log_files_count and log_file_size in contrail-vrouter-agent.conf are not parsed correctly

[Valentine Sinitsyn]

Steps to reproduce:
1. Add log_files_count = N to /etc/contrail/contrail-vrouter-agent.conf or whatever config file your Contrail vRouter Agent uses
2. Start the agent

Expected results:
1. The maximum number of agent log files to keep is set to N

Actual results:
1. The maximum number of agent log files to keep is undetermined. To testify this, one can start /usr/bin/contrail-vrouter-agent under debugger and set breakpoint at LoggingInit() function to verify maxBackupIndex argument, or check AgentParam object directly.

Possible cause:
AgentParam::ParseDefaultSectionArguments() tries to get DEFAULT.log_files_count and DEFAULT.log_file_size from the object's properties tree. However, AgentParam::InitFromConfig() only puts unregistered options in the tree, which is not the case for log_files_count and log_file_size. GetValueFromTree<int,long>() should really be GetOptValue<int,long>() for these options.

[Valentine Sinitsyn (valentine-sinitsyn)]

There is a not-so-evident consequence of this bug.

As log_files_count is undetermined, it can be pretty big, which makes log4cplus to rename many non-existent log files.

At least on some kernels we checked, continuously renaming a non-existing file (say, "while true; do mv a$i b$((++i)); done") wastes slab-allocated kernel memory for dentry cache. Under unfavourable conditions, this can lead to RAM starvation on the hypervisor and ultimately loss of the node.