Amazon ElastiCache for Memcached | Auto Discovery Flashcards
What popular Memcached libraries are compatible with Amazon ElastiCache?
Auto Discovery
Amazon ElastiCache for Memcached | Database
Amazon ElastiCache does not require specific client libraries and works with existing Memcached client libraries without recompilation or application re-linking (Memcached 1.4.5 and later); examples include libMemcached (C) and libraries based on it (e.g. PHP, Perl, Python), spyMemcached (Java) and fauna (Ruby).
What is Auto Discovery and what can I do with it?
Auto Discovery
Amazon ElastiCache for Memcached | Database
Auto Discovery is a feature that saves developers time and effort, while reducing complexity of their applications. Auto Discovery enables automatic discovery of cache nodes by clients when they are added to or removed from an Amazon ElastiCache cluster. Until now to handle cluster membership changes, developers must update the list of cache node endpoints manually. Depending on how the client application is architected, typically a client initialization, by shutting down the application and restarting it, is needed resulting in downtime. Through Auto Discovery we are eliminating this complexity. With Auto Discovery, in addition to being backwards protocol-compliant with the Memcached protocol, Amazon ElastiCache provides clients with information on cache cluster membership. A client capable of processing the additional information reconfigures itself, without any initialization, to use the most current nodes of an Amazon ElastiCache cluster.
How does Auto Discovery work?
Auto Discovery
Amazon ElastiCache for Memcached | Database
An Amazon ElastiCache cluster can be created with nodes that are addressable via named endpoints. With Auto Discovery the Amazon ElastiCache cluster is also given a unique Configuration Endpoint which is a DNS Record that is valid for the lifetime of the cluster. This DNS Record contains the DNS Names of the nodes that belong to the cluster. Amazon ElastiCache will ensure that the Configuration Endpoint always points to at least one such “target” node. A query to the target node then returns endpoints for all the nodes of the cluster in question. After this, you can connect to the cluster nodes just as before and use the Memcached protocol commands such as get, set, incr and decr. For more details, see here. To use Auto Discovery, you will need an Auto Discovery capable client. Auto Discovery clients for Java and PHP are available for download from the Amazon ElastiCache console. Upon initialization, the client will automatically determine the current members of the Amazon ElastiCache cluster using the Configuration Endpoint. When you make changes to your cache cluster by adding or removing nodes or if a node is replaced upon failure, the Auto Discovery client automatically determines the changes and you do not need to initialize your clients manually.
How can I get started using Auto Discovery?
Auto Discovery
Amazon ElastiCache for Memcached | Database
To get started, download the Amazon ElastiCache Cluster Client by clicking the “Download ElastiCache Cluster Client” link on the Amazon ElastiCache console. Before you can download, you must have an Amazon ElastiCache account; if you do not already have one, you can sign up from the Amazon ElastiCache detail page. After you download the client, you can begin setting up and activating your Amazon ElastiCache cluster by visiting the Amazon ElastiCache console. More details can be found here.
If I continue to use my own Memcached clients with my ElastiCache cluster – will I be able to get this feature?
Auto Discovery
Amazon ElastiCache for Memcached | Database
No, you will not get the Auto Discovery feature with the existing Memcached clients. To use the Auto Discovery feature a client must be able to use a Configuration Endpoint and determine the cluster node endpoints. You may either use the Amazon ElastiCache Cluster Client or extend your existing Memcached client to include the Auto Discovery command set.
What are the minimum hardware / software requirements for Auto Discovery?
Auto Discovery
Amazon ElastiCache for Memcached | Database
To take advantage of Auto Discovery, an Auto Discovery capable client must be used to connect to an Amazon ElastiCache Cluster. Amazon ElastiCache currently supports Auto Discovery capable clients for both Java and PHP. These can be downloaded from the Amazon ElastiCache console. Our customers can create clients for any other language by building upon the popular Memcached clients available.
How do I modify or write my own Memcached client to support auto-discovery?
Auto Discovery
Amazon ElastiCache for Memcached | Database
You can take any Memcached Client Library and add support for Auto Discovery. If you would like to add or modify your own client to enable Auto Discovery, please refer to the Auto Discovery command set documentation.
Can I continue to work with my existing Memcached client if I don’t need Auto-discovery?
Auto Discovery
Amazon ElastiCache for Memcached | Database
Yes, Amazon ElastiCache is still Memcached protocol compliant and does not require you to change your clients. However, for taking advantage of auto-discovery feature, we had to enhance the Memcached client capabilities. If you choose to not use the Amazon ElastiCache Cluster Client, you can continue to use your own clients or modify your own client library to understand the auto-discovery command set.
Can I have heterogeneous clients when using Auto Discovery?
Auto Discovery
Amazon ElastiCache for Memcached | Database
Yes, the same Amazon ElastiCache cluster can be connected through an Auto Discovery capable Client and the traditional Memcached client at the same time. Amazon ElastiCache remains 100% Memcached compliant.
