Streamline implementation of optional HA

Try to reduce the number of `if` statements in code, and remove the need
to specify `ha` as a Boolean plan parameter. Instead, do HA if HA
systems are specified, and don't if they aren't.

plans/configure.pp

@@ -1,13 +1,13 @@
 # @summary Configure first-time classification and HA setup
 #
 plan pe_xl::configure (
-  Boolean             $ha = true,
   String[1]           $master_host,
   String[1]           $puppetdb_database_host,
-  String[1]           $master_replica_host,
-  String[1]           $puppetdb_database_replica_host,
   Array[String[1]]    $compiler_hosts = [ ],
 
+  Optional[String[1]] $master_replica_host = undef,
+  Optional[String[1]] $puppetdb_database_replica_host, = undef,
+
   # This parameter exists primarily to enable the use case of running
   # pe_xl::configure over the PCP transport. An orchestrator restart happens
   # during provision replica. Running `bolt plan run` directly on the master
@@ -22,6 +22,18 @@
   String[1]           $stagingdir = '/tmp',
 ) {
 
+  $ha_hosts = [
+    $master_replica_host,
+    $puppetdb_database_replica_host,
+  ].pe_xl::flatten_compact()
+
+  # Ensure valid input for HA
+  $ha = $ha_hosts.size ? {
+    0       => false,
+    2       => true,
+    default => fail("Must specify either both or neither of master_replica_host, puppetdb_database_replica_host"),
+  }
+
   # Allow for the configure task to be run local to the master.
   $master_target = $executing_on_master ? {
     true  => "local://${master_host}",
@@ -43,43 +55,27 @@
 
   # Set up the console node groups to configure the various hosts in their
   # roles
-  if $ha {
-    run_task('pe_xl::configure_node_groups', $master_target,
-      master_host                    => $master_host,
-      master_replica_host            => $master_replica_host,
-      puppetdb_database_host         => $puppetdb_database_host,
-      puppetdb_database_replica_host => $puppetdb_database_replica_host,
-      compiler_pool_address          => $compiler_pool_address,
-    )
-  } else {
-    run_task('pe_xl::configure_node_groups', $master_target,
-      master_host                    => $master_host,
-      puppetdb_database_host         => $puppetdb_database_host,
-      compiler_pool_address          => $compiler_pool_address,
-    )
-  }
+  run_task('pe_xl::configure_node_groups', $master_target,
+    master_host                    => $master_host,
+    master_replica_host            => $master_replica_host,
+    puppetdb_database_host         => $puppetdb_database_host,
+    puppetdb_database_replica_host => $puppetdb_database_replica_host,
+    compiler_pool_address          => $compiler_pool_address,
+  )
 
   # Run Puppet in no-op on the compilers so that their status in PuppetDB
   # is updated and they can be identified by the puppet_enterprise module as
   # CMs
-  if $ha {
-    run_task('pe_xl::puppet_runonce', [$compiler_hosts, $master_replica_host],
-      noop => true,
-    )
-  } else {
-    run_task('pe_xl::puppet_runonce', $compiler_hosts, noop => true)
-  }
+  run_task('pe_xl::puppet_runonce', [$compiler_hosts, $master_replica_host].pe_xl::flatten_compact,
+    noop => true,
+  )
 
   # Run Puppet on the PuppetDB Database hosts to update their auth
   # configuration to allow the compilers to connect
-  if $ha {
-    run_task('pe_xl::puppet_runonce', [
-      $puppetdb_database_host,
-      $puppetdb_database_replica_host,
-    ])
-  } else {
-    run_task('pe_xl::puppet_runonce', $puppetdb_database_host)
-  }
+  run_task('pe_xl::puppet_runonce', [
+    $puppetdb_database_host,
+    $puppetdb_database_replica_host,
+  ].pe_xl::flatten_compact)
 
   # Run Puppet on the master to ensure all services configured and
   # running in prep for provisioning the replica. This is done separately so
@@ -99,27 +95,16 @@
       master_replica         => $master_replica_host,
       token_file             => $token_file,
     )
-
   }
 
   # Run Puppet everywhere to pick up last remaining config tweaks
-  if $ha {
-    $all_hosts = [
-      $master_target,
-      $puppetdb_database_host,
-      $compiler_hosts,
-      $master_replica_host,
-      $puppetdb_database_replica_host,
-    ].pe_xl::flatten_compact()
-  } else {
-    $all_hosts = [
-      $master_target,
-      $puppetdb_database_host,
-      $compiler_hosts,
-    ].pe_xl::flatten_compact()
-  }
-
-  run_task('pe_xl::puppet_runonce', $all_hosts)
+  run_task('pe_xl::puppet_runonce', [
+    $master_target,
+    $puppetdb_database_host,
+    $compiler_hosts,
+    $master_replica_host,
+    $puppetdb_database_replica_host,
+  ].pe_xl::flatten_compact)
 
   # Deploy an environment if a deploy environment is specified
   if $deploy_environment {

plans/init.pp

@@ -8,7 +8,6 @@
   Boolean $install   = false,
   Boolean $configure = false,
   Boolean $upgrade   = false,
-  Boolean $ha        = true,
 
   Optional[String[1]]        $master_host = undef,
   Optional[String[1]]        $puppetdb_database_host = undef,
@@ -30,7 +29,6 @@
 
   if $install {
     run_plan('pe_xl::install',
-      ha                             => $ha,
       master_host                    => $master_host,
       puppetdb_database_host         => $puppetdb_database_host,
       master_replica_host            => $master_replica_host,
@@ -48,7 +46,6 @@
 
   if $configure {
     run_plan('pe_xl::configure',
-      ha                             => $ha,
       master_host                    => $master_host,
       puppetdb_database_host         => $puppetdb_database_host,
       master_replica_host            => $master_replica_host,
@@ -65,7 +62,6 @@
 
   if $upgrade {
     run_plan('pe_xl::upgrade',
-      ha                             => $ha,
       master_host                    => $master_host,
       puppetdb_database_host         => $puppetdb_database_host,
       master_replica_host            => $master_replica_host,