Add note about 20 character limit for identifier

1 files changed, 2 insertions, 0 deletions

diff --git a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/identifiers/Identifier.java b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/identifiers/Identifier.java
index cccb41c27ef..8b24536c730 100644
--- a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/identifiers/Identifier.java
+++ b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/identifiers/Identifier.java
@@ -12,6 +12,8 @@ import java.util.regex.Pattern;
  */
 public abstract class Identifier {
 
+    // Note: The limit of 20 characters is due to hostname being 'cluster--app--tenant', which can be max. 63 characters.
+    // This is an issue for level 7 routing, with level 4 routing we do not have the same limitation
     protected static final String strictPatternExplanation =
             "Tenant, application and instance names must start with a letter, may contain no more than 20 " +
             "characters, and may only contain lowercase letters, digits or dashes, but no double-dashes.";