The main purpose of the Host Logger project is to handle and store host's console output data, such as boot logs or Linux kernel messages printed to the system console.
Host Logger is a standalone service (daemon) that works on top of the obmc-console-server module and uses its UNIX domain socket to read the console output.
+-------------+ +----------------+ | Host | State +---------------------+ Event | Host Logger | | |------->| D-Bus |------->| | | | +---------------------+ | +------------+ | | | D +--->| Log buffer | | | | +---------------------+ a | | +------+-----+ | | | | obmc-console-server | t | | | | | +---------+ | Data | +-------------+ | a | | +------+-----+ | | | console |--------->| | UNIX socket |---------+ | | Log file | | | +---------+ | | +-------------+ | | +------------+ | +-------------+ +---------------------+ +----------------+
Unlike the obmc-console project, where buffer with console output is a "black box" and exist only as a binary byte array, the Host Logger service interprets the input stream: splits it into separated messages, adds a time stamp and pushes the message into an internal buffer. The buffer will be written to a file when one of the external events occurs, such as a request for turn on the host or direct call of the function Flush via D-Bus. It gives us the ability to save the last boot log and subsequent messages in separated files. The service uses a set of rules (policy) that defines how large a buffer can be (limit by time or message numbers), in which cases the buffer should be flushed to a file, and how many previous log files can be saved on a flash drive (log rotation).
The policy can be defined in two ways:
--szlimit: Set maximum number of messages stored inside the buffer. Default value is 3000. The value 0 will disable the rule.--tmlimit: Set maximum age of a message (in hours), all messages that older then the specified value will be cleaned. This rule can be used to store, for example, only messages for the latest hour. Default value is 0 (rule disabled). Both of these options can be combined together, in this case a message will be cleaned if it complies any of limit types. You can create an unlimited buffer by passing 0 for both of these options.--path: Set the path used to store log files, default values is /var/lib/obmc/hostlogs.--flush: Set the period (in hours) to flush buffer to a file. Default value is 0, which means that the flush operation will be started at every significant host state change - power on/off or OS boot complete events.--rotate: Set the maximum number of files stored on the flash memory. Default value is 10. The service will remove the oldest files during the buffer flush procedure.The service provides an implementation of a D-Bus interface xyz.openbmc_project.HostLogger.service. Currently it has only one method Flush used for manually flushing logs.
# ls /var/lib/obmc/hostlogs host_20181024_092655.log.gz host_20181025_120520.log.gz host_20181024_114342.log.gz host_20181025_120910.log.gz # zcat /var/lib/obmc/hostlogs/host_20181025_120910.log.gz [ 12:05:30 ]: >>> Log collection started at 25.10.2018 12:05:30 [ 12:05:30 ]: --== Welcome to Hostboot v2.1-199-g38a9f30/hbicore.bin/ ==-- [ 12:05:34 ]: 5.52713|ISTEP 6. 3 - host_init_fsi [ 12:05:34 ]: 6.13176|ISTEP 6. 4 - host_set_ipl_parms [ 12:05:34 ]: 6.13309|ISTEP 6. 5 - host_discover_targets ...