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Doc: improve documentation for event loop statistics.
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‎doc/admin-guide/monitoring/statistics/core-statistics.en.rst‎

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core/http-header.en
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core/eventloop.en
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core/websocket.en
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core/misc.en
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‎doc/admin-guide/monitoring/statistics/core/eventloop.en.rst‎

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.. Licensed to the Apache Software Foundation (ASF) under one or more contributor license
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agreements. See the NOTICE file distributed with this work for additional information regarding
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copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software distributed under the License
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is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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or implied. See the License for the specific language governing permissions and limitations
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under the License.
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.. include:: ../../../../common.defs
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.. _admin-stats-core-eventloop:
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Event Loop
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**********
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The core of network processing in |TS| is the :term:`event loop`. This loop executes any pending
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events and performs I/O operations on network connections. The time spent in the event loop is a
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critical component of latency as any network connection has at most one I/O operation per loop. The
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general mechanism is
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* Dispatch any pending events.
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* Check for any pending I/O activity. This wait a variable amount of time. It is at most
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:ts:cv:`proxy.config.thread.max_heartbeat_mseconds` milliseconds. It is reduced to the amount of
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time until the next scheduled event. Although this is done in milliseconds, system timers are
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rarely that accurate.
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* For each network connection dispatch an event to the corresponding network virtual connection
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object.
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* Dispatch any events generated while handling I/O in the previous step
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Event loops that take a long time will have a noticeable impact on transaction latency. There are a
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number of statistics gathered to help determine if this is the problem. Because instantaneous values
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are not useful, the data is gathered in three different time buckets - 10, 100, and 1000 seconds.
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There is a parallel set of statistics for each, and each larger time period includes the smaller
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ones. The statistic values are all "for this time period". For example, the statistic
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"proxy.process.eventloop.count.100s" is "the number of event loops executed in the last 100
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seconds".
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In general, the maximum loop time will create a floor under response latency. If that is frequently
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high then it is likely transactions are experiencing significant latency.
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.. rubric:: 10 Second Metrics
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.. ts:stat:: global proxy.process.eventloop.count.10s integer
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Number of event loops executed in the last 10 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.10s integer
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Number of events dispatched in the last 10 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.min.10s integer
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Minimum number of events dispatched in a single loop in the last 10 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.max.10s integer
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Maximum number of events dispatched in a single loop in the last 10 seconds.
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.. ts:stat:: global proxy.process.eventloop.wait.10s integer
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Number of loops in which the I/O activity check was done with a non-zero time out in the last 10
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seconds.
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.. ts:stat:: global proxy.process.eventloop.time.min.10s integer
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:units: nanoseconds
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The minimum amount of time spent in a single loop in the last 10 seconds.
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.. ts:stat:: global proxy.process.eventloop.time.max.10s integer
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:units: nanoseconds
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The maximum amount of time spent in a single loop in the last 10 seconds.
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.. rubric:: 100 Second Metrics
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.. ts:stat:: global proxy.process.eventloop.count.100s integer
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Number of event loops executed in the last 100 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.100s integer
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Number of events dispatched in the last 100 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.min.100s integer
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Minimum number of events dispatched in a single loop in the last 100 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.max.100s integer
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Maximum number of events dispatched in a single loop in the last 100 seconds.
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.. ts:stat:: global proxy.process.eventloop.wait.100s integer
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Number of loops in which the I/O activity check was done with a non-zero time out in the last 100
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seconds.
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.. ts:stat:: global proxy.process.eventloop.time.min.100s integer
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:units: nanoseconds
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The minimum amount of time spent in a single loop in the last 100 seconds.
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.. ts:stat:: global proxy.process.eventloop.time.max.100s integer
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:units: nanoseconds
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The maximum amount of time spent in a single loop in the last 100 seconds.
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.. rubric:: 1000 Second Metrics
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.. ts:stat:: global proxy.process.eventloop.count.1000s integer
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Number of event loops executed in the last 1000 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.1000s integer
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Number of events dispatched in the last 1000 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.min.1000s integer
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Minimum number of events dispatched in a single loop in the last 1000 seconds.
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.. ts:stat:: global proxy.process.eventloop.events.max.1000s integer
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Maximum number of events dispatched in a single loop in the last 1000 seconds.
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.. ts:stat:: global proxy.process.eventloop.wait.1000s integer
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Number of loops in which the I/O activity check was done with a non-zero time out in the last 1000
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seconds.
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.. ts:stat:: global proxy.process.eventloop.time.min.1000s integer
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:units: nanoseconds
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The minimum amount of time spent in a single loop in the last 1000 seconds.
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.. ts:stat:: global proxy.process.eventloop.time.max.1000s integer
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:units: nanoseconds
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The maximum amount of time spent in a single loop in the last 1000 seconds.

‎doc/admin-guide/monitoring/statistics/core/misc.en.rst‎

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.. ts:stat:: global proxy.process.http.misc_count_stat integer
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.. ts:stat:: global proxy.process.http.misc_user_agent_bytes_stat integer
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.. ts:stat:: global proxy.process.eventloop.count integer
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Number of event loops executed.
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.. ts:stat:: global proxy.process.eventloop.events integer
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Number of events dispatched.
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.. ts:stat:: global proxy.process.eventloop.events.min integer
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Minimum number of events dispatched in a loop.
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.. ts:stat:: global proxy.process.eventloop.events.max integer
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Maximum number of events dispatched in a loop.
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.. ts:stat:: global proxy.process.eventloop.wait integer
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Number of loops that did a conditional wait.
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.. ts:stat:: global proxy.process.eventloop.time.min integer
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:units: nanoseconds
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Shortest time spent in a loop.
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.. ts:stat:: global proxy.process.eventloop.time.max integer
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:units: nanoseconds
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Longest time spent in a loop.

‎doc/admin-guide/monitoring/statistics/index.en.rst‎

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