[GitHub] [skywalking] wu-sheng commented on a change in pull request #4816: Provide agent-side meter api

[GitBox <gi...@apache.org>]

wu-sheng commented on a change in pull request #4816:
URL: https://github.com/apache/skywalking/pull/4816#discussion_r442904242



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File path: docs/en/setup/service-agent/java-agent/Application-toolkit-meter.md
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@@ -0,0 +1,51 @@
+* Dependency the toolkit, such as using maven or gradle
+```xml
+   <dependency>
+      <groupId>org.apache.skywalking</groupId>
+      <artifactId>apm-toolkit-meter</artifactId>
+      <version>${skywalking.version}</version>
+   </dependency>
+```
+
+* `Counter` API represents a single monotonically increasing counter, automatic collect data and report to backend.
+```java
+Counter counter = Counter.create(meterName).tag("tagKey", "tagValue").build();
+counter.increment(1d);
+```
+1. `Counter.create` Create a new counter builder with the meter name.
+1. `Counter.Builder.tag(String key, String value)` Mark a tag key/value pair.
+1. `Counter.Builder.build()` To build a new `Counter` and it will register to the agent, automatically collect data and report to the backend.
+1. `Counter.increment(double count)` Increment count to the `Counter`, It could be a positive/negative value.
+
+* `Gauge` API represents a single numerical value.
+```java
+ThreadPoolExecutor threadPool = ...;
+Gauge gauge = Gauge.create(meterName, () -> threadPool.getActiveCount()).tag("tagKey", "tagValue").build();
+```
+1. `Gauge.create(String name, Supplier<Double> getter)` Create a new gauge builder with the meter name and supplier function, this function need to return a `double` value.
+1. `Gauge.Builder.tag(String key, String value)` Mark a tag key/value pair.
+1. `Gauge.Builder.build()` To build a new `Gauge` and it will register to the agent, automatically collect data and report to the backend.
+
+* `Histogram` API represents a summary sample observations with customize buckets.
+```java
+Histogram histogram = Histogram.create("test").tag("tagKey", "tagValue").steps(Arrays.asList(1, 5, 10)).exceptMinValue(0).build();

Review comment:
       `exceptMinValue`? What do you mean? `Exclude`? But still a little confusing.




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