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diff --git a/ncp-previewgenerator/README.md b/ncp-previewgenerator/README.md new file mode 100644 index 00000000..98bb4103 --- /dev/null +++ b/ncp-previewgenerator/README.md @@ -0,0 +1,96 @@ +# Preview Generator + +Nextcloud app that allows admins to pre-generate previews. The app listens to +edit events and stores this information. Once a cron job is triggered it will +start preview generation. This means that you can better utilize your +system by pre-generating previews when your system is normally idle and thus +putting less load on your machine when the requests are actually served. + +The app does not replace on demand preview generation so if a preview is +requested before it is pre-generated it will still be shown. + +## How to install + +* Install directly from within your Nextcloud from the [app store](https://apps.nextcloud.com/apps/previewgenerator) +* Clone this repository in you Nextcloud app folder + +## How to use the app + +1. Install the app +2. Enable the app +3. Run `./occ preview:generate-all` once after installation. +4. Add a (system) cron job for ` ./occ preview:pre-generate` + * I run it every 10 minutes + +## Known issues + +* The app does not work with encryption enabled + +## How does the app work + +1. Listen to events that a file has been written or modified and store it in the database +2. On cron run request previews for the files that have been written or modified + +If a preview already exists at step 2 then requesting it is really cheap. If not +it will be generated. Depending on the sizes of the files and the hardware you +are running on the time this takes can vary. + +## Commands + +### preview:delete_old + +This removes the previews from the old preview location that was used before +Nextcloud 11. That has some issues. Note that the gallery shipped with Nextcloud +11 did not yet use this location. So you might want to run it again with Nextcloud 12. + +### preview:generate-all [user-id] + +Loop over all files and try to generate previews for them. If `user-id` is supplied +just loop over the files for that user. + +### preview:pre-generate + +Do the actual pregeneration. This means only for new or modified files (since +the app was enabled or the last pregeneration was done). + +## FAQ + +### Why can't I use webcron? + +Preview generation can be a very long running job. Thus we need a system that +does not time out. + +### It sometimes crashed + +Yes this happens. Most of it is due to corrupted files not being handled that gracefully +in the Nextcloud server. Improvements in this area are coming with Nextcloud 12 + +### I get "Command already running" + +Yes this happens when the `pre-generate` command crashes. No worries the lock +will be released after 30 minutes of inactivity from the app. So go grab a cookie. + +### I don't want to generate all the preview sizes + +This is possible since version 1.0.8. Just set the correct values via the command line + +``` +./occ config:app:set --value="32 64 1024" previewgenerator squareSizes +./occ config:app:set --value="64 128 1024" previewgenerator widthSizes +./occ config:app:set --value="64 256 1024" previewgenerator heightSizes +``` + +This will only generate: + * square previews of: 32x32, 64x64 and 1024x1024 + * aspect ratio previews with a width of: 64, 128 and 1024 + * aspect ratio previews with a height of: 64, 256 and 1024 + +Note: + * preview sizes are always a power of 2. + * The smallest size is 32 + * The max size is determined by your preview settings in config.php + + ### I get "PHP Fatal error: Allowed memory size of X bytes exhausted" + You need to increase the memory allowance of PHP, by default it is 128 MB. You do that by changing the memory_limit in the php.ini file. + + If you use the docker container you need to create the php.ini file in /usr/local/etc/php first. |