From 0cf99d39c5fe547bda186112f9d7e2924305d45c Mon Sep 17 00:00:00 2001 From: Jon Bratseth Date: Sat, 15 Jun 2019 19:22:02 +0200 Subject: Add a comment warning about serialization format changes --- .../vespa/hosted/provision/persistence/LoadBalancerSerializer.java | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'node-repository') diff --git a/node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/LoadBalancerSerializer.java b/node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/LoadBalancerSerializer.java index a4b915a6128..fd2294c1b5d 100644 --- a/node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/LoadBalancerSerializer.java +++ b/node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/LoadBalancerSerializer.java @@ -27,6 +27,13 @@ import java.util.function.Function; */ public class LoadBalancerSerializer { + // 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 idField = "id"; private static final String hostnameField = "hostname"; private static final String dnsZoneField = "dnsZone"; -- cgit v1.2.3