Customizing metric outputs with views
Some applications may produce more metrics than an application developer is interested in. You may have noticed this with the example code for instruments; as we added more examples, it became difficult to find the metrics we were interested in. Recall the example mentioned earlier in this chapter: application A represents a client library making web requests that could produce metrics via three different meters. If each of those meters keeps a request counter, duplicate data is highly likely to be generated. Duplicated data may not be a problem on a small scale, but when scaling services up to handling thousands and millions of requests, unnecessary metrics can become quite expensive. Thankfully, views provide a way for users of OpenTelemetry to configure the SDK only to generate the metrics they want. In addition to providing a mechanism to filter metrics, views can also configure aggregation or be used to add a new dimension to metrics.
