External Logging

Introduction

As a development feature NSO supports sending log data as-is to an external command for reading on standard input. As this is a development feature there are a few limitations such as the data sent to the external command is not guaranteed to be processed before the external application is shut down.

Enabling external log processing

General configuration of the external log processing is done in ncs.conf. Global and per device settings controlling the external log processing for NED trace logs is stored in CDB.

To enable external log processing set /ncs-config/logs/external to true and /ncs-config/logs/command to the full path of the command that will receive the log data. The same executable will be used for all log types. External configuration example:

<external>
  <enabled>true</enabled>
  <command>./path/to/log_filter</command>
</external>

To support debugging of the external log command behavior a separate log file is used. This debugging log is configured under /ncs-config/logs/ext-log. The example below shows configuration for ./logs/external.log with the highest log level set:

<ext-log>
  <enabled>true</enabled>
  <filename>./logs/external.log</filename>
  <level>7</level>
</ext-log>

By default NED trace output is written to file preserving backwards compatibility. To write NED trace logs to file for all but the device test which will use external log processing the following configuration can be entered in the CLI:

# devices global-settings trace-output file
# devices device example trace-output external

When setting both external and file bits without setting /ncs-config/logs/external to true a warning message will be logged to ext-log. When only setting the external bit no logging will be done.

Processing logs using an external command

After enabling external log processing, NSO will start one instance of the external command for each configured log destination. Processing of the log data is done by reading from standard input and processing it as required.

The command line arguments provide information about the log that is being processed and in what format the data is sent.

The example below show how the configured command ./log_processor would be executed for NETCONF trace data configured to log in raw mode:

./log_processor 1 log "NETCONF Trace" netconf-trace raw

Command line argument position and meaning:

version. Protocol version, always set to 1. Added for forwards compatibility.
action. Action being performed, always set to log. Added for forwards compatibility.
name. Name of the log being processed.
log-type. Type of log data being processed. For all but NETCONF and NED trace logs this is set to system. Depending on the type of NED one of ned-trace-java, ned-trace-netconf and ned-trace-snmp is used. NETCONF trace is set to netconf-trace.
log-mode. Format of log data being sent. For all but NETCONF and NED trace logs this will be raw. NETCONF and NED trace logs can be pretty printed and then format will be pretty.