Update tail.js

[andrewnguyen92]

Removing the error thrown in "latestPosition()". The application is can't catch this exception so it'll crash. An example scenario would be to tail a file and then delete the file from the system.

[lucagrulla]

Hi @andrewnguyen92 ,

In that scenario, when the library cannot access the underline file anymore, rethrowing the exception is the expected behaviour.

If the exception is just swallowed, tail could stay stuck forever (no file to read but also no exiting).

Can you share your specific scenario where swallow the exception would be better?

[andrewnguyen92]

Hi Luca, would that case be handled by the previous line that emits the error event? I am running tail on a file that may get deleted and recreated shortly thereafter in the background. Removing this exception throwing and setting up an event handler for my Tail object on the "error" event allows my application to cleanly handle this scenario without crashing. Is there another way for the application to catch this exception?

[lucagrulla]

you app should handle the exception on its side:

try {

 tail = new Tail("fileToTail");
 tail.on("line", function(data) {
  console.log(data);
});

tail.on("error", function(error) {
  console.log('ERROR: ', error);
});
} catch (ex) {
 //check for file to come back first
// create a new instance of tail on the newly created file
}

[andrewnguyen92]

Hey Luca,

I've tried that previously but it's unable to catch the exception. I've tried it again and this is what I get when the file is deleted and the application crashes:

ERROR:  size check for ./file.log failed: Error: ENOENT: no such file or directory, stat './file.log'
/home/user/test/node_modules/tail/lib/tail.js:78
            throw err;
            ^

Error: ENOENT: no such file or directory, stat './file.log'
    at Object.fs.statSync (fs.js:948:11)
    at Tail.latestPosition (/home/user/test/node_modules/tail/lib/tail.js:74:23)
    at Tail.change (/home/user/test/node_modules/tail/lib/tail.js:118:22)
    at Tail.watchEvent (/home/user/test/node_modules/tail/lib/tail.js:183:18)
    at FSWatcher.watcher.fs.watch (/home/user/test/node_modules/tail/lib/tail.js:143:101)
    at emitTwo (events.js:126:13)
    at FSWatcher.emit (events.js:214:7)
    at FSEvent.FSWatcher._handle.onchange (fs.js:1364:12)

Looks like the function throwing the exception is called as a callback by fs.watch, so I don't believe there's a way to catch the exception in that case.

[lucagrulla]

tracked with issues #129 Will be fixed with v2.2.1. Tail will emit an error event if a file is deleted.