cdcf::Logger - thoughtworks-hpc/cdcf GitHub Wiki

Log Format

Log is in the following format:

[2020-07-10 07:50:36.860] [log_level] [source_file:line_number] Some message

Logger Initialization

You should init logger when program start and only once.

cdcf::Logger::Init(cfg);

cfg is instance of CDCFConfig or it's child.

Logger Initialization will read following config:

  1. log_file: log file name
  2. log_file_size: maximum rotating log file size in bytes
  3. log_file_num: maximum rotating log file number, each file has size log_file_size_in_bytes
  4. log_no_display_filename_and_line_num: whether display filename and line num in log
  5. log_level: log level, default: info
  6. no_log_to_console：whether print to console
  7. print-ping-log(node keeper only): whether print ping log, default: false

Logger print to console per default, print to file if you provide log_file in config and enable rotating if you provide log_file, log_file_size and log_file_num.

Basic file logger

Logger initialize with log_file_size_in_bytes_ = 0 have no limitation on its log file size.

Rotating logger

When the max file size is reached, close the file, rename it, and create a new file, the number of new file that can be created is limited by the log file number.

The following example creates a rotating logger that has maximum log file size of 1024 bytes and allows 1 extra log file, when 1024 bytes are reached, the logger will rename cdcf.log to cdcf.1.log and create a new cdcf.log, when the new cdcf.log is filled again, the same renaming happens and the old cdcf.1.log will be deleted, hence the ROTATING LOGGER.

cfg.log_file_size_in_bytes_ = 1024;
cfg.log_file_number_ = 1;
cdcf::Logger::Init(cfg);

Logger Usage

Log Level

The logger has the following log levels:

"trace", "debug", "info", "warning", "error", "critical", "off"

Use certain function like 'Info' to log in that level:

CDCF_LOGGER_INFO("Hello World");
// [2020-07-10 07:50:36.860] [info] [/cdcf/main.cc:8] Hello World

Message Formatting

The logger use the fmt formatting library

CDCF_LOGGER_DEBUG("detect node {}:{} up.", "127.0.0.1", 55555);
// [2020-07-10 07:50:36.860] [info] [/cdcf/node_keeper/src/membership.cc:379] detect node 127.0.0.1:55555 up

Working with Elastic Stack

Use the following filter in LogStash to process logs generated by cdcf::Logger:

filter {
    grok {
        match => { "message" => "%{DATA}%{TIMESTAMP_ISO8601:timestamp}]%{DATA} %{DATA}%{WORD:level}%{DATA} %{DATA}%{PATH:source}:%{NUMBER:line_num}%{DATA} %{GREEDYDATA:line}" }
    }
}