[Bug]: flaky test TestLaunchProcess

[levisyin]

Is there an existing issue for this?

• I have searched the existing issues

What happened?

=== RUN   TestProcessTestSuite
=== RUN   TestProcessTestSuite/TestLaunchProcess
    /home/levisyin/github.com/cosmos/cosmos-sdk/tools/cosmovisor/buffer.go:261: ���������������process.go:52: �[90m<nil>�[0m �[32mINF�[0m �[1mrunning app�[0m �[36margs=�[0m["foo","bar","1234","/tmp/TestProcessTestSuiteTestLaunchProcess3792210110/001/data/upgrade-info.json"] �[36mmodule=�[0mcosmosvisor �[36mpath=�[0m/tmp/TestProcessTestSuiteTestLaunchProcess3792210110/001/cosmovisor/genesis/bin/dummyd
panic: failed to parse upgrade info file: empty upgrade-info.json in "/tmp/TestProcessTestSuiteTestLaunchProcess3792210110/001/data/upgrade-info.json"

goroutine 62 [running]:
cosmossdk.io/tools/cosmovisor.(*fileWatcher).CheckUpdate(0xc0002574a0, {{0x0, 0x0}, {0x0, 0x0, 0x0}, 0x0, {0x0, 0x0}, 0x0})
	/home/levisyin/github.com/cosmos/cosmos-sdk/tools/cosmovisor/scanner.go:120 +0x39d
cosmossdk.io/tools/cosmovisor.(*fileWatcher).MonitorUpdate.func1()
	/home/levisyin/github.com/cosmos/cosmos-sdk/tools/cosmovisor/scanner.go:86 +0xc8
created by cosmossdk.io/tools/cosmovisor.(*fileWatcher).MonitorUpdate in goroutine 40
	/home/levisyin/github.com/cosmos/cosmos-sdk/tools/cosmovisor/scanner.go:82 +0x131
exit status 2
FAIL	cosmossdk.io/tools/cosmovisor	1.023s

Cosmos SDK Version

main

How to reproduce?

Run go test -timeout 30s -run ^TestProcessTestSuite$ -testify.m ^(TestLaunchProcess)$ cosmossdk.io/tools/cosmovisor -v -count=1

[levisyin]

I think the reason may be in the function CheckUpdate.

If the upgrade-info.json file was created, but the content hasn't been written into it, would cause the issue.

At the first time, fw.lastModTime is time.Time{}, after a file is created, the modTime of os.Stat(file).ModTime() would be the creation time, so the expression stat.ModTime().After(fw.lastModTime) would always be true.

This would cause the issue: the upgrade-info.json file was created but hasn't been updated, and the file content length verification inner parseUpgradeInfoFile would fail.

func (fw *fileWatcher) CheckUpdate(currentUpgrade upgradetypes.Plan) bool {
	if fw.needsUpdate {
		return true
	}

	stat, err := os.Stat(fw.filename)
	if err != nil {
		// file doesn't exists
		return false
	}

	if !stat.ModTime().After(fw.lastModTime) {
		return false
	}

	info, err := parseUpgradeInfoFile(fw.filename, fw.disableRecase)
	if err != nil {
		panic(fmt.Errorf("failed to parse upgrade info file: %w", err))
	}
       ...
}