Diagnosing and preventing Network Problems with Health Check

how-to

In today’s distributed and virtual environments, users will often not have full administrative control over their whole network. Health Check introduces Ping to check nodes are still healthy, and to force idle connections to be kept alive in environments with eager shutdowns of unused resources. Diagnostics requests a report from a node, giving instant health check information.

Diagnosing problems in distributed environments is far from easy, so Couchbase provides a Health Check API with Ping() for active monitoring. ans Diagnostics() for a look at what the client believes is the current state of the cluster. More extensive discussion of the uses of Health Check can be found in the Health Check Concept Guide.

Ping

At the simplest lcb_PING_SERVICE is an enumeration used to indicate the type of service in PING responses. You can customize the type of services to ping through this service. Service types include:

LCB_PING_SERVICE_KV
LCB_PING_SERVICE_VIEWS
LCB_PING_SERVICE_QUERY
LCB_PING_SERVICE_SEARCH
LCB_PING_SERVICE_ANALYTICS

lcb_PING_STATUS returns the current status of the service.

void ping_callback(lcb_INSTANCE *, int, const lcb_RESPPING *resp)
{
    lcb_STATUS rc = lcb_respping_status(resp);
    if (rc != LCB_SUCCESS) {
        fprintf(stderr, "failed: %s\n", lcb_strerror_short(rc));
    } else {
        const char *json;
        size_t njson;
        lcb_respping_value(resp, &json, &njson);
        while (njson > 1 && json[njson - 1] == '\n') {
            njson--;
        }
        if (njson) {
            printf("%.*s", int(njson), json);
        }
    }
}

Diagnostics

Diagnostics work in a similar fashion to lcb_PING_SERVICE in the sense that it returns a report of how all the sockets/end-points are doing, but the main difference is that it is passive. While lcb_PING_SERVICE proactively sends an operation across the network, a diagnostics report just returns whatever current state the client is in. This makes it much cheaper to call on a regular basis, but does not provide any live insight into network slowness, et al..

lcb_install_callback(instance, LCB_CALLBACK_DIAG, diag_callback);
void diag_callback(lcb_INSTANCE, int, const lcb_RESPBASE *rb)
{
    const lcb_RESPDIAG *resp = (const lcb_RESPDIAG *)rb;
    char* json;
    size_t json_len;
    lcb_STATUS rc = lcb_respdiag_status(resp);
    if (rc != LCB_SUCCESS) {
        fprintf(stderr, "failed: %s\n", lcb_strerror_short(rc));
    } else {
        lcb_respdiag_value(resp, &json, &json_len);
        if (json) {
            fprintf(stderr, "\n%.*s", json_len, json);
        }
    }
}

For more information on lcb_diag(), refer to API Documentation.