Scripting: Add instance and compiled classes to script contexts (#24868)

This commit modifies the compile method of ScriptService to be context
aware. The ScriptContext is now a generic class which contains both the
instance type and compiled type for a script. Instance type may be
stateful (for example, pre loading field information for the index a
script will execute on, like in expressions), while the compiled type is
stateless and used to construct instance type instances. This change is
only a first step to cutover ScriptService to the new paradigm. It only
converts callers to the script service, and has a small shim to wrap
compilation from the script engines to support the current two fixed
instance types, SearchScript and ExecutableScript.

2 files changed, 8 insertions, 16 deletions

diff --git a/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/MustacheScriptEngine.java b/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/MustacheScriptEngine.java
index 28ba360025..e31b97099f 100644
--- a/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/MustacheScriptEngine.java
+++ b/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/MustacheScriptEngine.java
@@ -27,10 +27,7 @@ import org.apache.logging.log4j.util.Supplier;
 import org.elasticsearch.SpecialPermission;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.io.FastStringReader;
-import org.elasticsearch.common.io.UTF8StreamWriter;
-import org.elasticsearch.common.io.stream.BytesStreamOutput;
 import org.elasticsearch.common.logging.ESLoggerFactory;
-import org.elasticsearch.script.CompiledScript;
 import org.elasticsearch.script.ExecutableScript;
 import org.elasticsearch.script.GeneralScriptException;
 import org.elasticsearch.script.Script;
@@ -40,7 +37,6 @@ import org.elasticsearch.search.lookup.SearchLookup;
 
 import java.io.Reader;
 import java.io.StringWriter;
-import java.lang.ref.SoftReference;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.Collections;
@@ -86,14 +82,12 @@ public final class MustacheScriptEngine implements ScriptEngine {
     }
 
     @Override
-    public ExecutableScript executable(CompiledScript compiledScript,
-            @Nullable Map<String, Object> vars) {
-        return new MustacheExecutableScript(compiledScript, vars);
+    public ExecutableScript executable(Object compiledScript, @Nullable Map<String, Object> vars) {
+        return new MustacheExecutableScript((Mustache) compiledScript, vars);
     }
 
     @Override
-    public SearchScript search(CompiledScript compiledScript, SearchLookup lookup,
-            @Nullable Map<String, Object> vars) {
+    public SearchScript search(Object compiledScript, SearchLookup lookup, @Nullable Map<String, Object> vars) {
         throw new UnsupportedOperationException();
     }
 
@@ -102,7 +96,7 @@ public final class MustacheScriptEngine implements ScriptEngine {
      * */
     private class MustacheExecutableScript implements ExecutableScript {
         /** Compiled template object wrapper. */
-        private CompiledScript template;
+        private Mustache template;
         /** Parameters to fill above object with. */
         private Map<String, Object> vars;
 
@@ -110,7 +104,7 @@ public final class MustacheScriptEngine implements ScriptEngine {
          * @param template the compiled template object wrapper
          * @param vars the parameters to fill above object with
          **/
-        MustacheExecutableScript(CompiledScript template, Map<String, Object> vars) {
+        MustacheExecutableScript(Mustache template, Map<String, Object> vars) {
             this.template = template;
             this.vars = vars == null ? Collections.emptyMap() : vars;
         }
@@ -127,7 +121,7 @@ public final class MustacheScriptEngine implements ScriptEngine {
                 // crazy reflection here
                 SpecialPermission.check();
                 AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
-                    ((Mustache) template.compiled()).execute(writer, vars);
+                    template.execute(writer, vars);
                     return null;
                 });
             } catch (Exception e) {
diff --git a/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/TransportSearchTemplateAction.java b/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/TransportSearchTemplateAction.java
index 90678aba85..ca25147405 100644
--- a/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/TransportSearchTemplateAction.java
+++ b/modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/TransportSearchTemplateAction.java
@@ -27,7 +27,6 @@ import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.action.support.HandledTransportAction;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.common.bytes.BytesArray;
-import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
@@ -39,14 +38,13 @@ import org.elasticsearch.script.Script;
 import org.elasticsearch.script.ScriptService;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.template.CompiledTemplate;
-import org.elasticsearch.template.CompiledTemplate;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
 
 import java.io.IOException;
 import java.util.Collections;
 
-import static org.elasticsearch.script.ScriptContext.SEARCH;
+import static org.elasticsearch.script.ScriptContext.EXECUTABLE;
 
 public class TransportSearchTemplateAction extends HandledTransportAction<SearchTemplateRequest, SearchTemplateResponse> {
 
@@ -102,7 +100,7 @@ public class TransportSearchTemplateAction extends HandledTransportAction<Search
                                  NamedXContentRegistry xContentRegistry) throws IOException {
         Script script = new Script(searchTemplateRequest.getScriptType(), TEMPLATE_LANG, searchTemplateRequest.getScript(),
                 searchTemplateRequest.getScriptParams() == null ? Collections.emptyMap() : searchTemplateRequest.getScriptParams());
-        CompiledTemplate compiledScript = scriptService.compileTemplate(script, SEARCH);
+        CompiledTemplate compiledScript = scriptService.compileTemplate(script, EXECUTABLE);
         String source = compiledScript.run(script.getParams());
         response.setSource(new BytesArray(source));