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How to revert patches applied to WSO2 Carbon server

WSO2 Carbon based products are released with a well defined strategy for applying fixes to the system. If any customer faces an issue in the server, patches will be provided until that issue is fixed in the next product release. Once the patches are applied in to the server, it will fix that respective issue. In the practical world, there can be situations where users might want to revert the patches and restore the system into original status in terms of Carbon product. This blog post will describe the correct way to revert a patch applied in to a Carbon server.

How to apply a patch?

(i)  Shutdown the server, if you have already started.

(ii) Copy the wso2carbon-version.txt file to <CARBON_SERVER>/bin.

(iii) Copy the patchXXXX folder to  <CARBON_SERVER>/repository/components/patches/

(iv) Restart the server with :
       Linux/Unix :  sh wso2server.sh -DapplyPatches
       Windows    :  wso2server.bat -DapplyPatches


How to revert a patch?

1.) patch0000 folder is created the first time you apply a patch to a clean product, so this directory will actually contain the original jars that came with the release.

2.) If you apply a new patch, for instance patch0100 with synapse-core-2.1.0-wso2v8.jar inside, this jar will be copied over to the plugins directory.

3.) If you apply another patch, for instance patch0200 which also contains synapse-core-2.1.0-wso2v8.jar, this new jar will be copied over to the plugins directory.

4.) Now if you want to remove the patch0200 from your server, just remove the folder patch0200 from
<CARBON_SERVER>/repository/components/patches/ folder and start the server with -DapplyPatches option. Here synapse-core-2.1.0-wso2v8.jar inside patch0100 will be copied over to the plugins directory. Likewise, if you remove patch0100, leaving patch0200, there will be no change (i.e. plugins directory will contain the synapse-core jar from patch0200).

So in this manner, we can actually revert patches all the way to the original jars.

As for the incorrectly named jar in patch folder, -DapplyPatches corrects the names before applying as it cross checks the file name with the bundle name and version from the Manifest file.

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