feat(ecstore): implement decommission and rebalance (#2281)

Co-authored-by: weisd <im@weisd.in>
Co-authored-by: houseme <housemecn@gmail.com>

crates/ecstore/src/tier/tier.rs

@@ -49,7 +49,7 @@ use crate::{
     StorageAPI,
     config::com::{CONFIG_PREFIX, read_config},
     disk::{MIGRATING_META_BUCKET, RUSTFS_META_BUCKET},
-    global::{get_global_endpoints, is_first_cluster_node_local},
+    global::is_first_cluster_node_local,
     store::ECStore,
     store_api::{ObjectIO as _, ObjectOptions, PutObjReader},
 };
@@ -1006,7 +1006,7 @@ impl TierConfigMgr {
     #[tracing::instrument(level = "debug", name = "tier_save", skip(self))]
     pub async fn save(&self) -> std::result::Result<(), std::io::Error> {
         let Some(api) = new_object_layer_fn() else {
-            return Err(std::io::Error::other("errServerNotInitialized"));
+            return Err(tier_config_not_initialized_error("save tiering config"));
         };
         //let (pr, opts) = GLOBAL_TierConfigMgr.write().config_reader()?;
 
@@ -1231,6 +1231,10 @@ pub fn is_err_config_not_found(err: &StorageError) -> bool {
     matches!(err, StorageError::ObjectNotFound(_, _) | StorageError::BucketNotFound(_)) || err == &StorageError::ConfigNotFound
 }
 
+fn tier_config_not_initialized_error(operation: &str) -> std::io::Error {
+    std::io::Error::other(format!("failed to {operation}: object layer not initialized"))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -1335,4 +1339,13 @@ mod tests {
             Some("bucket-a")
         );
     }
+
+    #[test]
+    fn test_tier_config_not_initialized_error_formats_operation_context() {
+        let err = tier_config_not_initialized_error("save tiering config");
+        let rendered = err.to_string();
+
+        assert!(rendered.contains("failed to save tiering config"), "{rendered}");
+        assert!(rendered.contains("object layer not initialized"), "{rendered}");
+    }
 }