override def decide()

in management-cluster-bootstrap/src/main/scala/org/apache/pekko/management/cluster/bootstrap/LowestAddressJoinDecider.scala [39:114]
65 lines of code
13 McCabe index (conditional complexity)

  override def decide(info: SeedNodesInformation): Future[JoinDecision] =
    if (info.hasSeedNodes) {
      val seeds = joinOtherSeedNodes(info)
      if (seeds.isEmpty) KeepProbing.asCompletedFuture else JoinOtherSeedNodes(seeds).asCompletedFuture
    } else if (!hasEnoughContactPoints(info)) {
      log.info(
        BootstrapLogMarker.inProgress(info.contactPoints.map(contactPointString), info.allSeedNodes),
        "Discovered [{}] contact points, confirmed [{}], which is less than the required [{}], retrying",
        info.contactPoints.size,
        info.seedNodesObservations.size,
        settings.contactPointDiscovery.requiredContactPointsNr)
      KeepProbing.asCompletedFuture
    } else if (!isPastStableMargin(info)) {
      log.debug(
        BootstrapLogMarker.inProgress(info.contactPoints.map(contactPointString), info.allSeedNodes),
        "Contact points observations have changed more recently than the stable-margin [{}], changed at [{}], " +
        "not joining myself. This process will be retried.",
        settings.contactPointDiscovery.stableMargin,
        info.contactPointsChangedAt)
      KeepProbing.asCompletedFuture
    } else {
      // no seed nodes
      val contactPointsWithoutSeedNodesObservations =
        if (isConfirmedCommunicationWithAllContactPointsRequired(info))
          info.contactPoints -- info.seedNodesObservations.map(_.contactPoint)
        else
          Set.empty[ResolvedTarget]
      if (contactPointsWithoutSeedNodesObservations.isEmpty) {
        // got info from all contact points as expected
        val lowestAddress = lowestAddressContactPoint(info)
        // can the lowest address, if exists, join self
        val isJoinSelfAble = lowestAddress.exists(canJoinSelf(_, info))

        if (isJoinSelfAble && settings.newClusterEnabled)
          JoinSelf.asCompletedFuture
        else {
          if (settings.newClusterEnabled) {
            if (log.isInfoEnabled)
              log.info(
                BootstrapLogMarker.inProgress(info.contactPoints.map(contactPointString), info.allSeedNodes),
                "Exceeded stable margins without locating seed-nodes, however this node {} is NOT the lowest address " +
                "out of the discovered endpoints in this deployment, thus NOT joining self. Expecting node [{}] " +
                "(out of [{}]) to perform the self-join and initiate the cluster.",
                contactPointString(selfContactPoint),
                lowestAddress.map(contactPointString).getOrElse(""),
                info.contactPoints.map(contactPointString).mkString(", "))
          } else {
            if (log.isWarningEnabled)
              log.warning(
                BootstrapLogMarker.inProgress(info.contactPoints.map(contactPointString), info.allSeedNodes),
                "Exceeded stable margins without locating seed-nodes, however this node {} is configured with " +
                "new-cluster-enabled=off, thus NOT joining self. Expecting existing cluster or node [{}] " +
                "(out of [{}]) to perform the self-join and initiate the cluster.",
                contactPointString(selfContactPoint),
                lowestAddress.map(contactPointString).getOrElse(""),
                info.contactPoints.map(contactPointString).mkString(", "))
          }

          // the probing will continue until the lowest addressed node decides to join itself.
          // note, that due to DNS changes this may still become this node! We'll then await until the dns stableMargin
          // is exceeded and would decide to try joining self again (same code-path), that time successfully though.
          KeepProbing.asCompletedFuture
        }
      } else {
        // missing info from some contact points (e.g. because of probe failing)
        if (log.isInfoEnabled)
          log.info(
            BootstrapLogMarker.inProgress(info.contactPoints.map(contactPointString), info.allSeedNodes),
            "Exceeded stable margins but missing seed node information from some contact points [{}] (out of [{}])",
            contactPointsWithoutSeedNodesObservations.map(contactPointString).mkString(", "),
            info.contactPoints.map(contactPointString).mkString(", "))

        KeepProbing.asCompletedFuture
      }

    }