Issue 304: Chat Application Example (#306)

Created a Chat Application demo that exemplifies the user of Key-Value Tables, Streams, and Stream Cuts.

Signed-off-by: Andrei Paduroiu <andrei.paduroiu@emc.com>

README.md

@@ -28,6 +28,7 @@ more complex applications as sub-projects, which show use-cases exploiting one o
 | `noop` | Example of how to add a simple callback executed upon a read event. | [Java](pravega-client-examples/src/main/java/io/pravega/example/noop)
 | `statesynchronizer` | Application that allows users to work with `StateSynchronizer` API via CLI. | [Java](pravega-client-examples/src/main/java/io/pravega/example/statesynchronizer)
 | `streamcuts` | Application examples demonstrating the use of `StreamCut`s via CLI. | [Java](pravega-client-examples/src/main/java/io/pravega/example/streamcuts) 
+| `tables` | Application examples demonstrating the use of `KeyValueTable`s via CLI. | [Java](pravega-client-examples/src/main/java/io/pravega/example/tables) 
 
 The related documentation and instructions are [here](pravega-client-examples).
 

gradle.properties

@@ -8,7 +8,7 @@
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 ### Pravega dependencies
-pravegaVersion=0.10.0-2917.d58e537-SNAPSHOT
+pravegaVersion=0.10.0-2943.6c26515-SNAPSHOT
 pravegaKeycloakVersion=0.9.0
 
 ### Pravega-samples output library

pravega-client-examples/README.md

@@ -140,6 +140,24 @@ To demonstrate the use of `StreamCut`s, we provide a CLI. To use it, please exec
 $ bin/streamCutsCli [-scope myScope] [-name myStream] [-uri tcp://127.0.0.1:9090]
 ```
 
+## `tables` (ChatApplication)
+This application aims to demonstrate the use of `KeyValueTable`s, `Stream`s and`StreamCut`s 
+for implementing a "serverless" chat application (with Pravega being used as the sole "server" - 
+there is no specialized chat server). The sample application allows defining users, chat 
+channels and let users subscribe to those channels; it also enables uses to send messages to each
+other. Users receive messages in near-realtime and, upon logging in, get all the messages that
+they received while offline. Please refer to the 
+[ChatClientCli Javadoc](pravega-client-examples/src/main/java/io/pravega/example/tables/ChatClientCli)
+for all supported commands within the application.
+
+### Execution
+
+The `ChatApplication` can be run by means of a CLI. To use it, please execute:
+
+```
+$ bin/chatClientCli
+```
+
 ## `secure`
 This example includes three applications `SecureReader`, `SecureWriter` and a `SecureBatchReader` 
 which instantiate the corresponding Pravega clients on the data path. These applications illustrate

pravega-client-examples/build.gradle

@@ -134,6 +134,29 @@ task startStreamCutsCli(type: JavaExec) {
     }
 }
 
+task scriptChatClientCli(type: CreateStartScripts) {
+    outputDir = file('build/scripts')
+    mainClassName = 'io.pravega.example.tables.ChatClientCli'
+    applicationName = 'chatClientCli'
+    defaultJvmOpts = ["-Dlogback.configurationFile=file:conf/logback.xml"]
+    classpath = files(jar.archivePath) + sourceSets.main.runtimeClasspath
+}
+
+/**
+ * This will only work well from the console if all Gradle output is suppressed. That's because it requires user input
+ * and output using the Console.
+ *
+ * Example: ./gradlew startChatClientCli -q --console=plain
+ */
+task startChatClientCli(type: JavaExec) {
+    main = "io.pravega.example.tables.ChatClientCli"
+    standardInput = System.in
+    classpath = sourceSets.main.runtimeClasspath
+    if(System.getProperty("exec.args") != null) {
+        args System.getProperty("exec.args").split()
+    }
+}
+
 task scriptSecureWriter(type: CreateStartScripts) {
     outputDir = file('build/scripts')
     mainClassName = 'io.pravega.example.secure.SecureWriter'
@@ -195,6 +218,7 @@ distributions {
                 from project.scriptSharedConfigCli
                 from project.scriptNoopReader
                 from project.scriptStreamCutsCli
+                from project.scriptChatClientCli
                 from project.scriptSecureWriter
                 from project.scriptSecureReader
                 from project.scriptSecureBatchReader