Process management

[v0y4g3r]

What problem does the new feature solve?

GreptimeDB lacks process management and users cannot know what's currently happening inside GreptimeDB.

What does the feature do?

This issue proposes a process manager mechanism in GreptimeDB that:

• tracks running queries on GreptimeDB, by implementing an information_schema.process_list system table that records all running processes.
  • Implement process manager feat: implement process manager and information_schema.process_list  #5865
  • Track query in process manager
• allows user to manually kill long-running queries using kill <process_id> statement.
  • support KILL statement Support kill statement #5899
  • Handle ctrl+c signal in MySQL client feat: handle Ctrl-C command in MySQL client #6320
  • Handle ctrl+c signal in PostgreSQL client feat: implement cancel request on postgres protocol #6338

[evenyag]

related issue: #5072

[v0y4g3r]

We can implement the process tracking container using KvBackend. The design of keys is crucial. I'd propose using frontend ip/id + a sequence number. In that case, each frontend can register queries and get an id, and once the query finishes, frontend can deregister the query using that id returned. Once frontend instances shutdown, we can safely remove all query keys start with this frontend ip address.

pub struct ProcessKey {
    pub frontend_ip: String,
    pub id: u64,
}

pub struct ProcessValue {
    pub database: String,
    pub query: String,
    pub start_timestamp_ms: i64,
}

And when implementing kill statement, we can find the frontend which is running that query using the frontend_ip part in the key.

[killme2008]

@v0y4g3r In MySQL, the tables for processes is processlist: https://dev.mysql.com/doc/refman/8.4/en/information-schema-processlist-table.html

[v0y4g3r]

@v0y4g3r In MySQL, the tables for processes is processlist: https://dev.mysql.com/doc/refman/8.4/en/information-schema-processlist-table.html

I deliberately chose a different name for that because we have a very different schema for that table.