From 46edabe916a10c2cafe816b8fe01f0d5da8fffc8 Mon Sep 17 00:00:00 2001
From: discord9 <discord9@163.com>
Date: Thu, 20 Aug 2026 13:19:13 +0800
Subject: [PATCH] fix(event): preserve legacy DDL event context compatibility

Signed-off-by: discord9 <discord9@163.com>
---
 src/common/meta/src/rpc/ddl.rs        | 47 ++++++++++++++++++++++++---
 src/meta-srv/src/service/procedure.rs |  5 +++
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/src/common/meta/src/rpc/ddl.rs b/src/common/meta/src/rpc/ddl.rs
index 47bd537b9b..b1c5ca8f21 100644
--- a/src/common/meta/src/rpc/ddl.rs
+++ b/src/common/meta/src/rpc/ddl.rs
@@ -42,10 +42,10 @@ use api::v1::{
 };
 use base64::Engine as _;
 use base64::engine::general_purpose;
-use common_base::protocol::Channel;
 use common_catalog::{format_full_flow_name, format_full_table_name};
 use common_error::ext::BoxedError;
-pub use common_event_recorder::TriggerReason;
+pub use common_event_recorder::{PersistentEventContext, TriggerReason};
+use common_session::channel_protocol;
 use common_time::{DatabaseTimeToLive, Timestamp};
 use prost::Message;
 use serde::{Deserialize, Serialize};
@@ -68,6 +68,8 @@ use crate::key::table_name::{TableNameKey, TableNameManager};
 
 /// Reserved query-context extension key for the frontend peer address that submitted a DDL request.
 pub const ORIGIN_FRONTEND_ADDR_EXTENSION_KEY: &str = "__greptime_origin_frontend.addr";
+/// Reserved query-context extension key for the trigger reason supplied by a legacy frontend.
+pub const TRIGGER_REASON_EXTENSION_KEY: &str = "__greptime_event.trigger_reason";
 /// Reserved query-context extension key for the authenticated database creator.
 pub const CREATE_DATABASE_CREATOR_EXTENSION_KEY: &str = "__greptime_create_database.creator";
 /// Internal gRPC metadata key for the authenticated database creator.
@@ -1651,6 +1653,21 @@ pub struct QueryContext {
     pub sst_min_sequences: HashMap<u64, u64>,
 }
 
+/// Derives the persistent event context used by legacy DDL submitters that do
+/// not populate the newer protobuf `event_context` field.
+pub fn event_context_from_query_context(query_context: &QueryContext) -> PersistentEventContext {
+    let reason = query_context
+        .extensions
+        .get(TRIGGER_REASON_EXTENSION_KEY)
+        .map(|value| TriggerReason::from_extension(value))
+        .unwrap_or_default();
+    let mut context = PersistentEventContext::new(reason);
+    if let Some(protocol) = channel_protocol(query_context.channel) {
+        context = context.with_protocol(protocol);
+    }
+    context
+}
+
 impl QueryContext {
     /// Get the current catalog
     pub fn current_catalog(&self) -> &str {
@@ -1679,8 +1696,7 @@ impl QueryContext {
 
     /// Returns the protocol derived from the typed query channel.
     pub fn protocol(&self) -> Option<String> {
-        let channel = Channel::from(u32::from(self.channel));
-        (channel != Channel::Unknown).then(|| channel.as_ref().to_string())
+        channel_protocol(self.channel).map(str::to_string)
     }
 
     pub fn snapshot_seqs(&self) -> &HashMap<u64, u64> {
@@ -1856,6 +1872,29 @@ mod tests {
 
     use super::{AlterTableTask, CreateTableTask, *};
 
+    #[test]
+    fn test_legacy_event_context_fallback_uses_reason_and_typed_channel() {
+        let mut query_context = QueryContext::default();
+        query_context.channel = 4;
+        query_context.extensions.insert(
+            TRIGGER_REASON_EXTENSION_KEY.to_string(),
+            "auto_create".to_string(),
+        );
+        let request = api::v1::meta::DdlTaskRequest {
+            query_context: Some(query_context.clone().into()),
+            event_context: None,
+            ..Default::default()
+        };
+
+        // This is the wire shape sent by an older frontend: the new field is
+        // absent, while the legacy query context still carries both values.
+        assert!(request.event_context.is_none());
+        let query_context = QueryContext::from(request.query_context.unwrap());
+        let context = event_context_from_query_context(&query_context);
+        assert_eq!(context.reason, TriggerReason::AutoCreate);
+        assert_eq!(context.protocol.as_deref(), Some("prometheus"));
+    }
+
     #[test]
     fn test_ddl_timeout_secs() {
         assert_eq!(ddl_timeout_secs(Duration::ZERO), 0);
diff --git a/src/meta-srv/src/service/procedure.rs b/src/meta-srv/src/service/procedure.rs
index df27e2cb32..759a546c53 100644
--- a/src/meta-srv/src/service/procedure.rs
+++ b/src/meta-srv/src/service/procedure.rs
@@ -30,6 +30,7 @@ use common_meta::procedure_executor::ExecutorContext;
 use common_meta::rpc::ddl::{
     CREATE_DATABASE_CREATOR_EXTENSION_KEY, CREATE_DATABASE_CREATOR_METADATA_KEY,
     CreatorGrantIntent, DdlTask, QueryContext, SubmitDdlTaskRequest,
+    event_context_from_query_context,
 };
 use common_meta::rpc::procedure::{
     self, GcRegionsRequest as MetaGcRegionsRequest, GcResponse,
@@ -131,6 +132,10 @@ impl procedure_service_server::ProcedureService for Metasrv {
                 param: "query_context",
             })?
             .into();
+        // Older frontends omit `event_context` and carry its reason in the
+        // query-context extensions. Preserve that context at the DDL boundary.
+        let event_context =
+            event_context.or_else(|| Some(event_context_from_query_context(&query_context)));
         let mut task: DdlTask = task
             .context(error::MissingRequiredParameterSnafu { param: "task" })?
             .try_into()