libhoststat

libhoststat is a library intended for use in Event Store server for collecting statistics from hosts. Since we use performance counters on Windows, only Linux and macOS are supported by libhoststat. The statistics which can be collected currently are:

• 1, 5 and 15 minute load averages - get_host_load_averages
• Free memory - get_host_free_memory
• Total memory - get_host_total_memory

All other statistics in Event Store are handled by the .NET Core's event tracing mechanism. It is intended that PInvoke be used to invoke this library, although there is no reason it cannot be used from C or Rust instead if necessary.

All operations return HOSTSTAT_SUCCESS if they are successful, HOSTSTAT_UNAVAILABLE if the requested statistic is not available on the given host (e.g. if /proc is not readable), and HOSTSTAT_ERROR in case of all other errors.

PInvoke Signatures

const int HostStatSuccess = 0;
const int HostStatError = 1;
const int HostStatUnavailable = 2;

[DllImport("hoststat")]
static extern int get_host_total_memory(out ulong totalMemory);

[DllImport("hoststat")]
static extern int get_host_free_memory(out ulong freeMemory);

[StructLayout(LayoutKind.Sequential)]
public struct LoadAverages {
    public double Average1m;
    public double Average5m;
    public double Average15m;
}

[DllImport("hoststat")]
static extern int get_host_load_averages(out LoadAverages memory_size);

Usage Example

if (LibHostStat.get_host_total_memory(out var totalMemory) != LibHostStat.HostStatSuccess) {
	throw new InvalidOperationException();
}
Console.WriteLine($"Memory: {memory}");

if (LibHostStat.get_host_free_memory(out var freeMemory) != LibHostStat.HostStatSuccess) {
	throw new InvalidOperationException();
}
Console.WriteLine($"Free Memory: {freeMemory}");

if (LibHostStat.get_host_load_averages(out var lAvg) != LibHostStat.HostStatSuccess) {
	throw new InvalidOperationException();
}
Console.WriteLine($"Load Averages: {lAvg.Average1m} {lAvg.Average5m} {lAvg.Average15m}");