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https://issues.apache.org/jira/browse/IGNITE-13098?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17168963#comment-17168963
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Anton Kalashnikov commented on IGNITE-13098:
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[~ivan.glukos][~mstepachev], I took a look at it. LGTM.
> TcpCommunicationSpi split to independent classes
> ------------------------------------------------
>
> Key: IGNITE-13098
> URL: https://issues.apache.org/jira/browse/IGNITE-13098
> Project: Ignite
> Issue Type: Bug
> Environment: TcpCommunicationSpi split to independent classes
> Reporter: Stepachev Maksim
> Assignee: Stepachev Maksim
> Priority: Major
> Fix For: 2.10
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> h2. Description
> This ticket describes requirements for TcpCommunicationSpi refactoring. The
> main goal is to split the class without changing behavior and public API.
> *Actual problem:*
> CurrentlyTcpCommunicationSpi has over 5K lines and includes about15+ inner
> classes like:
> # ShmemAcceptWorker
> # SHMemHandshakeClosure
> # ShmemWorker
> # CommunicationDiscoveryEventListener
> # CommunicationWorker
> # ConnectFuture
> # ConnectGateway
> # ConnectionKey
> # ConnectionPolicy
> # DisconnectedSessionInfo
> # FirstConnectionPolicy
> # HandshakeTimeoutObject
> # RoundRobinConnectionPolicy
> # TcpCommunicationConnectionCheckFuture
> # TcpCommunicationSpiMBeanImpl
> In addition, it contains logic of client connection life cycle, nio server
> handler, and handshake handler.
> The classes above have cyclic dependencies and high coupling.The whole
> mechanism works because classes have access to each other via parent class
> references. As a result, initialization of class isn't consistent. By
> consistent I mean that class created via constructor is ready to be used. All
> of the classes work with context and shareproperties everywhere.
> Many methods of TcpCommunicationSpi don’t have a single responsibility.
> Example is getNodeAttribute:,it makes client reservation, takes the IP
> address of the node and provides attributes.
> It works fine and we usually don’t have reasons to change anything. But if
> you want to create a test that has a little different behavior than a
> blocking message, you can't mock or change the behavior of inner classes. For
> example, test covering change in the handshake process. Some people make test
> methods in public API like "closeConnections" or "openSocketChannel" because
> the current design isn't fine for it. It also takes a lot of time for test
> development for minor changes.
> *Solution:*
> The scope of work is big and communication spi is place which should be
> changed carefully. I recommend to make this refactoring step by step.
> * The first idea is to split the parent class into independent classes and
> move them to the internal package. We should achieveSOLID when it’s done.
> * Extract spread logic to appropriate classes like ClientPool,
> HandshakeHandler, etc.
> * Make a common transfer object for TCSpi configuration.
> * Make dependencies direct if it is possible.
> * Initialize all dependencies in one place.
> * Make child classes context-free.
> * Try to do classes more testable.
> * Use the idea of dependency injection without a framework for it.
> *Benefits:*
> With the ability to write truly jUnit-style tests and cover functionality
> with better testing we get a way to easier develop new features and
> optimizations needed in such low-level components as TcpCommunicationSpi.
> Examples of features that improve usability of Apache Ignite a lot are:
> inverse communication connection with optimizations and connection
> multiplexing. Both of the features could be used in environments with
> restricted network connectivity (e.g. when connections between nodes could be
> established only in one direction).
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