milvus-io
/
milvus
mirror of https://github.com/milvus-io/milvus.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

[skip ci]Update docs about datanode recovery design (#11627) 

Signed-off-by: shiyu22 <shiyu.chen@zilliz.com>
pull/11637/head
shiyu22 2021-11-11 13:23:03 +08:00 committed by GitHub
parent 89c17c265b
commit 4b1d414329
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 3 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
docs/design_docs/datanode_recovery_design_0513_2021.md
View File

@ -6,16 +6,15 @@ update: 6.21.2021, by [Goose](https://github.com/XuanYang-cn)
## What's DataNode? ## What's DataNode?
DataNode processes insert data and persists them. DataNode processes insert data and persist them.
DataNode is based on flowgraph; each flowgraph cares about only one vchannel. There are ddl messages, dml DataNode is based on flowgraph; each flowgraph cares about only one vchannel. There are ddl messages, dml
messages, and timetick messages inside one vchannel, FIFO log stream. messages, and timetick messages inside one vchannel, FIFO log stream.
One vchannel only contains dml messages of one collection. A collection consists of many segments, hence One vchannel only contains dml messages of one collection. A collection consists of many segments, hence
a vchannel contains dml messages of many segments. **Most importantly, the dml messages of the same segment a vchannel contains dml messages of many segments. **Most importantly, the dml messages of the same segment can appear anywhere in vchannel.**
can appear in anywhere in vchannel.**
## What does DataNode recovery really mean? ## What is the real meaning of DataNode recovery?
DataNode is stateless, but vchannel has states. DataNode's statelessness is guaranteed by DataCoord, which DataNode is stateless, but vchannel has states. DataNode's statelessness is guaranteed by DataCoord, which
means the vchannel's state is maintained by DataCoord. So DataNode recovery is no different from starting. means the vchannel's state is maintained by DataCoord. So DataNode recovery is no different from starting.