Feat: watches use a persistent http connection to prevent zombification.

To configure the keep alive timeout, instanciate KubeClient::Client with
the `:keep_alive_timeout` keyword argument, defaulting to 60 (seconds).

Fixes issue ManageIQ#512.

lib/kubeclient.rb

@@ -54,6 +54,8 @@ class Client
  DEFAULT_HTTP_PROXY_URI = nil
  DEFAULT_HTTP_MAX_REDIRECTS = 10
 
+ DEFAULT_KEEP_ALIVE_TIMEOUT = 60
+
  SEARCH_ARGUMENTS = {
  'labelSelector' => :label_selector,
  'fieldSelector' => :field_selector,
@@ -88,6 +90,7 @@ class Client
  attr_reader :auth_options
  attr_reader :http_proxy_uri
  attr_reader :http_max_redirects
+ attr_reader :keep_alive_timeout
  attr_reader :headers
  attr_reader :discovered
 
@@ -117,6 +120,7 @@ def initialize_client(
  timeouts: DEFAULT_TIMEOUTS,
  http_proxy_uri: DEFAULT_HTTP_PROXY_URI,
  http_max_redirects: DEFAULT_HTTP_MAX_REDIRECTS,
+ keep_alive_timeout: DEFAULT_KEEP_ALIVE_TIMEOUT,
  as: :ros
  )
  validate_auth_options(auth_options)
@@ -134,6 +138,7 @@ def initialize_client(
  @timeouts = DEFAULT_TIMEOUTS.merge(timeouts)
  @http_proxy_uri = http_proxy_uri ? http_proxy_uri.to_s : nil
  @http_max_redirects = http_max_redirects
+ @keep_alive_timeout = keep_alive_timeout
  @as = as
 
  validate_bearer_token_file
@@ -789,6 +794,7 @@ def http_options(uri)
  headers: @headers,
  http_proxy_uri: @http_proxy_uri,
  http_max_redirects: http_max_redirects,
+ keep_alive_timeout: keep_alive_timeout,
  bearer_token_file: @auth_options[:bearer_token_file],
  bearer_token: @auth_options[:bearer_token]
  }

lib/kubeclient/watch_stream.rb

@@ -11,6 +11,7 @@ def initialize(uri, http_options, formatter:)
  @http_client = nil
  @http_options = http_options
  @http_options[:http_max_redirects] ||= Kubeclient::Client::DEFAULT_HTTP_MAX_REDIRECTS
+ @http_options[:keep_alive_timeout] ||= Kubeclient::Client::DEFAULT_KEEP_ALIVE_TIMEOUT
  @formatter = formatter
  end
 
@@ -65,6 +66,10 @@ def build_client
  )
  end
 
+ if @http_options[:keep_alive_timeout].positive?
+ client = client.persistent(@uri.origin, timeout: @http_options[:keep_alive_timeout])
+ end
+
  bearer_token = nil
  if @http_options[:bearer_token_file]
  bearer_token_file = @http_options[:bearer_token_file]