特定状况下速度上不去的问题

现已经遇到几种情况，
1.有速度但是慢，经查询是对端数据库繁忙，但是对端数据库进行优化后，速度依旧上不去，需重新kill掉导数
2.特殊情况断了下网或者其他原因，导致速度为0后，一直卡住恢复不回来，一直卡十几个小时

The report names no files, tests, or entry points. Start by reproducing the slow and zero-speed cases and tracing the affected DataX task, then identify logs or tests that show recovery after database load or network interruption. Done means the task recovers without being killed and its behavior is covered by a reproducible verification.

Written by the indexing model from the issue text.