Use Single Log File in E2E

[nisdas]

What type of PR is this?

Cleanup

What does this PR do? Why is it needed?

• Simplifies our component startup to only write stderr to a file. This prevents us from having stdout logs in our artifacts which do not provide any new information.
• Remove debug flag on bootnode component to prevent unnecessary noisy logs from being saved to our E2E artifacts.

Which issues(s) does this PR fix?

N.A

Other notes for review

[prestonvanloon]

Can you elaborate a bit more on the purpose of this PR? Were the stdout logs empty or just not useful?

[prestonvanloon]

What about piping stdout and stderr to the same log file? The validator does have some logging to stdout because it is not using the proper logger when importing keystores (the progress bar goes to stdout)

[kasey]

What about piping stdout and stderr to the same log file? The validator does have some logging to stdout because it is not using the proper logger when importing keystores (the progress bar goes to stdout)

If you do this, depending on the size of log lines and exactly how writes are buffered (line-wise vs flush-when-full), you may wind up getting some interleaved log lines, like... .0001% of the time. Odds of that happening could be orders of magnitude higher in programs that write to stdout a lot. But ours don't, so it would be very rare. We shouldn't ever be writing meaningful information to stdout - stdout is for data to move between programs in pipes, stderr is for human readable things, like logs.

That said, IMO we either want stdout, in which case we should update this PR to only change the behavior of bootnode (which already writes both out&err to the same file), or we don't care about stdout, in which case we should stop writing it to disk. I vote for dropping it, because it adds no value and dropping it makes things simpler - less files, less lines of code, and no one will ever have to look at this code and wonder "are these going to the same file intentionally? which log lines are coming from stdout and which from stderr?".

Here's what we would lose:

$ ls -al | grep stdout
-rw-r--r-- 1 kasey kasey        0 Dec 22 18:01 beacon_node_0_stdout.log
-rw-r--r-- 1 kasey kasey        0 Dec 22 18:01 beacon_node_1_stdout.log
-rw-r--r-- 1 kasey kasey      169 Dec 22 18:01 validator_0_stdout.log
-rw-r--r-- 1 kasey kasey      169 Dec 22 18:01 validator_1_stdout.log

The validator log is... a progress bar:

$ cat validator_1_stdout.log 
Adding optimizations for validator slashing protection 100% [=========]  [0s:0s]

[prestonvanloon]

Thank for the context @kasey. LGTM