* Fix multi client search crash in tracing module fix #1789 fix #1832
Signed-off-by: Nwxyu <xy.wang@zilliz.com>

* add lock for every context_map_ access
Signed-off-by: Nwxyu <xy.wang@zilliz.com>

* remove never used variable
Signed-off-by: Nwxyu <xy.wang@zilliz.com>