distributedlog-tutorials/distributedlog-basic/basic-2.md

Write Records using Write Proxy Client

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

Open a write proxy client

Create write proxy client builder.

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

Enable thrift mux.
```
    builder = builder.thriftmux(true);
```

Point the client to write proxy using finagle name.

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

Build the write proxy client.

    DistributedLogClient client = builder.build();

Write Records

Write records to a stream. Application does not 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));

    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.
        }
    });

Close the write proxy client

Close the write proxy client after usage.
```
    client.close();
```

Usage

Run the example in the following steps:

Start the local bookkeeper cluster. After the bookkeeper 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
```

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-proxy-server/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-proxy-server/conf/distributedlog_proxy.conf

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

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

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

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
    """

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] >