diff options
Diffstat (limited to 'controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java')
| -rw-r--r-- | controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java index 3e3c0df1673..88805f54d65 100644 --- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java +++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java @@ -26,6 +26,13 @@ import java.util.TreeMap; */ public class OsVersionStatusSerializer { + // WARNING: Since there are multiple servers in a ZooKeeper cluster and they upgrade one by one + // (and rewrite all nodes on startup), changes to the serialized format must be made + // such that what is serialized on version N+1 can be read by version N: + // - ADDING FIELDS: Always ok + // - REMOVING FIELDS: Stop reading the field first. Stop writing it on a later version. + // - CHANGING THE FORMAT OF A FIELD: Don't do it bro. + private static final String versionsField = "versions"; private static final String versionField = "version"; private static final String nodesField = "nodes"; |