Motivation

Users should be able to control thin client retry behavior in case of connection loss.

Description

• Automatic reconnect on failure is present in all thin clients (see Thin clients features).
• Java thin client also implements automatic operation retry. For example, if a cache.put() fails due to a connection issue, Ignite will try to establish a new connection (or use an existing one to another server), and execute cache.put() again. This behavior is dangerous for non-idempotent operations. In a case when the server completes an operation, but the connection fails during the response, the client will still retry the operation. For example, an SQL query that increments a column by 1 can be executed two or more times, leading to unexpected results.
• Non-Java thin clients do not include automatic operation retry, so the users have to implement it like this:

while (maxRetries-- > 0)
{
    try
    {
        cache.Put(1, "Hello");
        break;
    }
    catch (Exception e) when (e.GetBaseException() is SocketException)
    {
        // Retry.
    }
}

Current State Summary

• Java thin client has retry, but it can be dangerous and can't be fine tuned
• Other thin client don't have retry and user has to write cumbersome code

Proposal

TODO: ClientRetryPolicy interface.

Risks and Assumptions

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Discussion Links

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Reference Links

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• Code sample: https://github.com/apache/ignite/pull/9586

Tickets

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