srkukarni commented on a change in pull request #1587: [WIP] Add key/value 
operations in StateContext
URL: https://github.com/apache/incubator-pulsar/pull/1587#discussion_r181881196
 
 

 ##########
 File path: 
pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/instance/state/StateContext.java
 ##########
 @@ -18,15 +18,61 @@
  */
 package org.apache.pulsar.functions.instance.state;
 
+import java.nio.ByteBuffer;
 import java.util.concurrent.CompletableFuture;
 
 /**
  * A state context per function.
  */
 public interface StateContext {
 
+    /**
+     * Increment the given <i>key</i> by the given <i>amount</i>.
+     *
+     * @param key key to increment
+     * @param amount the amount incremented
+     */
     void incr(String key, long amount);
 
+    /**
+     * Update the given <i>key</i> to the provide <i>value</i>.
+     *
+     * <p>NOTE: the put operation might or might not be applied directly to 
the global state until
+     * the state is flushed via {@link #flush()} at the completion of function 
execution.
+     *
+     * <p>The behavior of `PUT` is non-deterministic, if two function 
instances attempt to update
+     * same key around the same time, there is no guarantee which update will 
be the final result.
+     * That says, if you attempt to get amount via {@link #getAmount(String)}, 
increment the amount
+     * based on the function computation logic, and update the computed amount 
back. one update will
+     * overwrite the other update. For this case, you are encouraged to use 
{@link #incr(String, long)}
+     * instead.
+     *
+     * @param key key to update.
+     * @param value value to update
+     */
+    void put(String key, ByteBuffer value);
 
 Review comment:
   Why not putValue/getValue or put/get?

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