com.google.cloud.spanner.watcher

Class SpannerTableTailer

java.lang.Object

com.google.api.core.AbstractApiService

com.google.cloud.spanner.watcher.SpannerTableTailer

All Implemented Interfaces:

com.google.api.core.ApiService, SpannerTableChangeWatcher

public class SpannerTableTailer
extends com.google.api.core.AbstractApiService
implements SpannerTableChangeWatcher

Implementation of the SpannerTableChangeWatcher interface that continuously polls a table for changes based on a commit timestamp column in the table.

Usage:

{@code
 String instance = "my-instance";
 String database = "my-database";
 String table = "MY_TABLE";

 Spanner spanner = SpannerOptions.getDefaultInstance().getService();
 TableId tableId =
     TableId.of(DatabaseId.of(SpannerOptions.getDefaultProjectId(), instance, database), table);
 SpannerTableChangeWatcher watcher = SpannerTableTailer.newBuilder(spanner, tableId).build();
 watcher.addCallback(
     new RowChangeCallback() {

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SpannerTableTailer.Builder Builder for a SpannerTableTailer.

Nested classes/interfaces inherited from interface com.google.cloud.spanner.watcher.SpannerTableChangeWatcher

SpannerTableChangeWatcher.Row, SpannerTableChangeWatcher.RowChangeCallback

Nested classes/interfaces inherited from interface com.google.api.core.ApiService

com.google.api.core.ApiService.Listener, com.google.api.core.ApiService.State

Method Summary

Modifier and Type	Method and Description
void	addCallback(SpannerTableChangeWatcher.RowChangeCallback callback) Adds a SpannerTableChangeWatcher.RowChangeCallback for this SpannerTableChangeWatcher.
protected void	doStart()
protected void	doStop()
com.google.cloud.spanner.Statement	getLastPollStatement() Returns the last poll statement of this tailer.
TableId	getTable() Returns the id of the table that is monitored by this watcher.
boolean	isLastPollReturnedChanges() Returns true if the last poll for changes actually returned changes.
static SpannerTableTailer.Builder	newBuilder(com.google.cloud.spanner.Spanner spanner, TableId table)
protected void	notifyFailed(Throwable cause)

Methods inherited from class com.google.api.core.AbstractApiService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, failureCause, isRunning, notifyStarted, notifyStopped, startAsync, state, stopAsync

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.google.api.core.ApiService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, failureCause, isRunning, startAsync, state, stopAsync

Method Detail

newBuilder

public static SpannerTableTailer.Builder newBuilder(com.google.cloud.spanner.Spanner spanner,
                                                    TableId table)

addCallback

public void addCallback(SpannerTableChangeWatcher.RowChangeCallback callback)

Description copied from interface: SpannerTableChangeWatcher

Adds a SpannerTableChangeWatcher.RowChangeCallback for this SpannerTableChangeWatcher. Callbacks may only be added when the ApiService.state() of this SpannerTableChangeWatcher is State#NEW. Callbacks should be lightweight and non-blocking. The callback should hand off any heavy computations or blocking operations to a non-blocking executor or buffer.

The SpannerTableChangeWatcher guarantees that at most one SpannerTableChangeWatcher.RowChangeCallback will be active at any given time, and all callbacks will receive all changes in order of commit timestamp. There is no guarantee as to the order of which callback is called first if a SpannerTableChangeWatcher has registered multiple callbacks.

Specified by:

addCallback in interface SpannerTableChangeWatcher

getTable

public TableId getTable()

Description copied from interface: SpannerTableChangeWatcher

Returns the id of the table that is monitored by this watcher.

Specified by:

getTable in interface SpannerTableChangeWatcher

getLastPollStatement

public com.google.cloud.spanner.Statement getLastPollStatement()

Returns the last poll statement of this tailer. This can be used to monitor the polling activity by querying the SPANNER_SYS views for query statistics for this statement.

isLastPollReturnedChanges

public boolean isLastPollReturnedChanges()

Returns true if the last poll for changes actually returned changes. This can be used to monitor the polling activity.

doStart

protected void doStart()

Specified by:

doStart in class com.google.api.core.AbstractApiService

notifyFailed

protected void notifyFailed(Throwable cause)

Overrides:

notifyFailed in class com.google.api.core.AbstractApiService

doStop

protected void doStop()

Specified by:

doStop in class com.google.api.core.AbstractApiService