ESQL: Fix limit task test (elastic#117270)

Fix a test for the task results when running the `LIMIT` operation. We
were releasing a few permits to get the query started. And when you
combine that with the page worth of permits that the test was releasing
we'd sometimes finish the entire limited query, stopping the task too
early to find a running task.

Closes elastic#107293

Author: nik9000

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EsqlActionTaskIT.java

@@ -79,6 +79,11 @@ public class EsqlActionTaskIT extends AbstractPausableIntegTestCase {
     private String REDUCE_DESCRIPTION;
     private boolean nodeLevelReduction;
 
+    /**
+     * Number of docs released by {@link #startEsql}.
+     */
+    private int prereleasedDocs;
+
     @Before
     public void setup() {
         assumeTrue("requires query pragmas", canUseQueryPragmas());
@@ -104,6 +109,7 @@ public void testTaskContents() throws Exception {
         ActionFuture<EsqlQueryResponse> response = startEsql();
         try {
             getTasksStarting();
+            logger.info("unblocking script");
             scriptPermits.release(pageSize());
             List<TaskInfo> foundTasks = getTasksRunning();
             int luceneSources = 0;
@@ -216,9 +222,15 @@ private ActionFuture<EsqlQueryResponse> startEsql() {
         return startEsql("from test | stats sum(pause_me)");
     }
 
+    /**
+     * Start an ESQL query, releasing a few docs from the {@code pause_me}
+     * script so it'll actually start but won't finish it's first page.
+     */
     private ActionFuture<EsqlQueryResponse> startEsql(String query) {
         scriptPermits.drainPermits();
-        scriptPermits.release(between(1, 5));
+        // Allow a few docs to calculate os the query gets "started"
+        prereleasedDocs = between(1, pageSize() / 2);
+        scriptPermits.release(prereleasedDocs);
         var settingsBuilder = Settings.builder()
             // Force shard partitioning because that's all the tests know how to match. It is easier to reason about too.
             .put("data_partitioning", "shard")
@@ -444,6 +456,7 @@ public void testTaskContentsForTopNQuery() throws Exception {
         ActionFuture<EsqlQueryResponse> response = startEsql("from test | sort pause_me | keep pause_me");
         try {
             getTasksStarting();
+            logger.info("unblocking script");
             scriptPermits.release(pageSize());
             getTasksRunning();
         } finally {
@@ -455,7 +468,6 @@ public void testTaskContentsForTopNQuery() throws Exception {
         }
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/107293")
     public void testTaskContentsForLimitQuery() throws Exception {
         String limit = Integer.toString(randomIntBetween(pageSize() + 1, 2 * numberOfDocs()));
         READ_DESCRIPTION = """
@@ -475,7 +487,8 @@ public void testTaskContentsForLimitQuery() throws Exception {
         ActionFuture<EsqlQueryResponse> response = startEsql("from test | keep pause_me | limit " + limit);
         try {
             getTasksStarting();
-            scriptPermits.release(pageSize());
+            logger.info("unblocking script");
+            scriptPermits.release(pageSize() - prereleasedDocs);
             getTasksRunning();
         } finally {
             scriptPermits.release(numberOfDocs());
@@ -504,6 +517,7 @@ public void testTaskContentsForGroupingStatsQuery() throws Exception {
         ActionFuture<EsqlQueryResponse> response = startEsql("from test | stats max(foo) by pause_me");
         try {
             getTasksStarting();
+            logger.info("unblocking script");
             scriptPermits.release(pageSize());
             getTasksRunning();
         } finally {