ESQL: Log partial failures

docs/changelog/129164.yaml

@@ -0,0 +1,5 @@
+pr: 129164
+summary: Log partial failures
+area: ES|QL
+type: feature
+issues: []

server/src/main/java/org/elasticsearch/rest/RestResponse.java

@@ -9,9 +9,9 @@
 
 package org.elasticsearch.rest;
 
+import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.apache.logging.log4j.util.Supplier;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.common.bytes.BytesArray;
@@ -126,18 +126,8 @@ public RestResponse(RestChannel channel, RestStatus status, Exception e) throws
         this.status = status;
         ToXContent.Params params = channel.request();
         if (e != null) {
-            Supplier<?> messageSupplier = () -> String.format(
-                Locale.ROOT,
-                "path: %s, params: %s, status: %d",
-                channel.request().rawPath(),
-                channel.request().params(),
-                status.getStatus()
-            );
-            if (status.getStatus() < 500 || ExceptionsHelper.isNodeOrShardUnavailableTypeException(e)) {
-                SUPPRESSED_ERROR_LOGGER.debug(messageSupplier, e);
-            } else {
-                SUPPRESSED_ERROR_LOGGER.warn(messageSupplier, e);
-            }
+            Level level = status.getStatus() < 500 || ExceptionsHelper.isNodeOrShardUnavailableTypeException(e) ? Level.DEBUG : Level.WARN;
+            logSuppressedError(level, channel.request().rawPath(), channel.request().params(), status, e);
         }
         // if "error_trace" is turned on in the request, we want to render it in the rest response
         // for that the REST_EXCEPTION_SKIP_STACK_TRACE flag that if "true" omits the stack traces is
@@ -254,4 +244,17 @@ public Map<String, List<String>> filterHeaders(Map<String, List<String>> headers
     public void close() {
         Releasables.closeExpectNoException(releasable);
     }
+
+    /**
+     * Log failures to the {@code rest.suppressed} logger.
+     */
+    public static void logSuppressedError(Level level, String rawPath, Map<String, String> params, RestStatus status, Exception e) {
+        if (SUPPRESSED_ERROR_LOGGER.isEnabled(level)) {
+            SUPPRESSED_ERROR_LOGGER.log(
+                level,
+                String.format(Locale.ROOT, "path: %s, params: %s, status: %d", rawPath, params, status.getStatus()),
+                e
+            );
+        }
+    }
 }

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

@@ -9,6 +9,7 @@
 
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.search.ShardSearchFailure;
 import org.elasticsearch.core.Releasable;
 import org.elasticsearch.core.Releasables;
 import org.elasticsearch.core.TimeValue;
@@ -30,6 +31,7 @@
 
 import java.io.IOException;
 import java.util.Locale;
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
 
@@ -121,6 +123,7 @@ private EsqlResponseListener(RestChannel channel, RestRequest restRequest, Strin
 
     @Override
     protected void processResponse(EsqlQueryResponse esqlQueryResponse) throws IOException {
+        logPartialFailures(channel.request().rawPath(), channel.request().params(), esqlQueryResponse.getExecutionInfo());
         channel.sendResponse(buildResponse(esqlQueryResponse));
     }
 
@@ -229,4 +232,16 @@ private void checkDelimiter() {
             throw new IllegalArgumentException(message);
         }
     }
+
+    /**
+     * Log all partial request failures to the {@code rest.suppressed} logger
+     * so an operator can categorize them after the fact.
+     */
+    static void logPartialFailures(String rawPath, Map<String, String> params, EsqlExecutionInfo exeuctionInfo) {
+        for (EsqlExecutionInfo.Cluster cluster : exeuctionInfo.getClusters().values()) {
+            for (ShardSearchFailure failure : cluster.getFailures()) {
+                RestResponse.logSuppressedError(org.apache.logging.log4j.Level.WARN, rawPath, params, RestStatus.OK, failure);
+            }
+        }
+    }
 }

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/action/EsqlResponseListenerTests.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql.action;
+
+import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.appender.AbstractAppender;
+import org.apache.logging.log4j.core.config.Configurator;
+import org.apache.logging.log4j.core.filter.RegexFilter;
+import org.elasticsearch.action.search.ShardSearchFailure;
+import org.elasticsearch.common.logging.Loggers;
+import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.shard.ShardId;
+import org.elasticsearch.search.SearchShardTarget;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.transport.RemoteClusterAware;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class EsqlResponseListenerTests extends ESTestCase {
+    private final String LOCAL_CLUSTER_ALIAS = RemoteClusterAware.LOCAL_CLUSTER_GROUP_KEY;
+
+    private static MockAppender appender;
+    static Logger restSuppressedLogger = LogManager.getLogger("rest.suppressed");
+
+    @BeforeClass
+    public static void init() throws IllegalAccessException {
+        appender = new MockAppender("testAppender");
+        appender.start();
+        Configurator.setLevel(restSuppressedLogger, Level.DEBUG);
+        Loggers.addAppender(restSuppressedLogger, appender);
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        appender.stop();
+        Loggers.removeAppender(restSuppressedLogger, appender);
+    }
+
+    public void testLogPartialResponseErrors() {
+        EsqlExecutionInfo executionInfo = new EsqlExecutionInfo(false);
+        executionInfo.swapCluster(
+            LOCAL_CLUSTER_ALIAS,
+            (k, v) -> new EsqlExecutionInfo.Cluster(
+                LOCAL_CLUSTER_ALIAS,
+                "idx",
+                false,
+                EsqlExecutionInfo.Cluster.Status.SUCCESSFUL,
+                10,
+                10,
+                3,
+                0,
+                List.of(
+                    new ShardSearchFailure(new Exception("dummy"), target(0)),
+                    new ShardSearchFailure(new Exception("error"), target(1))
+                ),
+                new TimeValue(4444L)
+            )
+        );
+        EsqlResponseListener.logPartialFailures("/_query", Map.of(), executionInfo);
+
+        LogEvent logEvent = appender.events.get(0);
+        assertThat(logEvent.getLevel(), equalTo(Level.WARN));
+        assertThat(logEvent.getMessage().getFormattedMessage(), equalTo("path: /_query, params: {}, status: 200"));
+        assertThat(logEvent.getThrown().getCause().getMessage(), equalTo("dummy"));
+        logEvent = appender.events.get(1);
+        assertThat(logEvent.getLevel(), equalTo(Level.WARN));
+        assertThat(logEvent.getMessage().getFormattedMessage(), equalTo("path: /_query, params: {}, status: 200"));
+        assertThat(logEvent.getThrown().getCause().getMessage(), equalTo("error"));
+    }
+
+    private SearchShardTarget target(int shardId) {
+        return new SearchShardTarget("node", new ShardId("idx", "uuid", 0), LOCAL_CLUSTER_ALIAS);
+    }
+
+    private static class MockAppender extends AbstractAppender {
+        public final List<LogEvent> events = new ArrayList<>();
+
+        MockAppender(final String name) throws IllegalAccessException {
+            super(name, RegexFilter.createFilter(".*(\n.*)*", new String[0], false, null, null), null, false);
+        }
+
+        @Override
+        public void append(LogEvent event) {
+            events.add(event.toImmutable());
+        }
+    }
+}