A CodeChain node keeps emitting "sendError"

This phenomenon was found on 2019.12.17 at about 2 P.M.
The monitor sends a codechain death confirmation because the node monitor that was watching had been dead. The log is like the following:
```
#364967762 2019-12-17 05:37:18.685152917 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:19.224282592 UTC P2P Worker #1 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:19.355859641 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:19.553804053 UTC P2P Worker #1 WARN netapi block-propagation cannot message Global 35.230.2.230:3485: "SendError(..)"
#364967762 2019-12-17 05:37:19.590484103 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:19.638622014 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 35.233.0.162:3485: "SendError(..)"
#364967762 2019-12-17 05:37:19.642450809 UTC P2P Worker #0 WARN netapi block-propagation cannot message Global 34.85.92.6:3485: "SendError(..)"
#364967762 2019-12-17 05:37:19.685322323 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:20.593226243 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:20.685409734 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:21.548407383 UTC P2P Worker #3 WARN netapi block-propagation cannot message Global 35.230.2.230:3485: "SendError(..)"
#364967762 2019-12-17 05:37:21.595849899 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:21.614647820 UTC P2P Worker #0 WARN netapi block-propagation cannot message Global 35.233.0.162:3485: "SendError(..)"
#364967762 2019-12-17 05:37:21.641915189 UTC P2P Worker #3 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:21.685501929 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:22.059731325 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 34.85.92.6:3485: "SendError(..)"
#364967762 2019-12-17 05:37:22.357984173 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:22.598637390 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:22.685612250 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:23.086173404 UTC P2P Worker #1 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:23.211959453 UTC P2P Worker #3 WARN netapi block-propagation cannot message Global 35.230.2.230:3485: "SendError(..)"
#364967762 2019-12-17 05:37:23.420002722 UTC P2P Worker #1 WARN netapi block-propagation cannot message Global 34.85.92.6:3485: "SendError(..)"
#364967762 2019-12-17 05:37:23.601295048 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:23.641766807 UTC P2P Worker #3 WARN netapi block-propagation cannot message Global 35.233.0.162:3485: "SendError(..)"
#364967762 2019-12-17 05:37:23.685702369 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:24.604211465 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:24.685837824 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:25.183168256 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 35.230.2.230:3485: "SendError(..)"
#364967762 2019-12-17 05:37:25.344193384 UTC P2P Worker #1 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:25.359482897 UTC P2P Worker #0 WARN netapi block-propagation cannot message Global 35.233.0.162:3485: "SendError(..)"
#364967762 2019-12-17 05:37:25.361471308 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:25.391840906 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 34.85.92.6:3485: "SendError(..)"
#364967762 2019-12-17 05:37:25.606731117 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:25.685960279 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:26.609702715 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:26.686112553 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:26.860126470 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 34.85.92.6:3485: "SendError(..)"
#364967762 2019-12-17 05:37:26.861161222 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:26.929697545 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 35.230.2.230:3485: "SendError(..)"
#364967762 2019-12-17 05:37:26.937245993 UTC P2P Worker #2 WARN netapi block-propagation cannot message Global 35.233.0.162:3485: "SendError(..)"
#364967762 2019-12-17 05:37:27.612464839 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:27.686310331 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
#364967762 2019-12-17 05:37:28.364441429 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:28.615200476 UTC http.worker0 INFO rpc RPC call(chain_getBestBlockNumber([]))
#364967762 2019-12-17 05:37:28.658031061 UTC P2P Worker #0 WARN netapi block-propagation cannot message Global 34.85.31.119:3485: "SendError(..)"
#364967762 2019-12-17 05:37:28.686393587 UTC timer.worker.1 WARN netapi block-propagation cannot timeout 0: "SendError(..)"
```

Issue cung cấp các log runtime cho thấy các thông báo SendError lặp lại trong quá trình truyền khối, nhưng không nêu tên tệp nguồn, bài kiểm thử hoặc điểm vào nào. Hãy bắt đầu bằng cách xác định cảnh báo truyền khối và truy vết thông báo thất bại cùng việc xử lý timeout; hoàn tất phải có nghĩa là đã xác định được nguyên nhân và các lỗi lặp lại đã được giải quyết hoặc xử lý phù hợp.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.