indexer-apache-errorlog.conf is causing the slowness problem, even though there are ZERO event in it's flow

indexer-apache-accesslog.conf

input {
  redis {
    host           => "log1a.us-east-1"
    type           => "apache-accesslog"
    data_type      => "list"
    key            => "logstash:apache:accesslog"
    message_format => "json_event"
    charset        => "UTF-8"
    db             => 0
    debug          => false
    threads        => 1
  }
}

output {
  elasticsearch_http {
    tags         => [ "apache-accesslog" ]
    host         => "log1a.us-east-1"
    index        => "apache-accesslog-%{+YYYY.MM.dd}"
    flush_size   => 100
    exclude_tags => [ "metric" ]
  }
}

indexer-apache-errorlog.conf

input {
  redis {
    host      => "log1a.us-east-1"
    type      => "apache-errorlog"
    tags      => [ "apache-errorlog" ]
    data_type => "list"
    key       => "logstash:apache:errorlog"
    format    => "plain"
    charset   => "UTF-8"
    db        => 0
    debug     => false
    threads   => 1
  }
}

filter {
  grok {
    tags           => [ "apache-errorlog" ]
    patterns_dir   => [ "/opt/logstash/patterns", "/etc/logstash/patterns.d" ]
    match          => [ "@message", "%{PHPAPACHEERROR}" ]
    match          => [ "@message", "%{GENERICAPACHEERROR}" ]
    break_on_match => true
  }
  date {
    tags         => [ "apache-errorlog" ]
    match        => [ "timestamp", "EEE MMM dd HH:mm:ss yyyy" ]
    exclude_tags => [ "_grokparsefailure" ]
  }
  mutate {
    tags    => [ "apache-errorlog" ]
    replace => [ "@message", "%{message}" ]
    remove  => [ "message" ]
  }
}

output {
  elasticsearch_http {
    tags         => [ "apache-accesslog" ]
    host         => "log1a.us-east-1"
    index        => "apache-errorlog-%{+YYYY.MM.dd}"
    flush_size   => 1
    exclude_tags => [ "metric" ]
  }
}

indexer-metrics.conf

filter {
  metrics {
    meter   => "events"
    add_tag => [ "metric" ]
  }

  grep {
    tags      => [ "metric" ]
    match     => [ "events.rate_1m", ".*" ]
    drop      => false
    negate    => true
    add_field => [ "events.rate_1m", "0.0" ]
  }
}

output {
#  stdout {
#    debug        => true
#    debug_format => "json"
#  }

  stdout {
    tags    => [ "metric" ]
    message => "events rate: %{events.rate_1m}"
  }
}

patterns

APACHEERRORTIME %{DAY} %{MONTH} %{MONTHDAY} %{TIME} %{YEAR}
APACHEERRORPREFIX \[%{APACHEERRORTIME:timestamp}\] \[%{NOTSPACE:apacheseverity}\] \[client %{IPORHOST:sourcehost}\]
GENERICAPACHEERROR %{APACHEERRORPREFIX} %{GREEDYDATA:message}

PHPSEVERITY PHP %{WORD:phpseverity}( error)?\:
PHPMESSAGE %{PHPSEVERITY} %{GREEDYDATA}
PHPAPACHEERROR %{APACHEERRORPREFIX} %{PHPMESSAGE:message}