jm + sync   10

How I reverse-engineered Google Docs to play back any document's keystrokes « James Somers (
Excellent write-up of this little-known undocumented GDocs behaviour, an artifact of its operational-transformation sync mechanism
operational-transformation  ot  google  gdocs  coding  docs  sync  undocumented  reversing 
november 2014 by jm
NTP's days are numbered for consumer devices
An accurate clock is required to negotiate SSL/TLS, so clock sync is important for internet-of-things usage. but:
Unfortunately for us, the traditional and most widespread method for clock synchronisation (NTP) has been caught up in a DDoS issue which has recently caused some ISPs to start blocking all NTP communication. [....] Because the DDoS attacks are so widespread, and the lack of obvious commercial pressure to fix the issue, it’s possible that the days of using NTP as a mechanism for setting clocks may well be numbered. Luckily for us there is a small but growing project that replaces it.

tlsdate was started by Jacob Appelbaum of the Tor project in 2012, making use of the SSL handshake in order to extract time from a remote server, and its usage is on the rise. [....] Since we started encountering these problems, we’ve incorporated tlsdate into an over-the-air update, and have successfully started using this in situations where NTP is blocked.
tlsdate  ntp  clocks  time  sync  iot  via:gwire  ddos  isps  internet  protocols  security 
august 2014 by jm
modern JVM concurrency primitives are broken if the system clock steps backwards
'The implementation of the concurrency primitive LockSupport.parkNanos(), the function that controls *every* concurrency primitive on the JVM, is flawed, and any NTP sync, or system time change, can potentially break it with unexpected results across the board when running a 64bit JVM on Linux 64bit.'

Basically, LockSupport.parkNanos() calls pthread_cond_timedwait() using a CLOCK_REALTIME instead of CLOCK_MONOTONIC. 'tinker step 0' in ntp.conf may be a viable workaround.
clocks  timing  ntp  slew  sync  step  pthreads  java  jvm  timers  clock_realtime  clock_monotonic 
september 2013 by jm
BitTorrent’s Secure Dropbox Alternative Goes Public
As kragen says, 'a decentralized way to sync a folder of large files, using BitTorrent instead of an untrustworthy central server'. Windows, OSX, and Linux supported
bittorrent  dropbox  cloud  storage  filesharing  sharing  sync  synchronization 
april 2013 by jm
TouchDB's reverse-engineered write-up of the Couch replication protocol
There really isn’t a separate “protocol” per se for replication. Instead, replication uses CouchDB’s REST API and data model. It’s therefore a bit difficult to talk about replication independently of the rest of CouchDB. In this document I’ll focus on the algorithm used, and link to documentation of the APIs it invokes. The “protocol” is simply the set of those APIs operating over HTTP.
couchdb  protocols  touchdb  nosql  replication  sync  mvcc  revisions  rest 
april 2013 by jm
Dropbox Sync API
Give your app its own private Dropbox client and leave the syncing to us.
apps  dropbox  synchronization  sync  ios  android  api 
march 2013 by jm
High performance network programming on the JVM, OSCON 2012
by Erik Onnen of Urban Airship. very good presentation on the current state of the art in large-scale low-latency service operation using the JVM on Linux. Lots of good details on async vs sync, HTTPS/TLS/TCP tuning, etc.
http  https  scaling  jvm  async  sync  oscon  presentations  tcp 
july 2012 by jm
Upload and store your files in the cloud with Google Docs
no sync or automated backup yet, so more like sendspace than dropbox, limited usefulness
google  backup  online-backup  sync  storage  from delicious
january 2010 by jm
'Lsyncd uses rsync to synchronize local directories with a remote machine running rsyncd. Lsyncd watches multiple directories trees through inotify. The first step after adding the watches is to rsync all directories with the remote host, and then sync single file by collecting the inotify events. So lsyncd is a light-weight live mirror solution that should be easy to install and use while blending well with your system.' (via adulau)
via:adulau  lsyncd  mirroring  linux  inotify  backup  sysadmin  synchronization  sync  dropbox  from delicious
december 2009 by jm

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