mars/ChangeLog

Release Conventions / Branches / Tagnames

	light0.1 series (now stable):
		 - Asynchronous replication for the internal needs of
		   shared hosting and other ITOPS departments at 1&1.
		 - Unstable tagnames: light0.1beta%d.%d
		 - Stable branch: light0.1.y
		 - Stable tagnames: light0.1stable%02d

	light0.2 series (planned):
		 - Improve network throughput by parallel TCP connections
		   (in particular under packet loss).
		   Also for the internal needs of shared hosting at 1&1.
		 - Unstable tagnames: light0.2beta%d.%d (planned)
		 - Stable branch: light0.2.y (planned)
		 - Stable tagnames: light0.2stable%02d (planned)

	light0.3 series (planned):
		 - Improve replication latency.
		 - New pseudo-synchronous replication modes.
		   For the internal needs of database folks at 1&1.
		 - Unstable tagnames: light0.3beta%d.%d (planned)
		 - Stable branch: light0.3.y (planned)
		 - Stable tagnames: light0.3stable%02d (planned)

	light1.0 series (planned):
		 - New symlink tree structure (future-proof)
		 - Trying to additionally address public needs.
		 - Potentially for Linux kernel upstream,
		 - Unstable tagnames: light1.0beta%d.%d (planned)
		 - Stable branch: light1.0.y (planned)
		 - Stable tagnames: light1.0stable%02d (planned)

	full* (somewhen in future)

	WIP-* branches are for development and may be rebased onto anything
	at any time without notice. They will disappear eventually.

light0.1stable01
--------
	 * Fix parallelism of logfile propagation: sometimes a secondary
	   could get a more recent version than the primary had on stable
	   storage after its crash, eventually leading to an (annoying)
	   split brain. Some people might take this as a feature instead
	   of a bug, but now the logfile transfer starts only after the
	   primary _knows_ that the data is successfully committed to
	   stable storage.
	 * Fix memory leaks in error path.
	 * Fix error propagation between client and server.
	 * Make string allocation fully dynamic (remove limitation).
	 * Fix some annoying messages.
	 * Fix usage output of marsadm.
	 * Userspace: contributed bugfix for Debian udev rules by Jörg Mann.
	 * Improved debugging (only for testing).

light0.1beta0.18 (feature release)
--------
	 * New commands marsadm view-$macroname
	 * New customizable macro processor
	 * New err/warn/inf reporting via symlinks
	 * Per-resource emergency mode
	 * Allow limiting the sync parallelism
	 * New flood-protected syslogging
	 * Some smaller improvements
	 * Update docs
	 * Update test suite

light0.1beta0.17
--------
	 * Major bugfix: race in logfile switchover could sometimes
	   lead to the wrong logfile (extremely rare to hit, but
	   potentially harmful).
	 * Disallow primary switching when some secondaries are
	   syncing.
	 * Fix logfile fetch from multiple peers.
	 * Fix computation of transitive closure (affected
	   log-purge-all, split brain detection, and many others).
	 * Fix incorrect emergency mode detection.
	 * Primaries no longer fetch logfiles (unnecessarily, only
	   makes a difference at concurrent split brain operations).
	 * Detached resources no longer fetch logfiles (unexpectedly).
	 * Myriads of smaller fixes.
	
light0.1beta0.16
--------
	
	 * Critical bugfix: "marsadm primary --force" was assumed to be given
	   by sysadmins only in case of emergency, when the network is down.
	   When given in non-emergency cases where the old primary continues
	   to run (/dev/mars/* being actively used and written), the
	   old primary could suddendly do a "logrotate" to the
	   new split-brain logfile produced by the new (second) primary.
	   Now two primaries should be able to run concurrently in split-brain
	   mode without mutually trashing their logfiles.
	 * primary --force now only works in disconnected mode, in order
	   to hinder unintended forceful creation of split brain during
	   normal operation.
	 * Stop fetching of logfiles behind split brain points (save space
	   at the target hosts - usually the data will be discarded later).
	 * Fixed split brain detection in userspace.
	 * leave-resource now waits for local actions to take place
	   (remote actions stay asynchronously).
	 * invalidate / join-resource now work only if a designated primary
	   exists (otherwise they would not know uniquely from whom
	   to start initial sync).
	 * Update docs, clarify scenarios intended <-> emergengy switching.
	 * Fixed mutual overwrite of deletion symlinks in case of racing
	   log-deletes spawned in parallel by cron jobs (resilience).
	 * Fixed races between deletion and re-erection (e.g. fresh
	   join-resource after leave-resource during network partitions).
	 * Fixed duration of network timeouts in case the network is down
	   (replaced non-working TCP_KEEPALIVE by explicit timeouts).
	 * New option --dry-run which does not really create symlinks.
	 * New command "delete-resource" (VERY DANGEROUS) for
	   forcefully destroying a resource, even when it is in use.
	   Intended only for _emergency_ cases when sysadmins are
	   desperate. Use only by hand, first run with --dry-run in order
	   to check what will happen!
	 * New command "log-purge-all" (potentially DANGEROUS) for
	   resolving split brain in desperate situations (cleanup of
	   leftovers). Only use by hand, first run with --dry-run!
	 * Lots of smaller imprevements / usability / readability etc.
	 * Update test suite.

light0.1beta0.15
--------
	
	 * Introduce write throttling of bulk writers.
	 * Update test suite.

light0.1beta0.14
--------
	
	 * Fix logfile transfer in case of "holes" created by
	   emergency mode.
	 * Fix "marsadm invalidate" after emergency mode had been entered.
	 * Fix "marsadm resize" capacity propagation from underlying LVM.
	 * Update test suite.

light0.1beta0.13
--------
	
	 * Fix shutdown during operation (flying requests).
	 * Fix unnecessary Lamport clock propagation storms.
	 * Improve unnecessary page cache utilisation (mapfree).
	 * Update test suite.

	
light0.1beta0.12 and earlier
--------
	
	There was no dedicated ChangeLog. For details, look at the
	commit history.
	
Release Policy / Software Lifecycle
-----------------------------------

	New source releases are simply announced by appearance of git tags.

General Conventions
-------------------
	
The git tags have the following meaning:

	full* for future use.

	light1.0 The first number indicates the main symlink tree revision, the second number indicates the sub revision. The main symlink tree revision is only updated upon (potentially) incompatible changes. Upgrades of main revisions will always be possible, but downgrades are not automatically supported. The sub revision will indicate new releases, and they may also indicate symlink tree extersions which are both forwards and backwards compatible. It may just happen that new features are not available with elder releases :)
	Example: 1.0 ff will indicate the future main production revision.
	Extensions: suffixes like pre1 indicate pre-releases. Other suffixes like testing2 are reserved for future use.
	Hint: you may automatically convert the MARS git tags into Debian release tags by a regex inserting a ~ after any transition from a digit to an alpha character. We just omitted the ~ because git treats it as an invalid character. The corresponding Debian tags _should_ result in the correct ordering according to the Debian guidelines. Please report a bug if not :)

	light0.1beta* Internal 1&1 releases during the pilot phase. May be used by the public, but you should know that the 1.0 symlink tree revision will appear soon.

	light0.0alpha* Very old prototypes; never use them. Vital feature were missing. Only for historic inspection.