Server-side and agent-side plugins can become out-of-sync if you manually add or remove plugins and do not apply updates consistently to the server and to every agent.

To detect plugin mismatches caused by inconsistent manual deployment, the vCenter Hyperic server checks for out-of-sync plugins every time it starts up, and every time an agent connects to it upon agent start or restart. (The server does the post-startup checks five minutes after startup, so that any agents that were restarted while the server was down to sync their plugin inventory.) In the case of a mismatch between server-side and agent-side plugins, the server updates the agent.

When an up-to-date agent starts up and loads the plugins in its plugin directory, it sends a plugin status report to the server, including the MD5 checksum of each plugin it loaded.

On receipt of a plugin status report from an up-to-date agent, the vCenter Hyperic server compares the MD5 checksum of each plugin that the agent loaded with the the MD5 checksum of the corresponding plugin (a plugin with the same name) currently deployed on the server.

For a mismatch:

If the agent loaded a plugin with the same name but different MD5 checksum than one that is currently deployed to the server, the server pushes its version to the agent.

If the agent did not load a plugin that is currently deployed to the server (the agent did not load a plugin with the same name as one that the server loaded), the server pushes the plugin to the agent.

If the agent loaded a plugin that is not deployed to the vCenter Hyperic server (there is no plugin with the same name on the server), the server removes the plugin from the agent.

After adding or removing agent plugins as necessary, the server restarts the agent.

When the vCenter Hyperic server starts up and loads the plugins in its deployment directories, it compares the MD5 checksum of the plugins it loaded with the MD5 checksums in the plugin status report last received from each agent.

For a mismatch:

If an agent's last plugin status report included a plugin with the same name but different MD5 checksum than one that is currently deployed to the vCenter Hyperic server, the server pushes its version to the agent.

If an agent's last plugin status report does not include a plugin that is currently deployed to the server (the agent did not load a plugin with the same name as one that the server loaded), the server pushes the plugin to the agent.

If an agent's last plugin status report included a plugin that is not deployed to the server (there is no plugin with the same name on the server), the server removes the plugin from the agent.

After updating the agent plugins appropriately, the server restarts the agent.