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fix: ensure atomicity in create_lock_revision #16907

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merged 3 commits into from
Nov 22, 2024
Merged

fix: ensure atomicity in create_lock_revision #16907

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f1316c2
fix: double lock ownership due to concurrent race
zhyass Nov 21, 2024
ab87b25
fix review commend
zhyass Nov 22, 2024
641d3ba
fmt
zhyass Nov 22, 2024
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56 changes: 38 additions & 18 deletions src/meta/api/src/schema_api_impl.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@ use databend_common_meta_app::app_error::UnknownTableId;
use databend_common_meta_app::app_error::ViewAlreadyExists;
use databend_common_meta_app::data_mask::MaskPolicyTableIdListIdent;
use databend_common_meta_app::id_generator::IdGenerator;
use databend_common_meta_app::id_generator::IdGeneratorValue;
use databend_common_meta_app::schema::catalog_id_ident::CatalogId;
use databend_common_meta_app::schema::catalog_name_ident::CatalogNameIdentRaw;
use databend_common_meta_app::schema::database_name_ident::DatabaseNameIdent;
Expand Down Expand Up @@ -2738,30 +2739,49 @@ impl<KV: kvapi::KVApi<Error = MetaError> + ?Sized> SchemaApi for KV {
&self,
req: CreateLockRevReq,
) -> Result<CreateLockRevReply, KVAppError> {
debug!(req :? =(&req); "SchemaApi: {}", func_name!());
let ctx = func_name!();
debug!(req :? =(&req); "SchemaApi: {}", ctx);

let lock_key = &req.lock_key;
let id_generator = IdGenerator::table_lock_id();

let revision = fetch_id(self, IdGenerator::table_lock_id()).await?;
let key = lock_key.gen_key(revision);
let mut trials = txn_backoff(None, ctx);
loop {
trials.next().unwrap()?.await;

let lock_meta = LockMeta {
user: req.user.clone(),
node: req.node.clone(),
query_id: req.query_id.clone(),
created_on: Utc::now(),
acquired_on: None,
lock_type: lock_key.lock_type(),
extra_info: lock_key.get_extra_info(),
};
let current_rev = self.get_seq(&id_generator).await?;
let revision = current_rev + 1;
let key = lock_key.gen_key(revision);
let lock_meta = LockMeta {
user: req.user.clone(),
node: req.node.clone(),
query_id: req.query_id.clone(),
created_on: Utc::now(),
acquired_on: None,
lock_type: lock_key.lock_type(),
extra_info: lock_key.get_extra_info(),
};

// Revision is unique. if it presents, consider it as success.
// Thus, we could just ignore create result
let _ = self
.crud_try_insert(&key, lock_meta, Some(req.ttl), || Ok::<(), Infallible>(()))
.await?;
let condition = vec![
txn_cond_seq(&id_generator, Eq, current_rev),
// assumes lock are absent.
txn_cond_seq(&key, Eq, 0),
];
let if_then = vec![
txn_op_put(&id_generator, b"".to_vec()),
txn_op_put_pb(&key, &lock_meta, Some(req.ttl))?,
];
let txn_req = TxnRequest {
condition,
if_then,
else_then: vec![],
};
let (succ, _responses) = send_txn(self, txn_req).await?;

Ok(CreateLockRevReply { revision })
if succ {
return Ok(CreateLockRevReply { revision });
}
}
}

#[logcall::logcall]
Expand Down
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