Is AppEngine caching content?

[Iñigo Martínez de Ubago Vela]

Hi everyone!

I would like to expose a problem I'm facing with AppEngine services.

I have a Python application, based on Rest services.

I have one service which is in charge of upload a document and store it into a Cloud Storage bucket, create and identifier and store such identifier in a database,

For example:

POST /uploaddocument

Request body:

{

    "base64document":"base64_encoded_document"

}

Response:

{

    "document_id":"abc1234def5678"

}

Now, I have another service which retrieve such document from the storage, like this:

GET /retrievedocument?document_id=abc1234def5678

This service returns an "application/pdf" mime type.

For the moment everything works perfect. However, if I upload a new version of this document, the service "/retrievedocument" returns the old version, like if it would be cached, and request is not being processed by my service because I don't see any logs about this request. It is like this request would being served by a CDN or something like this, not by my application.

In addition, if I wait some time (more than an hour) then the request is again processed by my application and return the correct version of the document, like if cache would be expired.

I would like my service to be returning always the latest version of the document, not a cached one.

Have anyone of you faced this kind of problem any time?

Does anyone know how to solve it?

Thank you!

Kind regards,

Iñigo.

[Elliott (Cloud Platform Support)]

Hello,

I think the first thing to do is recreate your scenario. Would you be able to provide functioning code to do so?

[Iñigo Martínez de Ubago Vela]

Hi Elliot, thank you very much for your support.

Actually, it is not easy to isolate a pece of code to reproduce this scenario but, as far as I could find, it looks the behavior is like CDN caching, explained here: 

https://cloud.google.com/cdn/docs/caching

Specially, the part which talks about static files:

https://cloud.google.com/cdn/docs/caching#static

This is exactly the behavior I'm observing in my AppEngine service, I mean, I see how "application/pdf" responses are being cached. However, in case of CDN you can invalidate cache, but I don't know how to do that in AppEngine.

In my service, it is true that the request "/retrievedocument?document_id=abc1234def5678" returns an "application/json", however, I don't want it to be cached.

My understanding is that this would happen with all GET request which return "text/css", "application/javascript", "font/woff2", "image/jpg", "image/png", "video/mp4", "image/mpeg", "audio/mp4" and "application/pdf", according to CDN's documentation.

So, does anyone know how to avoid this?

Thank you very much.

Kind regards,

Iñigo. 

[Christian Gonzalez]

Hello,

 

I think that by including the Cache-Control tag in the metadata pointing to no-cache as specified in this document should help us to avoid this https://cloud.google.com/storage/docs/metadata#cache-control

 

Could you please try this and let us know if this stopped the caching?