WebServer with microdot and utemplate raise Exception when Template is called #198

rebe21 · 2024-01-10T13:56:20Z

rebe21
Jan 10, 2024

Hello everyone,
i'm testing the microdot strenghts for a future project with an ES8266 microcontroller, and I'm interested in use utemplate to manage simple html pages (I had previous experience with flask and jinja).

It looks working properly when i call the index page with simple text "Hello World", but
unfortunately i'm having the following exception when I'm try to GET the orders page which requires to be rendered :

MemoryError: memory allocation failed, allocating 252 bytes

Trace is :

Orders - All method
Traceback (most recent call last):
File "microdot.py", line 1327, in dispatch_request
File "microdot.py", line 41, in invoke_handler
File "orders.py", line 15, in index
File "./utemplate.py", line 34, in init
File "recompile.py", line 22, in load
File "source.py", line 188, in load
File "compiled.py", line 14, in load
MemoryError: memory allocation failed, allocating 252 bytes
GET /all 500

The code of orders.py is as follow:

`
import gc
from main import app
from microdot.utemplate import Template

@app.route('/all', methods=['GET'])
 async def index(req):
    print("Orders - All method")
    name = "mickey"
    orders = ["item1", "item2", "item3"]

    t = Template('orders.html')
    print("Orders - Template created")

    return await t.render_async(name=name, orders=orders)

`

it seems that as soon as the Template is created, the memory exception happens. Anyone knows how to overcome this issue ?
PS. I've already compressed to binary microdot.mpy, utemplate.mpy and other "library" files.

Thanks in advance
Paolo

miguelgrinberg · 2024-01-10T14:21:00Z

miguelgrinberg
Jan 10, 2024
Maintainer

How big is your orders.html file?

0 replies

rebe21 · 2024-01-10T14:25:19Z

rebe21
Jan 10, 2024
Author

Hi Miguel, thanks for answering.
The html is pretty small. 18 lines of code. I paste it here below:

{% args name, orders %}
<!doctype html>
<title>Microdot + uTemplate example</title>
List of Orders:
{% if name %}
Customer Name: {{ name }}!
{% endif %}
{% for order in orders %}
{{ order }}
{% endfor %}

5 replies

rebe21 Jan 11, 2024
Author

Hi Miguel,
your question brought me on the right track. The issue is due to the html file. I've tried to compact it on a single line deleting all the blank spaces and carriage returns and it worked.

{% args name, orders %}<!doctype html><html><body>{% if name %}<p>CN: <b>{{ name }}</b>!</p>{% endif %}<ul>{% for o in orders %}<li>{{ o }}</li>{% endfor %}</ul></body></html>

So i'm limited to a small html file with this current device (It's a D1 Mini ESp8266 equivalent type with 33Kb of ram)

What if i split the html files in multiple html's files one for each let's say "section" ?

{% include 'section1.html' %} {% include 'section2.html' %} {% include 'section3.html' %}

Do the framework execute multi requests to load the entire page or it does it build the entire page in memory ?
Would it work ? Otherwise do you have any other suggestions how to optimize it ?

Thanks in advance.
Paolo

miguelgrinberg Jan 11, 2024
Maintainer

You have two possible optimizations that you can research:

You probably noticed that your templates are compiled to .py files. You could pre-compile your templates on your desktop/laptop and upload the compiled versions to your device. Then you can initialize Microdot's utemplate extension to not compile templates, just load compiled versions from disk:
```
from utemplate import compiled
from microdot.utemplate import Template

Template.initialize(loader_class=compiled.Loader)
```
You can switch from render() to generate() as rendering method. The former generates the entire template in memory before returning it, the latter returns an iterator that renders portions of the template in sequence, without ever having to have the entire template in memory.
```
return t.generate_async(name=name, orders=orders)
```

Let me know if any of this helps!

sophiedegran Jan 12, 2024

Oo! thanks Miguel I didn't use Template because of that compiled file... Think it will be good to add in documentation ☺

hstarmans Apr 14, 2024

@miguelgrinberg
The return t.generate_async(name=name, orders=orders solved my issues, please use this in your examples (https://github.com/miguelgrinberg/microdot/tree/main/examples/templates/utemplate) or mention it. It is in the documentation, but I spent quite sometime figuring out how to solve my memory issues.

valentingregoire Jan 8, 2025

For me, the expanding of the keyword arguments simply didn't work. So in the generated Python template, I would have this:

def render(*args, **kwargs):
    yield """<html><body>
"""
yield str(name)
yield """</body></html>"""

My generation would simply be:

return await Template("index.html").render_async(name="blabla")

I simply fixed this by providing my parameters by name in the template, since I will only use these predefined templates:

def render(*args, name):
    yield """<html><body>
"""
yield str(name)
yield """</body></html>"""

For loading predefined templates without regenerating them each time, use this:

from microdot.utemplate import Template
from utemplate import compiled

Template.initialize(loader_class=compiled.Loader)

WebServer with microdot and utemplate raise Exception when Template is called #198

Uh oh!

Uh oh!

rebe21 Jan 10, 2024

Replies: 2 comments · 5 replies

Uh oh!

miguelgrinberg Jan 10, 2024 Maintainer

Uh oh!

Uh oh!

rebe21 Jan 10, 2024 Author

List of Orders:

Uh oh!

rebe21 Jan 11, 2024 Author

Uh oh!

Uh oh!

miguelgrinberg Jan 11, 2024 Maintainer

Uh oh!

sophiedegran Jan 12, 2024

Uh oh!

Uh oh!

hstarmans Apr 14, 2024

Uh oh!

Uh oh!

valentingregoire Jan 8, 2025

rebe21
Jan 10, 2024

Replies: 2 comments 5 replies

miguelgrinberg
Jan 10, 2024
Maintainer

rebe21
Jan 10, 2024
Author

rebe21 Jan 11, 2024
Author

miguelgrinberg Jan 11, 2024
Maintainer