What inspired **FastAPI**, how it compares to alternatives and what it learned from them.

## Intro { #intro }

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

I have been avoiding the creation of a new framework for several years. First I tried to solve all the features covered by **FastAPI** using many different frameworks, plug-ins, and tools.

    HTTP/2 to 16 MiB of unacknowledged data per connection. With this fix there is a limit of 16 MiB
    of unacknowledged data per stream and no per-connection limit.

 *  Fix: Don't operate on a connection after it's been returned to the pool. This race occurred
    on failed web socket connection attempts.

 *  Upgrade: [Okio 3.6.0][okio_3_6_0].

 *  Upgrade: [Kotlin 1.8.21][kotlin_1_8_21].


## Version 4.11.0

_2023-04-22_

    if (stream != null) return

    val hasRequestBody = request.body != null
    val requestHeaders = http2HeadersList(request)
    stream = http2Connection.newStream(requestHeaders, hasRequestBody)
    // We may have been asked to cancel while creating the new stream and sending the request
    // headers, but there was still no stream to close.
    if (canceled) {
      stream!!.closeLater(ErrorCode.CANCEL)
      throw IOException("Canceled")

            }

            List<TaskSegment> taskSegments = calculateTaskSegments(session);
            if (taskSegments.isEmpty()) {
                throw new NoGoalSpecifiedException("No goals have been specified for this build."
                        + " You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or"

   * 3.7.0 this is also true. But OkHttp 3.3.1 through 3.6.0 treated these as different.
   */
  @Test
  fun forJavaName_fromLegacyEnumName() {
    // These would have been considered equal in OkHttp 3.3.1, but now aren't.
    assertThat(forJavaName("SSL_RSA_EXPORT_WITH_RC4_40_MD5"))
      .isEqualTo(forJavaName("TLS_RSA_EXPORT_WITH_RC4_40_MD5"))

                    String message = artifact instanceof RelocatedArtifact relocated ? relocated.getMessage() : null;
                    logger.warn("The artifact " + child.getRelocations().get(0) + " has been relocated to " + artifact
                            + (message != null ? ": " + message : ""));
                }
            }
        }

        if (logger.isDebugEnabled()) {

   * response, or null if this response wasn't triggered by an automatic retry. The body of the
   * returned response should not be read because it has already been consumed by the redirecting
   * client.
   */
  @get:JvmName("priorResponse") val priorResponse: Response?,
  /**
   * Returns a [timestamp][System.currentTimeMillis] taken immediately before OkHttp

   * and response body streams; otherwise resources may be leaked.
   *
   * This method is safe to be called concurrently, but provides limited guarantees. If a transport
   * layer connection has been established (such as a HTTP/2 stream) that is terminated. Otherwise,
   * if a socket connection is being established, that is terminated.
   */
  override fun cancel() {
    if (canceled) return // Already canceled.

    allocateAndLeakAllocation(poolApi, c1)
    awaitGarbageCollection()
    assertThat(pool.closeConnections(100L)).isEqualTo(0L)
    assertThat(c1.calls).isEmpty()

    // Can't allocate once a leak has been detected.
    assertThat(c1.noNewExchanges).isTrue()
  }

  @Test fun interruptStopsThread() {
    val taskRunnerThreads = mutableListOf<Thread>()
    val taskRunner =
      TaskRunner(

    return writer
  }

  /**
   * Shortens the last frame from its original length to `length`. This will cause the peer to
   * close the socket as soon as this frame has been written; otherwise the peer stays open until
   * explicitly closed.
   */
  fun truncateLastFrame(length: Int): Http2Writer {
    val lastFrame = outFrames.removeAt(outFrames.size - 1)