Why is flask using all of my memory?

Question

I created the simplest Flask app I could imagine:

import flask
from flask import Flask

application = Flask(__name__)

@application.route('/')
def index():
    return flask.jsonify(ok=True)

I deployed this app on 1/26 to Elastic Beanstalk. It has served 0 requests since deployment. Here is a graph of the memory usage, using Amazon's memory monitoring scripts:

You can see the little dip where (I assume) garbage collection happened on 1/29. But what on earth is allocating so much memory? If this is normal, how should I be monitoring memory so I can actually figure out if my (real) application has a memory leak? Is this Flask's fault, Python's fault, AWS's fault, ...something else?

Edited to add: I switched over to using mod_wsgi this aftenoon, but it didn't seem to have any effect. Updated graph (the dips are deploying new versions, it took a few tries to get the config right):

Output of free -m:

             total       used       free     shared    buffers     cached
Mem:           532        501         31          0         81         37
-/+ buffers/cache:        381        150
Swap:            0          0          0

MrName · Accepted Answer · 2018-01-29 23:17:47Z

5

Is that memory actually being used or is it cached? SSH into your beanstalk instance and use the free command to determine this. This article has a good breakdown of how to determine whether your RAM is actually used or cached and what it means.

answered Jan 29, 2018 at 23:17

MrName

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3 Comments

kristina Over a year ago

Unfortunately, free on Elastic Beanstalk doesn't have the available column! (I'd guess it's too old?) However, it sounds like the buffers/cache line's free column is a reasonable proxy for that, and that's holding steady at ~145MB.

kristina Over a year ago

I added the output of free to the bottom my question.

MrName Over a year ago

Cool, so yes, the line that says -/+ buffers/cache shows the actual memory being used. The rest is being held in cache and will be released by the OS as required for other programs.

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