I have a requirement to log to an excel sheet in the server, the same way a normal log4j appender would except to an excel sheet (This is in java).
I currently have found no proper information about this. Is there any library that provides an appender or such which can be used? Also was wondering are there any implications of appending to an excel file instead of a normal text file log, performance, probable errors and such?
Directly logging to an excel sheet does not seems to be good idea. You are mixing two responsibilities "logging" and "analyzing the logs" into one code.
You may want to import data to a spreadsheet for specific analysis. In that case you may want specific formatting (about which data goes to what table )as well. Consider writing a specific parser and then importing data to an excel sheet- Using api like apache-poi this will be straight forward.
If you really want a special logging, start with Log to a database using log4j which explains about database logging and then make excel out out it.
Logging is unlimited as long as file system allows. Excel --depending on its version -- has limit on number of records that can be stored. (other problems in bemace's comments).