Cassandra Transaction with ZooKeeper

Cassandra Transaction with ZooKeeper - Does this work?

I am trying to implement a transaction system for Cassandra with the help of ZooKeeper. Since I don't think I have enough experience in database implementation, I would like to know if my idea would work in principle, or is there any major flaw.

Here is the high level description of the steps:

identify all the rows(keys) and columns to be edited. Let the keys be [K0..Kn]

apply write lock on all the rows involved (locks are in-memory Zookeeper implementation)

copy the old values to separate locations in Cassandra which are uniquely identified by key: [K'0..K'n]

store [K'0..K'n] and the mapping of them to [K0..Kn] in ZooKeeper using persistent mode

go ahead apply the update to the data

delete the entries in ZooKeeper

unlock the rows

delete the entries of [K'0..K'n] lazily on a maintenance thread (cassandra deletion uses timestamp, so K'0..K'n can be reused for another transaction with a newer time stamp)

Justification:

if the transaction failed on step 1-4, no change is applied, I can abort the transaction and delete whatever is stored in zookeeper and backup-ed in cassandra, if any.

if the transaction failed on step 5, the information saved on step 3 is used to rollback the any changes.

if the server happen to be failed/crashed/stolen by cleaning man, upon restart before serving any request, I check if there is any keys persisted in the zookeeper from step 4, if so, i will use those keys to fetch backed up data stored by step 3, and put those data to where they were, thus roll-back any failed transactions.

One of my concern is what would happen if some of the servers are partitioned from the cluster. I have no experience in this area, does my scheme work at all? and does it work if partition happens?

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

guess i will have to find it out myself and let you guys know...
– Viele
Jun 30 '10 at 18:32

add a comment |

Here is the high level description of the steps:

identify all the rows(keys) and columns to be edited. Let the keys be [K0..Kn]

apply write lock on all the rows involved (locks are in-memory Zookeeper implementation)

copy the old values to separate locations in Cassandra which are uniquely identified by key: [K'0..K'n]

store [K'0..K'n] and the mapping of them to [K0..Kn] in ZooKeeper using persistent mode

go ahead apply the update to the data

delete the entries in ZooKeeper

unlock the rows

delete the entries of [K'0..K'n] lazily on a maintenance thread (cassandra deletion uses timestamp, so K'0..K'n can be reused for another transaction with a newer time stamp)

Justification:

if the transaction failed on step 1-4, no change is applied, I can abort the transaction and delete whatever is stored in zookeeper and backup-ed in cassandra, if any.

if the transaction failed on step 5, the information saved on step 3 is used to rollback the any changes.

if the server happen to be failed/crashed/stolen by cleaning man, upon restart before serving any request, I check if there is any keys persisted in the zookeeper from step 4, if so, i will use those keys to fetch backed up data stored by step 3, and put those data to where they were, thus roll-back any failed transactions.

One of my concern is what would happen if some of the servers are partitioned from the cluster. I have no experience in this area, does my scheme work at all? and does it work if partition happens?

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

guess i will have to find it out myself and let you guys know...
– Viele
Jun 30 '10 at 18:32

add a comment |

Here is the high level description of the steps:

identify all the rows(keys) and columns to be edited. Let the keys be [K0..Kn]

apply write lock on all the rows involved (locks are in-memory Zookeeper implementation)

copy the old values to separate locations in Cassandra which are uniquely identified by key: [K'0..K'n]

store [K'0..K'n] and the mapping of them to [K0..Kn] in ZooKeeper using persistent mode

go ahead apply the update to the data

delete the entries in ZooKeeper

unlock the rows

delete the entries of [K'0..K'n] lazily on a maintenance thread (cassandra deletion uses timestamp, so K'0..K'n can be reused for another transaction with a newer time stamp)

Justification:

if the transaction failed on step 1-4, no change is applied, I can abort the transaction and delete whatever is stored in zookeeper and backup-ed in cassandra, if any.

if the transaction failed on step 5, the information saved on step 3 is used to rollback the any changes.

if the server happen to be failed/crashed/stolen by cleaning man, upon restart before serving any request, I check if there is any keys persisted in the zookeeper from step 4, if so, i will use those keys to fetch backed up data stored by step 3, and put those data to where they were, thus roll-back any failed transactions.

One of my concern is what would happen if some of the servers are partitioned from the cluster. I have no experience in this area, does my scheme work at all? and does it work if partition happens?

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

Here is the high level description of the steps:

identify all the rows(keys) and columns to be edited. Let the keys be [K0..Kn]

apply write lock on all the rows involved (locks are in-memory Zookeeper implementation)

copy the old values to separate locations in Cassandra which are uniquely identified by key: [K'0..K'n]

store [K'0..K'n] and the mapping of them to [K0..Kn] in ZooKeeper using persistent mode

go ahead apply the update to the data

delete the entries in ZooKeeper

unlock the rows

delete the entries of [K'0..K'n] lazily on a maintenance thread (cassandra deletion uses timestamp, so K'0..K'n can be reused for another transaction with a newer time stamp)

Justification:

if the transaction failed on step 1-4, no change is applied, I can abort the transaction and delete whatever is stored in zookeeper and backup-ed in cassandra, if any.

if the transaction failed on step 5, the information saved on step 3 is used to rollback the any changes.

if the server happen to be failed/crashed/stolen by cleaning man, upon restart before serving any request, I check if there is any keys persisted in the zookeeper from step 4, if so, i will use those keys to fetch backed up data stored by step 3, and put those data to where they were, thus roll-back any failed transactions.

One of my concern is what would happen if some of the servers are partitioned from the cluster. I have no experience in this area, does my scheme work at all? and does it work if partition happens?

database database-design transactions nosql cassandra

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

edited Jun 30 '10 at 16:13

asked Jun 30 '10 at 14:56

Viele

9612925

asked Jun 30 '10 at 14:56

Viele

9612925

asked Jun 30 '10 at 14:56

Viele

9612925

guess i will have to find it out myself and let you guys know...
– Viele
Jun 30 '10 at 18:32

add a comment |

guess i will have to find it out myself and let you guys know...
– Viele
Jun 30 '10 at 18:32

guess i will have to find it out myself and let you guys know...
– Viele
Jun 30 '10 at 18:32

add a comment |

1 Answer
1

active

oldest

votes

You should look into Cages: http://ria101.wordpress.com/2010/05/12/locking-and-transactions-over-cassandra-using-cages/

http://code.google.com/p/cages/

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

You should look into Cages: http://ria101.wordpress.com/2010/05/12/locking-and-transactions-over-cassandra-using-cages/

http://code.google.com/p/cages/

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

add a comment |

You should look into Cages: http://ria101.wordpress.com/2010/05/12/locking-and-transactions-over-cassandra-using-cages/

http://code.google.com/p/cages/

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

add a comment |

You should look into Cages: http://ria101.wordpress.com/2010/05/12/locking-and-transactions-over-cassandra-using-cages/

http://code.google.com/p/cages/

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

You should look into Cages: http://ria101.wordpress.com/2010/05/12/locking-and-transactions-over-cassandra-using-cages/

http://code.google.com/p/cages/

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

answered Jul 13 '10 at 2:05

jbellis

18.8k23144

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

add a comment |

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

it's not bad. The first thing I looked at. However, what it supplies is still far away from transaction.
– Viele
Jul 13 '10 at 13:33

add a comment |

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