-
Notifications
You must be signed in to change notification settings - Fork 0
Glossary
A set of nodes responsible for one or more services.
A responsibility handled by a set of distributed service members, each responsible of a small portion of the service. The data required by each service members may be replicated from a master to slaves to increase redundancy. Also referred to simply as a service (a service is not necessarily consistent, and therefore does not necessarily replicate).
A term used to describe a distributed a type of store in which all messages modifying the data on master replica are also applied on slave replicas in order to replicate the data, creating redundancy and increasing fault tolerance.
The consistency state is a set of multiple possible states describing the integrity of the data in the store based on the content of the transaction logs. See the "Service Member Statuses and Consistency States" section for more information.
The consistent state, also known as the OK state, is one of multiple replication consistency state in which a given service member's log of all applied transaction reflects the data present in the store, therefore assuring the integrity of the data on the current service member.
A timestamp used to express the exact point in time at which every older transaction is guaranteed to be committed in the storage and written in the transaction logs. This timestamp is constantly updated, as log records are appended in the transaction log.
A log entry describing a portion of a transaction, carried by a single message. Log records are written in the transaction logs.
A transaction container for network exchange between multiple service members.
An operation that modifies a single record in the store.
A set of one or more mutation operations that modifies the store. Also sometimes referred to simply as Transaction, which is a more general term describing any operation applied on the store. All mutations are applied together, so that they will all succeed or all fail.
A server process with a unique network ip and port combination. Multiple service member may target a single node, allowing a node to be responsible for multiple shards.
All data associated with a given shard, needed by service members to operate properly. A replica can either be master or slave. Once a service member is created with its replica, the replica becomes a master. Otherwise, the replica stays a slave, and it simply replicates data from the master. A set of replicas associated with a given shard have at most a single master.
-
Master Replica: A term used to describe the main service member responsible for a specific portion of the storage (also referred to as master). The transactions contained in messages are originally applied on the master service member. The master plays the role of the server in the replication session, acting as the source of the replication.
-
Slave Replica: A term used to describe a replica targeting a master service member on which the transaction contained in messages are replicated (also referred to as slave). The slave is responsible for initiating the replication session with the proper master, acting as the target of the replication.
A service member represents the membership of a given node to a service. Every service member is responsible of a specific shard, which will handle a portion of the cluster’s traffic. A single node may be assigned to multiple service members.
A shard is a token range defined by an upper bound and a lower bound. It is sometimes used to refer to the data associated with the shard or to describe a fragment of the distributed store.
A term used to describe an abstract form of data storage.
A process used to copy a store’s content from a node to another for increased availability, by applying transactions on slave replica exactly as they are performed on the master replicas.
A token is a non-unique computed ID (generally through hashing) designed to associated a given task to a position in the hash ring. Each position is associated to a shard, and each shard is associated to a node, allowing the service to be distributed. More info on tokens & shards.
A log of all transactions. See the Transaction logs section for details.
A special kind of message carrying a mutation transaction operation to apply on the consistent store.