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Chapter 16. The Memcached Interface
16.1. The Memcached Interface
Memcached is an in-memory caching system used to improve response and operation times for database-driven websites. The Memcached caching system defines a text based protocol called the Memcached protocol. The Memcached protocol uses in-memory objects or (as a last resort) passes to a persistent store such as a special memcached database.
Red Hat JBoss Data Grid offers a server that uses the Memcached protocol, removing the necessity to use Memcached separately with JBoss Data Grid. Additionally, due to JBoss Data Grid’s clustering features, its data failover capabilities surpass those provided by Memcached.
16.2. About Memcached Servers
Red Hat JBoss Data Grid contains a server module that implements the memcached protocol. This allows memcached clients to interact with one or multiple JBoss Data Grid based memcached servers.
The servers can be either:
- Standalone, where each server acts independently without communication with any other memcached servers.
- Clustered, where servers replicate and distribute data to other memcached servers.
16.3. Memcached Statistics
The following table contains a list of valid statistics available using the memcached protocol in Red Hat JBoss Data Grid.
| Statistic | Data Type | Details |
|---|---|---|
| uptime | 32-bit unsigned integer. | Contains the time (in seconds) that the memcached instance has been available and running. |
| time | 32-bit unsigned integer. | Contains the current time. |
| version | String | Contains the current version. |
| curr_items | 32-bit unsigned integer. | Contains the number of items currently stored by the instance. |
| total_items | 32-bit unsigned integer. | Contains the total number of items stored by the instance during its lifetime. |
| cmd_get | 64-bit unsigned integer | Contains the total number of get operation requests (requests to retrieve data). |
| cmd_set | 64-bit unsigned integer | Contains the total number of set operation requests (requests to store data). |
| get_hits | 64-bit unsigned integer | Contains the number of keys that are present from the keys requested. |
| get_misses | 64-bit unsigned integer | Contains the number of keys that were not found from the keys requested. |
| delete_hits | 64-bit unsigned integer | Contains the number of keys to be deleted that were located and successfully deleted. |
| delete_misses | 64-bit unsigned integer | Contains the number of keys to be deleted that were not located and therefore could not be deleted. |
| incr_hits | 64-bit unsigned integer | Contains the number of keys to be incremented that were located and successfully incremented |
| incr_misses | 64-bit unsigned integer | Contains the number of keys to be incremented that were not located and therefore could not be incremented. |
| decr_hits | 64-bit unsigned integer | Contains the number of keys to be decremented that were located and successfully decremented. |
| decr_misses | 64-bit unsigned integer | Contains the number of keys to be decremented that were not located and therefore could not be decremented. |
| cas_hits | 64-bit unsigned integer | Contains the number of keys to be compared and swapped that were found and successfully compared and swapped. |
| cas_misses | 64-bit unsigned integer | Contains the number of keys to be compared and swapped that were not found and therefore not compared and swapped. |
| cas_badval | 64-bit unsigned integer | Contains the number of keys where a compare and swap occurred but the original value did not match the supplied value. |
| evictions | 64-bit unsigned integer | Contains the number of eviction calls performed. |
| bytes_read | 64-bit unsigned integer | Contains the total number of bytes read by the server from the network. |
| bytes_written | 64-bit unsigned integer | Contains the total number of bytes written by the server to the network. |
16.4. The Memcached Interface Connector
16.4.1. The Memcached Interface Connector
The following enables a Memcached server using the memcached socket binding, and exposes the memcachedCache cache declared in the local container, using defaults for all other settings.
<memcached-connector socket-binding="memcached" cache-container="local"/>
<memcached-connector socket-binding="memcached"
cache-container="local"/>Due to the limitations in the Memcached protocol, only one cache can be exposed by a connector. To expose more than one cache, declare additional memcached-connectors on different socket-bindings. See Configure Memcached Connectors.
16.4.2. Configure Memcached Connectors
The following procedure describes the attributes used to configure the memcached connector within the connectors element in Red Hat JBoss Data Grid’s Remote Client-Server Mode.
Configuring the Memcached Connector in Remote Client-Server Mode
The memcached-connector element defines the configuration elements for use with memcached.
-
The
socket-bindingparameter specifies the socket binding port used by the memcached connector. This is a mandatory parameter. -
The
cache-containerparameter names the cache container used by the memcached connector. This is a mandatory parameter. -
The
worker-threadsparameter specifies the number of worker threads available for the memcached connector. The default value for this parameter is 160. This is an optional parameter. -
The
idle-timeoutparameter specifies the time, in seconds, that the connector can remain idle before the connection times out. The default value for this parameter is0, which means that no timeout period is set. This is an optional parameter. -
The
tcp-nodelayparameter specifies whether TCP packets will be delayed and sent out in batches. Valid values for this parameter aretrueandfalse. The default value for this parameter istrue. This is an optional parameter. -
The
send-buffer-sizeparameter indicates the size of the send buffer for the memcached connector. The default value for this parameter is the size of the TCP stack buffer. This is an optional parameter. -
The
receive-buffer-sizeparameter indicates the size of the receive buffer for the memcached connector. The default value for this parameter is the size of the TCP stack buffer. This is an optional parameter.
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