Perf: cache regex pattern and result, optimize string concatenation (#7199)

The possible metrics names are relatively fixed in an OAP run, we previously always escape the metrics names, building a new regex Pattern from scratch, which is cpu-consuming.

In this patch, I cache the escaped metrics names, and if it missed, use a pre-compiled regex Pattern to escape the metrics name.

This patch also replace string concatenation `+` with `StringBuilder` in generated classes, which won't get optimized by Java compiler

This may reduce 1~1.5 vCPU under 20K RPS environment.

CHANGES.md

@@ -47,6 +47,7 @@ Release Notes.
 * Performance: optimize Envoy ALS analyzer performance in high traffic load scenario (reduce ~1cpu in ~10k RPS).
 * Performance: trim useless metadata fields in Envoy ALS metadata to improve performance.
 * Fix: slowDBAccessThreshold dynamic config error when not configured.
+* Performance: cache regex pattern and result, optimize string concatenation in Envy ALS analyzer.
 
 #### UI
 * Fix the date component for log conditions.

oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/prometheus/PrometheusMetricConverter.java

@@ -18,9 +18,17 @@
 
 package org.apache.skywalking.oap.meter.analyzer.prometheus;
 
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
 import com.google.common.collect.ImmutableMap;
 import io.vavr.Tuple;
 import io.vavr.Tuple2;
+import java.util.Collections;
+import java.util.Optional;
+import java.util.concurrent.ExecutionException;
+import java.util.regex.Pattern;
+import java.util.stream.Stream;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.skywalking.oap.meter.analyzer.MetricConvert;
 import org.apache.skywalking.oap.meter.analyzer.dsl.Sample;
@@ -34,10 +42,6 @@ import org.apache.skywalking.oap.server.library.util.prometheus.metrics.Histogra
 import org.apache.skywalking.oap.server.library.util.prometheus.metrics.Metric;
 import org.apache.skywalking.oap.server.library.util.prometheus.metrics.Summary;
 
-import java.util.Collections;
-import java.util.Optional;
-import java.util.stream.Stream;
-
 import static com.google.common.collect.ImmutableMap.toImmutableMap;
 import static io.vavr.API.$;
 import static io.vavr.API.Case;
@@ -51,11 +55,23 @@ import static org.apache.skywalking.oap.meter.analyzer.Analyzer.NIL;
  */
 @Slf4j
 public class PrometheusMetricConverter {
+    private final Pattern metricsNameEscapePattern;
+
+    private final LoadingCache<String, String> escapedMetricsNameCache =
+        CacheBuilder.newBuilder()
+                    .maximumSize(1000)
+                    .build(new CacheLoader<String, String>() {
+                        @Override
+                        public String load(final String name) {
+                            return metricsNameEscapePattern.matcher(name).replaceAll("_");
+                        }
+                    });
 
     private final MetricConvert convert;
 
     public PrometheusMetricConverter(Rule rule, MeterSystem service) {
         this.convert = new MetricConvert(rule, service);
+        this.metricsNameEscapePattern = Pattern.compile("\\.");
     }
 
     /**
@@ -146,6 +162,11 @@ public class PrometheusMetricConverter {
 
     // Returns the escaped name of the given one, with "." replaced by "_"
     protected String escapedName(final String name) {
-        return name.replaceAll("\\.", "_");
+        try {
+            return escapedMetricsNameCache.get(name);
+        } catch (ExecutionException e) {
+            log.error("Failed to get escaped metrics name from cache", e);
+            return metricsNameEscapePattern.matcher(name).replaceAll("_");
+        }
     }
 }

oap-server/oal-rt/src/main/resources/code-templates/metrics/id.ftl

 public String id() {
-String splitJointId = String.valueOf(getTimeBucket());
+StringBuilder splitJointId = new StringBuilder(String.valueOf(getTimeBucket()));
 <#list fieldsFromSource as sourceField>
     <#if sourceField.isID()>
-        <#if sourceField.getTypeName() == "java.lang.String">
-            splitJointId += org.apache.skywalking.oap.server.core.Const.ID_CONNECTOR + ${sourceField.fieldName};
-        <#else>
-            splitJointId += org.apache.skywalking.oap.server.core.Const.ID_CONNECTOR + String.valueOf(${sourceField.fieldName});
-        </#if>
+        splitJointId.append(org.apache.skywalking.oap.server.core.Const.ID_CONNECTOR)
+                    .append(${sourceField.fieldName});
     </#if>
 </#list>
-return splitJointId;
-}
\ No newline at end of file
+return splitJointId.toString();
+}