ADBA (Asynchronous Database Access)

Copyright © 2018, Oracle and/or its affiliates. All rights reserved. |
Asynchronous Database Access (ADBA)
#JJUG_CCC #ccc_g7
Akihiro Nishikawa
Oracle Corporation Japan
May 26, 2018
JDBC API

Copyright © 2018, Oracle and/or its affiliates. All rights reserved.
Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
2

First of All...
3

NOTICE
• Today’s topic is now discussed actively.
• Everything is subject to change.
• This has not been in Java specifications yet.
4

Agenda
Introduction
Basic Concepts
More Concepts with Codes
Wrap up
1
2
3
4
5

Introduction
6

Nowadays...
• JDBC APIs are based on synchronous access.
• You might think it is no problem at all since you use pooled
connections.
7
!

But...
• What do you do if application requires high throughput?
• What if does the application run standalone as an AOT compiled
native image or a function?
8
!

Copyright © 2018, Oracle and/or its affiliates. All rights reserved. 9
How about introducing
asynchronous paradigm
to database access?

Asynchronous Database Access (ADBA)
• Being developed by the JDBC Expert Group with community input
• Targeted for a near future release of Java
• Asynchronous apps have better throughput
– Fewer threads means less thread scheduling, less thread contention
– Database access is slow so blocked threads leave resources idle for a long time
– Simultaneous access to multiple databases (map/reduce, sharded databases, ...)
– Fire and forget (DML, stored procedures, ...)
10
Java standard database access API that never blocks user threads

Goals
• No user thread blocks
– Minimize the number of threads used for database access
• Alternate API for database access
– Not an extension of the standard JDBC API
– Not a replacement for the standard JDBC API
• Target high throughput apps
– Not a completely general purpose database access API
– The initial version will have a limited feature set
• Build on the Java SE class library
11

Goals
• No user thread blocks
– Minimize the number of threads used for database access
• Alternate API for database access
– Not an extension of the standard JDBC API
– Not a replacement for the standard JDBC API
• Target high throughput apps
– Not a completely general purpose database access API
– The initial version will have a limited feature set
• Build on the Java SE class library
12
Neither replacement
nor enhancement,
but complementary

Design choices
• Minimal or no reference to java.sql
• Rigorous use of types
• Builder pattern
• Fluent API
• Immutable after initialization
• One way to do something is enough
• Avoid SQL processing
• Avoid callback hell
13

ADBA (Asynchronous Database Access)
• Package
–java.sql2 (jdk.incubator.sql2)
• Module
–jdk.adba (jdk.incubator.adba)
[Note]
• Implementation-specific features are out of scope of this session.
– Statement cache
– Connection cache...
14

We have lots of ways to
access databases
asynchronously, don’t we?

What About... ?
• Streams
– Java streams are inherently synchronous
• Reactive Streams
– Not integrated into the Java SE class library
• Node.js
– JavaScript... (Indeed this runs on Graal VM, but...)
• ADBCJ - Asynchronous Database Connectivity in Java (ADBCJ)
https://code.google.com/archive/p/adbcj/
16
There are already multiple asynchronous/non-blocking Java and JavaScript APIs...

Basic Concepts
17

CompletionStage & CompletableFuture
• Java class library mechanism for asynchronous style programming
– Brings reactive programming to Java
– Enables the composition of asynchronous tasks
– A task has a state and it might be...
• running
• completed normally with a result
• completed exception all with an exception
– Event thread : the result of the completion is pushed to dependent tasks
• Push model à higher scalability than pull or poll
• Supports lambda expressions and fluent programming
18

Execution Model (1/2)
• Operation consists of a result and a CompletionStage
• SQL or other database operation
• Parameter assignments
• Result handling
• Submission and CompletableFuture
19
Everything is an Operation

Execution Model (2/2)
• User thread creates and submits Operations
– User thread is never blocked when creating and submitting Operations.
• Implementation executes those Operations asynchronously
– Performs round trip(s) to the database
– Executes result handling
– Completes CompletableFutures
20

More concepts with Codes
21

public void trivialInsert(DataSource ds) {
String sql = "insert into tab values (:id, :name, :answer)";
try (Connection conn = ds.getConnection()) {
conn.countOperation(sql)
.set("id", 1, AdbaType.NUMERIC)
.set("name", "Deep Thought", AdbaType.VARCHAR)
.set("answer", 42, AdbaType.NUMERIC)
.submit();
}
}
Trivial Insert

All SQL is Vendor Specific
• No escape sequences
• No specified parameter markers
• Non vendor specific syntax requires processing by the driver
– Adds overhead
– Increases code complexity
– Minimal benefit as most apps are tied to a specific database regardless
23

All SQL is Vendor Specific
• DB2 (:foo)
• MySQL (?)
• Oracle Database (:foo)
• PostgresSQL ($1)
• SQL Server (@foo)
24
Note: Code examples use parameter markers from a variety of databases.

public void trivialSelect(DataSource ds, List<Integer> result) {
String sql = "select id, name, answer from tab where answer = $1";
conn.<List<Integer>>rowOperation(sql)
.set("1", 42, AdbaType.NUMERIC)
.collect((ignore, row) -> {
result.add(row.get("id", Integer.class));
return null;
})
.submit();
}
}
Trivial Select

public DataSource getDataSource(String url, String user, String pass) {
return DataSourceFactory.forName("Oracle Database")
.builder()
.url("jdbc:oracle:nonblocking:@//ccc18.example.org:5521/ccc18")
.username("scott")
.password("tiger")
.connectionProperty(AdbaConnectionProperty.TRANSACTION_ISOLATION,
AdbaConnectionProperty.TransactionIsolation.SERIALIZABLE)
.connectionProperty(NLS_LANGUAGE, "Japanese")
.build();
}
ConnectionProperties

in interface DataSource:
public default Connection getConnection() {
return builder().build().connect();
}
in interface Connection:
public default Connection connect() {
holdForMoreMembers();
submit();
connectOperation().submit();
return this;
}
Getting Connection

Connection Pooling
public Connection activate();
public Connection deactivate();
public registerLifecycleListener(LifecycleListener listener);
28
If you remove registered LifecycleListener, call deregisterLifecycleListener()

public Future<Integer> selectIdForAnswer(DataSource ds, int answer) {
String sql = "select id, name, answer from tab where answer = @target";
return conn.<List<Integer>>rowOperation(sql)
.set("target", 42, AdbaType.NUMERIC)
.collect((list, row) -> {
list.add(row.get("id", Integer.class));
return list; }
)
.submit()
.toCompletableFuture()
.thenApply(l -> l.get(0));
}
}
Basic SELECT

public class Item {
protected int id;
protected String name;
protected int answer;
@SqlColumns({"ID", "USER", "RESPONSE"})
public Item(int id, String name, int answer) {
this.id = id;
this.name = name;
this.answer = answer;
}
@SqlParameter(marker = "id", sqlType = "NUMERIC")
public int getId() {
return id;
}
(cont.)
POJOs (1/2)

(cont.)
@SqlParameter(marker = "name", sqlType = "VARCHAR")
public String getName() {
return name;
}
@SqlParameter(marker = "answer", sqlType = "NUMERIC")
public int getAnswer() {
return answer;
}
}
POJOs (2/2)

OperationGroup (1/2)
• OperationGroup has its own result handling and CompletableFuture
• Members submitted to group.OperationGroup is submitted as a unit
• Execution Order
– Default : Sequential in order submitted
– parallel() : should be marked if having member Operations executed in any order
including in parallel.
32
group of Operations

OperationGroup (1/2)
• Error response
– Default : Skip remaining group members if failure of one member Operation
happens. (with a SqlSkippedException with the cause set to the original exception).
– independent(): should be marked if remaining group members unaffected
• Conditional or unconditional
• Connection is an OperationGroup
– Sequential, dependent, unconditional by default
33

public void insertListHold(List<Item> list, DataSource ds) {
String sql = "insert into tab values (@elem_id, @elem_name, @elem_answer)";
OperationGroup group = conn.operationGroup().independent();
group.submitHoldingForMoreMembers();
for (Item elem : list) {
group.countOperation(sql)
.set("elem_", elem).submit().getCompletionStage()
.exceptionally(t -> {
System.out.println(elem.getId());
return null;
});
}
group.releaseProhibitingMoreMembers();
}
}
Independent INSERT

public void deposit(Connection conn, int accountId, double amount) {
String selectSql = "select balance from account where id = $1";
CompletableFuture<Double> newBalanceF =
conn.<Double>rowOperation(selectSql)
.set("1", accountId, AdbaType.INTEGER)
.collect((p, row) -> row.get("balance", Double.class))
.submit()
.thenApply(b -> b + amount);
String updateSql = "update account set balance=$2 where id = $1";
conn.countOperation(updateSql).set("1", accountId, AdbaType.INTEGER)
.set("2", newBalanceF, AdbaType.DOUBLE)
.submit();
}
Future Parameters

public void updateListParallel(List<Item> list, DataSource ds) {
String query = "select id from tab where answer = ?";
String update = "update tab set answer = ? where id = ?";
OperationGroup<Object, Object> group =
conn.operationGroup()
.independent()
.parallel();
group.submitHoldingForMoreMembers();
(cont.)
Parallel UPDATE (1/3)

(cont.)
for (Item elem : list) {
CompletableFuture<Integer> idF
= group.<Integer>rowOperation(query)
.set("1", elem.getAnswer(), AdbaType.NUMERIC)
.collect((ignore, row) -> {
return row.get("id", Integer.class);
})
.submit()
.toCompletableFuture();
(cont.)

(cont.)
group.countOperation(update).set("1", idF)
.set("2", "42")
.submit()
.getCompletionStage()
System.out.println("Update failed: " + elem.getId());
return null;
});
}
group.releaseProhibitingMoreMembers();
}
}

Close
public default void close() {
closeOperation().submit();
releaseProhibitingMoreMembers();
}
39
CloseOperation is never skipped.

public static class NlsLanguageProperty implements ConnectionProperty {
public static final ConnectionProperty NLS_LANGUAGE
= new NlsLanguageProperty();
private NlsLanguageProperty() {
}
public String name() {
return "NLS_LANGUAGE";
}
public Class range() {
return String.class;
}
ConnectionProperty (1/2)

public String defaultValue() {
return "American";
}
public boolean isSensitive() {
return false;
}
public Operation configureOperation(OperationGroup group, Object value) {
String sql = "ALTER SESSION SET NLS_LANGUAGE TO " + value;
return group.operation(sql);
}
}
ConnectionProperty (2/2)

@SqlStruct(sqlTypeName = "STUDENT", fields = {
@SqlStruct.Field(sqlFieldName = "NAME", sqlTypeName = "VARCHAR(100)",
javaFieldName = "name"),
@SqlStruct.Field(sqlFieldName = "EMAIL", sqlTypeName = "VARCHAR(100)",
javaFieldName = "email")
})
public class Student {
String name;
String email;
...
}
@SqlArray(elementSqlTypeName = "STUDENT")
public class Roster extends LinkedList<Student> {
public Roster() {}
}
ARRAYs and STRUCTs

public void transfer(Connection conn, double amount,
int fromAccount, int toAccount) {
String sql = "update account set balance=balance+@amount where id = @account";
.set("amount", -amount, AdbaType.DECIMAL)
.set("account", fromAccount, AdbaType.INTEGER)
.submit();
.set("amount", amount, AdbaType.DECIMAL)
.set("account", toAccount, AdbaType.INTEGER)
.submit();
conn.commit();
}
Transactions (1/2)

public void transfer(Connection conn, double amount,
int fromAccount, int toAccount) {
String sql = "update account set balance=balance+@amount where id = @account";
final Transaction tran = conn.transaction();
.set("amount", -amount, AdbaType.DECIMAL)
.set("account", fromAccount, AdbaType.INTEGER)
.onError( e -> tran.setRollbackOnly() )
.submit();
.set("amount", amount, AdbaType.DECIMAL)
.set("account", toAccount, AdbaType.INTEGER)
.onError( e -> tran.setRollbackOnly() )
.submit();
conn.commit();
}
Transactions (2/2)

public void paycheck(Connection conn, Employee emp) {
String sql = "call generate_paycheck(?, ?)";
CompletableFuture<CheckDetail> details = conn.<CheckDetail>outOperation(sql)
.set("1", emp, AdbaType.STRUCT)
.outParameter("2", AdbaType.STRUCT)
.resultProcessor(m -> m.get("2", CheckDetail.class))
.submit()
.toCompletableFuture();
(cont.)
Local Operations (1/2)

(cont.)
conn.localOperation()
.onExecution(() -> {
printPaycheck(details);
return null;
})
.submit()
.thenRun(() -> reportPrintSuccess(details))
reportPrintFailure(details);
return null;
});
}
Local Operations (2/2)

Wrap up
47

Key takeaways
• Asynchronous
• Geared toward high-throughput programs
• Does not attempt to support every database feature
• Does not attempt to abstract the database
• Uses the builder pattern
• Supports the fluent programming style
48

Status
• Now developed by the JDBC Expert Group through the Java Community
Process
• Targeted for a near future release of Java
• Send feedback to jdbc-spec-discuss@openjdk.java.net
49
Everything is subject to change!

Resources
• Available for download from OpenJDK
http://oracle.com/goto/java-async-db
• AoJ (ADBA over JDBC) [JDK 9 or later is required]
https://github.com/oracle/oracle-db-examples/tree/master/java/AoJ
• JavaDoc
http://cr.openjdk.java.net/~lancea/8188051/apidoc/jdk.incubator.adba-summary.html
50

Safe Harbor Statement
The preceding is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
51

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ADBA (Asynchronous Database Access)

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