OAL 直譯器實現
OAL 直譯器是基於 Antlr4 實現的，我們先來了解下 Antlr4
在 pom.xml 中配置 antlr4 的依賴和外掛
grammar Calc; //名稱需要和檔名一致root : expr EOF; //解決問題: no viable alternative at input '<EOF>'expr : expr '+' expr #add //標籤會生成對應訪問方法方便我們實現呼叫邏輯編寫 | expr '-' expr #sub | INT #int ;INT : [0-9]+ //定義整數 ;WS : [ \r\n\t]+ -> skip //跳過空白類字元 ;執行一下： mvn compile -Dmaven.test.skip=true ，在 target/generated-sources/antlr4 會生成相應的 Java 程式碼。
使用方式預設是監聽器模式，也可以配置成訪問者模式。
監聽器模式：主要藉助了 ParseTreeWalker 這樣一個類,相當於是一個 hook ，每經過一個樹的節點,便會觸發對應節點的方法。好處就算是比較方便,但是靈活性不夠,不能夠自主性的呼叫任意節點進行使用。
訪問者模式：將每個資料的節點型別高度抽象出來夠,根據你傳入的上下文型別來判斷你想要訪問的是哪個節點,觸發對應的方法
PS：結論，簡單語法監聽器模式就可以了，如果語法比較靈活可以考慮使用訪問者模式。
Antlr4 在 Skywalking 的應用
透過“ Antlr4 基本介紹”一節，基本上對 Antlr4 使用有了個大概的認識。下面來看看 Skywalking 中 Antlr4 是如何使用的。
在 oap-server/oal-grammar/src/main/antlr4/org/apache/skywalking/oal/rt/grammar/OALLexer.g4 檔案中，我們能看到 OAL 的詞法定義
// Observability Analysis Language lexerlexer grammar OALLexer;@Header {package org.apache.skywalking.oal.rt.grammar;}// KeywordsFROM: 'from';FILTER: 'filter';DISABLE: 'disable';SRC_ALL: 'All';SRC_SERVICE: 'Service';SRC_SERVICE_INSTANCE: 'ServiceInstance';SRC_ENDPOINT: 'Endpoint';SRC_SERVICE_RELATION: 'ServiceRelation';SRC_SERVICE_INSTANCE_RELATION: 'ServiceInstanceRelation';SRC_ENDPOINT_RELATION: 'EndpointRelation';SRC_SERVICE_INSTANCE_JVM_CPU: 'ServiceInstanceJVMCPU';SRC_SERVICE_INSTANCE_JVM_MEMORY: 'ServiceInstanceJVMMemory';SRC_SERVICE_INSTANCE_JVM_MEMORY_POOL: 'ServiceInstanceJVMMemoryPool';SRC_SERVICE_INSTANCE_JVM_GC: 'ServiceInstanceJVMGC';SRC_SERVICE_INSTANCE_JVM_THREAD: 'ServiceInstanceJVMThread';SRC_SERVICE_INSTANCE_JVM_CLASS:'ServiceInstanceJVMClass';SRC_DATABASE_ACCESS: 'DatabaseAccess';SRC_SERVICE_INSTANCE_CLR_CPU: 'ServiceInstanceCLRCPU';SRC_SERVICE_INSTANCE_CLR_GC: 'ServiceInstanceCLRGC';SRC_SERVICE_INSTANCE_CLR_THREAD: 'ServiceInstanceCLRThread';SRC_ENVOY_INSTANCE_METRIC: 'EnvoyInstanceMetric';// Browser keywordsSRC_BROWSER_APP_PERF: 'BrowserAppPerf';SRC_BROWSER_APP_PAGE_PERF: 'BrowserAppPagePerf';SRC_BROWSER_APP_SINGLE_VERSION_PERF: 'BrowserAppSingleVersionPerf';SRC_BROWSER_APP_TRAFFIC: 'BrowserAppTraffic';SRC_BROWSER_APP_PAGE_TRAFFIC: 'BrowserAppPageTraffic';SRC_BROWSER_APP_SINGLE_VERSION_TRAFFIC: 'BrowserAppSingleVersionTraffic';// Constructors symbolsDOT: '.';LR_BRACKET: '(';RR_BRACKET: ')';LS_BRACKET: '[';RS_BRACKET: ']';COMMA: ',';SEMI: ';';EQUAL: '=';DUALEQUALS: '==';ALL: '*';GREATER: '>';LESS: '<';GREATER_EQUAL: '>=';LESS_EQUAL: '<=';NOT_EQUAL: '!=';LIKE: 'like';IN: 'in';CONTAIN: 'contain';NOT_CONTAIN: 'not contain';// LiteralsBOOL_LITERAL: 'true' | 'false' ;NUMBER_LITERAL : Digits+;CHAR_LITERAL: '\'' (~['\\\r\n] | EscapeSequence) '\'';STRING_LITERAL: '"' (~["\\\r\n] | EscapeSequence)* '"';DelimitedComment : '/*' ( DelimitedComment | . )*? '*/' -> channel(HIDDEN) ;LineComment : '//' ~[\u000A\u000D]* -> channel(HIDDEN) ;SPACE: [ \t\r\n]+ -> channel(HIDDEN);// IdentifiersIDENTIFIER: Letter LetterOrDigit*;// Fragment rulesfragment EscapeSequence : '\\' [btnfr"'\\] | '\\' ([0-3]? [0-7])? [0-7] | '\\' 'u'+ HexDigit HexDigit HexDigit HexDigit ;fragment HexDigits : HexDigit ((HexDigit | '_')* HexDigit)? ;fragment HexDigit : [0-9a-fA-F] ;fragment Digits : [0-9] ([0-9_]* [0-9])? ;fragment LetterOrDigit : Letter | [0-9] ;fragment Letter : [a-zA-Z$_] // these are the "java letters" below 0x7F | ~[\u0000-\u007F\uD800-\uDBFF] // covers all characters above 0x7F which are not a surrogate | [\uD800-\uDBFF] [\uDC00-\uDFFF] // covers UTF-16 surrogate pairs encodings for U+10000 to U+10FFFF ;在 oap-server/oal-grammar/src/main/antlr4/org/apache/skywalking/oal/rt/grammar/OALParser.g4 檔案中，我們能看到 OAL 的語法定義
parser grammar OALParser;@Header {package org.apache.skywalking.oal.rt.grammar;}options { tokenVocab=OALLexer; }// Top Level Descriptionroot : (aggregationStatement | disableStatement)* ;aggregationStatement : variable (SPACE)? EQUAL (SPACE)? metricStatement DelimitedComment? LineComment? (SEMI|EOF) ;disableStatement : DISABLE LR_BRACKET disableSource RR_BRACKET DelimitedComment? LineComment? (SEMI|EOF) ;metricStatement : FROM LR_BRACKET source (sourceAttributeStmt+) RR_BRACKET (filterStatement+)? DOT aggregateFunction ;filterStatement : DOT FILTER LR_BRACKET filterExpression RR_BRACKET ;filterExpression : expression ;source : SRC_ALL | SRC_SERVICE | SRC_DATABASE_ACCESS | SRC_SERVICE_INSTANCE | SRC_ENDPOINT | SRC_SERVICE_RELATION | SRC_SERVICE_INSTANCE_RELATION | SRC_ENDPOINT_RELATION | SRC_SERVICE_INSTANCE_JVM_CPU | SRC_SERVICE_INSTANCE_JVM_MEMORY | SRC_SERVICE_INSTANCE_JVM_MEMORY_POOL | SRC_SERVICE_INSTANCE_JVM_GC | SRC_SERVICE_INSTANCE_JVM_THREAD | SRC_SERVICE_INSTANCE_JVM_CLASS |// JVM source of service instance SRC_SERVICE_INSTANCE_CLR_CPU | SRC_SERVICE_INSTANCE_CLR_GC | SRC_SERVICE_INSTANCE_CLR_THREAD | SRC_ENVOY_INSTANCE_METRIC | SRC_BROWSER_APP_PERF | SRC_BROWSER_APP_PAGE_PERF | SRC_BROWSER_APP_SINGLE_VERSION_PERF | SRC_BROWSER_APP_TRAFFIC | SRC_BROWSER_APP_PAGE_TRAFFIC | SRC_BROWSER_APP_SINGLE_VERSION_TRAFFIC ;disableSource : IDENTIFIER ;sourceAttributeStmt : DOT sourceAttribute ;sourceAttribute : IDENTIFIER | ALL ;variable : IDENTIFIER ;aggregateFunction : functionName LR_BRACKET ((funcParamExpression (COMMA funcParamExpression)?) | (literalExpression (COMMA literalExpression)?))? RR_BRACKET ;functionName : IDENTIFIER ;funcParamExpression : expression ;literalExpression : BOOL_LITERAL | NUMBER_LITERAL | IDENTIFIER ;expression : booleanMatch | stringMatch | greaterMatch | lessMatch | greaterEqualMatch | lessEqualMatch | notEqualMatch | booleanNotEqualMatch | likeMatch | inMatch | containMatch | notContainMatch ;containMatch : conditionAttributeStmt CONTAIN stringConditionValue ;notContainMatch : conditionAttributeStmt NOT_CONTAIN stringConditionValue ;booleanMatch : conditionAttributeStmt DUALEQUALS booleanConditionValue ;stringMatch : conditionAttributeStmt DUALEQUALS (stringConditionValue | enumConditionValue) ;greaterMatch : conditionAttributeStmt GREATER numberConditionValue ;lessMatch : conditionAttributeStmt LESS numberConditionValue ;greaterEqualMatch : conditionAttributeStmt GREATER_EQUAL numberConditionValue ;lessEqualMatch : conditionAttributeStmt LESS_EQUAL numberConditionValue ;booleanNotEqualMatch : conditionAttributeStmt NOT_EQUAL booleanConditionValue ;notEqualMatch : conditionAttributeStmt NOT_EQUAL (numberConditionValue | stringConditionValue | enumConditionValue) ;likeMatch : conditionAttributeStmt LIKE stringConditionValue ;inMatch : conditionAttributeStmt IN multiConditionValue ;multiConditionValue : LS_BRACKET (numberConditionValue ((COMMA numberConditionValue)*) | stringConditionValue ((COMMA stringConditionValue)*) | enumConditionValue ((COMMA enumConditionValue)*)) RS_BRACKET ;conditionAttributeStmt : conditionAttribute ((DOT conditionAttribute)*) ;conditionAttribute : IDENTIFIER ;booleanConditionValue : BOOL_LITERAL ;stringConditionValue : STRING_LITERAL ;enumConditionValue : IDENTIFIER DOT IDENTIFIER ;numberConditionValue : NUMBER_LITERAL ;Antlr4 生成 Java 程式碼在 oap-server/oal-grammar 下執行 mvn compile -Dmaven.test.skip=true 會在 oap-server/oal-grammar/target/generated-sources/antlr4 目錄下生成相應的 Java 程式碼
.├── OALLexer.tokens├── OALParser.tokens└── org └── apache └── skywalking └── oal └── rt └── grammar ├── OALLexer.interp ├── OALLexer.java # 詞法解析器 ├── OALParser.interp ├── OALParser.java # 語法解析器 ├── OALParserBaseListener.java # 監聽器 └── OALParserListener.javaSkywalking 的使用透過“ Antlr4 使用案例”一節，可以知道 Antlr4 有兩種功能實現方式：監聽器或者訪問器。
透過“ Antlr4 生成 Java 程式碼”一節，知道 Skywalking 使用的是監聽器模式。
Skywalking 關於 OAL 的相應的程式碼都在 oap-server/oal-rt 模組中。
org.apache.skywalking.oal.rt.grammar.OALParserBaseListener 的繼承類座標是 org.apache.skywalking.oal.rt.parser.OALListener
package org.apache.skywalking.oal.rt.parser;import java.util.Arrays;import java.util.List;import org.antlr.v4.runtime.misc.NotNull;import org.apache.skywalking.oal.rt.grammar.OALParser;import org.apache.skywalking.oal.rt.grammar.OALParserBaseListener;import org.apache.skywalking.oap.server.core.source.DefaultScopeDefine;public class OALListener extends OALParserBaseListener { private List<AnalysisResult> results; private AnalysisResult current; private DisableCollection collection; private ConditionExpression conditionExpression; private final String sourcePackage; public OALListener(OALScripts scripts, String sourcePackage) { this.results = scripts.getMetricsStmts(); this.collection = scripts.getDisableCollection(); this.sourcePackage = sourcePackage; } @Override public void enterAggregationStatement(@NotNull OALParser.AggregationStatementContext ctx) { current = new AnalysisResult(); } @Override public void exitAggregationStatement(@NotNull OALParser.AggregationStatementContext ctx) { DeepAnalysis deepAnalysis = new DeepAnalysis(); results.add(deepAnalysis.analysis(current)); current = null; } @Override public void enterSource(OALParser.SourceContext ctx) { current.setSourceName(ctx.getText()); current.setSourceScopeId(DefaultScopeDefine.valueOf(metricsNameFormat(ctx.getText()))); } @Override public void enterSourceAttribute(OALParser.SourceAttributeContext ctx) { current.getSourceAttribute().add(ctx.getText()); } @Override public void enterVariable(OALParser.VariableContext ctx) { } @Override public void exitVariable(OALParser.VariableContext ctx) { current.setVarName(ctx.getText()); current.setMetricsName(metricsNameFormat(ctx.getText())); current.setTableName(ctx.getText().toLowerCase()); } @Override public void enterFunctionName(OALParser.FunctionNameContext ctx) { current.setAggregationFunctionName(ctx.getText()); } @Override public void enterFilterStatement(OALParser.FilterStatementContext ctx) { conditionExpression = new ConditionExpression(); } @Override public void exitFilterStatement(OALParser.FilterStatementContext ctx) { current.addFilterExpressionsParserResult(conditionExpression); conditionExpression = null; } @Override public void enterFuncParamExpression(OALParser.FuncParamExpressionContext ctx) { conditionExpression = new ConditionExpression(); } @Override public void exitFuncParamExpression(OALParser.FuncParamExpressionContext ctx) { current.addFuncConditionExpression(conditionExpression); conditionExpression = null; } ///////////// // Expression //////////// @Override public void enterConditionAttribute(OALParser.ConditionAttributeContext ctx) { conditionExpression.getAttributes().add(ctx.getText()); } @Override public void enterBooleanMatch(OALParser.BooleanMatchContext ctx) { conditionExpression.setExpressionType("booleanMatch"); } @Override public void enterStringMatch(OALParser.StringMatchContext ctx) { conditionExpression.setExpressionType("stringMatch"); } @Override public void enterGreaterMatch(OALParser.GreaterMatchContext ctx) { conditionExpression.setExpressionType("greaterMatch"); } @Override public void enterGreaterEqualMatch(OALParser.GreaterEqualMatchContext ctx) { conditionExpression.setExpressionType("greaterEqualMatch"); } @Override public void enterLessMatch(OALParser.LessMatchContext ctx) { conditionExpression.setExpressionType("lessMatch"); } @Override public void enterLessEqualMatch(OALParser.LessEqualMatchContext ctx) { conditionExpression.setExpressionType("lessEqualMatch"); } @Override public void enterNotEqualMatch(final OALParser.NotEqualMatchContext ctx) { conditionExpression.setExpressionType("notEqualMatch"); } @Override public void enterBooleanNotEqualMatch(final OALParser.BooleanNotEqualMatchContext ctx) { conditionExpression.setExpressionType("booleanNotEqualMatch"); } @Override public void enterLikeMatch(final OALParser.LikeMatchContext ctx) { conditionExpression.setExpressionType("likeMatch"); } @Override public void enterContainMatch(final OALParser.ContainMatchContext ctx) { conditionExpression.setExpressionType("containMatch"); } @Override public void enterNotContainMatch(final OALParser.NotContainMatchContext ctx) { conditionExpression.setExpressionType("notContainMatch"); } @Override public void enterInMatch(final OALParser.InMatchContext ctx) { conditionExpression.setExpressionType("inMatch"); } @Override public void enterMultiConditionValue(final OALParser.MultiConditionValueContext ctx) { conditionExpression.enterMultiConditionValue(); } @Override public void exitMultiConditionValue(final OALParser.MultiConditionValueContext ctx) { conditionExpression.exitMultiConditionValue(); } @Override public void enterBooleanConditionValue(OALParser.BooleanConditionValueContext ctx) { enterConditionValue(ctx.getText()); } @Override public void enterStringConditionValue(OALParser.StringConditionValueContext ctx) { enterConditionValue(ctx.getText()); } @Override public void enterEnumConditionValue(OALParser.EnumConditionValueContext ctx) { enterConditionValue(ctx.getText()); } @Override public void enterNumberConditionValue(OALParser.NumberConditionValueContext ctx) { conditionExpression.isNumber(); enterConditionValue(ctx.getText()); } private void enterConditionValue(String value) { if (value.split("\\.").length == 2 && !value.startsWith("\"")) { // Value is an enum. value = sourcePackage + value; } conditionExpression.addValue(value); } ///////////// // Expression end. //////////// @Override public void enterLiteralExpression(OALParser.LiteralExpressionContext ctx) { if (ctx.IDENTIFIER() == null) { current.addFuncArg(new Argument(EntryMethod.LITERAL_TYPE, Arrays.asList(ctx.getText()))); return; } current.addFuncArg(new Argument(EntryMethod.IDENTIFIER_TYPE, Arrays.asList(ctx.getText().split("\\.")))); } private String metricsNameFormat(String source) { source = firstLetterUpper(source); int idx; while ((idx = source.indexOf("_")) > -1) { source = source.substring(0, idx) + firstLetterUpper(source.substring(idx + 1)); } return source; } /** * Disable source */ @Override public void enterDisableSource(OALParser.DisableSourceContext ctx) { collection.add(ctx.getText()); } private String firstLetterUpper(String source) { return source.substring(0, 1).toUpperCase() + source.substring(1); }}簡單來說，就是透過監聽器封裝了個 org.apache.skywalking.oal.rt.parser.OALScripts 物件
package org.apache.skywalking.oal.rt.parser;import java.util.LinkedList;import java.util.List;import lombok.Getter;@Getterpublic class OALScripts { // 解析出來的分析結果集合 private List<AnalysisResult> metricsStmts; // 禁用表示式集合 private DisableCollection disableCollection; public OALScripts() { metricsStmts = new LinkedList<>(); disableCollection = new DisableCollection(); }}org.apache.skywalking.oal.rt.parser.ScriptParser 類讀取 oal 檔案，使用 Antlr 生成的 Java 類進行解析
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