return jsonify({"success": False, "message": "No runner", "host":}) @app.route("/stop") @self.auth_required_if_enabled def stop() -> Response: if self._swarm_greenlet is not None: self._swarm_greenlet.kill(block=True) self._swarm_greenlet = None if environment.runner is not None: environment.runner.stop() return jsonify({"success": True, "message": "Test stopped"}) @app.route("/stats/reset") @self.auth_required_if_enabled def reset_stats() -> str: if environment.runner is not None: environment.runner.stats.reset_all() environment.runner.exceptions = {} return "ok" @app.route("/stats/report") @self.auth_required_if_enabled def stats_report() -> Response: theme = request.args.get("theme", "") res = get_html_report( self.environment, show_download_link=not request.args.get("download"), theme=theme, ) if request.args.get("download"): res = app.make_response(res) res.headers["Content-Disposition"] = f"attachment;filename=report_{time()}.html" return res def _download_csv_suggest_file_name(suggest_filename_prefix: str) -> str: """Generate csv file download attachment filename suggestion. Arguments: suggest_filename_prefix: Prefix of the filename to suggest for saving the download. Will be appended with timestamp. """ return f"{suggest_filename_prefix}_{time()}.csv" def _download_csv_response(csv_data: str, filename_prefix: str) -> Response: """Generate csv file download response with 'csv_data'. Arguments: csv_data: CSV header and data rows. filename_prefix: Prefix of the filename to suggest for saving the download. Will be appended with timestamp. """ response = make_response(csv_data) response.headers["Content-type"] = "text/csv" response.headers["Content-disposition"] = ( f"attachment;filename={_download_csv_suggest_file_name(filename_prefix)}" ) return response @app.route("/stats/requests/csv") @self.auth_required_if_enabled def request_stats_csv() -> Response: data = StringIO() writer = csv.writer(data) self.stats_csv_writer.requests_csv(writer) return _download_csv_response(data.getvalue(), "requests") @app.route("/stats/requests_full_history/csv") @self.auth_required_if_enabled def request_stats_full_history_csv() -> Response: options = self.environment.parsed_options if options and options.stats_history_enabled and isinstance(self.stats_csv_writer, StatsCSVFileWriter): return send_file( os.path.abspath(self.stats_csv_writer.stats_history_file_name()), mimetype="text/csv", as_attachment=True, download_name=_download_csv_suggest_file_name("requests_full_history"), etag=True, max_age=0, conditional=True, last_modified=None, ) return make_response("Error: Server was not started with option to generate full history.", 404) @app.route("/stats/failures/csv") @self.auth_required_if_enabled def failures_stats_csv() -> Response: data = StringIO() writer = csv.writer(data) self.stats_csv_writer.failures_csv(writer) return _download_csv_response(data.getvalue(), "failures") @app.route("/stats/requests") @self.auth_required_if_enabled @memoize(timeout=DEFAULT_CACHE_TIME, dynamic_timeout=True) def request_stats() -> Response: stats: list[dict[str, Any]] = [] errors: list[StatsErrorDict] = [] if environment.runner is None: report = { "stats": stats, "errors": errors, "total_rps": 0.0, "total_fail_per_sec": 0.0, "fail_ratio": 0.0, "current_response_time_percentile_1": None, "current_response_time_percentile_2": None, "state": STATE_MISSING, "user_count": 0, } if isinstance(environment.runner, MasterRunner): report.update({"workers": []}) return jsonify(report) for s in chain(sort_stats(environment.runner.stats.entries), []): stats.append(s.to_dict()) errors = [e.serialize() for e in environment.runner.errors.values()] # Truncate the total number of stats and errors displayed since a large number of rows will cause the app # to render extremely slowly. Aggregate stats should be preserved. truncated_stats = stats[:500] if len(stats) > 500: truncated_stats += [stats[-1]] report = {"stats": truncated_stats, "errors": errors[:500]} total_stats = stats[-1] if stats: report["total_rps"] = total_stats["current_rps"] report["total_fail_per_sec"] = total_stats["current_fail_per_sec"] report["total_avg_response_time"] = total_stats["avg_response_time"] report["fail_ratio"] = report["current_response_time_percentiles"] = { f"response_time_percentile_{percentile}": percentile ) for percentile in stats_module.PERCENTILES_TO_CHART } if isinstance(environment.runner, MasterRunner): workers = [] for worker in environment.runner.clients.values(): workers.append( { "id":, "state": worker.state, "user_count": worker.user_count, "cpu_usage": worker.cpu_usage, "memory_usage": worker.memory_usage, } ) report["workers"] = workers report["state"] = environment.runner.state report["user_count"] = environment.runner.user_count return jsonify(report) @app.route("/exceptions") @self.auth_required_if_enabled def exceptions() -> Response: return jsonify( { "exceptions": [ { "count": row["count"], "msg": escape(row["msg"]), "traceback": escape(row["traceback"]), "nodes": ", ".join(row["nodes"]), } for row in (environment.runner.exceptions.values() if environment.runner is not None else []) ] } ) @app.route("/exceptions/csv") @self.auth_required_if_enabled def exceptions_csv() -> Response: data = StringIO() writer = csv.writer(data) self.stats_csv_writer.exceptions_csv(writer) return _download_csv_response(data.getvalue(), "exceptions") @app.route("/tasks") @self.auth_required_if_enabled def tasks() -> dict[str, dict[str, dict[str, float]]]: runner = self.environment.runner user_spawned: dict[str, int] if runner is None: user_spawned = {} else: user_spawned = ( runner.reported_user_classes_count if isinstance(runner, MasterRunner) else runner.user_classes_count ) task_data = { "per_class": get_ratio(self.environment.user_classes, user_spawned, False), "total": get_ratio(self.environment.user_classes, user_spawned, True), } return task_data @app.route("/logs") @self.auth_required_if_enabled def logs(): return jsonify({"master": get_logs(), "workers": self.environment.worker_logs}) @app.route("/login") def login(): if not self.web_login: return redirect(url_for("index")) return render_template( "auth.html", auth_args=self.auth_args, ) @app.route("/user", methods=["POST"]) def update_user(): assert request.method == "POST" user_settings = json.loads( self.environment.update_user_class(user_settings) return {}, 201 def start(self): self.greenlet = gevent.spawn(self.start_server) self.greenlet.link_exception(greenlet_exception_handler) def start_server(self): if self.tls_cert and self.tls_key: self.server = pywsgi.WSGIServer( (, self.port),, log=None, keyfile=self.tls_key, certfile=self.tls_cert ) else: class RewriteFilter(logging.Filter): def filter(self, record) -> bool: msg = record.msg if "gevent._socket3.socket at" in msg and "Invalid HTTP method: '\x16\x03" in msg: record.msg = f"An https request was made against Locust's Web UI (which was expecting http). Underlying error was: {record.msg}" return True logger.addFilter(RewriteFilter()) self.server = pywsgi.WSGIServer((, self.port),, log=None, error_log=logger) self.server.serve_forever()
[docs] def stop(self): """ Stop the running web server """ self.server.stop()
[docs] def auth_required_if_enabled(self, view_func): """ Decorator that can be used on custom route methods that will turn on Flask Login authentication if the ``--web-login`` flag is used. Example::"/my_custom_route") @web_ui.auth_required_if_enabled def my_custom_route(): return "custom response" """ @wraps(view_func) def wrapper(*args, **kwargs): if self.web_login: try: return login_required(view_func)(*args, **kwargs) except Exception as e: return f"Locust auth exception: {e} See for configuring authentication." else: return view_func(*args, **kwargs) return wrapper
def update_template_args(self): override_host_warning = False if host = elif self.environment.runner.user_classes: all_hosts = { for l in self.environment.runner.user_classes} if len(all_hosts) == 1: host = list(all_hosts)[0] else: # since we have multiple User classes with different host attributes, we'll # inform that specifying host will override the host for all User classes override_host_warning = True host = None else: host = None options = self.environment.parsed_options if is_distributed := isinstance(self.environment.runner, MasterRunner): worker_count = self.environment.runner.worker_count else: worker_count = 0 stats = self.environment.runner.stats extra_options = argument_parser.ui_extra_args_dict() available_user_classes = None users = None if self.environment.available_user_classes: available_user_classes = sorted(self.environment.available_user_classes) users = { user_class_name: user_class.json() for (user_class_name, user_class) in self.environment.available_user_classes.items() } available_shape_classes = ["Default"] if self.environment.available_shape_classes: available_shape_classes += sorted(self.environment.available_shape_classes.keys()) available_user_tasks = ( { user_class_name: [task.__name__ for task in user_class] for (user_class_name, user_class) in self.environment.available_user_tasks.items() } if self.environment.available_user_tasks else None ) self.template_args = { "locustfile": self.environment.locustfile, "state": self.environment.runner.state, "is_distributed": is_distributed, "user_count": self.environment.runner.user_count, "version": version, "host": host if host else "", "history": stats.history if stats.num_requests > 0 else [], "override_host_warning": override_host_warning, "num_users": options and options.num_users, "spawn_rate": options and options.spawn_rate, "worker_count": worker_count, "hide_common_options": ( self.environment.shape_class and not (self.userclass_picker_is_active or self.environment.shape_class.use_common_options) ), "stats_history_enabled": options and options.stats_history_enabled, "tasks": dumps({}), "extra_options": extra_options, "run_time": options and options.run_time, "show_userclass_picker": self.userclass_picker_is_active, "available_user_classes": available_user_classes, "available_shape_classes": available_shape_classes, "available_user_tasks": available_user_tasks, "users": users, "percentiles_to_chart": stats_module.PERCENTILES_TO_CHART, "percentiles_to_statistics": stats_module.PERCENTILES_TO_STATISTICS, } def _update_shape_class(self, shape_class_name): if shape_class_name: shape_class = self.environment.available_shape_classes[shape_class_name] shape_class.runner = self.environment.runner else: shape_class = None # Validating ShapeClass self.environment.shape_class = shape_class self.environment._validate_shape_class_instance() def _update_user_classes(self, user_classes): self.environment.user_classes = list(user_classes.values()) # populate the locustfile which used in web ui title only if self.environment.locustfile is None: self.environment.locustfile = ",".join(self.environment.user_classes_by_name.keys()) # Validating UserClasses self.environment._remove_user_classes_with_weight_zero() self.environment._validate_user_class_name_uniqueness() def _stop_runners(self): self.environment.runner.stop()