More easily extend web UI

[solowalker27]

Addresses #1530. Includes the following additions and changes:

• index.html is extendable with blocks for tabs, panes, and scripts
• Args required to properly render index.html are retrievable via web_ui.update_template_args()
• Event for web UI's Reset Stats button to aid in custom data resetting
• Make some UI classes and functions more generic and more easily reusable for extended UI

[codecov]

Codecov Report

Merging #1574 into master will decrease coverage by 0.82%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #1574      +/-   ##
==========================================
- Coverage   82.34%   81.52%   -0.83%     
==========================================
  Files          28       28              
  Lines        2572     2593      +21     
  Branches      392      395       +3     
==========================================
- Hits         2118     2114       -4     
- Misses        363      381      +18     
- Partials       91       98       +7     

Impacted Files	Coverage Δ
locust/main.py	20.08% <ø> (ø)
locust/web.py	92.46% <82.60%> (+1.08%)	⬆️
locust/event.py	87.80% <100.00%> (+0.30%)	⬆️
locust/clients.py	90.19% <0.00%> (-4.91%)	⬇️
locust/runners.py	81.54% <0.00%> (-2.88%)	⬇️
locust/user/task.py	94.65% <0.00%> (-1.03%)	⬇️
locust/contrib/fasthttp.py	85.37% <0.00%> (-0.95%)	⬇️
locust/stats.py	89.87% <0.00%> (-0.21%)	⬇️
... and 1 more

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[cyberw]

Cool stuff!

Can you add some documentation and an example for how to extend the UI?

As I dont use the web ui and dont know the code behind very well, I'll take your word for it being sensible & working :) If something does break in the UI related to these changes, will you have some time to help fix it? Maybe you'd even be interested in being "the" UI maintainer for Locust :) (deciding what PRs are good, what direction we want to take the UI etc)

[solowalker27]

Added example of extending the web UI.

I can help with the UI code where I can. I'm not exactly an expert, just hacking away at it. I needed to do this for my work and decided to pass the improvements upstream so I didn't have to maintain them in a fork. I don't know if I can sign on to be a maintainer of the web UI but I can provide feedback and review PRs if I can.

[cyberw]

Lgtm. Can you just add a reference to the example in the documentation (extending-locust.rst)

[solowalker27]

How's that?

[mihai-craita]

Question: is there anyway to extend the root page / ? or I can only add new routes?
I tried with blueprints but it doesn't work.

I mention I have no experience with Flask

Thanks,

[mihai-craita]

Question: is there anyway to extend the root page / ? or I can only add new routes? I tried with blueprints but it doesn't work.

I mention I have no experience with Flask

Thanks,

I found a hacky solution. I am rewriting the url_map rules and adding a different http method for the default index so that it is not matched anymore:

url_map = environment.web_ui.app.url_map
rule = url_map._rules_by_endpoint["index"][0]
if rule:
    rule.methods = ("POST")