Where do logs show up for other processes? Is it in a sibling file to chrome_debug.log? 

I'm trying to repro and not able to find the spam. 

My canary's debug.log looks like this:

[0916/034155:ERROR:main_dll_loader_win.cc(182)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded
[0916/034155:ERROR:main_dll_loader_win.cc(182)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded
[0916/034155:ERROR:main_dll_loader_win.cc(182)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded
[0916/034156:ERROR:main_dll_loader_win.cc(182)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded
[0916/034156:ERROR:main_dll_loader_win.cc(182)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded

on and on and on. I must confess that I've never caught it in the act, but I figured from staring at the code that this must be something other than the browser process. Ah, it can't be the watcher since the watcher doesn't set dll_. So it must be another child process that does die an orderly death. Maybe a first step would be to log the process type in that message so we'd know for certain that it's not the browser process (which would be bad, I think).

Starting by logging the process type SGTM, I'll send the CL for that.

Additional noob questions: 
- do you launch your canary with some flags (e.g. --enable-logging)? I don't have a debug.log
- what's the difference between debug.log and chrome_debug.log?

Thanks. To answer your questions:
- I don't use any special flags. chrome.log is dropped next to chrome.exe. Simple inspection of the code tells me that this shouldn't happen (see https://cs.chromium.org/chromium/src/chrome/common/logging_chrome.cc?dr&q=file:logging_chrome%5C.cc+NDEBUG&sq=package:chromium&l=125). Except that logging is torn down during shutdown (see https://cs.chromium.org/chromium/src/chrome/app/chrome_main_delegate.cc?type=cs&q=processexiting+file:chrome_main_delegate%5C.cc&sq=package:chromium&l=941). I think that any LOG invocation after CleanupChromeLogging will result in a debug.log next to chrome.exe.
- I think (but am not certain) that chrome_debug.log is what you get if you run chrome.exe with --enable-logging.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c5442858e4f80adbd8afe5dfcfee95b4aba1d487

commit c5442858e4f80adbd8afe5dfcfee95b4aba1d487
Author: manzagop <manzagop@chromium.org>
Date: Tue Sep 20 23:08:35 2016

Investigate RelaunchChromeBrowserWithNewCommandLineIfNeeded log spam

BUG= 648185 

Review-Url: https://codereview.chromium.org/2351533004
Cr-Commit-Position: refs/heads/master@{#419889}

[modify] https://crrev.com/c5442858e4f80adbd8afe5dfcfee95b4aba1d487/chrome/app/main_dll_loader_win.cc

Summarizing status:
- proceeding with adhoc investigation: hoping grt@ gets more of the log spam on canary to identify the case he's hitting
- we're holding off until then on the change to early exit from RelaunchChromeBrowserWithNewCommandLineIfNeeded if not in the browser process.

Gotcha!

[0926/024723:ERROR:main_dll_loader_win.cc(185)] Could not find exported function RelaunchChromeBrowserWithNewCommandLineIfNeeded (utility process)

Great! 

Assuming you're familiar with the utility process, does this hint at some issue? (If you're not familiar, I can have a quick look.)

Basically, should we go ahead with the discussed fix?

I wonder what it is that is launching 10 utility procs every 24h on my canary Chrome...

Anyway, yes, it seems that renderers are likely terminated by the browser proc and therefore never reach the Relaunch code. Utility procs aren't (at least under some circumstances). Maybe a good option is for MainDllLoader::RelaunchChromeBrowserWithNewCommandLineIfNeeded to look like this:

...
  if (relaunch_function) {
    relaunch_function();
  } else if (ProcessTypeUsesMainDll(process_type_) {
    LOG(DFATAL) << "...";
  }

where ProcessTypeUsesMainDll is the logic on line 89. I propose DFATAL so that developers get popped into a debugger if the relaunch function is ever not found in chrome.dll. What do you think?

Sgtm! Sending you that as a CL.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/70545eff7b8d5b7502e652965d673f88f871d33a

commit 70545eff7b8d5b7502e652965d673f88f871d33a
Author: manzagop <manzagop@chromium.org>
Date: Wed Sep 28 19:29:20 2016

Remove RelaunchChromeBrowserWithNewCommandLineIfNeeded log spam

Only a subset of processes are expected to have a
RelaunchChromeBrowserWithNewCommandLineIfNeeded function. Only log a
message for those processes.

BUG= 648185 

Review-Url: https://codereview.chromium.org/2381543002
Cr-Commit-Position: refs/heads/master@{#421603}

[modify] https://crrev.com/70545eff7b8d5b7502e652965d673f88f871d33a/chrome/app/main_dll_loader_win.cc

I am also getting this now. Windows 10 Insider Build 14955 - Chrome Version 54.0.2840.71 m

Deleted: debug.log 12.5 KB

debug.log 12.5 KB View Download

The messages should be gone as of Chrome 55.