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kubernetes_metadata_watch_pods.rb
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/
kubernetes_metadata_watch_pods.rb
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# frozen_string_literal: true
#
# Fluentd Kubernetes Metadata Filter Plugin - Enrich Fluentd events with
# Kubernetes metadata
#
# Copyright 2017 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# TODO: this is mostly copy-paste from kubernetes_metadata_watch_namespaces.rb unify them
require_relative 'kubernetes_metadata_common'
module KubernetesMetadata
module WatchPods
include ::KubernetesMetadata::Common
def set_up_pod_thread
# Any failures / exceptions in the initial setup should raise
# Fluent:ConfigError, so that users can inspect potential errors in
# the configuration.
pod_watcher = start_pod_watch
Thread.current[:pod_watch_retry_backoff_interval] = @watch_retry_interval
Thread.current[:pod_watch_retry_count] = 0
# Any failures / exceptions in the followup watcher notice
# processing will be swallowed and retried. These failures /
# exceptions could be caused by Kubernetes API being temporarily
# down. We assume the configuration is correct at this point.
loop do
pod_watcher ||= get_pods_and_start_watcher
process_pod_watcher_notices(pod_watcher)
rescue GoneError => e
# Expected error. Quietly go back through the loop in order to
# start watching from the latest resource versions
@stats.bump(:pod_watch_gone_errors)
log.info('410 Gone encountered. Restarting pod watch to reset resource versions.', e)
pod_watcher = nil
rescue KubeException => e
if e.error_code == 401
# recreate client to refresh token
log.info("Encountered '401 Unauthorized' exception in watch, recreating client to refresh token")
create_client()
namespace_watcher = nil
else
# treat all other errors the same as StandardError, log, swallow and reset
@stats.bump(:pod_watch_failures)
if Thread.current[:pod_watch_retry_count] < @watch_retry_max_times
# Instead of raising exceptions and crashing Fluentd, swallow
# the exception and reset the watcher.
log.info(
'Exception encountered parsing pod watch event. The ' \
'connection might have been closed. Sleeping for ' \
"#{Thread.current[:pod_watch_retry_backoff_interval]} " \
'seconds and resetting the pod watcher.', e
)
sleep(Thread.current[:pod_watch_retry_backoff_interval])
Thread.current[:pod_watch_retry_count] += 1
Thread.current[:pod_watch_retry_backoff_interval] *= @watch_retry_exponential_backoff_base
pod_watcher = nil
else
# Since retries failed for many times, log as errors instead
# of info and raise exceptions and trigger Fluentd to restart.
message =
'Exception encountered parsing pod watch event. The ' \
'connection might have been closed. Retried ' \
"#{@watch_retry_max_times} times yet still failing. Restarting."
log.error(message, e)
raise Fluent::UnrecoverableError, message
end
end
rescue StandardError => e
@stats.bump(:pod_watch_failures)
if Thread.current[:pod_watch_retry_count] < @watch_retry_max_times
# Instead of raising exceptions and crashing Fluentd, swallow
# the exception and reset the watcher.
log.info(
'Exception encountered parsing pod watch event. The ' \
'connection might have been closed. Sleeping for ' \
"#{Thread.current[:pod_watch_retry_backoff_interval]} " \
'seconds and resetting the pod watcher.', e
)
sleep(Thread.current[:pod_watch_retry_backoff_interval])
Thread.current[:pod_watch_retry_count] += 1
Thread.current[:pod_watch_retry_backoff_interval] *= @watch_retry_exponential_backoff_base
pod_watcher = nil
else
# Since retries failed for many times, log as errors instead
# of info and raise exceptions and trigger Fluentd to restart.
message =
'Exception encountered parsing pod watch event. The ' \
'connection might have been closed. Retried ' \
"#{@watch_retry_max_times} times yet still failing. Restarting."
log.error(message, e)
raise Fluent::UnrecoverableError, message
end
end
end
def start_pod_watch
get_pods_and_start_watcher
rescue StandardError => e
message = 'start_pod_watch: Exception encountered setting up pod watch ' \
"from Kubernetes API #{@apiVersion} endpoint " \
"#{@kubernetes_url}: #{e.message}"
message += " (#{e.response})" if e.respond_to?(:response)
log.debug(message)
raise Fluent::ConfigError, message
end
# List all pods, record the resourceVersion and return a watcher starting
# from that resourceVersion.
def get_pods_and_start_watcher
options = {
resource_version: '0' # Fetch from API server cache instead of etcd quorum read
}
if ENV['K8S_NODE_NAME']
options[:field_selector] = 'spec.nodeName=' + ENV['K8S_NODE_NAME']
end
if @last_seen_resource_version
options[:resource_version] = @last_seen_resource_version
else
pods = @client.get_pods(options)
pods[:items].each do |pod|
cache_key = pod[:metadata][:uid]
@cache[cache_key] = parse_pod_metadata(pod)
@stats.bump(:pod_cache_host_updates)
end
# continue watching from most recent resourceVersion
options[:resource_version] = pods[:metadata][:resourceVersion]
end
watcher = @client.watch_pods(options)
reset_pod_watch_retry_stats
watcher
end
# Reset pod watch retry count and backoff interval as there is a
# successful watch notice.
def reset_pod_watch_retry_stats
Thread.current[:pod_watch_retry_count] = 0
Thread.current[:pod_watch_retry_backoff_interval] = @watch_retry_interval
end
# Process a watcher notice and potentially raise an exception.
def process_pod_watcher_notices(watcher)
watcher.each do |notice|
# store version we processed to not reprocess it ... do not unset when there is no version in response
version = ( # TODO: replace with &.dig once we are on ruby 2.5+
notice[:object] && notice[:object][:metadata] && notice[:object][:metadata][:resourceVersion]
)
@last_seen_resource_version = version if version
case notice[:type]
when 'MODIFIED'
reset_pod_watch_retry_stats
cache_key = notice.dig(:object, :metadata, :uid)
cached = @cache[cache_key]
if cached
@cache[cache_key] = parse_pod_metadata(notice[:object])
@stats.bump(:pod_cache_watch_updates)
elsif ENV['K8S_NODE_NAME'] == notice[:object][:spec][:nodeName]
@cache[cache_key] = parse_pod_metadata(notice[:object])
@stats.bump(:pod_cache_host_updates)
else
@stats.bump(:pod_cache_watch_misses)
end
when 'DELETED'
reset_pod_watch_retry_stats
# ignore and let age out for cases where pods
# deleted but still processing logs
@stats.bump(:pod_cache_watch_delete_ignored)
when 'ERROR'
if notice[:object] && notice[:object][:code] == 410
@last_seen_resource_version = nil # requested resourceVersion was too old, need to reset
@stats.bump(:pod_watch_gone_notices)
raise GoneError
else
@stats.bump(:pod_watch_error_type_notices)
message = notice[:object][:message] if notice[:object] && notice[:object][:message]
raise "Error while watching pods: #{message}"
end
else
reset_pod_watch_retry_stats
# Don't pay attention to creations, since the created pod may not
# end up on this node.
@stats.bump(:pod_cache_watch_ignored)
end
end
end
end
end