Store and update JSON Data on a Server -

my web-application should able store , update (also load) json data on server. however, data may contain big arrays every time saved new entry appended.

my solution:

send updates server key-path within json data.

currently i'm sending data xmlhttprequest jquery, this

/**  * asynchronously writes file on server (via php-script).  * @param {string} file complete filename (path/to/file.ext)  * @param content content should written. may js object.  * @param {array} updatepath (optional), json only. not entire file written,  * given path within object updated. default path supposed contain array ,  * content appended it.  * @param {string} key (optional) in combination updatepath. if key provided, content written  * field named parameters content @ data located @ updatepath old content.  *  * @returns {promise}  */ io.write = function (file, content, updatepath, key) {     if (utils.isobject(content)) content = json.stringify(content, null, "\t");     file = io.parsepath(file);     var data = {f: file, t: content};     if (typeof updatepath !== "undefined") {         if (array.isarray(updatepath)) updatepath = updatepath.join('.');         data.a = updatepath;         if (typeof key !== "undefined") data.k = key;     }     return new promise(function (resolve, reject) {         $.ajax({             type: 'post',             url: io.url.write,             data: data,             success: function (data) {                 data = data.split("\n");                 if (data[0] == "ok") resolve(data[1]);                 else reject(new error((data[0] == "error" ? "php error:\n" : "") + data.slice(1).join("\n")));             },             cache: false,             error: function (j, t, e) {                 reject(e);                 //throw new error("error writing file '" + file + "'\n" + json.stringify(j) + " " + e);             }         });     }); }; 

on server, php script manages rest this:

1. recieves data , checks if valid
2. check if given file path writable
3. if file exists , .json
   
   • read , decode json
   • return error on invalid json
4. if there no update path given
   
   • just write data
5. if there update path given
   
   • return error if update path in json data can't traversed (or file didn't exist)
6. update data @ update-path
7. write pretty-printed json file

however i'm not happy , problems kept coming last weeks.

my questions

1. generally: how approach problem? alternative suggestions, databases? libraries help?
   note: prefer solutions, use php or standart apache stuff.
2. one problem was, sometimes, multiple writes on same file triggered. avoid used promises (wrapped because read jquerys deferred stuff isnt promise/a compliant) client side, dont feel 100% sure working. there (file) lock in php works across multiple requests?
3. every , json files break , not clear me how reproduce problem. @ time breaks, don't have history of happened. general debugging strategies client/server saving/loading process this?

1. i wrote comet enable web server diffs on updates of json data structures. same reason. server keeps few version of json document , serves client different version of json document update need reason version of json data.

maybe reuse of code, written in c++ , coffeescript: https://github.com/torstenrobitzki/sioux

3. if have concurrent write accesses data structure, sure, ever writes file has right version of file in mind when reading file?