While diagnosing balancing performance, sometime we have to look into the config.actionlogs for the balancing round information, or config.changelog/mongod logs for the time spent on each move Chunk step. It would be nice if we can also have some metrics around these in FTDC. For example:

• On CSRS primary:
  • Balancing around currently running (something like "wt transaction transaction checkpoint currently running")
  • Number of candidate chunks found 
  • Number of chunks moved
  • Number of chunks aborted
  • Number of chunk migrations in progress.
  • These may help us to understand how long the time is spent on moving chunks, and the other steps like finding chunks to move.
• On shard primary:
  • moveChunk currently running
  • step X currently running.
  • These may help us to understand the slowest step(s) for the chunk migration.