Patent Grant
9262229
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
The present invention is generally related to computer cluster environments, and data and resource management in such environments, and is particularly related to a system and method for supporting service level quorum in a data grid cluster.
Modern computing systems, particularly those employed by larger organizations and enterprises, continue to increase in size and complexity. Particularly, in areas such as Internet applications, there is an expectation that millions of users should be able to simultaneously access that application, which effectively leads to an exponential increase in the amount of content generated and consumed by users, and transactions involving that content. Such activity also results in a corresponding increase in the number of transaction calls to databases and metadata stores, which have a limited capacity to accommodate that demand.
In order to meet these requirements, a distributed data management and cache service can be run in the application tier so as to run in-process with the application itself, e.g., as part of an application server cluster. However, there is a need to be able to configure and manage the application server cluster for effectively providing the distributed data management and cache service to the users. These are the generally areas that embodiments of the invention are intended to address.
In accordance with an embodiment, a system and method is described for use with a data grid cluster, for supporting service level quorum in the data grid cluster. The data grid cluster includes a plurality of cluster nodes that support performing at least one service action. A quorum policy, defined in a cache configuration file associated with the data grid cluster, can specify a minimum number of service members that are required in the data grid cluster for performing the service action. The data grid cluster uses the quorum policy to determine whether the service action is allowed to be performed, based on a present state of the plurality of cluster nodes in the data grid cluster.
In accordance with an embodiment, as referred to herein a “data grid cluster”, or “data grid”, is a system comprising a plurality of computer servers which work together to manage information and related operations, such as computations, within a distributed or clustered environment. The data grid cluster can be used to manage application objects and data that are shared across the servers. Preferably, a data grid cluster should have low response time, high throughput, predictable scalability, continuous availability and information reliability. As a result of these capabilities, data grid clusters are well suited for use in computational intensive, stateful middle-tier applications. Some examples of data grid clusters, e.g., the Oracle Coherence data grid cluster, can store the information in-memory to achieve higher performance, and can employ redundancy in keeping copies of that information synchronized across multiple servers, thus ensuring resiliency of the system and the availability of the data in the event of server failure. For example, Coherence provides replicated and distributed (partitioned) data management and caching services on top of a reliable, highly scalable peer-to-peer clustering protocol, with no single points of failure, and can automatically and transparently fail over and redistribute its clustered data management services whenever a server becomes inoperative or disconnected from the network.
Data Grid Cluster Services
In accordance with an embodiment, the functionality of a data grid cluster is based on using different cluster services. The cluster services can include root cluster services, partitioned cache services, and proxy services. Within the data grid cluster, each cluster node can participate in a number of cluster services, both in terms of providing and consuming the cluster services. Each cluster service has a service name that uniquely identifies the service within the data grid cluster, and a service type, which defines what the cluster service can do. Other than the root cluster service running on each cluster node in the data grid cluster, there may be multiple named instances of each service type. The services can be either configured by the user, or provided by the data grid cluster as a default set of services.
In accordance with various embodiments, servers that store data within the data grid cluster can support a set of quorum features. The quorum features can be used to make decisions on physical resource planning (e.g. server, RAM memory, etc), and to determine how the data grid cluster behaves in the absence of such physical resources. As referred to herein, a quorum refers to the minimum number of service members in a cluster that is required before a particular service action is allowed or disallowed. By way of illustration, during deployment, the physical resources of the data grid cluster can be selected according to a plan that is based on the amount of data and requests that will be processed by the grid. For example, a data grid cluster can have 10 servers with totally 10 gigabytes of random access memory (RAM) for handling the grid computing. However, in the event that a subset of those servers and/or RAM fail, it may be important to implement a system to manage how the data grid cluster will behave in their absence. In accordance with an embodiment, the quorum feature enables the data grid cluster to manage the cluster processing in the event of losing some of those resources.
Service Level Quorum Features
In accordance with an embodiment, the quorum features enable the configuring of the data grid cluster at service level. The service level quorum involves resource planning and provides policies and behaviors per service (e.g. cache writes, proxy connects, distribution, etc) when the data grid cluster physical resources (e.g. number of servers, RAM/cache etc.) are unavailable.
In accordance with an embodiment, quorums can control service behavior at different service member levels, and help ensure an optimal cluster and cache environment for a particular application or solution. The quorum policy can define different types of quorum thresholds that provide benefits with respect to a particular service. Quorums are beneficial because they provide assurances on how a cluster should behave when certain member thresholds (e.g., resource thresholds) are reached.
In accordance with an embodiment, there can be a cluster quorum policy for the root cluster service running on each cluster node in the data grid cluster, a partitioned quorum policy for the partitioned cache service and a proxy quorum policy for the proxy service. Quorum policies can be provided as out of the box membership based policies per service. Additionally, a pluggable interface can be provided for enabling custom policies and behaviors.
Quorum Policies for Root Cluster Services
In accordance with an embodiment, quorum policies for root cluster services, or cluster quorum, can enable management of cluster/machine network membership. For example, the cluster quorum can control the ability of a machine to join and become a member of the cluster and get evicted from the cluster. In accordance with an embodiment, the cluster quorum can control what happens when members connect to the cluster, and when members leave the cluster. A root cluster service is automatically started when a cluster node joins a cluster, and typically there is exactly one root cluster service running on each cluster node. The root cluster service keeps track of the membership and services in the cluster. For example, the root cluster service is responsible for detecting other cluster nodes, monitoring the failure or death of other cluster nodes, and can be responsible for registering the availability of other services in the cluster.
The cluster quorum feature is useful in environments where network performance varies. For example, in some environments intermittent network outages may cause a high number of cluster members to be removed from the cluster. Using the cluster quorum, a certain number of members can be maintained during the outage, and will be available once the network recovers. This behavior also minimizes the manual intervention required to restart members. Naturally, requests that require cooperation by the nodes that are not responding will not be able to complete, and will be either blocked for the duration of the outage or will be timed out.
In accordance with an embodiment, the cluster quorum can be specified generically across all members or constrained to members that have a specific role in the cluster, such as client or server members. In one embodiment, a <role-name> element in “member-identity” section of a cache configuration file can be used to define role names for cluster members. A timeout survivor quorum threshold can be configured in an operational override file using the <timeout-survivor-quorum> element and optionally the role attribute. This element can be used within a <cluster-quorum-policy> element. Listing 1 illustrates configuring the timeout survivor quorum threshold to ensure that 5 cluster members with the server role are always kept in the cluster while removing suspect members, in accordance with an embodiment.
Quorum Policies for Partitioned Cache Services
In accordance with an embodiment, quorums can be used by the distributed data management system to support partitioned cache services. For example, a partitioned cache backup quorum can require at least five storage-enabled members before the partitioned cache service is allowed to back up partitions.
As described above, the different quorums can be used to indicate at what service member levels the different service operations are best performed, given the intended usage and requirements of a distributed cache. For example, a small distributed cache may only require three storage-enabled members to adequately store data and handle projected request volumes, while a large distributed cache may require ten or more storage-enabled members to adequately store data and handle projected request volumes. Optimal member levels can be tested during development and then set accordingly to ensure that the minimum service member levels are provisioned in a production environment.
Some considerations include that, if the number of storage-enabled nodes running the service drops below the configured level of read or write quorum, then the corresponding client operation is rejected and an exception thrown. If the number of storage-enabled nodes drops below the configured level of distribution quorum, some data can become “endangered,” or without backup until the quorum is reached. Additionally, dropping below the restore quorum can cause an operation to be blocked until the quorum is reached; otherwise, the operation will be timed out.
In accordance with an embodiment, partitioned cache quorums can be configured in a cache configuration file within the <partitioned-quorum-policy-scheme> element. The element can be used within a <distributed-scheme> element. Listing 2 illustrates configuring thresholds for the partitioned cache quorums, in accordance with an embodiment. In one embodiment, the threshold values indicate the minimum amount of service members that are required to perform the operation.
The <partitioned-quorum-policy-scheme> element also supports using scheme references. As illustrated in the embodiment shown in Listing 3, a <partitioned-quorum-policy-scheme>, with the name partitioned-cache-quorum, can be referenced from within the <distributed-scheme> element.
Quorum Policies for Proxy Services
In accordance with an embodiment, a proxy service can be used in a data grid cluster when it is desirable to have clients running outside the cluster. For example, the proxy service can be used in those cases where there may be thousands of client processes, where the clients are not running on the Java platform, or where a greater degree of coupling is desired. In one embodiment, the proxy service allows connections, for example TCP connections, from clients that run outside the cluster to the data grid.
In accordance with an embodiment, the proxy quorum can be used to ensure enough proxy service members are available to optimally support a given set of TCP clients. For example, a small number of clients may efficiently connect to a cluster using two proxy services, while a large number of clients may require three or more proxy services to efficiently connect to a cluster. Optimal levels can be tested during development and then set accordingly to ensure that the minimum service member levels are provisioned in a production environment.
In accordance with an embodiment, a connection quorum threshold can be configured in a <proxy-quorum-policy-scheme> element in the cache configuration file. The element can be used within a <proxy-scheme> element. Listing 4 illustrates configuring the connection quorum threshold to ensures that three proxy service members are present in the cluster before the proxy service is allowed to accept TCP client connections, in accordance with an embodiment.
The <proxy-quorum-policy-scheme> element also supports using scheme references. As illustrated in the embodiment shown in Listing 5, a <proxy-quorum-policy-scheme>, with the name proxy-quorum, is referenced from within the <proxy-scheme> element.
Enabling Custom Action Policies
In accordance with an embodiment, custom action policies can be used instead of the default quorum policies, in order to support different cluster services in the data grid. The custom policies specified in user applications can incorporate arbitrary external states to provide fine grained resource-driven control of the services, since the user applications are in the best position to manage these external states.
In accordance with an embodiment, the pluggable interface allows the users to implement custom policies to control the behaviors and features of a data grid cluster. One exemplary pluggable interface is a com.tangosol.net.ActionPolicy interface, provided in the Oracle Coherence data grid cluster.
In accordance with an embodiment, users can specify different types of custom action policies for a data grid. One exemplary custom action policy defines that cache requests are disallowed during a weekly maintenance window for the data grid cluster. Another exemplary custom action policy is a resource-driven policy that allows no write operations unless a database is available. Another exemplary use case allows a user to define externally-triggered policies that make the data grid cluster available unless certain external event happens. For example, the custom action policy can specify that “Start a cluster, and immediately preload data into the cache. Until this process completes, do not allow cache requests.”
In accordance with an embodiment, to enable a custom policy, a <class-name> element can be added within a quorum policy scheme element in the cache configuration file. The <class-name> element contains the fully qualified name of the implementation class. Listing 6 adds a custom action policy to the partitioned quorum policy for a distributed cache scheme definition:
As an alternative, a factory class can be used to create custom action policy instances. Listing 7 defines a factory class, that uses an <class-factory-name> element to enter the fully qualified class name and the <method-name> element to specify the name of a static factory method on the factory class, which will perform, object instantiation, in accordance with an embodiment.
Throughout the various contexts described in this disclosure, the embodiments of the invention further encompass computer apparatus, computing systems and machine-readable media configured to carry out the foregoing systems and methods. In addition to an embodiment consisting of specifically designed integrated circuits or other electronics, the present invention may be conveniently implemented using a conventional general purpose or a specialized digital computer or microprocessor programmed according to the teachings of the present disclosure, as will be apparent to those skilled in the computer art.
Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art. The invention may also be implemented by the preparation of application specific integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art.
The various embodiments include a computer program product which is a storage medium (media) having instructions stored thereon/in which can be used to program a general purpose or specialized computing processor(s)/device(s) to perform any of the features presented herein. The storage medium can include, but is not limited to, one or more of the following: any type of physical media including floppy disks, optical discs, DVDs, CD-ROMs, microdrives, magneto-optical disks, holographic storage, ROMs, RAMs, PRAMS, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs); paper or paper-based media; and any type of media or device suitable for storing instructions and/or information. The computer program product can be transmitted in whole or in parts and over one or more public and/or private networks wherein the transmission includes instructions which can be used by one or more processors to perform any of the features presented herein. The transmission may include a plurality of separate transmissions. In accordance with certain embodiments, however, the computer storage medium containing the instructions is non-transitory (i.e. not in the process of being transmitted) but rather is persisted on a physical device.
The foregoing description of the preferred embodiments of the present invention has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations can be apparent to the practitioner skilled in the art. Embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the relevant art to understand the invention. It is intended that the scope of the invention be defined by the following claims and their equivalents.
This application claims the benefit of priority to U.S. Provisional Patent Application No. 61/437,546, titled “QUORUM IN A DISTRIBUTED DATA GRID”, filed Jan. 28, 2011, which application is herein incorporated by reference.
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