This is a Paxos term which identifies a node that can vote on a proposal. In Content Distribution an acceptor is the recipient node for an incoming Agreement message initiated by a Proposer.

An legacy product which, due to it being implemented as a proxy, enabled more granular authorization for Subversion than is possible by Apache alone.

Product which provides a single solution to fully protect valuable intellectual property across widely distributed Subversion and Git repositories.

A node in a replication group which has been enabled to request changes be made to a set of repositories. It may or may not be a voter. If it is not a voter then it does not play a role in scheduling the changes it requests.

An Active node which also votes on the order in which transactions are played out.

Provides administrators with a UI based mechanism for controlling the application.

Each step that the DConE replicated state machine executes is called an agreement.

Individual agreement steps of the replicated state machine are executed under the purview of one or more Agreement Managers.

Application program interface.

Verifies the credentials presented - essentially proving you are who you say you are.

Defines, with rules, what users are allowed to do on a system.

See Authentication

See Authorization

Objects changed in a batch of user transactions are replicated in a single replication transaction. Irrespective of whether a replication is transactional or batch based only the part of the transaction that is of interest to that site is applied at the receiving site. Batched transactions can utilize the self-healing features. For example, the network connection can be disabled between the distinguished node site and the other sites on a periodic basis (e.g. twice a day). When the network is reconnected, the remote replicator will reach out to the distinguished node to pick up all of the commits that were done at the distinguished node site during the network outage.
Only relevant to SVN MultiSite 4.x or earlier.

A transaction is bypassable if all nodes in Replication Group fail on this exact transaction.
Only relevant to SVN MultiSite 4.x or earlier.

See Certificate Authority

See Change Block Tracking.

The implementation of Git written in C. This is not to be confused with cgit, a fast web interface for the git version control system. For GitMS you need to install the matching binaries for your version of GitMS.

A community-supported, free and open source operating system based on Red Hat Enterprise Linux. It exists to provide a free enterprise class computing platform and strives to maintain 100% binary compatibility with its upstream distribution. CentOS stands for Community ENTerprise Operating System.

A body which issues digital certificates.
A certificate is a digitally signed statement from one entity (the issuer), saying that the public key (and some other information) of another entity (the subject) has some specific value. These trusted certificates can then be used to create secure connections to a server.

A technology which allows the incremental backup of VMs. This means that only the blocks which have changed are backed up, rather than every block. If CBT is enabled make sure to account for it, for example when restoring repositories.

Clustering products are implemented as a transparent gateway between the clients and the servers, and acts as a network proxies for the local server. There is a one-to-one relationship between replicator and SVN Server. With clustering, a load balancer directs a user to one node in the cluster but clients write activity must be replicated from one node to the others in the cluster.

An object which transfers data between software application subsystems.

Distributed Coordinated Engine, the software engine underlying replication. Read the Whitepaper on our DConE technology.

An object whose principle job is obtaining agreements on the ordering of proposals as part of the DConE engine. Each DSM has a membership of nodes. Each node can have one or more of the Paxos roles (Proposer, Acceptor, Learner).

Used for unique identification in LDAP.

A node whose vote is slightly more than 1 (also known as a Tiebreaker).

See Distinguished Name.

See Deterministic State Machine.

See Data Transfer Object.

The combined set of nodes that have been inducted together.

A tool which allows one or more lost nodes to be removed from membership, allowing the remaining nodes to continue replicating using a new membership. This is a permanent change to the replication system which cannot be undone. EMR is only necessary if the remaining nodes are missing quorum from 1 or more voting memberships.

See Emergency Reconfiguration.

Flume is an Apache product for efficiently collecting, aggregating and moving large amounts of log data.

See Fully Qualified Domain Name.

A Subversion filesystem implementation.

A domain name that specifies its exact location within the tree hierarchy of the DNS. It is unambiguous.

A type of automatic memory management. It allows system resources to be freed up by removing objects that are no longer required.

An open source code review tool which integrates closely with Git. It was named after the Dutch designer Gerrit Rietveld.

Allows Gerrit events to be replicated to and from any location with no single point of failure.

An open source version control system.

Allows Git repositories to be replicated to and from any location with no single point of failure and no downtime.

An access control layer on top of Git which can be integrated with Git MultiSite.

The ordered number of an agreement associated with a DSM.

Each node is assigned a GUID when added to a Replication Group. The nodes identify each other by their GUIDs.

A feature that allows changes to a previously defined Replication Group.

Growl messages provide immediate feedback in response to a user’s interactions with the Admin UI. They appear in the top right-hand corner of the screen and persist for a brief period or until the screen is refreshed or changed.

See Global Sequence Number

See Globally Unique Identifier

A node that is used as part of a repository repair procedure. The helper node is suspended from receiving updates to the repositories in the replication group so that a copy of the repositories can be transferred (rsync’ed etc) to the damaged node.

Provides continuous hot backup, while making failover and disaster recovery automatic and transparent for both developers and administrators.

Scripts triggered by specific repository events, they allow administrators to have more control over their repository environment.

A node yet to be inducted.

The node where you run the product install program. This is the first node in your ecosystem. This term is only relevant to SVN MultiSite 4.x or earlier.

The Java library from Eclipse. This is installed as part of GitMS.

Browser-based bug, issue, task and defect tracking system, and project management software solution used for open source and enterprise projects. JIRA isn’t an acronym, it’s a contraction of 'Gojira'. When listing product features and bug fixes we’ll usually add a reference code for the corresponding JIRA issue.

An open source automation server.

See Knowledgebase.

A network authentication system.

The Knowledgebase contains updates and product information.

See Lightweight Directory Access Protocol.

This is a Paxos term that identifies any node that wants to learn the outcome of an Agreement step. In Content Distribution a learner is any node that has a repository and needs to have agreements delivered and executed.

An Internet protocol that enables client programs to access distributed directory services.

A mechanism to enforce access limits. Locks need to be the same on all connected nodes.

In the context of node distinction, master is a legacy term used to describe the "primary" instance. The "primary" instance is "read-write" while the "secondary" instance is "read-only".

In the context of a replication model, a legacy term used to describe "primary-secondary" replication.

A term that is used to describe sets of nodes that are connected to each other as part of a replication group (or other DSM).

A server on which a replicator product (e.g. Git MultiSite) is installed.

All replicas are functionally equivalent copies of each other. The theory and practice is that if two or more nodes start with identical copies of data and all changes to that data are applied in the same order to each copy, at the end of X transactions, the copies will all remain equivalent.

A fan of Sheffield Wednesday Football Club.

A node on which repositories receive updates from other nodes, but does not permit any modifications to be requested locally (cannot propose changes). This node type is currently deprecated and should no longer be used.

A passive node which also takes part in the vote for transaction ordering agreement but cannot propose any changes.

The preferences file is used in SVN MultiSite 4.2 or earlier (or the old CVS MultiSite product). prefs.xml contains configuration information and is specific to each node. The file is located in svn-replicator/config (or cvs-replicator/config). See the knowledgebase article Prefs.xml Basic Syntax.

In the context of node distinction, the "primary" instance is "read-write" while the "secondary" instance is "read-only".

Similar to the legacy term "master-slave". Primary-secondary replication indicates the "primary" instance is "read-write" while the "secondary" instance is "read-only".

This is a Paxos term which identifies a node which can propose changes. In Content Distribution, as well as proposing changes the proposer is also involved in conflict resolution as part of the voting process. Resolution comes from interactions between proposers and accepters and the losers are expect to re-propose.

When activating a membership or Replication Group, new nodes start in quarantined mode. This means they will not participate in replication until they gain membership. This is to allow for testing of the new node’s SCM configuration before executing replicating transactions. Only relevant to SVN MultiSite 4.x or earlier.

Any subset of a membership that can reach agreement to determine transaction order. In the case of an even number of nodes, the distinguished node (tiebreaker) settles a conflict.

As a result of a failed write operation a DSM (or node in the MS 4.x product or earlier) can go into read-only mode. Write operations cannot proceed until the problematic transaction has been fixed. This can be Global (on all nodes) or local (just for users at this node).

In disaster recovery the RPO is the time before a system failure at which the recovered system will restart. An RPO of 2 hours means that, in the event of a failure, the system would be brought back to the point that is no more than 2 hours before the failure occurred.

In disaster recovery the RTO is the time in which the system should be recovered from a failure. With an RTO of 2 hours, the system should be recovered no more than two hours after the failure occurred. High Availability offers an RTO approaching 0, meaning that recovery is nearly immediate.

See Read only

An SVN/Git repository that is an exact equivalent or copy of another SVN/Git repository.

A collection of repositories that share a membership and are therefore all present on the same set of nodes.

A replicator is synonymous with an installed instance of the product or "node".

A collection of files and directories, grouped together in a specific database which also records a complete history of all the changes that have ever been made to these files.

In Access Control Plus, resources are repositories that have been activated by being associated with a repository template.

Representational State Transfer Application Program Interface.

See Recovery Point Objective.

A file copying tool.

See Recovery Time Objective.

See Software Configuration Management

In the context of node distinction, the "secondary" instance is "read-only" while the "primary" instance is "read-write".

Secure Hash Algorithm 1. This is a 160-bit hash value normally rendered as a 40 digit hexadecimal number. Although originally developed for security purposes, SHA1 is used in Git to ensure data hasn’t changed, for example due to accidental corruption.

A sidelined repository replica is a replica that will no longer get updates from other replicas in the family. The other replicas will not preserve operations for a sidelined replica thereby preventing them from running out of memory. Replicas become sidelined if they are out of communication for an extended amount of time and the number of outstanding agreements exceeds a tunable maximum. Sidelined replicas can be brought back into normal operation via a repair procedure.

A physical location containing servers or virtual machines where one or more replication products are installed.

The field dedicated to tracking and controlling changes in the software. Products that support two popular SCM solutions: SVN and Git.

Secure Shell (SSH) is a means of getting secure access to a remote computer. It can be used for authentication.

Secure Socket Layer (SSL) is a commonly used encryption protocol.

An open source version control system.

See Subversion.

Product which allows SVN events to be replicated to and from any location with no single point of failure and no downtime.

A special transaction that will prevent further write transactions from happening. A replicator will process transactions normally up to this special transaction and the node will enter a "stopping" state. This causes all nodes to stop after processing up through the exact same GSN. A Synchronized Stop is typically actioned prior to administrative tasks such as a product upgrade. This transaction requires Unanimous Agreement in order to complete. Even if one of the nodes is not available, the other nodes will enter the stopping state and prevent write transactions. Unanimous Agreement means that all nodes need to be available for a synchronized stop to complete.

For up to date information see the GitHub page for systemd news.

A bash script that is provided in your product installation to collect product meta-data in case you need to report an issue to the Support team.

A node which gets to cast the determining vote if there are an even number of voters in the Replication Group. The Tiebreaker can be applied any type of voter node. This term is specific to 4.x and earlier.
In MSP, the tiebreaker role is assigned on a per-Replication Group basis and is not one specific node.

User interface. The console with which users interact.

A 128-bit identifier that is created in such a way that no other identifier will ever be its equal (see GUID).

See Universally unique identifier.

A Voter only node doesn’t store any repository data, it’s only purpose is to cast a vote on transaction ordering. Voter only nodes are currently deprecated and should no longer be used.

Web-based Distributed Authoring and Versioning, or WebDAV is a set of extensions to the Hypertext Transfer Protocol (HTTP) that allows computer-users to edit and manage files collaboratively on remote web servers.

A symbol used to replace or represent one or more characters.

Extensible Markup Language.

Dr Aahlad, chief scientist and is recognized as a authority on distributed computing in which he currently holds 3 patents.

A software project of Apache which is not relevant to these ALM products but is a word which begins with Z (and there aren’t many). It is however relevant to our Big Data products.