[7.17] Remove translog from bwc testRecovery (#101068) (#101104)

* Remove translog from bwc testRecovery (#101068)

When the test was trying to test recovering translog ops,
since we flush on close/shutdown, it failed because it never
recovered any translog ops.

The code for translog recovery is irrelevant due to that and
this PR proposes to remove it.

Alternatively, we could simulate killing nodes forcibly before
upgrading, but (a) that seems out of the ordinary for upgrades,
and (b) in trying that, it did not consistently pass the test
because sometimes the flush on close still happened.

Fixes #52031

* Fix

qa/full-cluster-restart/src/javaRestTest/java/org/elasticsearch/upgrades/FullClusterRestartIT.java

@@ -742,20 +742,12 @@ public void testEmptyShard() throws IOException {
     }
 
     /**
-     * Tests recovery of an index with or without a translog and the
-     * statistics we gather about that.
+     * Tests recovery of an index.
      */
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/52031")
     public void testRecovery() throws Exception {
         int count;
-        boolean shouldHaveTranslog;
         if (isRunningAgainstOldCluster()) {
             count = between(200, 300);
-            /* We've had bugs in the past where we couldn't restore
-             * an index without a translog so we randomize whether
-             * or not we have one. */
-            shouldHaveTranslog = randomBoolean();
-
             indexRandomDocuments(count, true, true, i -> jsonBuilder().startObject().field("field", "value").endObject());
 
             // make sure all recoveries are done
@@ -770,19 +762,8 @@ public void testRecovery() throws Exception {
             if (randomBoolean()) {
                 performSyncedFlush(index, randomBoolean());
             }
-            if (shouldHaveTranslog) {
-                // Update a few documents so we are sure to have a translog
-                indexRandomDocuments(
-                    count / 10,
-                    false, // flushing here would invalidate the whole thing
-                    false,
-                    i -> jsonBuilder().startObject().field("field", "value").endObject()
-                );
-            }
-            saveInfoDocument("should_have_translog", Boolean.toString(shouldHaveTranslog));
         } else {
             count = countOfIndexedRandomDocuments();
-            shouldHaveTranslog = Booleans.parseBoolean(loadInfoDocument("should_have_translog"));
         }
 
         // Count the documents in the index to make sure we have as many as we put there
@@ -793,63 +774,13 @@ public void testRecovery() throws Exception {
         assertTotalHits(count, countResponse);
 
         if (false == isRunningAgainstOldCluster()) {
-            boolean restoredFromTranslog = false;
             boolean foundPrimary = false;
             Request recoveryRequest = new Request("GET", "/_cat/recovery/" + index);
             recoveryRequest.addParameter("h", "index,shard,type,stage,translog_ops_recovered");
             recoveryRequest.addParameter("s", "index,shard,type");
             String recoveryResponse = toStr(client().performRequest(recoveryRequest));
-            for (String line : recoveryResponse.split("\n")) {
-                // Find the primaries
-                foundPrimary = true;
-                if (false == line.contains("done") && line.contains("existing_store")) {
-                    continue;
-                }
-                /* Mark if we see a primary that looked like it restored from the translog.
-                 * Not all primaries will look like this all the time because we modify
-                 * random documents when we want there to be a translog and they might
-                 * not be spread around all the shards. */
-                Matcher m = Pattern.compile("(\\d+)$").matcher(line);
-                assertTrue(line, m.find());
-                int translogOps = Integer.parseInt(m.group(1));
-                if (translogOps > 0) {
-                    restoredFromTranslog = true;
-                }
-            }
+            foundPrimary = recoveryResponse.split("\n").length > 0;
             assertTrue("expected to find a primary but didn't\n" + recoveryResponse, foundPrimary);
-            assertEquals("mismatch while checking for translog recovery\n" + recoveryResponse, shouldHaveTranslog, restoredFromTranslog);
-
-            String currentLuceneVersion = Version.CURRENT.luceneVersion.toString();
-            String bwcLuceneVersion = getOldClusterVersion().luceneVersion.toString();
-            if (shouldHaveTranslog && false == currentLuceneVersion.equals(bwcLuceneVersion)) {
-                int numCurrentVersion = 0;
-                int numBwcVersion = 0;
-                Request segmentsRequest = new Request("GET", "/_cat/segments/" + index);
-                segmentsRequest.addParameter("h", "prirep,shard,index,version");
-                segmentsRequest.addParameter("s", "prirep,shard,index");
-                String segmentsResponse = toStr(client().performRequest(segmentsRequest));
-                for (String line : segmentsResponse.split("\n")) {
-                    if (false == line.startsWith("p")) {
-                        continue;
-                    }
-                    Matcher m = Pattern.compile("(\\d+\\.\\d+\\.\\d+)$").matcher(line);
-                    assertTrue(line, m.find());
-                    String version = m.group(1);
-                    if (currentLuceneVersion.equals(version)) {
-                        numCurrentVersion++;
-                    } else if (bwcLuceneVersion.equals(version)) {
-                        numBwcVersion++;
-                    } else {
-                        fail("expected version to be one of [" + currentLuceneVersion + "," + bwcLuceneVersion + "] but was " + line);
-                    }
-                }
-                assertNotEquals(
-                    "expected at least 1 current segment after translog recovery. segments:\n" + segmentsResponse,
-                    0,
-                    numCurrentVersion
-                );
-                assertNotEquals("expected at least 1 old segment. segments:\n" + segmentsResponse, 0, numBwcVersion);
-            }
         }
     }