Logging to log files

There are several benefits of using the OpenAF’s log* functions. One of them is to quickly have a logs folder with automated housekeeping with just a couple of lines of code.

Let’s start with a simple script with log functions:

log("Init");

try {
    log("Writing file...");
    io.writeFileString("test.txt", "test");
    log("File test.txt written.");
} catch(e) {
    logErr("Couldn't write file test.txt. Error: " + String(e));
}

log("Done");

Executing you will get the expected standard output:

2019-12-08 09:19:00.540 | INFO | Init
2019-12-08 09:19:00.750 | INFO | Writing file...
2019-12-08 09:19:00.780 | INFO | File test.txt written.
2019-12-08 09:19:00.785 | INFO | Done

Log to a folder

Let’s log to a folder:

ow.loadCh();
// Setting default logging to the logs folder
ow.ch.utils.setLogToFile({ logFolder: "logs" });
// Ensuring logs are written synchronously
setLog({ async: true });

log("Init");

try {
    log("Writing file...");
    io.writeFileString("test.txt", "test");
    log("File test.txt written.");
} catch(e) {
    logErr("Couldn't write file test.txt. Error: " + String(e));
}

log("Done");

Executing again the result seems similar but a new “logs” folder was created with a daily log file containing all the log messages. When creating a new daily log file it will automatically gzip all old daily log files.

But that’s the standard behaviour that can, of course, be customizable. Let’s add housekeeping to delete files older than one week:

ow.loadCh();
ow.ch.utils.setLogToFile({ 
    logFolder: "logs",
    HKhowLongAgoInMinutes: 7200
});
//...

p.s.: you can specify a different folder to hold the previous compressed log files using _backupFolder. You can also control if old log files should be compressed or not with dontCompress._

Logging to files by hour

The default is logging to daily files but you can customize to any date time grouping. To group files by hour can simply add a specific fileDateFormat. Additionally let’s change the log filenames generated using filenameTemplate (that uses handlebars notation).

Since we are changing the log filenames for the housekeeping process to be able to identify the new log filenames you need to provide a HKRegExPattern regular expression pattern also.

ow.loadCh();
ow.ch.utils.setLogToFile({ 
    logFolder: "logs",
    filenameTemplate: "hourly-logs-{{timedate}}.log",
    fileDateFormat: "yyyy-MM-dd-HH",
    HKhowLongAgoInMinutes: 7200,
    HKRegExPattern: "hourly-log-\\d{4}-\\d{2}-\\d{2}-\\d{2]\\.log"
});
//...

Logging as CSV files

To log into CSV files you just need to change the filenameTemplate and the lineTemplate:

ow.loadCh();
ow.ch.utils.setLogToFile({ 
    logFolder: "logs",
    filenameTemplate: "log-{{timedate}}.csv",
    lineTemplate: "\"{{timedate}}\";\"{{type}}\";\"{{{message}}}\"\n",
    HKhowLongAgoInMinutes: 7200
});
//...

Logging as NDJSON files

To log as NDJSON:

ow.loadCh();
ow.ch.utils.setLogToFile({ 
    logFolder: "logs",
    filenameTemplate: "log-{{timedate}}.csv",
    lineTemplate: "{d:\"{{timedate}}\",t:\"{{type}}\",m:\"{{{message}}}\"}\n",
    HKhowLongAgoInMinutes: 7200
});

Keeping log entries only on files

You can also specify that log entries should only be recorded in the log files and not shown on the standard output console:

ow.loadCh();
ow.ch.utils.setLogToFile({
    logFolder: "logs",
    setLogOff: true
});

And more...

You can check all the available options by executing:

> help ow.ch.utils.setLogToFile

on an openaf-console prompt.