Minify Painless script before sending to OpenSearch (#6785)

Strip comment lines and blank lines from the Painless script source at
initialization time. This reduces the script payload size sent to
OpenSearch on every bulk request, improving network efficiency.

The minification is done once in the ScriptManager constructor and the
result is reused for all subsequent buildScript calls. Only full-line
comments (lines starting with //) and empty lines are removed. Inline
comments after code are preserved.

Signed-off-by: Dinu John <86094133+dinujoh@users.noreply.github.com>

Author: dinujoh

data-prepper-plugins/opensearch/src/main/java/org/opensearch/dataprepper/plugins/sink/opensearch/ScriptManager.java

@@ -28,10 +28,12 @@ public class ScriptManager {
 
     private final ScriptConfiguration scriptConfiguration;
     private final ExpressionEvaluator expressionEvaluator;
+    private final String minifiedSource;
 
     public ScriptManager(final ScriptConfiguration scriptConfiguration, final ExpressionEvaluator expressionEvaluator) {
         this.scriptConfiguration = scriptConfiguration;
         this.expressionEvaluator = expressionEvaluator;
+        this.minifiedSource = scriptConfiguration != null ? minifyScript(scriptConfiguration.getSource()) : null;
     }
 
     public boolean isScriptEnabled() {
@@ -61,10 +63,27 @@ public Script buildScript(final JsonNode jsonNode, final Map<String, Object> res
             resolvedParams.forEach((k, v) -> scriptParams.put(k, JsonData.of(v)));
         }
         final InlineScript inlineScript = new InlineScript.Builder()
-                .source(scriptConfiguration.getSource())
+                .source(minifiedSource)
                 .lang(PAINLESS)
                 .params(scriptParams)
                 .build();
         return Script.of(s -> s.inline(inlineScript));
     }
+
+    static String minifyScript(final String source) {
+        if (source == null) {
+            return null;
+        }
+        final StringBuilder sb = new StringBuilder();
+        for (final String line : source.split("\n")) {
+            final String trimmed = line.trim();
+            if (!trimmed.isEmpty() && !trimmed.startsWith("//")) {
+                if (sb.length() > 0) {
+                    sb.append('\n');
+                }
+                sb.append(trimmed);
+            }
+        }
+        return sb.toString();
+    }
 }

data-prepper-plugins/opensearch/src/test/java/org/opensearch/dataprepper/plugins/sink/opensearch/ScriptManagerMinifyTest.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ */
+
+package org.opensearch.dataprepper.plugins.sink.opensearch;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.nullValue;
+
+class ScriptManagerMinifyTest {
+
+    @Test
+    void minifyScript_removes_comment_lines() {
+        final String source = "// This is a comment\nctx._source.field = params.value;\n// Another comment\nctx.op = 'none';";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("ctx._source.field = params.value;\nctx.op = 'none';"));
+    }
+
+    @Test
+    void minifyScript_removes_blank_lines() {
+        final String source = "ctx._source.a = 1;\n\n\nctx._source.b = 2;";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("ctx._source.a = 1;\nctx._source.b = 2;"));
+    }
+
+    @Test
+    void minifyScript_trims_leading_whitespace() {
+        final String source = "  ctx._source.a = 1;\n    ctx._source.b = 2;";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("ctx._source.a = 1;\nctx._source.b = 2;"));
+    }
+
+    @Test
+    void minifyScript_handles_mixed_comments_blanks_and_code() {
+        final String source = "// Header comment\n\nString table = params.table;\n// Inline explanation\nlong version = Long.parseLong(params.version);\n\n// Footer\n";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("String table = params.table;\nlong version = Long.parseLong(params.version);"));
+    }
+
+    @Test
+    void minifyScript_returns_null_for_null_input() {
+        assertThat(ScriptManager.minifyScript(null), nullValue());
+    }
+
+    @Test
+    void minifyScript_preserves_inline_comments_after_code() {
+        final String source = "ctx._source.a = 1; // keep this line";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("ctx._source.a = 1; // keep this line"));
+    }
+
+    @Test
+    void minifyScript_single_line_no_comments() {
+        final String source = "ctx._source.counter += 1;";
+        final String result = ScriptManager.minifyScript(source);
+        assertThat(result, equalTo("ctx._source.counter += 1;"));
+    }
+}