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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Modeling the operation of a distributed high-load monitoring system for a data transmission network in a non-stationary mode</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Kirill Shardakov</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Vladimir Bubnov</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Svetlana Kornienko</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Emperor Alexander I St. Petersburg State Transport University</institution>
          ,
          <addr-line>Moskovskiy avenue, 9, Saint-Petersburg, 190031, Russian Federation</addr-line>
        </aff>
      </contrib-group>
      <fpage>107</fpage>
      <lpage>116</lpage>
      <abstract>
        <p>The article discusses the numerical-analytical and simulation models of a high-load monitoring system. The examples of modeling are presented and the technical problem of choosing the hardware configuration of the simulated monitoring system is solved, which makes it possible to reduce the time spent by the task in the system by more than 2 times.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Non-stationary queuing system</kwd>
        <kwd>monitoring system</kwd>
        <kwd>modeling</kwd>
        <kwd>simulation model</kwd>
        <kwd>numericalanalytical model</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Automated monitoring systems are an
important part of any information system.
Monitoring is a continuous process of
observing and registering object parameters,
processing them, and comparing them with
threshold values. This monitoring system must
cope with the increasing workload. Zabbix is
the most popular and easily scalable for load
adaptation free monitoring system for
information systems [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].1
      </p>
      <p>
        Most often, the authors consider the
stationary mode of operation of such systems
in the context of queuing systems, however, it
is the non-stationary mode of operation that is
of greatest interest. The current state of the
issue of non-stationary queuing systems is
considered in more detail in [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. The beginning
of the “nonstationary” queueing theory was
laid in [
        <xref ref-type="bibr" rid="ref3 ref4 ref5">3–5</xref>
        ] and continued in [
        <xref ref-type="bibr" rid="ref6 ref7">6–7</xref>
        ].
      </p>
      <p>
        In [
        <xref ref-type="bibr" rid="ref8 ref9">8-9</xref>
        ], a model is proposed that allows
one to simulate the behavior of such a
1 Models and Methods for Researching Information Systems
in Transport, Dec. 11-12, St. Petersburg, Russia
EMAIL: k.shardakov@gmail.com (K.S. Shardakov);
bubnov1950@yandex.ru (V.P. Bubnov); sv.diass99@yandex.ru
(S.V. Kornienko);
ORCID: 0000-0002-6742-3011 (V.P.Bubnov); ORCID:
00000003-2683-0697 (S.V. Kornienko)
©️ 2020 Copyright for this paper byits authors. Use permitted under Creative
Commons License Attribution 4.0 International (CC BY 4.0).
      </p>
      <p>
        CEUR Workshop Proceedings (CEUR-WS.org)
monitoring system under various loads. The
proposed model uses an improved recursive
algorithm for generating a list of system states
and a matrix of coefficients of an ODE system
without constructing a graph of states and
transitions of the non-stationary queueing
system and deriving the general equation of
the ODE system as in [
        <xref ref-type="bibr" rid="ref10 ref11 ref12 ref13">10-13</xref>
        ]. On the basis of
a parallel-serial model, numerical-analytical
[
        <xref ref-type="bibr" rid="ref14">14</xref>
        ] and simulation [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ] models of a
distributed high-load monitoring system for a
data transmission network were developed and
implemented.
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. Brief description of simulated monitoring system the</title>
      <p>As it already known, the monitoring system
under consideration allows you to distribute
the load and scale it through the use of proxy
servers. Each proxy server collects data from a
separate set of devices, and then sends the data
to the main server that processes it.</p>
      <p>Figure 1 shows a general diagram of the
interaction of system components. Such a
system can also be considered as a queuing
system. The queuing system representation is
shown in Figure 2.
distribution at time moment 0, as we can see,
this is the initial state of the system and its
probability is equal to one, while the
probabilities of other states are equal to zero.</p>
      <p>As can be seen from Figure 5, the
probability distribution of states at time
moment 5 allows us to say that at this time
moment the final states have the highest
probabilities, which indicate that new requests
can arrive in the system with the least
probability, and those that have already arrived
will be processed with a higher probability.</p>
      <p>Figure 6 allows us to say that at time
moment 18 the absorbing state has the highest
probability, while the probability of the system
being in other states is negligible.
shifted from 18 to 16, which, as expected,
indicates a slightly higher throughput of such a
system compared to the system in which there
are 2 proxies.</p>
    </sec>
    <sec id="sec-3">
      <title>4. Simulation modeling</title>
      <p>
        Simulation modeling was carried out using
the software package [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ]. The result of this
model is the following statistical data for each
application:
1. Time in the queue to the proxy server;
2. Service time on the proxy server;
3. Time in the queue to the main server;
4. Service time on the main server;
5. The total time spent by the task in the
system.
      </p>
      <p>Additionally, the model allows tracing the
full path through the system state graph.</p>
      <p>Consider a model with the following initial
inputs:
1. Amount of proxy servers – 2;
2. Amount of incoming tasks – 1000;
3. Intensity of tasks arriving – 3;
4. Intensity of processing tasks for proxy
– 1;
5. Intensity of processing tasks for main
server – 2.</p>
      <p>The arrival intensity of tasks higher than
the service rates allows one to simulate the
non-stationary operation of the system.</p>
      <p>The path of such a model through the state
graph was 3001 states. Figure 8 shows the
number of tasks in queues to proxy servers and
to the main server, as well as the number of
tasks they have already served. Values are
listed for each condition passed by the system.
As we can see, the queue to proxy servers is
constantly increasing until all requests has
arrive to the system, after which the queue to
proxy begins to decreasing rapidly. At the
same time, the queue to the main server and
the gap in the number of requests served by
proxy servers and the main server is minimal.</p>
      <p>In Figure 9, we can see that the residence
time of each new request in the system
increases up to 200 conventional units of time,
which is obviously due to the low throughput
of proxy servers.
task in the system is still close to 200. From
this we can conclude that the growth of the
queue to the proxy in this configuration is
insignificant, but it is impossible to reduce
their number or performance, since this will
reduce the queue to the main server, but
increase the queue to the proxy. Thus, the
changes are leveled and the total time spent by
the order in the system will not change.</p>
      <p>Let's simulate the behavior of the system
once again with an increase in the intensity of
processing requests on the main server to 2.5.</p>
      <p>As it can be seen from Figure 12, queues
accumulate almost evenly and are small.</p>
      <p>From Figure 13, we can see that the time in
the queue to the proxy and to the main server
is approximately the same, and the maximum
time for a request to be in the system is about
80 conventional units of time, which is more
than 2 times less than the values obtained in
the simulation with the initial conditions.</p>
      <p>So, the simulation model allows solving the
technical problem of determining the
minimum required hardware configuration of
the system to service a finite number of tasks
with a certain level of service - the time the
task is in the system.</p>
    </sec>
    <sec id="sec-4">
      <title>5. Conclusion</title>
      <p>The article discusses the
numericalanalytical and simulation models of the
operation of a high-load distributed monitoring
system for a data transmission network in a
non-stationary mode. These models make it
possible to determine the probabilistic
characteristics of the system's behavior, as
well as to determine the necessary hardware
configuration to maintain the required service
level of tasks.</p>
      <p>Further development of the topic can be
adding priorities to requests and adding the
transfer of packages of requests from the
proxy to the main server.</p>
      <p>Research support. Research carried out on this
topic was carried out within the framework of
the budget topic No. 0073–2019–0004
queueing tasks in a non-stationary
acyclic queueing network with a finite
number of tasks. The Certificate on
Official Registration of the Computer
Program. No. 2020663070, 2020.</p>
    </sec>
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