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| <title>ACID Transactions</title> |
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| <section id="java" class="page-section"> |
| <h1 class="first">ACID Transactions</h1> |
| <div class="col-sm-12 col-md-12 col-xs-12" style="padding:0 0 20px 0;"> |
| <div class="col-sm-6 col-md-8 col-xs-12" style="padding-left:0; padding-right:0"> |
| <p> |
| Apache Ignite is a strongly consistent platform that fully supports distributed ACID transactions. |
| The consistency guarantees are met for both memory and disk tiers. |
| </p> |
| <p> |
| Transactions in Apache Ignite can span multiple cluster nodes, caches (aka. tables) and partitions. |
| Both pessimistic and optimistic locking are available for applications. The optimistic mode |
| also supports deadlock-free transactions that help avoid distributed deadlocks in user code. |
| </p> |
| </div> |
| <div class="col-sm-6 col-md-4 col-xs-12" style="padding-right:0"> |
| <img class="img-responsive" src="/images/in_memory_data.png" width="500" style="float:right;"/> |
| </div> |
| </div> |
| |
| <div class="page-heading">Two-Phase-Commit Protocol</div> |
| <p> |
| In a distributed system, a transaction may span multiple cluster nodes. Obviously, this poses some |
| challenges when we want to ensure that the data is consistent across all the participating nodes. |
| For example, in the event of a cluster node failure, the transaction may not have fully committed on |
| the lost node. A widely-used approach to ensuring data consistency in this type of scenario is the |
| two-phase commit protocol (2PC). |
| </p> |
| <p> |
| Ignite comes with one the fastest implementations of 2PC protocol. Moreover, |
| often when transactions span only one node or one partition, Ignite will utilize a much faster |
| one-phase-commit (1PC) protocol. Whenever the data is updated within a transaction, |
| Ignite will keep the transactional state in a local transaction map until the changes are committed, |
| at which point the data is transferred to the participating remote nodes. Only the nodes that hold the |
| primary or backup copies of the data will participate in the transaction. |
| </p> |
| <div class="page-heading">Consistency and Ignite Persistence</div> |
| <p> |
| If Ignite native persistence is used then all the updates are written to the write-ahead log (WAL) file |
| that guarantees data consistency, even if the cluster or individual nodes go down in the middle |
| of a transaction. |
| </p> |
| <p> |
| The purpose of the WAL is to propagate updates to the disk in the append-only mode, which is the fastest |
| way to persist data to disk. WAL provides a recovery mechanism for failure scenarios when a single node |
| or the whole cluster go down. A cluster can always be recovered to the |
| latest successfully committed transaction. |
| </p> |
| <div class="page-heading">Consistency and 3rd Party Persistence</div> |
| <p> |
| In scenarios when Ignite is used as a caching layer on top of 3rd party databases, such as |
| RDBMS, Ignite transactions will span both, the cached data and the external database. |
| For instance, when an RDBMS is used as a persistence layer, Ignite will write the |
| transactional changes to the database before it sends the commit message to participating cluster nodes. |
| This way, if a transaction fails at the database level, Ignite can still send the rollback message |
| to every node involved, keeping the data consistent between the in-memory cache and the external database. |
| </p> |
| |
| <div class="code-examples"> |
| <div class="page-heading">Code Examples</div> |
| <!-- Nav tabs --> |
| <ul id="messaging-examples" class="nav nav-tabs"> |
| <li class="active"><a href="#java-ex" aria-controls="home" data-toggle="tab">Java</a></li> |
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| <div class="tab-content"> |
| <div class="tab-pane active" id="java-ex"> |
| <pre class="brush:java"> |
| try (Transaction tx = transactions.txStart()) { |
| Integer hello = cache.get("Hello"); |
| |
| if (hello == 1) |
| cache.put("Hello", 11); |
| |
| cache.put("World", 22); |
| |
| tx.commit(); |
| } |
| </pre> |
| </div> |
| <div class="tab-pane" id="dotnet-ex"> |
| <pre class="brush:csharp"> |
| using (ITransaction tx = transactions.TxStart()) |
| { |
| var hello = cache.Get(1); |
| |
| if (hello != "Hello") |
| cache.Put(1, "Hello"); |
| |
| cache.Put(2, "World"); |
| |
| tx.Commit(); |
| } |
| </pre> |
| </div> |
| <div class="tab-pane" id="cpp-ex"> |
| <pre class="brush:cpp"> |
| Transaction tx = transactions.TxStart(); |
| |
| int hello = cache.Get("Hello"); |
| |
| if (hello == 1) |
| cache.Put("Hello", 11); |
| |
| cache.Put("World", 22); |
| |
| tx.Commit(); |
| </pre> |
| </div> |
| </div> |
| </div> |
| |
| <div class="page-heading">More on Ignite Transactions</div> |
| <table class="formatted" name="More on Ignite Transactions"> |
| <thead> |
| <tr> |
| <th width="35%" class="left">Feature</th> |
| <th>Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="features-left">ACID Transactions</td> |
| <td> |
| <p> |
| Ignite provides fully ACID compliant distributed transactions that ensure guaranteed consistency. |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="features-left">2-Phase-Commit</td> |
| <td> |
| <p> |
| Ignite utilizes a Two-Phase-Commit (2PC) protocol for its transactions and optimizes |
| to one-phase-commit whenever possible: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions#two-phase-commit-2pc" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="features-left">Write-Ahead Log</td> |
| <td> |
| <p> |
| Ignite persistence maintains the WAL that propagates updates to disk in the fastest way possible and |
| provides a recovery mechanism for scenarios where a single node or the whole cluster goes down: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/write-ahead-log" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="features-left">Deadlock-Free Transactions</td> |
| <td> |
| <p> |
| Ignite supports deadlock-free, optimistic transactions, which do not acquire any locks. |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions#deadlock-free-transactions" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="features-left">Deadlocks Detection</td> |
| <td> |
| <p> |
| Debugging and troubleshooting distributed deadlocks in Ignite: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions#deadlock-detection" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="left" width="35%">Transactional Entry Processor</td> |
| <td> |
| <p> |
| Ignite transactional entry processor allows executing collocated user logic on the server |
| side within a transaction: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/affinity-collocation#ignitecompute-vs-entryprocessor" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="left" width="35%">Cross-Partition Transactions</td> |
| <td> |
| <p> |
| In Ignite, transactions can be performed on all partitions of a cache across the whole |
| cluster: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions#ignitetransactions" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="left" width="35%">Locks</td> |
| <td> |
| <p> |
| Ignite allows developers to define explicit locks enforcing mutual exclusion on cached objects: |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/distributed-locks" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| <tr> |
| <td class="left">XA/JTA</td> |
| <td> |
| <p> |
| Ignite can be configured with a Java Transaction API (JTA) transaction manager lookup class. |
| </p> |
| <div class="page-links"> |
| <a href="https://apacheignite.readme.io/docs/transactions#integration-with-jta" target="docs">Docs for this feature <i class="fa fa-angle-double-right"></i></a> |
| </div> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </section> |
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