Error on rotated file if new file takes time to appear

[martinj]

If the file is rotated and it takes a while for the new file to appear it will fail.

The first error ENOENT will be caught and _readRemainderFromFileHandle will be executed, this will set this[kFileHandle] = null and on the next succeding poll it will detect a file rename and call _readRemainderFromFileHandle again but this[kFileHandle] is now null.

Example

'use strict'

const TailFile = require('@logdna/tail-file');
const fs = require('fs');

async function go() {
	const tail = new TailFile('./foo.log');
	tail.on('retry', () => console.log('retry'));
	tail.on('error', console.log)

	await tail.start();

	setTimeout(() => {
		fs.renameSync('./foo.log', './foo.log.1');
	}, 1000);

	setTimeout(() => {
		fs.copyFileSync('./data.txt', './foo.log');
	}, 2100);

}

go().catch(console.log);

Output

retry
TypeError: Cannot read property 'stat' of null
    at TailFile._readRemainderFromFileHandle (/node_modules/@logdna/tail-file/lib/tail-file.js:123:43)
    at TailFile._pollFileForChanges (/node_modules/@logdna/tail-file/lib/tail-file.js:171:20)

[darinspivey]

Ah, right you are! Thank you for reporting this, and for providing a working example. Looks like this edge case was just missed. There are 2 places that will read 'the remainder' from the FH; one for when the inode changes and one for if the file disappears. The former condition can happen if the file changes in between polls, thus never throwing an ENOENT error. This edge case is sort of a combination of the two and should definitely be handled. After all, the code is designed to be configurable for wait time and number of retries after a file disappears.

I've completed the coding fix, but need to update the tests. This can be merged asap after the US is back from the holiday weekend in a few days. Thanks again.