IGNITE-27684 Update IGNITE_HEADER for discovery protocol #12671

chesnokoff · 2026-01-28T20:44:34Z

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chesnokoff · 2026-01-29T12:50:01Z

modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java

+    public static final byte[] IGNITE_HEADER_V1 = intToBytes(0x00004747);
+
+    /** Network packet header. */
+    public static final byte[] IGNITE_HEADER_V2 = intToBytes(0x0049474E);


Do we really need any header? What it used for?

We still need a header as a simple magic prefix to quickly reject non-Ignite or wrong-endpoint connections before we try to parse any data. IGNITE_HEADER_v2 makes the new handshake path explicit and helps keep backward compatibility and clearer diagnostics for version mismatches.

chesnokoff · 2026-01-29T12:50:13Z

modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java


    /** Network packet header. */
-    public static final byte[] IGNITE_HEADER = intToBytes(0x00004747);
+    public static final byte[] IGNITE_HEADER_V1 = intToBytes(0x00004747);


chesnokoff · 2026-01-30T06:31:33Z

modules/core/src/main/java/org/apache/ignite/spi/discovery/tcp/ServerImpl.java

+                                log.debug("Remote node uses legacy discovery protocol (V1), local expects V2 " +
+                                    "(check Ignite versions / rolling upgrade compatibility) [rmtAddr=" + rmtAddr +
+                                    ", locAddr=" + sock.getLocalSocketAddress() + "]");
+


We discussed to send message to old node with legacy protocol. I tried it but new node fails with
Failed to deserialize object with given class loader: jdk.internal.loader.ClassLoaders$AppClassLoader@311d617d at org/apache/ignite/spi/discovery/tcp/ServerImpl.java:6955

It is Caused by: org.apache.ignite.spi.discovery.tcp.messages.TcpDiscoveryAbstractTraceableMessage; local class incompatible: stream classdesc serialVersionUID = 5764055654892291162, local class serialVersionUID = -2609852714099079963

It looks like deserialization is impossible because we changed structure of our messages after refactoring. So it would be challenging to support all legacy formats. As a quick solution, let's just log message about legacy protocol

Vladsz83 · 2026-02-03T07:07:16Z

modules/core/src/main/java/org/apache/ignite/internal/util/IgniteUtils.java

-    public static final byte[] IGNITE_HEADER = intToBytes(0x00004747);
+    public static final byte[] IGNITE_HEADER_V1 = intToBytes(0x00004747);
+
+    /** Network packet header. */


Let's describe in the javadoc what is this new header for.

Vladsz83 · 2026-02-03T07:11:17Z

...va/org/apache/ignite/spi/discovery/tcp/ipfinder/multicast/TcpDiscoveryMulticastIpFinder.java

-                            if (!U.bytesEqual(U.IGNITE_HEADER, 0, data, 0, U.IGNITE_HEADER.length)) {
+                            if (!U.bytesEqual(U.IGNITE_HEADER_V2, 0, data, 0, U.IGNITE_HEADER_V2.length)) {
+                                if (U.bytesEqual(U.IGNITE_HEADER_V1, 0, data, 0, U.IGNITE_HEADER_V1.length)) {
+                                    log.warning("Received message with old header.");


Suggestion: 'old header' -> 'the old header'

Vladsz83 · 2026-02-03T07:36:18Z

modules/core/src/main/java/org/apache/ignite/spi/discovery/tcp/ServerImpl.java

+                    if (!Arrays.equals(buf, U.IGNITE_HEADER_V2)) {
+                        if (Arrays.equals(buf, U.IGNITE_HEADER_V1)) {
+                            if (log.isDebugEnabled())
+                                log.debug("Remote node uses legacy discovery protocol (V1), local expects V2 " +


Suggestion: 'Remote node uses legacy discovery protocol (V1), local expects V2' -> 'Remote node uses legacy discovery protocol (V1) (before the rolling upgrade compatibility). Local node expects V2.'

Vladsz83 · 2026-02-03T07:50:11Z

.../core/src/main/java/org/apache/ignite/internal/util/nio/GridConnectionBytesVerifyFilter.java


            if (magicBuf == null)
-                magicBuf = new byte[U.IGNITE_HEADER.length];
+                magicBuf = new byte[U.IGNITE_HEADER_V1.length];


Do we need to use V2 header here?

The suggestion is to keep IGNITE_HEADER unchanged in the communication SPI and update it only in discovery. As I understand, this is not related to the discovery SPI

Vladsz83 · 2026-02-03T07:57:40Z

.../org/apache/ignite/compatibility/spi/discovery/TcpDiscoveryDifferentClusterVersionsTest.java

+    }
+
+    /**
+     * Compatibility test that ensures previous-version client fails to connect to current server


suggestion: 'Tests that connection from client of old version is properly refused.'

Vladsz83 · 2026-02-03T08:04:01Z

.../org/apache/ignite/compatibility/spi/discovery/TcpDiscoveryDifferentClusterVersionsTest.java

+
+        GridTestUtils.assertThrows(
+            log,
+            () -> startGrid("old-client", OLD_VERSION.toString(), cfg -> cfg.setClientMode(true)),


Why do we check only client node?

Initial problem was related to connection between client and server node

Probably it would be a good idea to check server node too, but there is race condition between two nodes to become an initiator. As a result, new node may try to connect to old one and we won't get anything from logs

chesnokoff force-pushed the ignite-27684 branch 4 times, most recently from a3b7907 to 8715e94 Compare January 29, 2026 09:15

chesnokoff commented Jan 29, 2026

View reviewed changes

chesnokoff commented Jan 30, 2026

View reviewed changes

Vladsz83 reviewed Feb 3, 2026

View reviewed changes

chesnokoff added 2 commits February 3, 2026 13:32

IGNITE-27684 Update IGNITE_HEADER

5d48e5f

IGNITE-27684 Renamings

a8474c8

chesnokoff force-pushed the ignite-27684 branch from fe32a7a to a8474c8 Compare February 3, 2026 10:32

chesnokoff changed the title ~~IGNITE-27684 Update IGNITE_HEADER~~ IGNITE-27684 Update IGNITE_HEADER for discovery protocol Feb 3, 2026

IGNITE-27684 Fix comments

19f4703

IGNITE-27684 Update IGNITE_HEADER for discovery protocol #12671

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IGNITE-27684 Update IGNITE_HEADER for discovery protocol #12671

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chesnokoff commented Jan 28, 2026

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chesnokoff Jan 30, 2026 •

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