Loads old, incorrect, picture from it's cache instead of new picture

[IanQuilter]

I'm using Home Assistant to send a picture in a Gotify notification when a cctv camera is triggered. It's working and has been working since I started using last July. The pictures have a name and a number ie Drive1, Front3, Side1 etc. The number is incremented up to 100 then reset and starts from 1 again. ie Drive98 then Drive 99 then back to Drive1 then Drive2 etc.
The problem is that sometimes an old picture is served up from the app's cache instead of the new picture. Clearing the cache stops it happening for a while, then it does it again.

This has been doing it since I started using it. It's annoying and I have put up with it until now but it's happening more often and has finally made me annoyed enough report it.

The way the pictures are handled in Home Assistant means that the numbers added to the picture name aren't always consecutive and can have quite a few left out, ie Drive 34 may be followed by Drive 45 then Drive46 then Drive50 etc. Which means that it can be a day, or a week or more, before a picture is sent with the same number as one already in the cache.
Is there anything that can be done to the app to correct this?

[jmattheis]

Are you able to modify the image url before pushing the message to gotify? You could include the current timestamp inside the url e.g. https://example.org/images/drive98.png?timestamp=1706353928517 then the cache won't use an old images because the url is unique.

[IanQuilter]

Thanks for your suggestion of the time stamp I'll see if I can use it. I should have thought of that myself!

The reason I used a rotating 1 - 100 number suffix was that the pictures are stored locally and by re-using the numbers the old pictures eventually get overwritten as they don't need to be kept forever, but might need to be looked at again in a short period of time. Using 100 gives a long enough retention time without using too much storage space.

I'm not sure there is an easy way of deleting the old pictures if they all have unique file names. I'll see what I can do.

[IanQuilter]

I've looked at changing the Home Assistant automation to add a time stamp to the picture. While it can do it it would mean completely recreating my automations and it will not be easy to do as multiple cameras use the same automation, using variables to enter camera name, picture name, number etc.

As a temporary test I've increased the number 100 that it resets to 1 at to 200 in the hope that the pictures in Gotify's cache will have expired by the time the same picture name reappears.

Do you know how long items in Gotify's cache are kept for?

[jmattheis]

It is a LRU cache with a fixed size of 50mb, if it's more than that the least recently used picture is removed. Default caching of the http client is used here, so it's likely configurable via cache-control headers on the server that hosts the images.

[IanQuilter]

Thanks for the reply. A 50mb cache may allow my picture number increase to 200 to work, as last time I cleared the cache it was around 35mb if I remember correctly. If 200 isn't enough increasing it a bit more may be all that's needed. I'll have to wait and see, which may take a few days or even a week or two.

By "server that hosts the images" do you mean the server that hosts Gotify or the Home Assistant server that is sending the images? I've never had to configure "cache-control headers" before so I'll need to look into exactly how they can be configured.

Thanks for your help and prompts replies.

[jmattheis]

By "server that hosts the images" do you mean the server that hosts Gotify or the Home Assistant server that is sending the images?

Neither, or at least they are not required to be one of the ones listed. Example, if you push a message like this.

{
  "title": "Nextcloud",
  "message": "![](https://goverter.jmattheis.de/favicon.png)",
  "extras": {
    "client::display": {
      "contentType": "text/markdown"
    }
  }
}

The "server that hosts the images" is the one behind goverter.jmattheis.de.

[IanQuilter]

Thanks for the explanation.

Home Assistant sends the Gotify notifications using a Rest api. I've added the cache-control: "no-cache" line to it and changed my reset number back to 100. Now I just need to wait and see if it's worked! I'll post back when I know in case it helps someone else.

Thanks for your help

[IanQuilter]

Unfortunately adding the line cache-control: "no-cache" hasn't worked as I've started to get old pictures sent again. It's taken a while to show as there have been less notification being triggered recently. Checking the Gotify cache it has reached 50Mb so it appears that adding the no-cache line hasn't stopped Gotify caching the pictures.

The configuration entry in Home Assistant contains :-

platform: rest
resource: http://192.168.0.36:9080/message
method: POST_JSON
headers:
  cache-control: "no-cache"
  X-Gotify-Key: XXXXXXXXXXX
message_param_name: message
title_param_name: title
target_param_name: priority
data:
  priority: 1

It's possible I've not entered the command correctly, although I think it's correct. If it is correct do you have any other suggestions for stopping Gotify caching the pictures?
Thanks.

[jmattheis]

Your setup looks fine. This then has to be fixed in the app, maybe the image loading framework has to be replaced with something supporting expiring images.

[IanQuilter]

Thanks for the confirmation. As it doesn't look like this issue effects many users, or at least no one else seems to have reported it, I assume it won't be high on your fix agenda. But if you do make future changes to the app are you likely to fix this at the same time?

[jmattheis]

Maybe, but I can't say this for sure.

[cyb3rko]

As Picasso has not been updated in 4 years, switching to a more modern solution sounds reasonable.
Coil is a very modern and well maintained alternative:
https://coil-kt.github.io/coil
https://github.com/coil-kt/coil

By default it also respects cache headers of network responses.
Maybe that would already fix your issue.

[cyb3rko]

I've tried it out and it works well for all kinds of image loading in the app as far as I can tell.
I will upload it soon so you two can test it out.

[IanQuilter]

Sorry, I'm away and replying using a mobile and couldn't work out how to add a comment to the pull thread.
Yes, can you provide an apk as I have no idea how to make use of the coil code myself.
Thanks.

[aagit]

method: POST_JSON
headers:
cache-control: "no-cache"
X-Gotify-Key: XXXXXXXXXXX

The cache-control of the http POST HA sends to gotify server isn't going to alter the caching behavior of the images you receive in gotify, you probably need to tweak the GET request on the http server that delivers the image to alter the behavior of the image cache.