Hector Is A High Level Apache Computer Science Essay

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A range is basically refers to a range of mathematics, where you have a set of ordered elements, you have to specify a defined start and end elements, a subset of these elements. Range between the start and end points, inclusive and representative of all the elements. Is usually in the range is within the range of key (row). Piece of the term is used to refer to the column within the line. When you specify a range, query and use random partition really no way to specify a more narrow range than "all". This is obviously an expensive proposition, because you may generate additional network operations. It may also result in a miss key. This is because it is likely to occur update miss an update for your line scan at the same time as early as in the index than you are currently being processed.

One more thing, first of all, can be confusing. When you use the random partition, you have to remember, the first hash key range queries. So, if you are using "Alice" "Alison" range, the query will first run a hash on each key and did not return between Alice and Alison simple natural values, but these values hash value.

Find below a specific key, use the random partitioning program, the basic flow of a read operation. First, the key is the hash, and then the client to connect to any node in the cluster. The node will route the request to the node with key. MemTable Consulting, the key is whether there is, if it is not found, then the Bloom filter for each file is scanned, starting with the latest one. Once the key is found in the Bloom filter, which is used to consult the corresponding data file, and column values found.


API foundation, Thrift

In Cassandra0.6 and earlier, Thrift served as the basis of the entire client API. With the start of version 0.7, Avro, due to certain restrictions, second-hand thrift development is no longer particularly active interface and the facts support. It is not clear at the time of this writing, will support addition to Avro Used for how long, they are now both in the current tree. Because it is unclear will eventually support, I have included a little and they are all here.

Thrift is a driver-level interface, which provides a wide variety of language API client implementation. Used Facebook and Development Incubator donated by the state in 2008 as an Apache project. The thrift is a code generation library in C + +, C #, Erlang, Haskell, Java, target C / OCaml for customers, cocoa Perl, PHP, Python and Ruby, Smalltalk, and Squeak. Its goal is to provide a simple way to support efficient RPC calls in a variety of popular languages without requiring the overhead of SOAP.

Hector is a high-level Apache Cassandra's client API. Hector, the name of the Greek mythology, the Trojan warrior named Cassandra Java client, Thrift, Hector package of alternatives. It also has access to the Maven repository.

Hector is a good support and full-featured Cassandra client, with many users and

Active community. It provides the following functions:

High-level object-oriented API - Java developers find Hector such as key space and column, it is natural to use interface.

Failover support - thrift failure of customer support. This is because Cassandra is used in a highly decentralized manner, and has good support for the failed node in the database ring. However, if your client is connected to a node has declined, it will be very happy to have your client failover to another node to complete your request automatic search.

Cassandra is specifically built very high scalability, therefore, it has also become client supports connection pooling, so that your application does not become a bottleneck to deprive you of Cassandra speed. It is expensive, just as it is in the JDBC opens and closes connections. The Hector connection pool, using Apache GenericObjectPool. Cassandra free to use JMX, which is very convenient monitoring. Hector direct support for JMX exposure indicators, such as a poor connection, a free connection, free connection, and more.

Hector slowly toward the CQL integration. The first step has been made, but because the experience of the unstable API, developers seem to have postponed a new version. CQL API is fairly new, as it should be almost the equivalent of a SQL syntax. I did some basic CRUD operations steps to verify that the data can be written and read by CQL. However, unpacking the CQL JAR not available now like a standard JDBC driver, and missed some important functions. More or less difficult to understand thrift API does not really much simpler Hector API to look at, I believe, CQL will establish a state-of-the-state-of-the-art access API Cassandra 0.8.1 and 1.0 versions , the thrifty period of time will keep the native raw access. The competition between these two APIs Hector irrelevant to the

decision. Hector provides additional services, such as cluster faults and connection handling. Function is neither a flea, nor is it CQL is being processed.

Cassandra, CQL parity with traditional API and command-line interface (CLI) shipments have been for several years, and Cassandra CQL to the DBMS interface. Cassandra 1.1 beta CQL3. The the CLI commands CQL supplement based on CQL specification. The CQL specification is still the default, because CQL2 application is not compatible with the CQL specification 3. Compact storage instructions, use the CREATE TABLE command provides backward compatible with older Kassandra application, a new application should be avoided.


Cassandra with ebay

EBay Cassandra as follows - social signals on ebay products and projects page, mobile phones to notify the user record and tracking, fraud detection and tracking. Why eBay adaptation Cassandra basic reason is that it has excellent write performance, scalable counters, real-time analysis of data collected, rather than read delay-sensitive. When it comes to deployment, the user requests the affinity data center and Cassandra regular backup of data, in order to prevent or system error.

A row in a Column Family with composite columns in Cassandra(by Jay Patel at eBay)

This table is not a relational database, rather than its map data model. The eBay programmers tend to take the table and its rows primary keys Cassandra column family. This table in your favorite eBay.com.

Design data model, this operation is idempotent or to ensure that your usage, you can live, inaccurate or untrue, and ultimately can be corrected. "Cassandra is how to use eBay.com calculate how many users prefer a an example of a lot of items. In order to keep the model updated idempotent, they keep a list of user IDs, rather than just counting up. A "Like" button is clicked, the system records the user ID associated with it. If the recording process fails, the system can be a bold attempt to write it again. The end to find out who likes the total number of users of the project, we can read all the user ID, and then count the number.

Cassandra multi-master, in the normal relational database, the write failure does not ensure that the data in the database is not written. This means that a failure in writing sometimes can actually lead to a successful write. This design uses the Cassandra implementation of social signals in ebay.com.