aboutsummaryrefslogtreecommitdiffstats
path: root/lib/sasl/doc/src/overload.xml
diff options
context:
space:
mode:
authorSiri Hansen <[email protected]>2016-02-19 12:00:47 +0100
committerSiri Hansen <[email protected]>2016-02-19 12:05:18 +0100
commitc56cdb91d057cdb40bb79d4f49e88966c0244017 (patch)
tree3a4976ce883b357da73f7b658bbf031280c17479 /lib/sasl/doc/src/overload.xml
parent33f8fe899ec052ab0a33566f7e9e92fadf3f0a68 (diff)
downloadotp-c56cdb91d057cdb40bb79d4f49e88966c0244017.tar.gz
otp-c56cdb91d057cdb40bb79d4f49e88966c0244017.tar.bz2
otp-c56cdb91d057cdb40bb79d4f49e88966c0244017.zip
Remove module 'overload' from SASL
The reason is that the module is not used, and that we se no obvious use case for it.
Diffstat (limited to 'lib/sasl/doc/src/overload.xml')
-rw-r--r--lib/sasl/doc/src/overload.xml152
1 files changed, 0 insertions, 152 deletions
diff --git a/lib/sasl/doc/src/overload.xml b/lib/sasl/doc/src/overload.xml
deleted file mode 100644
index 2f19cd9088..0000000000
--- a/lib/sasl/doc/src/overload.xml
+++ /dev/null
@@ -1,152 +0,0 @@
-<?xml version="1.0" encoding="utf-8" ?>
-<!DOCTYPE erlref SYSTEM "erlref.dtd">
-
-<erlref>
- <header>
- <copyright>
- <year>1996</year><year>2013</year>
- <holder>Ericsson AB. All Rights Reserved.</holder>
- </copyright>
- <legalnotice>
- 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.
-
- </legalnotice>
-
- <title>overload</title>
- <prepared>Peter H&ouml;gfeldt</prepared>
- <responsible>Peter H&ouml;gfeldt</responsible>
- <docno></docno>
- <approved>(Joe Armstrong)</approved>
- <checked></checked>
- <date>1996-10-29</date>
- <rev>A</rev>
- <file>overload.sgml</file>
- </header>
- <module>overload</module>
- <modulesummary>An Overload Regulation Process</modulesummary>
- <description>
- <warning>
- <p>
- All functions in this module are deprecated and will be
- removed in a future release.
- </p>
- </warning>
- <p><c>overload</c> is a process that indirectly regulates the CPU
- usage in the system. The idea is that a main application calls
- function
- <seealso marker="#request/0"><c>request/0</c></seealso>
- before starting a major job and
- proceeds with the job if the return value is positive; otherwise
- the job must not be started.</p>
- <p><c>overload</c> is part of the <c>SASL</c> application and all
- configuration parameters are defined there.</p>
- <p>A set of two intensities are maintained, the <c>total intensity</c>
- and the <c>accept intensity</c>. For that purpose,
- there are two configuration parameters, <c>MaxIntensity</c>
- and <c>Weight</c>; both are measured in 1/second.</p>
- <p>Then total and accept intensities are calculated as
- follows. Assume that the time of the current call to
- <c>request/0</c> is <c>T(n)</c> and that the time of the
- previous call was <c>T(n-1)</c>.</p>
- <list type="bulleted">
- <item>
- <p>The current <c>total intensity</c>, denoted
- <c>TI(n)</c>, is calculated according to the formula</p>
- <p><c>TI(n) = exp(-Weight*(T(n) - T(n-1)) * TI(n-1) + Weight</c>,</p>
- <p>where <c>TI(n-1)</c> is the previous <c>total intensity</c>.</p>
- </item>
- <item>
- <p>The current <c>accept intensity</c>, denoted
- <c>AI(n)</c>, is determined by the formula</p>
- <p><c>AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1) + Weight</c>,</p>
- <p>where <c>AI(n-1)</c> is the previous <c>accept intensity</c>,
- if the value of <c>exp(-Weight*(T(n) - T(n-1)) * AI(n-1)</c>
- is less than <c>MaxIntensity</c>. Otherwise the value is</p>
- <p><c>AI(n) = exp(-Weight*(T(n) - T(n-1)) * AI(n-1)</c></p>
- </item>
- </list>
- <p>The value of configuration parameter <c>Weight</c> controls the
- speed with which the calculations of intensities react to
- changes in the underlying input intensity. The inverted value of
- <c>Weight</c>, <c>T = 1/Weight</c>, can be thought of as the
- "time constant" of the intensity calculation formulas. For example,
- if <c>Weight = 0.1</c>, a change in the underlying input intensity is
- reflected in <c>total intensity</c> and <c>accept intensity</c> within
- about 10 seconds.</p>
- <p>The overload process defines one alarm, which it sets using
- <c>alarm_handler:set_alarm(Alarm)</c>. <c>Alarm</c> is defined
- as follows:</p>
- <taglist>
- <tag><c>{overload, []}</c></tag>
- <item>
- <p>This alarm is set when the current <c>accept intensity</c> exceeds
- <c>MaxIntensity</c>.</p>
- </item>
- </taglist>
- <p>A new request is not accepted until the current <c>accept
- intensity</c> has fallen below <c>MaxIntensity</c>. To prevent the
- overload process from generating many set/reset alarms, the
- alarm is not reset until the current <c>accept intensity</c> has fallen
- below 75% of <c>MaxIntensity</c>; it is not until then that
- the alarm can be set again.</p>
- </description>
-
- <funcs>
- <func>
- <name>request() -> accept | reject</name>
- <fsummary>Requests to proceed with current job.</fsummary>
- <desc>
- <p>Returns <c>accept</c> or <c>reject</c> depending on the
- current value of the <c>accept intensity</c>.</p>
- <p>The application
- calling this function is to proceed with the job in
- question if the return value is <c>accept</c>; otherwise it
- is not to continue with that job.</p>
- </desc>
- </func>
-
- <func>
- <name>get_overload_info() -> OverloadInfo</name>
- <fsummary>Returns current overload information data.</fsummary>
- <type>
- <v>OverloadInfo = [{total_intensity, TotalIntensity},
- {accept_intensity, AcceptIntensity}, {max_intensity,
- MaxIntensity}, {weight, Weight}, {total_requests,
- TotalRequests}, {accepted_requests, AcceptedRequests}].</v>
- <v>TotalIntensity = float() > 0</v>
- <v>AcceptIntensity = float() > 0</v>
- <v>MaxIntensity = float() > 0</v>
- <v>Weight = float() > 0</v>
- <v>TotalRequests = integer()</v>
- <v>AcceptedRequests = integer()</v>
- </type>
- <desc>
- <p>Returns:</p>
- <list type="bulleted">
- <item>Current total and accept intensities</item>
- <item>Configuration parameters</item>
- <item>Absolute counts of the total number of requests</item>
- <item>Accepted number of requests (since the overload
- process was started)</item>
- </list>
- </desc>
- </func>
- </funcs>
-
- <section>
- <title>See Also</title>
- <p><seealso marker="alarm_handler"><c>alarm_handler(3)</c></seealso>,
- <seealso marker="sasl_app"><c>sasl(6)</c></seealso></p>
- </section>
-</erlref>
-