Currently, there are flooding logs in AppVeyor (in the console). This has been fine because we can download all the logs. However, (given my observations so far), logs are truncated when there are too many.
For example, see https://ci.appveyor.com/project/ApacheSoftwareFoundation/spark/build/1209-master
Even after the log is downloaded, it looks truncated as below:
[00:44:21] 17/05/04 18:56:18 INFO TaskSetManager: Finished task 197.0 in stage 601.0 (TID 9211) in 0 ms on localhost (executor driver) (194/200)
[00:44:21] 17/05/04 18:56:18 INFO Executor: Running task 199.0 in stage 601.0 (TID 9213)
[00:44:21] 17/05/04 18:56:18 INFO Executor: Finished task 198.0 in stage 601.0 (TID 9212). 2473 bytes result sent to driver
Probably, it looks better to use the same log4j configuration that we are using for Jenkins.