Friday, 8 April 2011

Patch Manager

We use a VW / Seaside based Patch Manager to send patches to our clients. Some of the design ideas may be of interest.

We cannot access our clients machines directly, but we can get permission for outbound ports through their firewalls. So our patch management process is based on polling: the remote patch clients connect to a patch server every minute, get a list of patch names and timestamps, and then request updates or send changes (for patches that are filed out at a client site). Commands, status, logs, exception walkback files are also passed along.

User access is though a Seaside interface to the patch server.  Developers select patches to send to a client from a table of published patches, filtered by applications and versions. Remotely filed-out patches can also be retrieved and published. If a patch is updated, the developer can choose to see the difference and can then send the updated patch. Our code file-out methods add a user and timestamp comment, which is extracted by the patch server.

In this example, = shows a patch that is published, > < shows an updated patch (current for one version, different for another), pressing an arrow either retrieves the updated patch or sends the older version (grey button for older). And + is for patches that have not been sent, pressing + sends the patch. Each patch is linked to an issue. Some developers prefer to prefix their patches with issues numbers, but it's not required.

Communication between the client and server images is by VW's Opentalk. As of version 7.7 it has been rock solid (version 7.6 has issues with brokers timing out).

Every ten minutes a 'retrieve client state' command is put on a 'pending commands' queue. At the next polling action, the command is retrieved by the patch client and a 'state file', generated by the client application, is send back to the server. If any of the client states indicate a problem an email is sent to the support team and a red notification icon is displayed on both the patch manager and issue library web page, as well as our in-house wiki. Pressing the icon shows a formatted view of the state file with errors in red. We are similarly notified if communication with the client fails, which is detected by an absence of polling activity.

A similar mechanism is used to retrieve client walkback files. The client image already emails the walkback file, so this is a backup process. It retrieves walkback files that were not able to be sent, and it builds a useful history of client errors (which, fortunately, continue to decline).

Not having to manage the patch files manually has proven to be a big productivity gain.

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