Metrics

To really get operational, we need metrics. Most production systems have metrics in one form or another. Thankfully, we don't have to start from scratch. There is a metric endpoint in Spring Boot Actuator. If we add this following setting to application.properties:

    endpoints.metrics.enabled=true

With this property setting, if we restart the application, we can get a quick read out on thing.

Assuming we have JSON Viewer installed, it's easy to surf to http://localhost:9000/application/metrics and get a listing on all sorts of metrics. We even have counters for every good/bad web hit, broken down on a per-page basis, as shown here:

    {
      "names": [
        "jvm.buffer.memory.used",
        "jvm.memory.used",
        "jvm.buffer.count",
        "logback.events",
        "process.uptime",
        "jvm.memory.committed",
        "jvm.buffer.total.capacity",
        "jvm.memory.max",
        "process.starttime",
        "http.server.requests"
      ]
    }

We can visit any one of these metrics by appending it's name to the metrics URL. For example, to view the http.server.requests, visit http://localhost:9000/application/metrics/http.server.requests:

    {
      "name": "http.server.requests",
      "measurements": [
        {
          "statistic": "TotalTime",
          "value": 3.53531643E8
        },
        {
          "statistic": "Count",
          "value": 57.0
        }
      ],
      "availableTags": [
        {
          "tag": "exception",
          "values": [
            "none",
            "none",
            "none",
            "none"
          ]
        },
        {
          "tag": "method",
          "values": [
            "GET",
            "GET",
            "GET",
            "GET"
          ]
        },
        {
          "tag": "uri",
          "values": [
            "/application/metrics/{requiredMetricName}",
            "/application/metrics/{requiredMetricName}",
            "/application/metrics",
            "/favicon.ico"
          ]
        },
        {
          "tag": "status",
          "values": [
            "200",
            "404",
            "200",
            "200"
          ]
        }
      ]
    }

This provides a basic framework of metrics to satisfy our manager's needs. It's important to understand that metrics gathered by Spring Boot Actuator aren't persistent across application restarts. To gather long-term data, we have to write them elsewhere (http://docs.spring.io/spring-boot/docs/2.0.0.M5/reference/htmlsingle/#production-ready-metrics).