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Monitoring macOS Content Caching with Zabbix

With the release of macOS 10.13 High Sierra, Apple have made a big change to their App and iCloud content caching services. This function used to be part of their add-on macOS Server package, but with 10.13 they've moved the feature into the regular macOS operating system. This means that any Macintosh computer running 10.13 High Sierra can serve as a content cache for a local network.

Why do I want to run this?

If you have more than one Apple device on your local netork you can see benefits from running the caching service. All iOS and macOS application downloads pass through the cache, meaning you only have to download them once. This saves your bandwidth and means that cached installs can run much faster.

If you enable the optional iCloud caching, you'll get similar (and even more noticeable) performance improvements for iCloud Photo Library syncing, iCloud Drive, and other data sharing across your Apple devices.

Take a photo with your iPhone and it's uploaded via the caching service to Apple's iCloud servers. When your MacBook syncs the photo via iCloud, it doesn't have to download from "the cloud" but instead pulls the local, cached image.

More Information

What was lost in the migration

The old macOS Server version had fancy logs and graphs that allowed you to monitor cahing performance and activity to keep an eye on the efficacy and health of the service. When they moved it all to regular macOS all that stuff disappeared. It's basically just an on/off checkbox.

Instead, there's just a command-line tool that outputs the raw data from the service. You can see the stats by running AssetCacheManagerUtil status from a Terminal window.

Monitoring via Zabbix

If you are running Zabbix 3.4 I've included a template which will make all kinds of pretty graphs and related items for the caching service. I can guarantee that it's not worth installing Zabbix just for this, but if you're already running it then the template is quite easy to get going. Just import the xml template file also found in this GitHub repo. This also requires that you enable RemoteCommands=1 in the agent configuration. It woudln't take much to change over to a UserParameter, but I didn't do that.

Example Output

2017-09-25 19:57:12.288 AssetCacheManagerUtil[20807:3449689] Built-in caching server status: {
    Activated = 1;
    Active = 1;
    CacheDetails =     {
        Books = 174082575;
        "Mac Software" = 24423474829;
        Other = 1738767542;
        iCloud = 12954227645;
        "iOS Software" = 37416034017;
    CacheFree = 298293413392;
    CacheLimit = 375000000000;
    CacheStatus = OK;
    CacheUsed = 76706586608;
    Parents =     (
    Peers =     (
    PersonalCacheFree = 362045772355;
    PersonalCacheLimit = 375000000000;
    PersonalCacheUsed = 12954227645;
    Port = 49242;
    PrivateAddresses =     (
    PublicAddress = "aaa.bbb.ccc.ddd";
    RegistrationStatus = 1;
    RestrictedMedia = 0;
    ServerGUID = "DEADBEEF-FOOD-A1AB-1040-EAB10CFEA18";
    StartupStatus = OK;
    TotalBytesDropped = 679075;
    TotalBytesImported = 128672588;
    TotalBytesReturnedToChildren = 0;
    TotalBytesReturnedToClients = 35798809867;
    TotalBytesReturnedToPeers = 0;
    TotalBytesStoredFromOrigin = 21063186167;
    TotalBytesStoredFromParents = 0;
    TotalBytesStoredFromPeers = 0;


macOS High Sierra Content Cache service monitoring with Zabbix 3.4





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