1e0940d58d
- Introduce Maven pom.xml. - Moved Asciidoctor files to src/main/asciidoc. - Moved notice.txt etc. to src/main/resources. - Add logback.xml - Update Makefile to use maven and pick build profiles. - Update template.mf to pick up versions in pom.xml - Add build matrix for spring versions to .travis.yml - Use container based travis infrastructure. - Update readme. Original pull request: #167.
51 lines
2.9 KiB
Plaintext
51 lines
2.9 KiB
Plaintext
[[scripting]]
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= Redis Scripting
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Redis versions 2.6 and higher provide support for execution of Lua scripts through the http://redis.io/commands/eval[eval] and http://redis.io/commands/evalsha[evalsha] commands. Spring Data Redis provides a high-level abstraction for script execution that handles serialization and automatically makes use of the Redis script cache.
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Scripts can be run through the `execute` methods of `RedisTemplate`. RedisTemplate uses a configurable `ScriptExecutor` to execute the provided script. By default, the `ScriptExecutor` takes care of serializing the provided keys and arguments and deserializing the script result. This is done with the `RedisTemplate` key and value serializers. There is an additional `execute` method that allows you to pass custom serializers for the script arguments and result.
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The default `ScriptExecutor` optimizes performance by retrieving the SHA1 of the script and attempting first to run `evalsha`, falling back to `eval` if the script is not yet present in the Redis script cache.
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Here's an example that executes a common "check-and-set" scenario using a Lua script. This is an ideal use case for a Redis script, as it requires that we execute a set of commands atomically and the behavior of one command is influenced by the result of another.
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[source,java]
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----
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@Bean
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public RedisScript<Boolean> script() {
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DefaultRedisScript<Boolean> redisScript = new DefaultRedisScript<Boolean>();
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redisScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("META-INF/scripts/checkandset.lua")));
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redisScript.setResultType(Boolean.class);
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}
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----
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[source,java]
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----
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public class Example {
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@Autowired
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RedisScript<Boolean> script;
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public boolean checkAndSet(String expectedValue, String newValue) {
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return redisTemplate.execute(script, Collections.singletonList("key"), expectedValue, newValue);
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}
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}
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----
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[source,lua]
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----
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-- checkandset.lua local
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current = redis.call('GET', KEYS[1])
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if current == ARGV[1]
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then redis.call('SET', KEYS[1], ARGV[2])
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return true
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end
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return false
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----
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The XML above configures a `DefaultRedisScript` pointing to a file called `checkandset.lua`, which is expected to return a boolean value. The script `resultType` should be one of Long, Boolean, List, or deserialized value type. It can also be null if the script returns a throw-away status (i.e "OK"). It is ideal to configure a single instance of `DefaultRedisScript` in your application context to avoid re-calculation of the script's SHA1 on every script execution.
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The checkAndSet method above then executes th
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Scripts can be executed within a `SessionCallback` as part of a transaction or pipeline. See <<tx>> and <<pipeline>> for more information.
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The scripting support provided by Spring Data Redis also allows you to schedule Redis scripts for periodic execution using the Spring Task and Scheduler abstractions. See the `Spring Framework` documentation for more details.
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