* When making an HTTPS connection through an HTTP proxy, the proxy may issue an authentication challenge. OkHttp will call the proxy [authenticator](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-authenticator/) and try again.
 * When making TLS connections with multiple [connection specs](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-connection-spec/), these are attempted in sequence until the TLS handshake succeeds.

var errDataTooSmall = errors.New("Object size smaller than expected")

// errServerNotInitialized - server not initialized.
var errServerNotInitialized = errors.New("Server not initialized, please try again")

// errRPCAPIVersionUnsupported - unsupported rpc API version.
var errRPCAPIVersionUnsupported = errors.New("Unsupported rpc API version")

// errServerTimeMismatch - server times are too far apart.

RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt

# (1)!
COPY ./main.py /code/

# (2)!
CMD ["fastapi", "run", "main.py", "--port", "80"]
```

1. Copy the `main.py` file to the `/code` directory directly (without any `./app` directory).

2. Use `fastapi run` to serve your application in the single file `main.py`.

    requestSendStarted: Boolean,
  ): Boolean {
    // The application layer has forbidden retries.
    if (!client.retryOnConnectionFailure) return false

    // We can't send the request body again.
    if (requestSendStarted && requestIsOneShot(e, userRequest)) return false

    // This exception is fatal.
    if (!isRecoverable(e, requestSendStarted)) return false

    // No more routes to attempt.

   * worker, and then the first thread's call to delegate.execute() returns. Without this counter,
   * it would observe the QUEUING state and set it to QUEUED, and the worker would never be
   * scheduled again for future submissions.
   */
  @GuardedBy("queue")
  private long workerRunCount = 0;

  @RetainedWith private final QueueWorker worker = new QueueWorker();

  /** Use {@link MoreExecutors#newSequentialExecutor} */

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

   * worker, and then the first thread's call to delegate.execute() returns. Without this counter,
   * it would observe the QUEUING state and set it to QUEUED, and the worker would never be
   * scheduled again for future submissions.
   */
  @GuardedBy("queue")
  private long workerRunCount = 0;

  @RetainedWith private final QueueWorker worker = new QueueWorker();

  /** Use {@link MoreExecutors#newSequentialExecutor} */

			case <-ctx.Done():
				return
			case <-lkctx.Context().Done():
				// The context of the lock is canceled, this can happen
				// if one lock lost quorum due to cluster instability
				// in that case, try to lock again.
				break keepLock
			case ld.lockContext <- lkctx:
				// Send the lock context to anyone asking for it
			}
		}
	}
}

func mergeContext(ctx1, ctx2 context.Context) (context.Context, context.CancelFunc) {

package grid

import "strconv"

func _() {
	// An "invalid array index" compiler error signifies that the constant values have changed.
	// Re-run the stringer command to generate them again.
	var x [1]struct{}
	_ = x[handlerInvalid-0]
	_ = x[HandlerLockLock-1]
	_ = x[HandlerLockRLock-2]
	_ = x[HandlerLockUnlock-3]
	_ = x[HandlerLockRUnlock-4]
	_ = x[HandlerLockRefresh-5]

{* ../../docs_src/sql_databases/tutorial002_an_py310.py ln[96:103] hl[101] *}

### Run the App Again

You can run the app again:

<div class="termy">

```console
$ fastapi dev main.py

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>