Cassandra System in Facebook

Cassandra System in Facebook Cassandra was designed to accomplish scalability and availability for the Inbox Storage problem. It was a system developed for Facebook. It would need to handle more than a billion write operations. It would also need to scale with the number of users. The data centers which serve the users are distributed across earths geography. Figure 1 Cassandra Symbol In order to keep the search latencies down, it would be necessary for the users to replicate the data over the data centers. Facebook has installed Cassandra as its back end storage system. This is done for multiple services available at Facebook. Distributed file systems have hierarchal name spaces. The existing systems allow operations which are disconnected. They are also strong against general issues like outages and network partitions. Conflicts resolution is different in different systems in Coda and Ficus there is level conflict resolution. Application level resolution is allowed by Bayou. Traditional relational databases seek at providing guarantee of consistent replicated data. Amazon uses the Dynamo storage system for storing and retrieving user details. It uses the Gossip member protocol to maintain node data. Vector clock scheme is used to detect conflict. It has more preference for client side conflict resolution mechanism. In systems which need to handle a high write through put, Dynamo can be disadvantages as read would be needed to manage the vector stamps. Casandra is a non-relational database. It has a distributed multi-dimensional map. This map is indexed by a key. The value which the key points to is highly structured. The size of the row key is a string which has no restrictions. It has size corresponding to 16 to 36 bytes. Like the Big table system, the columns are grouped together into sets. These sets are called as column families. The column families are divided into two type: 1) Simple column families These are the normal column families 2) Super column families The super family has a column family inside a column family. Sorted order of the column can be specified. The inbox display usually displays the messages in time sorted fashion. This can be used by Cassandra as it allows the sorting over the columns by time or by name. The results are displayed in easily for the inbox searches in a time sorted manner. The syntax used to access column family is column_family:column. For a super column family it is column_family: super_column: column. Cassandra cluster is used a part of an application. They are then managed as a part of a service. All the deployments have jsut one table in their schema. But it does support the notion of multiple tables. The API of Cassandra has the below three basic commands: insert (table, key, rowMutation) get (table, key, columnName) delete (table, key, columnName) column name stands for a super column family or simple column family, a specific column in the column family. Consider the architecture of storage system involves plenty of complicated scenarios. Many factors need to be handled such as configuration management, robustness, scalability, For this document we consider primary features of Cassandra that includes membership, partitioning, failure handling, scalability, replication For the various read write requests, the module works in synchrony. In order to confirm the completion of writes, the system routes requests to replica. Reads are handled differently. System reroutes the requests to the nearest replica / route and awaits a quorum of responses. Partitioning Ability to increase scaling is a critical feature provided by Cassandra. This is provided in dynamic way. In the cluster, the partition takes place over the storage hosts. Consistent hashing and also preserving has functions are performed to take care of partitioning. Consider the consistent hashing approach. Here the largest hash value covers the smallest hash value. All nodes are then provided another adhoc value represented by the position of ring. Application provides the key with Cassandra leverages that to move requests. Responsibility is established at a node level around the ring region. Main benefit of this approach is that transition of node impacts only the neighboring node, whereas other nodes are not impacted. There does exist some difficulties for this approach. There is lack of uniform data and load distributions due to the adhoc positions of nodes around the ring. The approach ignores the differences in performances of nodes. Replication In order to increase the durability and availability, Cassandra provides replication. For this purpose, all data item is copied over at N hosts. Each node is conscious aware of other nodes in network, thus high durability is established. Each row is replicated across various data centers that are further synced with very high speed network links. Bootstrapping A configuration is maintained for a node joining the cluster. Configuration file provides the necessary contact points to join the cluster. These are known as seeds. A service can also provide such configuration. Zookeeper is one of them. Scaling the Cluster Consider the case of adding a new node to system. For this purpose, a token is assigned to it. Goal is to reduce load on heavily loaded node. New node is split on a range wherein previous node was assigned for. Web dashboards are provided that can perform above tasks. These can also be achieved through command line utility. Local Persistence Local file system helps provide the necessary local persistence for Cassandra. For recovering data efficiently, disks are used to represent data. There are standard write operations. These include ability to commit and update into a data structure. After successful commit log, then write to in-memory data structure is performed. Implementation Details The Cassandra process on a single machine is primarily consists The process involves clustering, fault identification and storage modules. These apply for a specific machine. There exists event driven items. These split the message across the process pipeline and also task pipeline. These are performed across various steps as part of architecture. JAVA is primary source and all modules are built from scratch using Java. For the clustering and fault detection module, input output that is of type non-blocking is built upon. There are few lessons that were learnt over maintaining Cassandra. New features should be added after understanding its implications over the system. Few scenarios are stated below: 7TB of the data needed to be indexed for 00M users. It was extracted, transformed an loaded into the Cassandra database using Map reduce jobs. The Cassandra instance juts becomes a load over the network bandwidth as some of the data was sent over serialized data over the Cassandra network. Application requirement is to have an atomic operation per key per replica. Storage system features, architecture and implementation is described including partitioning, replication, bootstrapping, scaling, persistence and durability. These are explained through Cassandras perspective which provides those benefits. [1] Avinash Lakshman, Facebook Prashant Malik, Facebook, Cassandra A Decentralized Structured Storage System

Haircut by Ring Lardner Essay

In his short story, â€Å"Haircut,† Ring Lardner employs an atypical point of view style. Although the story is told completely from the point of view of a barber, what makes it unique is that the reader is a part of the story as the barber’s customer. Lardner makes use of the stereotype that barbers are very talkative while they do their work, and one can learn all the town gossip from them. The barber himself is very talkative by nature, inferred from when he says that he does not mind shaving corpses, except that he gets â€Å"kind of lonesome† with them because he cannot talk to them. He also seems unaware of his gossiping nature because, once, he actually stops himself by saying that he â€Å"shouldn’t ought to be gossipin’† even though he had been gossiping the entire time. This barber goes on with his stories with no input needed from the customer/reader, and so seems to skip from one topic to another, similar to the pattern of idle chatter. This random jumping of topics is actually essential to the story. Lardner builds his characters using little background stories that expose their personalities. This style involves so many characters and so many stories that a straightforward third-person story would not have been nearly as effective. One other importance of the barber’s point of view is that he makes no judgments as he tells his stories. He talks about Jim Kendall, who he has a â€Å"good ole boy† type of relationship with. From the stories, the reader can tell that Jim, the recently deceased funny barbershop patron, was in fact a rather bad man. Jim did not give his wife enough money to live on and cheated on her repeatedly, knowingly broke his children’s hearts, made fun of a mentally ill person, and almost assaulted a woman. Even knowing all these things, the barber still insists that Jim was a â€Å"good fella at heart. † Lardner uses the idle chatter of a friendly barber to tell the story of what was, most probably, a murder of a very unpleasant man.

level 3 business studiesUnit 3 introduction to Marketing P1 Essay

For this assignment I have been asked to do a report on†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(say what you have been asked to do) The company I chose for this marketing report is kellogs and Nestle. I will first start off by writing about Kellogs. About Kellogs Kellogs is a †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(Give history of Kellogs and background info) The types of products Kellogs produces are†¦.. (make sure you mention the products kellogs produces and the general target market for these producst E. g. cereals – aimed at consumers aged 5 onwards, can you think of any other products? ) Marketing strategies used by Kellogs Kellogs use a variety of marketing strategies. One of which is the growth strategy which can take many forma s as listed below.. 1. growth strategies (such as diversification, product development, market penetration or market development, Ansoff’s Matrix) I will write about the Growth strategies in greater detail. For Kellogs they use all the following strategies for growth. Growth strategies are: Market penetration – say what it is and how kellogs has used this for one of their products Market development -say what it is and how kellogs has used this for one of their products Product development – say what it is and how kellogs has used this for one of their products Diversification -say what it is and how kellogs has used this for one of their products About Nestle Nestle is a †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦(Give history of Nestle and background info) The types of products Kellogs produces are†¦.. (make sure you mention the products Nestle produces and the general target market for these producst E. g. cereals – aimed at consumers aged 5 onwards, can you think of any other products? ) Marketing strategies used by Nestle Nestle use a variety of marketing strategies. One of which is the growth strategy which can take many forms as as listed below.. 1. growth strategies (such as diversification, product development, market penetration or market development, Ansoff’s Matrix) I will write about the Growth strategies in greater detail. For Nestle they use all the following strategies for growth. Market penetration – say what it is and how Nestle has used this for one of their products Market development -say what it is and how Nestle has used this for one of their products Diversification -say what it is and how Nestle has used this for one of their products Product development -say what it is and how Nestle has used this for one of their products Other marketing strategies for Kellogs Now we will look at survival strategies and relationship marketing because they are other strategies that both nestle and Kellogs use. For kellogs their survival strategies are: survival strategies; Mention in detail Kellogs strategies such as branding (importance in influencing buyer behaviour, brand building, positioning, brand extension) look at resources on the U drive and also search the internet. U:Business StudiesStudentsBTEC Level 3 Sept 2010 onwardsUnit 3 Introduction to MarketingAssignment 1Lesson 3 And another strategy Kellogs use is relationship marketing: relationship marketing Mention definition, difference between transactional marketing and relationship marketing, value of lifetime customer and how Kellogs has used relationship marketing look at resources on the U drive and also search the internet. U:Business StudiesStudentsBTEC Level 3 Sept 2010 onwardsUnit 3 Introduction to MarketingAssignment 1Lesson 3 Other marketing strategies for Nestle Now we will look at survival strategies and relationship marketing because they are other strategies that both nestle and Nestle use. For Nestle their survival strategies are: survival strategies; Mention in detail Nestle strategies such as branding (importance in influencing buyer behaviour, brand building, positioning, brand extension) look at resources on the U drive and also search the internet. U:Business StudiesStudentsBTEC Level 3 Sept 2010 onwardsUnit 3 Introduction to MarketingAssignment 1Lesson 3 And another strategy Nestle use is relationship marketing: relationship marketing Mention the definition, difference between transactional marketing and relationship marketing, value of lifetime customer and how Nestle has used relationship marketing look at resources on the U drive and also search the internet. U:Business StudiesStudentsBTEC Level 3 Sept 2010 onwardsUnit 3 Introduction to MarketingAssignment 1Lesson 3

Supriya Panjiyar Essays (766 words) - Hip Hop, Music, Gangsta Rap

Supriya Panjiyar Essays (766 words) - Hip Hop, Music, Gangsta Rap Supriya Panjiyar Professor Tracie Hernandez English Composition 1302 2/7/2017 Straight Outta Compton Based on true events which happened in Compton, California during 1988 , "Straight Outta Compton" is a 2015 American biographical film directed by Felix Gary Gray. Aldis Hodge (Mc Ren), Corey Hawkins (Dr.Dre), Jason Mitchell (Eazy-E), Neil Brown Jr. (DJ. Yella) and O'Shea Jackson Jr. (Ice Cube) act as members of the group N.W.A.(Nigga's with attitude). The film takes audience to the life journey of N.W.A. members, starting with their struggles of being an African American living in a ghettos to the height of their fames and richness . The f ilm opens in the late nineties in an econ omically depressed and violent C ompton when " gangsta " rap music was just evolving. R acial discrimination was still prevalent in United States even after a century of its abolishment. The introduction of the group membe rs in the movie gives audience a brief glimpse on the severity of economical and moral injustice and backwardness majority of African Americans were going through . Eric "Eazy-E" Wright, a small time drug dealer, Andre "Dr. Dre", a talented but unappreciated DJ at a loca l club and O'Shea "Ice-cube", a high school student who writes poems. Their introduction shows them dealing with abuse, h umiliation, amidst gang violence, drug trading, police harassment and poverty. That is not just their introduction but it is trying to show how many of the African Americans lived. Their talent and love for music is what brings them together and helps them become a successful and influential group called N.W.A. A scene in the movie has picturized clearly how African Americans faced police harassment and violence. In the scene all the group members are busy recording their rap music while "Dr. Dre" comes out to meet his wife. After a while everyone comes out of the studio and that is when four police officers comes to them and ask questioning them without any reason and orders them to lie on the ground with their hands on the back interlocked. During this scene the director of the film has played beautifully with his camera. The high angle shot on the group members has shown how helpless and small they looked before the police even though they had committed nothing wrong and the four police officers are shown like they are powerful people. The group members in response to these kinds of harassment do not choose a violent way rather they choose to be quiet and lets their music do the talking. They use their "microphone as their weapon". This is how civil disobedience is shown in the film, through rap music. Another scene in the film shows how the group members morally disobey the police. This scene in the film specifically shows civil disobedience. The group members just gets a warning from the FBI before their concert. The group members does not show any kind of violence during that time rather they stay calm. When they get on stage ice cube asks every audience to "raise their middle finger high on t he sky" addressing to the police officers in the back stage. And then Ice cube starts singing "F**k da police" expressing the reality of police brutality and his anger in the song. Civil disobedience is not only about speaking against what is wrong in a moral way, it is also about a waring the people abou t it which the group members successfully do in the film because when the members get arrested the audiences stands up for them against the police. The audiences are shown high up in the building while the police are shown on the ground in the scene. After they get arrested they sit in a conference with the media and when questioned about their music "Eazy-E" replies they are simply using their civil right by the first amendment which is freedom of speech. The first half of the film has shown civil disobedience. African Americans were discriminated even though slavery was long gone. African Americans were left behind in poverty because the government focused on enhancing the life style of the white race. While the discrimination prevailed African Americans faced

Free Essays on The Making Of An Army Of One

In response to our military’s racial animosity, the armed forces implemented affirmative action plans during the 1970s. President Clinton’s 1999 review of affirmative action confirmed that these plans have succeeded in expanding representation of minorities and women, especially as officers, while improving race relations, promoting integration, and enhancing overall combat readiness. The Army has been characterized as â€Å"the only institution in America in which whites are routinely bossed around by blacks† (Moskos 1). How has the Army achieved these results? Many analysts have emphasized its special institutional characteristics as a highly closed, controlled, hierarchical, disciplined system with the ability to establish, and attain compliance with organizational goals. In addition, some specific features of Army affirmative action efforts have contributed to their success: (1) The pool of applicants accepted for Army service is highly selective. A senior military officer shared â€Å"it’s harder to get into the All-Volunteer Forces than into most colleges.† Further contributing to quality is the fact that the Army has become the career of choice for many African-Americans. (2) Army affirmative action plans employ goals: promotion of minorities and women within the eligible pool is to occur in the same percentages as overall promotions from that pool. In many cases, the goals are not linked to timetables. In addition, the goals serve as presumptions, not mandates; promotion boards that fail to meet them are deemed to have done their job correctly if they can demonstrate due diligence. (3) All candidates for promotion are placed in a common pool and are subject to the same standards. Race can serve as a factor, but only when other differences are very small. Promotion is based on well-established performance criteria which are not abandoned in pursuit of affirmative action. (4)... Free Essays on The Making Of An Army Of One Free Essays on The Making Of An Army Of One In response to our military’s racial animosity, the armed forces implemented affirmative action plans during the 1970s. President Clinton’s 1999 review of affirmative action confirmed that these plans have succeeded in expanding representation of minorities and women, especially as officers, while improving race relations, promoting integration, and enhancing overall combat readiness. The Army has been characterized as â€Å"the only institution in America in which whites are routinely bossed around by blacks† (Moskos 1). How has the Army achieved these results? Many analysts have emphasized its special institutional characteristics as a highly closed, controlled, hierarchical, disciplined system with the ability to establish, and attain compliance with organizational goals. In addition, some specific features of Army affirmative action efforts have contributed to their success: (1) The pool of applicants accepted for Army service is highly selective. A senior military officer shared â€Å"it’s harder to get into the All-Volunteer Forces than into most colleges.† Further contributing to quality is the fact that the Army has become the career of choice for many African-Americans. (2) Army affirmative action plans employ goals: promotion of minorities and women within the eligible pool is to occur in the same percentages as overall promotions from that pool. In many cases, the goals are not linked to timetables. In addition, the goals serve as presumptions, not mandates; promotion boards that fail to meet them are deemed to have done their job correctly if they can demonstrate due diligence. (3) All candidates for promotion are placed in a common pool and are subject to the same standards. Race can serve as a factor, but only when other differences are very small. Promotion is based on well-established performance criteria which are not abandoned in pursuit of affirmative action. (4)...

Contemp poetry Essay Example | Topics and Well Written Essays - 1250 words - 1

Contemp poetry - Essay Example For many contemporary poets, Wordsworth remains an inspiration as they continue to investigate their own feelings of loss and aging. However, they necessarily approach the subject from a more contemporary viewpoint that has only become more abstracted and disorganized with the increased speed of modern life. These ideas can be traced through the poetry of Elizabeth Bishop, Frank O’Hara and Rae Armantrout. Elizabeth Bishop employs imagery of the modern world to highlight the loss of youth and loneliness that she finds in the contemporary madness of everyday life. For example, although â€Å"Filling Station† is a playful exchange exploring synonyms, she uses the everyday image of a backwater gas station to investigate ideas of deterioration, loss of beauty and the feeble attempts of someone to cling to the pure. Everything within the filling station is â€Å"oil-soaked, oil-permeated / to a disturbing, over-all / black translucency† (3-5) which is only interrupted by a small stack of colorful comic books that â€Å"lie / upon a big dim doily / draping a taboret† (23-25). The metaphysical question, â€Å"Why, oh why, the doily?† (30) emphasizes the sense of lost meaning that is embodied in the presence of something beautiful in this world of aged mechanics. While the sense of self is represented in the presence of the doily and the small plant near it, it is nearly entirely subsumed by the oil and grease that permeates everything in the shop, turning all into a postmodern concept of cyborg automaton. The loneliness of the self is complicated by feelings of guilt and shame only acquired through the passage of time and loss in Bishop’s â€Å"Five Flights Up.† While the guilt permeates the poem, the memory of its cause does not make an appearance, indicating the inescapable nature of it in the new world. Any joy in the bird’s or the dog’s greeting for the new day is

How technology can affect the movie buessines in the future Essay - 1

How technology can affect the movie buessines in the future - Essay Example The movie industry has always supported and promoted new technological advancements even back in 1920’s when sound was first incorporated in a movie. (1) Digital revolution will be the landmark development made in the history of home entertainment. One of the best technological improvements made in the movie business is digital technology. The biggest transition in the movie industry is the evolution of digital technology. Digital technology is considered to be the revolution in every field of the film industry. One of the most important advantages of digital revolution is allowing people to download movies at any time through the internet broadband. Digital cinema provides clarity, high quality experience and greater flexibility in programming the details. Digital film making required the theaters to also adopt digital technology which would enhance the quality of film, provide the best visuals while being cost effective. (2) Audio programming, post production and exhibition continue to be digital and there is rapid progression towards digital technology in the movie industry. Visual effects, editing are also predominantly handled by digital technology. One can expect the actual film making process to become completely digitalized in the coming years .Moviemakers would be able to create movies and sell and distribute them on the internet. (2) Many movie directors and producers fear that the new technology can be a threat as people will easily download movies even before they are released rather than going to theaters.The movie and audio industry has already been negatively affected in the last few years. Since more people are listening to MP3’s and other digital formats, the use of CD’s are seldom and cassettes no longer used. The impact is more for the audio industry as music is downloaded free from many websites. With the introduction of Blu Ray technology, people can download movies and can watch them in excellent sound