_2020-04-06_

**This release fixes a severe bug where OkHttp incorrectly detected and recovered from unhealthy
connections.** Stale or canceled connections were incorrectly attempted when they shouldn't have
been, leading to rare cases of infinite retries. Please upgrade to this release!

 *  Fix: don't return stale DNS entries in `DnsOverHttps`. We were caching DNS results indefinitely

    val headers =
      Headers.Builder()
        .add(
          "WWW-Authenticate",
          "Digest realm=\"myrealm\", nonce=\"fjalskdflwejrlaskdfjlaskdjflaks" +
            "jdflkasdf\", qop=\"auth\", stale=\"FALSE\"",
        )
        .build()
    val challenges = headers.parseChallenges("WWW-Authenticate")
    assertThat(challenges.size).isEqualTo(1)
    assertThat(challenges[0].scheme).isEqualTo("Digest")

import okhttp3.internal.connection.RealRoutePlanner
import okhttp3.internal.connection.RouteDatabase

/**
 * Manages reuse of HTTP and HTTP/2 connections for reduced network latency. HTTP requests that
 * share the same [Address] may share a [Connection]. This class implements the policy
 * of which connections to keep open for future use.
 *
 * @constructor Create a new connection pool with tuning parameters appropriate for a single-user

   *
   * Once true this is always true. Guarded by this.
   */
  var noNewExchanges = false

  /**
   * If true, this connection may not be used for coalesced requests. These are requests that could
   * share the same connection without sharing the same hostname.
   */
  private var noCoalescedConnections = false

  /**
   * The number of times there was a problem establishing a stream that could be due to route

    @JvmField val PREFIX_DIRTY = "OkHttp DIRTY :(\n".encodeUtf8()
    private const val FILE_HEADER_SIZE = 32L

    /**
     * Creates a new relay that reads a live stream from [upstream], using [file] to share that data
     * with other sources.
     *
     * **Warning:** callers to this method must immediately call [newSource] to create a source and
     * close that when they're done. Otherwise a handle to [file] will be leaked.

        .minFresh(3, TimeUnit.SECONDS)
        .onlyIfCached()
        .noTransform()
        .immutable()
        .build()
    assertThat(cacheControl.toString()).isEqualTo(
      "no-cache, no-store, max-age=1, max-stale=2, min-fresh=3, only-if-cached, " +
        "no-transform, immutable",
    )
    assertThat(cacheControl.noCache).isTrue()
    assertThat(cacheControl.noStore).isTrue()
    assertThat(cacheControl.maxAgeSeconds).isEqualTo(1)

        if (isPrivate) append("private, ")
        if (isPublic) append("public, ")
        if (mustRevalidate) append("must-revalidate, ")
        if (maxStaleSeconds != -1) append("max-stale=").append(maxStaleSeconds).append(", ")
        if (minFreshSeconds != -1) append("min-fresh=").append(minFreshSeconds).append(", ")
        if (onlyIfCached) append("only-if-cached, ")

 *   // The resource was cached! Show it.
 * } else {
 *   // The resource was not cached.
 * }
 * ```
 *
 * This technique works even better in situations where a stale response is better than no response.
 * To permit stale cached responses, use the `max-stale` directive with the maximum staleness in
 * seconds:
 *
 * ```java
 * Request request = new Request.Builder()
 *     .cacheControl(new CacheControl.Builder()

/**
 * A set of tasks that are executed in sequential order.
 *
 * Work within queues is not concurrent. This is equivalent to each queue having a dedicated thread
 * for its work; in practice a set of queues may share a set of threads to save resources.
 */
class TaskQueue internal constructor(
  internal val taskRunner: TaskRunner,
  internal val name: String,
) {
  val lock: ReentrantLock = ReentrantLock()

  // TODO GET preferred order - with tests to confirm this
  // 1. successful fresh cached GET response
  // 2. unsuccessful (404, 500) fresh cached GET response
  // 3. successful network response
  // 4. successful stale cached GET response
  // 5. unsuccessful response
  @Test
  fun usesCache() {
    val cache = Cache(cacheFs, "cache".toPath(), (100 * 1024).toLong())