Curs Bnr

[curs-bnr]

Curs Bnr turned 2 today!

[rooksfury]

Introducing the Oracle-SimpleDB Hybrid

[curs-bnr]

rooksfury:

My company would like to migrate its systems to the cloud. As this will take several months, the engineering team needs to support data access in both the cloud and its data center in the interim. Also, the RDBMS system might be maintained until some functionality (e.g. Backup-Restore) is created in SimpleDB.

To this aim, for the past 9 months, I have been building an eventually-consistent, multi-master data store. This system is comprised of an Oracle replica and several SimpleDB replicas. As I near completion of this system, I’d like to share its design.

Here’s the system:

We plan on accepting reads and writes in our data center (Oracle) and in our AWS region (SimpleDB). There are 2 Incremental Replicators (IRs) that transmit the changes between Oracle and SimpleDB. One replicates data from Oracle to SimpleDB, the other replicates data back from SimpleDB to Oracle.

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[rooksfury]

The Oracle-SimpleDB Hybrid Part 1 : Pulling data out of Oracle Efficiently

[curs-bnr]

rooksfury:

Preamble : See my previous post titled “Introducing the Oracle-MySQL Hybrid”

In my previous post, I provided an overview of an Oracle-SimpleDB Hybrid system that I am building. It supports writes to multiple masters, replicates data between masters in single-digit seconds (i.e. in the absence of long-term network partitions), is eventually-consistent, and is designed for optimal AP — it survives Network Partitions and is highly available.

My company already relies on Oracle databases. In order to transition to SimpleDB, we will need to move one application at a time into the cloud while keeping our service running. As this cannot happen overnight, we need to keep both SimpleDB and Oracle in sync.

In Part 1 : Pulling data out of Oracle Efficiently, I’m going to discuss one of 3 methods we have devised to replicate data out of an RDBMS. This method is called Trigger-oriented Incremental Replication (a.k.a TIR) and is depicted below in the bottom gray-box.

Before the Oracle-SimpleDB Hybrid system could go live, we needed to copy a lot of data from Oracle to SimpleDB. There were 2 distinct goals:

Copy historical data from Oracle to SimpleDB - i.e. a one-time data fork-lift

Replicate incremental changes as they occur in the live system

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[rooksfury]

The Oracle-SimpleDB Hybrid Part 2 : Solving the Eventual Consistency Problem

[curs-bnr]

rooksfury:

Preamble: Read Part 1: Pulling Data out of Oracle Efficiently

Creating the Oracle-SimpleDB Hybrid system is a challenge. For one, it is a multihomed system, accepting writes in both the cloud (i.e. SimpleDB) and in our data center (i.e. Oracle). Secondly, the data center and the AWS reqion (i.e. US-east) are on opposite coasts of the US with network latency ~50-100ms. Thirdly, clocks are not synchronized via network protocols like NTP across WANs. NTP across WANs introduce tens of milliseconds of inaccuracy, which may not be good enough to resolve all forms of conflict.

To build a multi-homed system, we needed to keep our Oracle DB in our data center in sync with our SimpleDB domains in the East Coast region.

This is a tough problem to solve. How consistent do we want the data? What if we shoot for strong-consistency?

In order to build a strongly-consistent link between Oracle and SimpleDB, we could use dual-writes via a 2 Phase Commit (a.k.a 2PC) protocol. However, 2PC over a 50-100ms link would be an availability bottleneck, and hence 2PC is not a viable option. Any consensus protocol would suffer the same short-coming.

Since we cannot achieve Strong Consistency between Oracle and SimpleDB, can we achieve Eventual Consistency?

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[viafrank-deactivated20120702]

[curs-bnr]

viafrank:

Marcel Proust’s In Search of Lost Time is a challenge. (And many would say a pleasure.) During Proust’s life, an American woman living in Rome thought to write the author after devoting three years of her life to reading his work.

“I don’t understand a thing, but absolutely nothing. Dear...

[viafrank-deactivated20120702]

Sharing and Giving, Collections and Gifts

[curs-bnr]

viafrank:

This morning I launched a new blog called The Mavenist. Allow me to digress.

Most of our blogs, our new digital mantelpieces, are a collection of the things we find. Our collections are made public—others are given access, and we call this sharing. But it is an odd sort of sharing, where what we have found is indeed made available to others, but it is not quite a gift. A collection and a gift may both live in boxes, but they are different because the intent of each is conflicting. A collection is made for me (even if I let you look through it), while a gift is chosen for you. To truly share something is to give a gift, and if I am keeping an online collection for me, how can I make it a gift for you?

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[jonathanmoore]

[curs-bnr]

jonathanmoore:

Another Picnic Table

Wouter Nieuwendijk and Jair Straschnow teamed up to challenge the traditional picnic table that provided easier access at the table and with a flip of the seat it converts into a comfortable lounge chair.

Found on The Fox is Black

[viafrank-deactivated20120702]

Wan Hu, a sixteenth-century Chinese official, is said to have attempted to launch himself into outer space in a chair to which 47 rockets were attached. The rockets exploded and, it is said, neither he nor the chair were ever seen again.

List of Inventors Killed by Their Own Inventions on Wikipedia (via viafrank)

[viafrank-deactivated20120702]

I just write what I want. There’s so many rules right outside the door. What good’s a blog if you can’t light things on fire?

13 on The Black Hockey Jesus via Sippey (via viafrank)

[rufus]

[curs-bnr]

rufus:

Hudson river rafting guide leisure dive FTW.

[rufus]

[curs-bnr]

rufus:

Best goose attack video you’ll see all week.

[staff]

[curs-bnr]

staff:

A human error caused some sensitive server configuration information to be exposed this morning. Our technicians took immediate measures to protect from any issues that may come as a result. We’re triple checking everything and bringing in outside auditors to confirm, but we have no reason to...

[alexvincere--deactivated2011040]

[cameronmoll]

[curs-bnr]

cameronmoll:

Blake Allen, a man with impeccably good taste in music and the founder of Designers.MX, has just posted my mixtape: The Film Sessions, Volume One.

I’m a film score nut. For a short time during college I was a music major with aspirations of becoming a composer for films. Obviously, I...

[staff]

[curs-bnr]

staff:

A human error caused some sensitive server configuration information to be exposed this morning. Our technicians took immediate measures to protect from any issues that may come as a result. We’re triple checking everything and bringing in outside auditors to confirm, but we have no reason to...

[curs-bnr]

[curs-bnr]

Curs Valutar Bnr

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