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Demo App

This section will illustrate how to set up a demo Java application using Goblin.

Maven Dependency

Use the latest release of goblin-java-client.

<dependency>
    <groupId>com.ebay.magellan</groupId>
    <artifactId>goblin-java-client</artifactId>
    <version>3.5.0-RELEASE</version>
</dependency>

Create the Client Configuration

    RaftClusterClientConfig config = RaftClusterClientConfig.builder()
        .clusterInfo(clusterAddresses)
        .timeoutInMilliSeconds(timeoutInMilliSeconds)
        .stubTimeoutInMilliSeconds(stubTimeoutInMilliSeconds)
        .tlsEnabled(grpcTlsEnable)
        .clusterInfoResolver(new TessClusterInfoResolver())
        .poolType(poolType)
        .build();
Key Value
timeoutInMilliSeconds The overall timeout (in milliseconds) of a RaftClusterClient method call
RaftClusterClient ensures that a method call throws RaftInvokeTimeoutException exception shortly after timeoutInMilliSeconds milliseconds when the method was not completed.
Default value: 10000
stubTimeoutInMilliSeconds The gPRC timeout (in milliseconds) of a single API call between the client and Goblin server.
Change this value only when the connection between the server and client is very unstable.
In most cases, set #timeoutInMilliSeconds# for the overall timeout configuration.
Default value: 500
clusterInfo Goblin servers' addresses.
The format is:
"<node_id_1>@:,<node_id_2>@:,<node_id_3>@:,..."
e.g. experimental dev goblin
"1@om-expt-dev-fss-1.goblin-dev.stratus.qa.ebay.com:50055,2@om-expt-dev-fss-2.goblin-dev.stratus.qa.ebay.com:50055,3@om-expt-dev-fss-3.goblin-dev.stratus.qa.ebay.com:50055,4@om-expt-dev-fss-4.goblin-dev.stratus.qa.ebay.com:50055,5@om-expt-dev-fss-5.goblin-dev.stratus.qa.ebay.com:50055"
clusterInfoResolver The implementation of ClusterInfoResolver interface. It is used to resolve dns of the clusterInfo to a list of Goblin servers' ip addresses.
tlsEnabled true: enable TLS in the connection between the client and Goblin server.
false: disable TLS in the connection between the client and Goblin server.
sslContext io.grpc.netty.shaded.io.netty.handler.ssl.SslContext object for TLS connection. Mandatory if tlsEnabled is true.
poolType The configuration of read mode.
LeaderOnly: always found leader to connect.
RoundRobin: round robin to pick a client.
InSyncReplica: round robin to pick a client but it should be closed to leader enough. In-sync means the gap of the committed index between follower and leader is less than a pre-defined threshold. If you want strong consistency read, use LeaderOnly
Default value: LeaderOnly
ISRValidMinGap The threshold of the gap of committed index between follower and leader.
If the real gap is less than this threshold, the follower is considered as ISR follower, and can serve read traffic, otherwise the follower can't serve read traffic.
It takes effective only if poolType is configured as InSyncReplica.
Default value: 100
ISRRefreshTime Time interval to refresh ISR list.
Default value: 120000 (2min)
ISRLeaseTime Lease for an ISR List becomes invalid.
Default value: 600000 (10min)
intervalPerRound The backoff delay between gRPC call retry attempts
Default value: 5(ms)

Initialize the GoblinClient

GoblinClient is thread safe. Only one GoblinClient is needed for all API calls with a specific Goblin cluster. For the complete documents of Goblin APIs, please refer to Client API Reference for Java

    RaftClusterClientConfig config = RaftClusterClientConfig.builder()
        .clusterInfo("1@om-expt-dev-fss-1.goblin-dev.stratus.qa.ebay.com:50055,2@om-expt-dev-fss-2.goblin-dev.stratus.qa.ebay.com:50055,3@om-expt-dev-fss-3.goblin-dev.stratus.qa.ebay.com:50055,4@om-expt-dev-fss-4.goblin-dev.stratus.qa.ebay.com:50055,5@om-expt-dev-fss-5.goblin-dev.stratus.qa.ebay.com:50055")
        .timeoutInMilliSeconds(10000L)
        .tlsEnabled(false)
        .poolType(PoolType.LeaderOnly)
        .build();

    // build a Goblin client
    GoblinClient goblinClient = null;
    try {
        // build the client
        goblinClient = builder.build();
    } catch (GoblinException e) {
        // handle the exception here.
    } finally {
        if(goblinClient != null) {
            goblinClient.close();
        }
    }

GoblinClient implements the AutoCloseable interface. So the above sample could also be

try (GoblinClient client = builder.build()) {
    // call APIs
    // ... ...
} catch (GoblinException e) {
    // handle the exception here.
}