1   Basic Tutorial - Write Records using Write Proxy Client

This tutorial shows how to write records using write proxy client.

1.1   Open a write proxy client

1.1.1   Create write proxy client builder

DistributedLogClientBuilder builder = DistributedLogClientBuilder.newBuilder();
        .clientId(ClientId.apply("console-proxy-writer"))
        .name("console-proxy-writer");

1.1.2   Enable thrift mux

builder = builder.thriftmux(true);

1.1.3   Point the client to write proxy using finagle name

String finagleNameStr = "inet!127.0.0.1:8000";
builder = builder.finagleNameStr(finagleNameStr);

1.1.4   Build the write proxy client

DistributedLogClient client = builder.build();

1.2   Write Records

1.2.1   Write records to a stream

Application does not have to provide TransactionID on writing. The TransactionID of a record is assigned by the write proxy.

String streamName = "basic-stream-2";
byte[] data = ...;
Future<DLSN> writeFuture = client.write(streamName, ByteBuffer.wrap(data));

1.2.2   Register the write callback

Register a future listener on write completion. The writer will be notified once the write is completed.

writeFuture.addEventListener(new FutureEventListener<DLSN>() {
    @Override
    public void onFailure(Throwable cause) {
        // executed when write failed.
    }

    @Override
    public void onSuccess(DLSN value) {
        // executed when write completed.
    }
});

1.3   Close the write proxy client

Close the write proxy client after usage.

client.close();

1.4   Run the tutorial

Run the example in the following steps:

1.4.1   Start the local bookkeeper cluster

You can use follow command to start the distributedlog stack locally. After the distributedlog cluster is started, you could access it using distributedlog uri distributedlog://127.0.0.1:7000/messaging/distributedlog.

// dlog local ${zk-port}
./distributedlog-core/bin/dlog local 7000

1.4.2   Start the write proxy

Start the write proxy, listening on port 8000.

// DistributedLogServerApp -p ${service-port} --shard-id ${shard-id} -sp ${stats-port} -u {distributedlog-uri} -mx -c ${conf-file}
./distributedlog-service/bin/dlog org.apache.distributedlog.service.DistributedLogServerApp -p 8000 --shard-id 1 -sp 8001 -u distributedlog://127.0.0.1:7000/messaging/distributedlog -mx -c ${distributedlog-repo}/distributedlog-service/conf/distributedlog_proxy.conf

1.4.3   Create the stream

Create the stream under the distributedlog uri.

// Create Stream `basic-stream-2`
// dlog tool create -u ${distributedlog-uri} -r ${stream-prefix} -e ${stream-regex}
./distributedlog-core/bin/dlog tool create -u distributedlog://127.0.0.1:7000/messaging/distributedlog -r basic-stream- -e 2

1.4.4   Tail the stream

Tailing the stream using TailReader to wait for new records.

// Tailing Stream `basic-stream-2`
// runner run org.apache.distributedlog.basic.TailReader ${distributedlog-uri} ${stream}
./distributedlog-tutorials/distributedlog-basic/bin/runner run org.apache.distributedlog.basic.TailReader distributedlog://127.0.0.1:7000/messaging/distributedlog basic-stream-2

1.4.5   Write records

Run the example to write records to the stream in a console.

// Write Records into Stream `basic-stream-2`
// runner run org.apache.distributedlog.basic.ConsoleProxyWriter ${distributedlog-uri} ${stream}
./distributedlog-tutorials/distributedlog-basic/bin/runner run org.apache.distributedlog.basic.ConsoleProxyWriter 'inet!127.0.0.1:8000' basic-stream-2

1.4.6   Check the results

Example output from ConsoleProxyWriter and TailReader.

// Output of `ConsoleProxyWriter`
May 08, 2016 10:27:41 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[inet] = com.twitter.finagle.InetResolver(com.twitter.finagle.InetResolver@756d7bba)
May 08, 2016 10:27:41 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[fixedinet] = com.twitter.finagle.FixedInetResolver(com.twitter.finagle.FixedInetResolver@1d2e91f5)
May 08, 2016 10:27:41 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[neg] = com.twitter.finagle.NegResolver$(com.twitter.finagle.NegResolver$@5c707aca)
May 08, 2016 10:27:41 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[nil] = com.twitter.finagle.NilResolver$(com.twitter.finagle.NilResolver$@5c8d932f)
May 08, 2016 10:27:41 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[fail] = com.twitter.finagle.FailResolver$(com.twitter.finagle.FailResolver$@52ba2221)
May 08, 2016 10:27:41 AM com.twitter.finagle.Init$$anonfun$1 apply$mcV$sp
[dlog] > test-proxy-writer
[dlog] >


// Output of `TailReader`
Opening log stream basic-stream-2
Log stream basic-stream-2 is empty.
Wait for records starting from DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
Received record DLSN{logSegmentSequenceNo=1, entryId=0, slotId=0}
"""
test-proxy-writer
"""

1.4.7   Attempt a second writer

Open another terminal to run ConsoleProxyWriter. The write should succeed as write proxy is able to accept fan-in writes. Please checkout section Considerations to see the difference between Write Ordering and Read Ordering.

May 08, 2016 10:31:54 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[inet] = com.twitter.finagle.InetResolver(com.twitter.finagle.InetResolver@756d7bba)
May 08, 2016 10:31:54 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[fixedinet] = com.twitter.finagle.FixedInetResolver(com.twitter.finagle.FixedInetResolver@1d2e91f5)
May 08, 2016 10:31:54 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[neg] = com.twitter.finagle.NegResolver$(com.twitter.finagle.NegResolver$@5c707aca)
May 08, 2016 10:31:54 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[nil] = com.twitter.finagle.NilResolver$(com.twitter.finagle.NilResolver$@5c8d932f)
May 08, 2016 10:31:54 AM com.twitter.finagle.BaseResolver$$anonfun$resolvers$1 apply
INFO: Resolver[fail] = com.twitter.finagle.FailResolver$(com.twitter.finagle.FailResolver$@52ba2221)
May 08, 2016 10:31:54 AM com.twitter.finagle.Init$$anonfun$1 apply$mcV$sp
[dlog] > test-write-proxy-message-2
[dlog] >