Remove support for old translog checkpoint formats (elastic#44280)

This commit removes support for the translog checkpoint format from versions
before 6.0.0 since 7.x versions are incompatible with indices from these
versions.

Relates elastic#44720
Fixes elastic#44210

server/src/main/java/org/elasticsearch/index/translog/Checkpoint.java

@@ -51,7 +51,6 @@ final class Checkpoint {
     final long minTranslogGeneration;
     final long trimmedAboveSeqNo;
 
-    private static final int INITIAL_VERSION = 1; // start with 1, just to recognize there was some magic serialization logic before
     private static final int VERSION_6_0_0 = 2; // introduction of global checkpoints
     private static final int CURRENT_VERSION = 3; // introduction of trimmed above seq#
 
@@ -63,10 +62,10 @@ final class Checkpoint {
         + Integer.BYTES  // ops
         + Long.BYTES // offset
         + Long.BYTES // generation
-        + Long.BYTES // minimum sequence number, introduced in 6.0.0
-        + Long.BYTES // maximum sequence number, introduced in 6.0.0
-        + Long.BYTES // global checkpoint, introduced in 6.0.0
-        + Long.BYTES // minimum translog generation in the translog - introduced in 6.0.0
+        + Long.BYTES // minimum sequence number
+        + Long.BYTES // maximum sequence number
+        + Long.BYTES // global checkpoint
+        + Long.BYTES // minimum translog generation in the translog
         + Long.BYTES // maximum reachable (trimmed) sequence number, introduced in 6.4.0
         + CodecUtil.footerLength();
 
@@ -75,17 +74,10 @@ final class Checkpoint {
         + Integer.BYTES  // ops
         + Long.BYTES // offset
         + Long.BYTES // generation
-        + Long.BYTES // minimum sequence number, introduced in 6.0.0
-        + Long.BYTES // maximum sequence number, introduced in 6.0.0
-        + Long.BYTES // global checkpoint, introduced in 6.0.0
-        + Long.BYTES // minimum translog generation in the translog - introduced in 6.0.0
-        + CodecUtil.footerLength();
-
-    // size of 5.0.0 checkpoint
-    static final int V1_FILE_SIZE = CodecUtil.headerLength(CHECKPOINT_CODEC)
-        + Integer.BYTES  // ops
-        + Long.BYTES // offset
-        + Long.BYTES // generation
+        + Long.BYTES // minimum sequence number
+        + Long.BYTES // maximum sequence number
+        + Long.BYTES // global checkpoint
+        + Long.BYTES // minimum translog generation in the translog
         + CodecUtil.footerLength();
 
     /**
@@ -136,7 +128,7 @@ static Checkpoint emptyTranslogCheckpoint(final long offset, final long generati
         return new Checkpoint(offset, 0, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
     }
 
-    static Checkpoint readCheckpointV6_4_0(final DataInput in) throws IOException {
+    static Checkpoint readCheckpointV3(final DataInput in) throws IOException {
         final long offset = in.readLong();
         final int numOps = in.readInt();
         final long generation = in.readLong();
@@ -148,7 +140,7 @@ static Checkpoint readCheckpointV6_4_0(final DataInput in) throws IOException {
         return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
     }
 
-    static Checkpoint readCheckpointV6_0_0(final DataInput in) throws IOException {
+    static Checkpoint readCheckpointV2(final DataInput in) throws IOException {
         final long offset = in.readLong();
         final int numOps = in.readInt();
         final long generation = in.readLong();
@@ -160,19 +152,6 @@ static Checkpoint readCheckpointV6_0_0(final DataInput in) throws IOException {
         return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
     }
 
-    // reads a checksummed checkpoint introduced in ES 5.0.0
-    static Checkpoint readCheckpointV5_0_0(final DataInput in) throws IOException {
-        final long offset = in.readLong();
-        final int numOps = in.readInt();
-        final long generation = in.readLong();
-        final long minSeqNo = SequenceNumbers.NO_OPS_PERFORMED;
-        final long maxSeqNo = SequenceNumbers.NO_OPS_PERFORMED;
-        final long globalCheckpoint = SequenceNumbers.UNASSIGNED_SEQ_NO;
-        final long minTranslogGeneration = -1;
-        final long trimmedAboveSeqNo = SequenceNumbers.UNASSIGNED_SEQ_NO;
-        return new Checkpoint(offset, numOps, generation, minSeqNo, maxSeqNo, globalCheckpoint, minTranslogGeneration, trimmedAboveSeqNo);
-    }
-
     @Override
     public String toString() {
         return "Checkpoint{" +
@@ -192,17 +171,14 @@ public static Checkpoint read(Path path) throws IOException {
             try (IndexInput indexInput = dir.openInput(path.getFileName().toString(), IOContext.DEFAULT)) {
                 // We checksum the entire file before we even go and parse it. If it's corrupted we barf right here.
                 CodecUtil.checksumEntireFile(indexInput);
-                final int fileVersion = CodecUtil.checkHeader(indexInput, CHECKPOINT_CODEC, INITIAL_VERSION, CURRENT_VERSION);
-                if (fileVersion == INITIAL_VERSION) {
-                    assert indexInput.length() == V1_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV5_0_0(indexInput);
-                } else if (fileVersion == VERSION_6_0_0) {
+                final int fileVersion = CodecUtil.checkHeader(indexInput, CHECKPOINT_CODEC, VERSION_6_0_0, CURRENT_VERSION);
+                if (fileVersion == VERSION_6_0_0) {
                     assert indexInput.length() == V2_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV6_0_0(indexInput);
+                    return Checkpoint.readCheckpointV2(indexInput);
                 } else {
                     assert fileVersion == CURRENT_VERSION : fileVersion;
                     assert indexInput.length() == V3_FILE_SIZE : indexInput.length();
-                    return Checkpoint.readCheckpointV6_4_0(indexInput);
+                    return Checkpoint.readCheckpointV3(indexInput);
                 }
             } catch (CorruptIndexException | NoSuchFileException | IndexFormatTooOldException | IndexFormatTooNewException e) {
                 throw new TranslogCorruptedException(path.toString(), e);

server/src/test/java/org/elasticsearch/index/translog/TranslogTests.java

@@ -25,6 +25,7 @@
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.NumericDocValuesField;
 import org.apache.lucene.document.TextField;
+import org.apache.lucene.index.IndexFormatTooOldException;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.mockfile.FilterFileChannel;
 import org.apache.lucene.mockfile.FilterFileSystemProvider;
@@ -2791,6 +2792,18 @@ public void testCheckpointOnDiskFull() throws IOException {
         assertEquals(read, checkpoint);
     }
 
+    public void testLegacyCheckpointVersion() throws IOException {
+        expectThrows(
+            TranslogCorruptedException.class,
+            IndexFormatTooOldException.class,
+            () -> Checkpoint.read(getDataPath("/org/elasticsearch/index/checkpoint/v1.ckp.binary"))
+        );
+        assertThat(Checkpoint.read(getDataPath("/org/elasticsearch/index/checkpoint/v2.ckp.binary")),
+            equalTo(new Checkpoint(-1312746831014894010L, 44230819, 4168771208509507653L, 6217263213205155568L,
+                8590850694628654668L, 3768575734506660560L, 1476009383806516272L,
+                SequenceNumbers.UNASSIGNED_SEQ_NO)));
+    }
+
     /**
      * Tests that closing views after the translog is fine and we can reopen the translog
      */