dea305ca4a
In PR #10720, we introduced the makeCheapPathFunction in an effort to reduce the caching overhead for very frequently called (and already pretty quick) operations like files.stat. However, the default maximum LRU cache size of Math.pow(2, 16) can cause quite a bit of cache eviction churn for large applications, which @veered has identified as a potential source of build performance problems. By setting the maximum cache size to Math.pow(2, 20) instead, I am no longer seeing any files.stat calls in the profiling output for rebuilding a large internal app, saving several seconds of rebuild time. The obvious downside is that this cache might accumulate more memory over time, which is why I didn't just set the max to Infinity, though that might be a viable option if the total set of paths ever stat'd is small enough to fit into the available memory. In the future, I hope to find ways of managing LRU cache size that respond to actual memory pressure (relative to available memory), rather than pruning the cache after an arbitrary numeric threshold is reached.
This folder contains modules that help communicating with the file-system.
files vs fs and files.path* vs path
Since the Meteor tool was originally written to work on Mac OS X and Linux but
now is also required to work on Windows, there has been a decision to abstract
the file-system calls to fs and path modules and make them go through the
files.js lib.
All path and files manipulations in the tools code assumes it is running in a
unixy environment, where the path separator is / and the default line-break
symbol is \n; calls like rename and unlink are atomic and the file-system
always works as you expect.
The files.js file tries its best to simulate this behavior on Windows,
converting slashes, file contents and running FS operations in a
"try/sleep/repeat" loop when an EBUSY error is returned. Operations on Windows
happen to be slower, especially moving folders and symlinking (which is done by
copying the directory instead).
It is advised to use files.readFile and others instead of
fs.readFileSync. The methods are Fiberized and are converted on Windows.
Also files.pathJoin instead of path.join and others to properly preserve the
unixy feel of paths: /C/Users/IEUser/AppData/Local instead of
C:\Users\IEUser\AppData\Local.
File watching
Since node.js doesn't ship a stable library to watch a folder on all file-systems, a wrapper is used. The wrapper checks if the native functionality works, if not (while on Windows, or a virtualized shared file-system like in VirtualBox), polling is used.
Watchset
A specific data-structure that is a set of files and directories paths observed by the file-watcher.