ESQL: Log queries at debug level (#108257)

Previously we were logging all ESQL queries. That's a lot! Plus maybe
there's PII in there or something. Let's not do that unless you ask for
it. This changes the query logging to the `debug` log level you can
still get at these if you want them, but you don't have them by default.
you have to turn it on.

docs/changelog/108257.yaml

@@ -0,0 +1,5 @@
+pr: 108257
+summary: "ESQL: Log queries at debug level"
+area: ES|QL
+type: enhancement
+issues: []

x-pack/plugin/esql/qa/server/single-node/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/single_node/RestEsqlIT.java

@@ -14,15 +14,18 @@ import org.elasticsearch.Build;
 import org.elasticsearch.client.Request;
 import org.elasticsearch.client.Response;
 import org.elasticsearch.client.ResponseException;
+import org.elasticsearch.common.io.Streams;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.test.TestClustersThreadFilter;
 import org.elasticsearch.test.cluster.ElasticsearchCluster;
+import org.elasticsearch.test.cluster.LogType;
 import org.elasticsearch.xpack.esql.qa.rest.RestEsqlTestCase;
 import org.hamcrest.Matchers;
 import org.junit.Assert;
 import org.junit.ClassRule;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
@@ -31,6 +34,7 @@ import java.util.Map;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.not;
 import static org.hamcrest.core.Is.is;
 
 @ThreadLeakFilters(filters = TestClustersThreadFilter.class)
@@ -105,6 +109,58 @@ public class RestEsqlIT extends RestEsqlTestCase {
         assertThat(EntityUtils.toString(re.getResponse().getEntity()), containsString("[pragma] only allowed in snapshot builds"));
     }
 
+    public void testDoNotLogWithInfo() throws IOException {
+        try {
+            setLoggingLevel("INFO");
+            RequestObjectBuilder builder = requestObjectBuilder().query("ROW DO_NOT_LOG_ME = 1");
+            Map<String, Object> result = runEsql(builder);
+            assertEquals(2, result.size());
+            Map<String, String> colA = Map.of("name", "DO_NOT_LOG_ME", "type", "integer");
+            assertEquals(List.of(colA), result.get("columns"));
+            assertEquals(List.of(List.of(1)), result.get("values"));
+            try (InputStream log = cluster.getNodeLog(0, LogType.SERVER)) {
+                Streams.readAllLines(log, line -> { assertThat(line, not(containsString("DO_NOT_LOG_ME"))); });
+            }
+        } finally {
+            setLoggingLevel(null);
+        }
+    }
+
+    public void testDoLogWithDebug() throws IOException {
+        try {
+            setLoggingLevel("DEBUG");
+            RequestObjectBuilder builder = requestObjectBuilder().query("ROW DO_LOG_ME = 1");
+            Map<String, Object> result = runEsql(builder);
+            assertEquals(2, result.size());
+            Map<String, String> colA = Map.of("name", "DO_LOG_ME", "type", "integer");
+            assertEquals(List.of(colA), result.get("columns"));
+            assertEquals(List.of(List.of(1)), result.get("values"));
+            try (InputStream log = cluster.getNodeLog(0, LogType.SERVER)) {
+                boolean[] found = new boolean[] { false };
+                Streams.readAllLines(log, line -> {
+                    if (line.contains("DO_LOG_ME")) {
+                        found[0] = true;
+                    }
+                });
+                assertThat(found[0], equalTo(true));
+            }
+        } finally {
+            setLoggingLevel(null);
+        }
+    }
+
+    private void setLoggingLevel(String level) throws IOException {
+        Request request = new Request("PUT", "/_cluster/settings");
+        request.setJsonEntity("""
+            {
+                "persistent": {
+                    "logger.org.elasticsearch.xpack.esql.action": $LEVEL$
+                }
+            }
+            """.replace("$LEVEL$", level == null ? "null" : '"' + level + '"'));
+        client().performRequest(request);
+    }
+
     public void testIncompatibleMappingsErrors() throws IOException {
         // create first index
         Request request = new Request("PUT", "/index1");

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlResponseListener.java

@@ -154,13 +154,20 @@ public final class EsqlResponseListener extends RestRefCountedChunkedToXContentL
     }
 
     /**
-     * Log the execution time and query when handling an ES|QL response.
+     * Log internal server errors all the time and log queries if debug is enabled.
      */
     public ActionListener<EsqlQueryResponse> wrapWithLogging() {
+        ActionListener<EsqlQueryResponse> listener = ActionListener.wrap(this::onResponse, ex -> {
+            logOnFailure(LOGGER, ex);
+            onFailure(ex);
+        });
+        if (LOGGER.isDebugEnabled() == false) {
+            return listener;
+        }
         return ActionListener.wrap(r -> {
-            onResponse(r);
+            listener.onResponse(r);
             // At this point, the StopWatch should already have been stopped, so we log a consistent time.
-            LOGGER.info(
+            LOGGER.debug(
                 "Finished execution of ESQL query.\nQuery string: [{}]\nExecution time: [{}]ms",
                 esqlQuery,
                 stopWatch.stop().getMillis()
@@ -168,9 +175,8 @@ public final class EsqlResponseListener extends RestRefCountedChunkedToXContentL
         }, ex -> {
             // In case of failure, stop the time manually before sending out the response.
             long timeMillis = stopWatch.stop().getMillis();
-            LOGGER.info("Failed execution of ESQL query.\nQuery string: [{}]\nExecution time: [{}]ms", esqlQuery, timeMillis);
-            logOnFailure(LOGGER, ex);
-            onFailure(ex);
+            LOGGER.debug("Failed execution of ESQL query.\nQuery string: [{}]\nExecution time: [{}]ms", esqlQuery, timeMillis);
+            listener.onFailure(ex);
         });
     }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/RestEsqlAsyncQueryAction.java

@@ -47,7 +47,7 @@ public class RestEsqlAsyncQueryAction extends BaseRestHandler {
         }
 
         RestEsqlQueryAction.defaultVersionForOldClients(esqlRequest, request);
-        LOGGER.info("Beginning execution of ESQL async query.\nQuery string: [{}]", esqlRequest.query());
+        LOGGER.debug("Beginning execution of ESQL async query.\nQuery string: [{}]", esqlRequest.query());
 
         return channel -> {
             RestCancellableNodeClient cancellableClient = new RestCancellableNodeClient(client, request.getHttpChannel());

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/RestEsqlQueryAction.java

@@ -47,7 +47,7 @@ public class RestEsqlQueryAction extends BaseRestHandler {
         }
 
         defaultVersionForOldClients(esqlRequest, request);
-        LOGGER.info("Beginning execution of ESQL query.\nQuery string: [{}]", esqlRequest.query());
+        LOGGER.debug("Beginning execution of ESQL query.\nQuery string: [{}]", esqlRequest.query());
 
         return channel -> {
             RestCancellableNodeClient cancellableClient = new RestCancellableNodeClient(client, request.getHttpChannel());