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31.7. Script Execution Using the Hot Rod C++ Client

The Hot Rod C++ client allows tasks to be executed directly on JBoss Data Grid servers via Remote Execution. This feature executes logic close to the data, utilizing the resources of all nodes in the cluster. Tasks may be deployed to the server instances, and may then be executed programmatically.

Important

Remote Execution is a Technology Preview feature of the Hot Rod C++ client in JBoss Data Grid 7.0.0.
Installing a Task

Tasks may be installed on the server by being using the put(std::string name, std::string script) method of the ___script_cache. The extension of the script name determines the engine used to execute the script; however, this may be overridden by metadata in the script itself.

The following example demonstrates installing scripts:

Example 31.4. Installing a Task with the C++ Client

#include "infinispan/hotrod/ConfigurationBuilder.h"
#include "infinispan/hotrod/RemoteCacheManager.h"
#include "infinispan/hotrod/RemoteCache.h"
#include "infinispan/hotrod/Version.h"
#include "infinispan/hotrod/JBasicMarshaller.h"
using namespace infinispan::hotrod;
int main(int argc, char** argv) {
    // Configure the client
    ConfigurationBuilder builder;
    builder.addServer().host("127.0.0.1").port(11222).protocolVersion(
        Configuration::PROTOCOL_VERSION_24);
    RemoteCacheManager cacheManager(builder.build(), false);
    try {
    // Create the cache with the given marshallers
    auto *km = new JBasicMarshaller<std::string>();
    auto *vm = new JBasicMarshaller<std::string>();
    RemoteCache<std::string, std::string> cache = cacheManager.getCache<
        std::string, std::string>(km, &Marshaller<std::string>::destroy,
        vm, &Marshaller<std::string>::destroy,
        std::string("namedCache"));
    cacheManager.start();
    
    // Obtain a reference to the ___script_cache
    RemoteCache<std::string, std::string> scriptCache =
        cacheManager.getCache<std::string, std::string>(
        "___script_cache", false);
    // Install on the server the getValue script
    std::string getValueScript(
        "// mode=local,language=javascript\n "
        "var cache = cacheManager.getCache(\"namedCache\");\n "
        "var ct = cache.get(\"accessCounter\");\n "
        "var c = ct==null ? 0 : parseInt(ct);\n "
        "cache.put(\"accessCounter\",(++c).toString());\n "
        "cache.get(\"privateValue\") ");
    std::string getValueScriptName("getValue.js");
    std::string pGetValueScriptName =
        JBasicMarshaller<std::string>::addPreamble(getValueScriptName);
    std::string pGetValueScript =
        JBasicMarshaller<std::string>::addPreamble(getValueScript);
    scriptCache.put(pGetValueScriptName, pGetValueScript);
    // Install on the server the get access counter script
    std::string getAccessScript(
        "// mode=local,language=javascript\n "
        "var cache = cacheManager.getCache(\"namedCache\");\n "
        "cache.get(\"accessCounter\")");
    std::string getAccessScriptName("getAccessCounter.js");
    std::string pGetAccessScriptName =
        JBasicMarshaller<std::string>::addPreamble(getAccessScriptName);
    std::string pGetAccessScript =
        JBasicMarshaller<std::string>::addPreamble(getAccessScript);
    scriptCache.put(pGetAccessScriptName, pGetAccessScript);
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Executing a Task

Once installed, a task may be executed by using the execute(std::string name, std::map<std::string, std::string> args) method, passing in the name of the script to execute, along with any arguments that are required for execution.

The following example demonstrates executing a script:

Example 31.5. Executing a Script with the C++ Client

    // The following is a continuation of the above example
    cache.put("privateValue", "Counted Access Value");
    std::map<std::string, std::string> s;
    // Execute the getValue script
    std::vector<unsigned char> execValueResult = cache.execute(
        getValueScriptName, s);
    // Execute the getAccess script
    std::vector<unsigned char> execAccessResult = cache.execute(
        getAccessScriptName, s);

    std::string value(
        JBasicMarshallerHelper::unmarshall<std::string>(
            (char*) execValueResult.data()));
    std::string access(
        JBasicMarshallerHelper::unmarshall<std::string>(
            (char*) execAccessResult.data()));

    std::cout << "Returned value is '" << value
        << "' and has been accessed: " << access << " times."
        << std::endl;

  } catch (const Exception& e) {
  std::cout << "is: " << typeid(e).name() << '\n';
  std::cerr << "fail unexpected exception: " << e.what() << std::endl;
  return 1;
  }

	cacheManager.stop();
	return 0;
}
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