#!/usr/bin/env python

# Back up a list of ZFS filesystems, doing a full backup periodically
# and using incremental diffs in between

import commands, datetime, sys, os, bz2
from signal import *

pbc = os.getenv('PORTBUILD_CHECKOUT') \
    if os.getenv('PORTBUILD_CHECKOUT') else "/a/portbuild"

sys.path.insert(0, '%s/admin/lib/python' % pbc)

import zfs

# List of filesystems to backup
# XXX MCL
backuplist=["a", "a/nfs", "a/local", "a/portbuild",
            "a/portbuild/amd64", "a/portbuild/arm", "a/portbuild/i386",
            "a/portbuild/ia64", "a/portbuild/mips", "a/portbuild/powerpc",
            "a/portbuild/sparc64"]

# Directory to store backups
# XXX MCL
backupdir="/dumpster/pointyhat/backup"

# How many days between full backups
# XXX MCL
fullinterval=9

def validate():
    fslist = zfs.getallfs()

    missing = set(backuplist).difference(set(fslist))
    if len(missing) > 0:
        print "Backup list refers to filesystems that do not exist: %s" % missing
        sys.exit(1)

def mkdirp(path):

    plist = path.split("/")

    for i in xrange(2,len(plist)+1):
        sofar = "/".join(plist[0:i])
        if not os.path.isdir(sofar):
            os.mkdir(sofar)

class node(object):
    child=None
    parent=None
    name=None
    visited=0

    def __init__(self, name):
        self.name = name
        self.child = []
        self.parent = None
        self.visited = 0

print "zbackup: starting at " + datetime.datetime.now().ctime()

for fs in backuplist:

    print

    dir = backupdir + "/" + fs
    mkdirp(dir)

    snaplist = None
    try:
        snaplist = [snap[0] for snap in zfs.getallsnaps(fs) if snap[0].isdigit()]
    except zfs.NoSuchFS:
        print "no such fs %s, skipping" % fs
        continue

    dofull = 0

    # Mapping from backup date tag to node
    backups={}

    # list of old-new pairs seen
    seen=[]

    # Most recent snapshot date
    latest = "0"
    for j in os.listdir(dir):
        (old, sep, new) = j.partition('-')
        if not old.isdigit() or not new.isdigit():
            continue        

        seen.append("%s-%s" % (old, new))

        if int(old) >= int(new):
            print "Warning: backup sequence not monotonic: %s >= %s" % (old, new)
            continue

        try:
            oldnode = backups[old]
        except KeyError:
            oldnode = node(old)
            backups[old] = oldnode

        try:
            newnode = backups[new]
        except KeyError:
            newnode = node(new)
            backups[new] = newnode

        if int(new) > int(latest):
            latest = new

        oldnode.child.append(newnode)
        if newnode.parent:
            # We are not a tree!
            if not dofull:
                print "Multiple backup sequences found, forcing full dump!"
                dofull = 1
            continue

        newnode.parent = oldnode

    if not "0" in backups and not dofull:
        # No root!
        print "No full backup found!"
        dofull = 1

    if not latest in snaplist and not dofull:
        print "Latest dumped snapshot no longer exists: forcing full dump"
        dofull = 1

    now = datetime.datetime.now()
    nowdate = now.strftime("%Y%m%d%H%M")

    try:
        prev = datetime.datetime.strptime(latest, "%Y%m%d%H%M")
    except ValueError:
        if not dofull:
            print "Unable to parse latest snapshot as a date, forcing full dump!"
            dofull = 1

    print "Creating zfs snapshot %s@%s" % (fs, nowdate)
    zfs.createsnap(fs, nowdate)

    # Find path from latest back to root
    try:
        cur = backups[latest]
    except KeyError:
        cur = None

    chain = []
    firstname = "0"
    # Skip if latest doesn't exist or chain is corrupt
    while cur:
        chain.append("%s-%s" % (cur.parent.name, cur.name))
        par = cur.parent
        
        # Remove from the backup tree so we can delete the leftovers
        # below
        par.child.remove(cur)
        cur.parent=None
            
        if par.name == "0":
            firstname = cur.name
            break
        cur = par

    chain.reverse()

    print "chain is " + str( chain )

    # Prune stale links not in the backup chain
    for j in backups.iterkeys():
        cur = backups[j]
        for k in cur.child:
            stale="%s-%s" % (cur.name, k.name)
            print "Deleting stale backup %s" % stale
            os.remove("%s/%s/%s" % (backupdir, fs, stale))

    # Lookup date of full dump
    try:
        first = datetime.datetime.strptime(firstname, "%Y%m%d%H%M")
    except ValueError:
        if not dofull:
            print "Unable to parse first snapshot as a date, forcing full dump!"
            dofull = 1

    if not dofull and (now - first) > datetime.timedelta(days=fullinterval):
        print "Previous full backup too old, forcing full dump!"
        dofull = 1

    # In case we are interrupted don't leave behind a truncated file
    # that will corrupt the backup chain

    if dofull:
        latest = "0"

    outfile="%s/%s/.%s-%s" % (backupdir, fs, latest, nowdate)

    # zfs send aborts on receiving a signal
    signal(SIGTSTP, SIG_IGN)
    if not dofull:
        print "Doing incremental backup of %s: %s-%s" % (fs, latest, nowdate)
        (err, out) = \
            commands.getstatusoutput("zfs send -i %s %s@%s | bzip2 > %s" % 
                                     (latest, fs, nowdate, outfile))
    else:
        print "Doing full backup of %s" % fs
        latest = "0"
        (err, out) = \
            commands.getstatusoutput("zfs send %s@%s | bzip2 > %s" % 
                                     (fs, nowdate, outfile))
    signal(SIGTSTP, SIG_DFL)

    if err:
        print "Error from snapshot: (%s, %s)" % (err, out)
        try:
            os.remove(outfile)
            print "Deleted file %s" % outfile
        except OSError, err:
            print "OSError: " + repr(err)
            if err.errno != 2:
                raise
        finally:
            sys.exit(1)

    # We seem to be finished
    try:
        os.rename(outfile, "%s/%s/%s-%s" % (backupdir, fs, latest, nowdate))
    except:
        print "Error renaming dump file" + outfile + "!"
        raise

    if dofull:
        for i in seen:
            print "Removing stale snapshot %s/%s" % (dir, i)
            os.remove("%s/%s" % (dir, i))

print
print "zbackup: ending at " + datetime.datetime.now().ctime()