Abstract: A computer-implemented method may comprise receiving proposals to mutate a data stored in a distributed and replicated file system coupled to a network, the distributed and replicated data system comprising a plurality of nodes, each comprising a server. A metadata service maintains and updates a replica of a namespace of the distributed and replicated file system and coordinates updates to the data by generating an ordered set of agreements corresponding to the received proposals, the ordered set of agreements specifying an order in which the nodes are to mutate data stored in data nodes and cause corresponding changes to the state of the namespace. For each agreement in the generated ordered set of agreements, a corresponding writers list may be provided that comprises an ordered list of nodes to execute the agreement and make corresponding changes to the namespace.

Abstract: A computer-implemented method may comprise providing a first executed agreement cache in a first data center and a second executed agreement cache in a second data center; receiving agreements on proposals to create or make changes to files stored in the first and second data centers; storing metadata of the files referred to by the received agreements the first and/or second executed agreement caches; maintaining the first and second executed agreement caches synchronous with one another before the files referred to by the received agreements are created or changed; creating or making changes to the file referred to by the received agreements only after the first and second executed agreement caches have been synchronized; and searching the first and/or second executed agreement caches for updated metadata whenever requests for data of files stored in the first or second data centers are received in the first or the second data centers and, responsive to the received requests, providing data corresponding to

Abstract: A first plurality of replicated state machines may execute a sequence of ordered agreements to make mutations to a data stored in a first data storage service of a first type. A second plurality of replicated state machines may execute the sequence of ordered agreements to make mutations to the data stored in a second data storage service of a second type. First metadata of the mutated data stored in the first data storage service may then be received and stored, and second metadata of the mutated data may be stored in the second data storage service. The stored first and second metadata may then be compared when the data have settled, and a selected action carried out based upon the result of the comparison.

Abstract: A computer-implemented method may comprise receiving proposals to mutate a data stored in a distributed and replicated file system coupled to a network, the distributed and replicated data system comprising a plurality of nodes, each comprising a server. A metadata service maintains and updates a replica of a namespace of the distributed and replicated file system and coordinates updates to the data by generating an ordered set of agreements corresponding to the received proposals, the ordered set of agreements specifying an order in which the nodes are to mutate data stored in data nodes and cause corresponding changes to the state of the namespace. For each agreement in the generated ordered set of agreements, a corresponding writers list may be provided that comprises an ordered list of nodes to execute the agreement and make corresponding changes to the namespace.

Abstract: A computer-implemented method may comprise receiving proposals to mutate a data stored in a distributed and replicated file system coupled to a network, the distributed and replicated data system comprising a plurality of nodes, each comprising a server. A metadata service maintains and updates a replica of a namespace of the distributed and replicated file system and coordinates updates to the data by generating an ordered set of agreements corresponding to the received proposals, the ordered set of agreements specifying an order in which the nodes are to mutate data stored in data nodes and cause corresponding changes to the state of the namespace. For each agreement in the generated ordered set of agreements, a corresponding writers list may be provided that comprises an ordered list of nodes to execute the agreement and make corresponding changes to the namespace.

Abstract: A distributed system that implements an online exchange may comprise a plurality of server nodes, each of which being configured to receive exchange transaction proposals from customers of the online exchange over a computer network and each being configured to store a copy of a blockchain distributed ledger of completed exchange transactions. A consensus engine may be coupled, over the computer network, to the plurality of server nodes and may receive a plurality of exchange transaction proposals from the plurality of server nodes. The consensus engine may be being further configured to achieve consensus on the plurality of exchange transaction proposals and to generate, in response, an ordering of agreed-upon exchange transaction proposals that includes the plurality of exchange transaction proposals on which consensus has been reached.

Abstract: A computer-implemented method and distributed system for maintaining consistency of client applications on a plurality of server nodes may comprise providing a first and second versions of a distributed coordination engine (DConE). The first version of the DConE may receive proposals, reach agreements thereon and generate a first ordering of agreements that specifies an order in which the client applications are to execute the agreed-upon proposals and correspondingly update their respective states. A ChangeVersion proposal may then be processed by the first version of the DConE, whereupon the first version of the DConE may stop reaching any further agreements. A second version of the DConE may then take over reaching agreements on the proposals and generate a second ordering of agreements, beginning with the agreed-upon ChangeVersion proposal.

Abstract: A computer-implemented method of migrating metadata from a donor filesystem D having a rooted tree structure to a beneficiary filesystem B while processing commands that operate on the metadata may comprise, while a command to operate on the metadata is not received, replicating the donor filesystem D at the beneficiary filesystem B by sequentially copying metadata of nodes of the donor filesystem D to the beneficiary filesystem B. When a command is received to operate on the metadata, the command may be executed at both the donor filesystem D and the beneficiary filesystem B when all arguments of the command are present in both the donor filesystem D and the beneficiary filesystem B. When none of arguments are present in the beneficiary filesystem B, the command may be executed at the donor filesystem D only. When only some of the arguments are present in the beneficiary filesystem B, the command may be enqueued at least until all arguments of the command are present in the beneficiary filesystem B.

Abstract: A computer-implemented method may comprise providing a first executed agreement cache in a first data center and a second executed agreement cache in a second data center; receiving agreements on proposals to create or make changes to files stored in the first and second data centers; storing metadata of the files referred to by the received agreements the first and/or second executed agreement caches; maintaining the first and second executed agreement caches synchronous with one another before the files referred to by the received agreements are created or changed; creating or making changes to the file referred to by the received agreements only after the first and second executed agreement caches have been synchronized; and searching the first and/or second executed agreement caches for updated metadata whenever requests for data of files stored in the first or second data centers are received in the first or the second data centers and, responsive to the received requests, providing data corresponding to

Abstract: A distributed system that implements an online exchange may comprise a plurality of server nodes, each of which being configured to receive exchange transaction proposals from customers of the online exchange over a computer network and each being configured to store a copy of a blockchain distributed ledger of completed exchange transactions. A distributed coordination engine may be coupled, over the computer network, to the plurality of server nodes and may receive a plurality of exchange transaction proposals from the plurality of server nodes. The distributed coordination engine may be being further configured to achieve consensus on the plurality of exchange transaction proposals and to generate, in response, an ordering of agreed-upon exchange transaction proposals that includes the plurality of exchange transaction proposals on which consensus has been reached.

Abstract: A computer-implemented method may comprise receiving proposals to mutate a data stored in a distributed and replicated file system coupled to a network, the distributed and replicated data system comprising a plurality of nodes, each comprising a server. A metadata service maintains and updates a replica of a namespace of the distributed and replicated file system and coordinates updates to the data by generating an ordered set of agreements corresponding to the received proposals, the ordered set of agreements specifying an order in which the nodes are to mutate data stored in data nodes and cause corresponding changes to the state of the namespace. For each agreement in the generated ordered set of agreements, a corresponding writers list may be provided that comprises an ordered list of nodes to execute the agreement and make corresponding changes to the namespace.

Abstract: First and second pluralities of replicated state machines may execute a sequence of ordered agreements to make mutations to data stored in first and second data storage services of first and second types, respectively. First and second metadata of the mutated data stored in the first and second data storage services may then be received and stored. The first and second data storage services may then be synchronized using the received first and second metadata to determine when the data stored in the first and second data storage services have both settled after having mutated according to a predetermined agreement of the sequence of ordered agreements. A comparison of the stored first and second metadata may then be carried out when the data stored in the first data storage service and the data stored in the second data storage service have settled according to the predetermined agreement.

Abstract: A computer-implemented method and distributed system for maintaining consistency of client applications on a plurality of server nodes may comprise providing a first and second versions of a distributed coordination engine (DConE). The first version of the DConE may receive proposals, reach agreements thereon and generate a first ordering of agreements that specifies an order in which the client applications are to execute the agreed-upon proposals and correspondingly update their respective states. A ChangeVersion proposal may then be processed by the first version of the DConE, whereupon the first version of the DConE may stop reaching any further agreements. A second version of the DConE may then take over reaching agreements on the proposals and generate a second ordering of agreements, beginning with the agreed-upon ChangeVersion proposal.

Abstract: A distributed system that implements an online exchange may comprise a plurality of server nodes, each of which being configured to receive exchange transaction proposals from customers of the online exchange over a computer network and each being configured to store a copy of a blockchain distributed ledger of completed exchange transactions. A distributed coordination engine may be coupled, over the computer network, to the plurality of server nodes and may receive a plurality of exchange transaction proposals from the plurality of server nodes. The distributed coordination engine may be being further configured to achieve consensus on the plurality of exchange transaction proposals and to generate, in response, an ordering of agreed-upon exchange transaction proposals that includes the plurality of exchange transaction proposals on which consensus has been reached.

Abstract: A cluster of nodes implements a single distributed file system comprises at least first and second data centers and a coordination engine process. The first data center may comprise first DataNodes configured to store data blocks of client files, and first NameNodes configured to update a state of a namespace of the cluster. The second data center, geographically remote from and coupled to the first data center by a wide area network, may comprise second DataNodes configured to store data blocks of client files, and second NameNodes configured to update the state of the namespace. The first and second NameNodes are configured to update the state of the namespace responsive to data blocks being written to the DataNodes. The coordination engine process spans the first and second NameNodes and coordinates updates to the namespace stored such that the state thereof is maintained consistent across the first and second data centers.

Abstract: In one embodiment of the present invention, a replicated state machine comprises a proposal manager, an agreement manager, a collision/back-off timer and a storage reclaimer. The proposal manager facilitates management of proposals issued by a node of a distributed application for enabling coordinated execution of the proposals by all other nodes of the distributed application. The agreement manager facilitates agreement on the proposals. The collision/back-off timer precludes repeated pre-emptions of rounds in attempting to achieve agreement on the proposals. The storage reclaimer reclaims persistent storage utilized for storing at least one of proposal agreements and the proposals.

Abstract: A computer-implemented method of deploying a membership of nodes in a distributed computing system may comprise selecting nodes to be part of a membership of nodes; creating a membership task identifying a membership creator node as the node that is creating the membership and comprising a membership target identifying at least one node of the distributed computing system that is to become a member of the membership; and creating a beacon configured to send a create membership message to each identified node, the create membership message comprising at least an identity of the membership task and an identification of the membership. Upon receiving a response from a node in the membership target, the node from which the response was received may be removed from the beacon. The membership may be deployed when a response has been received from each of the nodes identified in the membership target.

Abstract: A cluster of nodes in a distributed file system may include; at least two namenodes, each coupled to a plurality of data nodes and each configured to store a state of a namespace of the cluster and each being configured to respond to a request from a client while other(s) of the namenodes are responding to other requests from other clients; and a coordination engine coupled to each of the namenodes. The coordination engine may be configured to receive proposals from the namenodes to change the state of the namespace by replicating, deleting and/or adding data blocks stored in the data nodes and to generate, in response, an ordered set of agreements that specifies an order in which the namenodes are to change the state of the namespace. The namenodes are configured to delay making changes thereto until after the ordered set of agreements is received from the coordination engine.

Abstract: A cluster of nodes in a distributed file system may include; at least two namenodes, each coupled to a plurality of data nodes and each configured to store a state of a namespace of the cluster and each being configured to respond to a request from a client while other(s) of the namenodes are responding to other requests from other clients; and a coordination engine coupled to each of the namenodes. The coordination engine may be configured to receive proposals from the namenodes to change the state of the namespace by replicating, deleting and/or adding data blocks stored in the data nodes and to generate, in response, an ordered set of agreements that specifies an order in which the namenodes are to change the state of the namespace. The namenodes are configured to delay making changes thereto until after the ordered set of agreements is received from the coordination engine.

Abstract: A computer-implemented method may comprise processing agreements received over a computer network at a first replicated state machine deployed on processes belonging to a first membership in an order defined by a first globally ordered set of agreements associated with the first membership; receiving an agreement to change membership that is configured to cause the first replicated state machine to be deployed on processes belonging to a second membership that is associated with a second globally ordered set of agreements; and processing the agreement to change membership at a point within the first globally ordered set of agreements.