[GitHub] [skywalking] wu-sheng opened a new pull request #4725: Support percentile function in the meter system.

[GitBox]

wu-sheng opened a new pull request #4725:
URL: https://github.com/apache/skywalking/pull/4725


   ## Percentile Function
   Read [percentile in WIKI](https://en.wikipedia.org/wiki/Percentile). Unlike 
in the OAL, we provide 50/75/90/95/99 in default, in the meter system function, 
percentile function accepts several ranks, which should be in the (0, 100) 
range.
   
   ## API Usage
   ```java
   meterSystem.create(
       "test_percentile_metrics", "percentile", ScopeType.SERVICE,
       PercentileFunction.PercentileArgument.class
   );
   
   // Percentile Example
   final AcceptableValue<PercentileFunction.PercentileArgument> 
testPercentileMetrics = service.buildMetrics(
       "test_percentile_metrics", PercentileFunction.PercentileArgument.class);
   
testPercentileMetrics.setTimeBucket(TimeBucket.getMinuteTimeBucket(System.currentTimeMillis()));
   testPercentileMetrics.accept(
       MeterEntity.newService("service-test"),
       new PercentileFunction.PercentileArgument(
           new BucketedValues(
               // Buckets
               new int[] {
                   0,
                   51,
                   100,
                   250
               },
               // Values
               new long[] {
                   10,
                   20,
                   30,
                   40
               }
           ),
           // Ranks
           new int[] {
               50,
               90
           }
       )
   );
   service.doStreamingCalculation(testPercentileMetrics);                   
   ```
   
   ## Constraint Condition
   1. The buckets and percentile ranks should be consistent for every metrics 
name. Otherwise, data will be abandoned. 
   
   ## GraphQL query
   ```graphql
   {
     readLabeledMetricsValues(condition : {
       name: "test_percentile_metrics",
       entity: {
         scope: Service,
         serviceName: "service-test",
         normal: true,
       }
     }, 
     labels: ["50", "90", "no-labled"]
     duration: {step:MINUTE, start: "2020-04-28 1100", end: "2020-04-28 1105"}
     ) {
       label,
       values {
         values {
           id,
           value
         }
       }
     }
   }
   ```
   
   ```graphql
   {
     "data": {
       "readLabeledMetricsValues": [
         {
           # Even label doesn't exist in the declaration stage, no error 
happens.
           "label": "no-labled",
           "values": {
             "values": [
               {
                 "id": "202004281100_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281101_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281102_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281103_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281104_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281105_c2VydmljZS10ZXN0.1",
                 "value": 0
               }
             ]
           }
         },
         {
           "label": "50",
           "values": {
             "values": [
               {
                 "id": "202004281100_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281101_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281102_c2VydmljZS10ZXN0.1",
                 "value": 100
               },
               {
                 "id": "202004281103_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281104_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281105_c2VydmljZS10ZXN0.1",
                 "value": 0
               }
             ]
           }
         },
         {
           "label": "90",
           "values": {
             "values": [
               {
                 "id": "202004281100_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281101_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281102_c2VydmljZS10ZXN0.1",
                 "value": 250
               },
               {
                 "id": "202004281103_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281104_c2VydmljZS10ZXN0.1",
                 "value": 0
               },
               {
                 "id": "202004281105_c2VydmljZS10ZXN0.1",
                 "value": 0
               }
             ]
           }
         }
       ]
     }
   }
   ```
   
   ## Data in the storage
   
![image](https://user-images.githubusercontent.com/5441976/80444786-2681a200-8945-11ea-8acb-38da206950c7.png)
   


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