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.

Uses

'Ping` provides a raw JSON payload suitable for feeding into reactive log and aggregation components, including monitoring systems like Splunk, ElasticSearch, and Nagios. It can also help keep connections alive if you are operating across an environment which aggressively closes down unused connections.

Diagnostics provides a strongly typed API for proactive, pull-based monitoring systems, such as:

This API does not provide binary yes/no answers about the health of the cluster; rather it summarizes as much information as possible, for the application developer to assemble a complete, contextual view and come to a conclusion.

Note: Ping may reopen a connection, so is not without side-effects. Diagnostics shows what the SDK perceives as the current state of the network and services — it is without side-effects, but may not be up to date.

Ping

At its simplest, ping provides information about the current state of the connections in the Couchbase Cluster, by actively polling:

const result = await cluster.ping();
console.log(result);
/*
{
  config_rev: 3,
  id: '0x103828d70/41115255fb1e3c76',
  sdk: 'libcouchbase/3.0.6-njs couchnode/3.0.7 (node/12.18.2; v8/7.8.279.23-node.39; ssl/1.1.1g)',
  services: {
    kv: [
        {
            id: '0x10410c8d0',
            latency_us: 5577,
            local: '127.0.0.1:54985',
            namespace: 'default',
            remote: 'localhost:54979',
            status: 'ok'
        },
        ...
    ],
    n1ql: [ ... ],
    views: [ ... ]
  },
  version: 1
}
*/

This will print the latency for each socket (endpoint) connected per service. More information is available on the classes.

By default the SDK will ping all services available on the target cluster. You can customize the type of services to ping through the PingOptions:

const result = await cluster.ping({
    serviceTypes: [
        couchbase.ServiceType.Query,
    ]
});

In this example, only the Query Service is included in the ping report.

Note that ping is available both on the Cluster and the Bucket level. The difference is that at the cluster level, the key-value service might not be included based on the Couchbase Server version in use. If you want to make sure the key-value service is included, perform it at the bucket level.

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.

const result = await bucket.diagnostics();
console.log(result)
/*
{
    "id":"0x10290d100","kv":[
        {
            "id":"0000000072b21d66",
            "last_activity_us":2363294,
            "local":"10.112.195.1:51473",
            "remote":"10.112.195.101:11210",
            "status":"connected"
        },
        {
            "id":"000000000ba84e5e",
            "last_activity_us":7369021,
            "local":"10.112.195.1:51486",
            "remote":"10.112.195.102:11210",
            "status":"connected"
        },
        {
            "id":"0000000077689398",
            "last_activity_us":4855640,
            "local":"10.112.195.1:51409",
            "remote":"10.112.195.103:11210",
            "status":"connected"
        }
    ],
    "sdk":"libcouchbase/2.9.5-njs couchnode/2.6.9 (node/10.16.0; v8/6.8.275.32-node.52; ssl/1.1.1b)",
    "version":1
}
*/