The Push Queue is mostly a normal queue, but it has some special logic to merge push requests for each given proxy. This results in each proxy having 0 or 1 outstanding push requests; if additional updates come in the existing push request is just expanded.

Another job polls this queue and triggers each client to start a push.

```mermaid
graph TD
    subgraph Config Flow

      weight: Int,
      exclusive: Boolean,
    )

    /**
     * HTTP/2 only. Receive a push promise header block.
     *
     * A push promise contains all the headers that pertain to a server-initiated request, and a
     * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent
     * as a part of the response to `streamId`.
     *

        flags = FLAG_ACK,
      )
      sink.flush()
    }
  }

  /**
   * HTTP/2 only. Send a push promise header block.
   *
   * A push promise contains all the headers that pertain to a server-initiated request, and a
   * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as
   * a part of the response to `streamId`. The `promisedStreamId` has a priority of one greater than

  private val writerQueue = taskRunner.newQueue()

  /** Ensures push promise callbacks events are sent in order per stream. */
  private val pushQueue = taskRunner.newQueue()

  /** Notifies the listener of settings changes. */
  private val settingsListenerQueue = taskRunner.newQueue()

  /** User code to run in response to push promise events. */
  private val pushObserver: PushObserver = builder.pushObserver

</p>
<p align="center">
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#### Implementation changes

 * Support Android `TrafficStats` socket tagging.
 * Drop authentication headers on redirect.
 * Added support for compressed data frames.
 * Process push promise callbacks in order.
 * Update to http/2 draft 12.
 * Update to HPACK draft 07.
 * Add ALPN support. Maven will use ALPN on OpenJDK 8.
 * Update NPN dependency to target `jdk7u60-b13` and `Oracle jdk7u55-b13`.