### [Fast Fallback](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-ok-http-client/-builder/fast-fallback/)

Since version 5.0, `OkHttpClient` supports fast fallback, which is our implementation of Happy Eyeballs [RFC 6555](https://datatracker.ietf.org/doc/html/rfc6555).

---
name: Bug report
about: A reproducible problem
title: ''
labels: bug
assignees: ''

---

Good bug reports include a failing test! Writing a test helps you to isolate and describe the problem, and it helps us to fix it fast. Bug reports without a failing test or reproduction steps are likely to be closed.

Here’s an example test to get you started.

    email: ******@****.***
identifiers:
repository-code: 'https://github.com/tiangolo/fastapi'
url: 'https://fastapi.tiangolo.com'
abstract: >-
  FastAPI framework, high performance, easy to learn, fast to code,
  ready for production
keywords:
  - fastapi
  - pydantic
  - starlette

ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.

* <a href="https://docs.withcoherence.com/docs/configuration/frameworks?utm_medium=advertising&utm_source=fastapi&utm_campaign=banner%20january%2024#fast-api-example" class="external-link" target="_blank">Coherence</a>...

 */
package okhttp3

import okio.IOException

/**
 * Listener for connection events. Extend this class to monitor the new connections and closes.
 *
 * All event methods must execute fast, without external locking, cannot throw exceptions,
 * attempt to mutate the event parameters, or be reentrant back into the client.
 * Any IO - writing to files or network should be done asynchronously.
 */
@ExperimentalOkHttpApi

- [Project Conventions](https://github.com/istio/istio/wiki/Development-Conventions) - describes the conventions we use within the code base
- [Creating Fast and Lean Code](https://github.com/istio/istio/wiki/Writing-Fast-and-Lean-Code) - performance-oriented advice and guidelines for the code base

You'll find many other useful documents on our [Wiki](https://github.com/istio/istio/wiki).

## Introduction

 *
 *  3. Attempt plans from prior connect attempts for this call. These occur as either follow-ups to
 *     failed connect attempts (such as trying the next [ConnectionSpec]), or as attempts that lost
 *     a race in fast follow-up.
 *
 *  4. If there's no existing connection, make a list of routes (which may require blocking DNS
 *     lookups) and attempt a new connection them. When failures occur, retries iterate the list of

* <a href="https://docs.withcoherence.com/docs/configuration/frameworks?utm_medium=advertising&utm_source=fastapi&utm_campaign=banner%20january%2024#fast-api-example" class="external-link" target="_blank">Coherence</a>...

        plusIsSpace = plusIsSpace,
        unicodeAllowed = unicodeAllowed,
        charset = charset,
      )
      return out.readUtf8()
    }
    i += Character.charCount(codePoint)
  }

  // Fast path: no characters in [pos..limit) required encoding.
  return substring(pos, limit)
}

internal fun Buffer.writePercentDecoded(
  encoded: String,
  pos: Int,
  limit: Int,
  plusIsSpace: Boolean,