Health Check

concept

Health Check provides ping() and diagnostics() tests for the health of the network and the cluster.

Working in distributed environments is hard. Latencies come and go, so do connections in their entirety. Is it a network glitch, or is the remote cluster down? Sometimes just knowing the likely cause is enough to get a good start on a workaround, or at least avoid hours wasted on an inappropriate solution.

Health Check enables useful diagnostics on the state of Couchbase Clusters across networks. Ping and diagnostics methods on the bucket and cluster objects respectively, can give us information about the current state of nodes, and their connections.

Ping

Ping actively queries the status of the specified services,giving status and latency information for every node reachable. In addition to its use as a monitoring tool, a regular Ping can be used in an environment which does not respect keep alive values for a connection.

A ping can be performed either at the Cluster or at the Bucket level. They are very similar, although at the Bucket level also the Key/Value and View connections for the specific bucket are taken into account.

The report can either be analyzed in code or can be turned into JSON and printed:

IPingReport report = await bucket.PingAsync(options =>
{
    options.ServiceTypes(new ServiceType[] {ServiceType.KeyValue, ServiceType.Query});
});

Console.WriteLine(report);

// alternatively, format the output with indenting:
//Console.WriteLine(JsonConvert.SerializeObject(report, Formatting.Indented));

You will see an output similar to this:

{
  "id": "174ad024-43d4-410c-9d80-61788b4f3bf4",
  "version": 1,
  "config_rev": 572,
  "sdk": "couchbase-net-sdk/3.0.7.0 (clr/.NET Core 3.1.9) (os/Microsoft Windows 10.0.18363)",
  "services": {
    "n1ql": [
      {
        "state": "ok",
        "remote": "[::1]:11210",
        "last_activity_us": 0,
        "latency_us": 135751,
        "scope": "Cluster"
      }
    ],
    "kv": [
      {
        "id": "2",
        "state": "ok",
        "local": "[::1]:53183",
        "remote": "[::1]:11210",
        "last_activity_us": 81526,
        "latency_us": 2330,
        "scope": "travel-sample"
      },
      {
        "id": "1",
        "state": "ok",
        "local": "[::1]:53184",
        "remote": "[::1]:11210",
        "last_activity_us": 94655,
        "latency_us": 312,
        "scope": "travel-sample"
      }
    ]
  }
}

Notice the scope of each service. Bucket level services like key/value will have a bucket name as scope, while cluster level services will have "Cluster" as their scope.

Diagnostics

Diagnostics returns a list of the nodes that the SDK currently has (or had) a connection to, and the current status of the connection. However this call does not actively poll the nodes, reporting instead the state the last time it tried to access each node. If you want the current status, then use Ping.

IDiagnosticsReport diagnosticsReport = await cluster.DiagnosticsAsync();

Console.WriteLine(diagnosticsReport);

// alternatively, format the output with indenting:
// Console.WriteLine(JsonConvert.SerializeObject(diagnosticsReport, Formatting.Indented));

You will see an output similar to this:

{
  "id": "b084360a-82b1-4602-b983-281d3cc11b3b",
  "version": 1,
  "sdk": "couchbase-net-sdk/3.0.7.0 (clr/.NET Core 3.1.9) (os/Microsoft Windows 10.0.18363)",
  "services": {
    "kv": [
      {
        "id": "2",
        "state": "authenticating",
        "local": "[::1]:53491",
        "remote": "[::1]:11210",
        "last_activity_us": 61153,
        "scope": "travel-sample"
      },
      {
        "id": "1",
        "state": "authenticating",
        "local": "[::1]:53492",
        "remote": "[::1]:11210",
        "last_activity_us": 66101,
        "scope": "travel-sample"
      }
    ],
    "view": [
      {
        "state": "new",
        "remote": "[::1]:11210",
        "last_activity_us": 0,
        "scope": "travel-sample"
      }
    ],
    "n1ql": [
      {
        "state": "new",
        "remote": "[::1]:11210",
        "last_activity_us": 0,
        "scope": "Cluster"
      }
    ],
    "cbas": [
      {
        "state": "new",
        "remote": "[::1]:11210",
        "last_activity_us": 0,
        "scope": "Cluster"
      }
    ],
    "fts": [
      {
        "state": "new",
        "remote": "[::1]:11210",
        "last_activity_us": 0,
        "scope": "Cluster"
      }
    ]
  }
}

Like with Ping, notice the scope of each service.