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Ilkka Seppälä 2020-09-13 18:26:52 +03:00
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throttling/README.md
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@ -10,12 +10,15 @@ tags:
---
## Intent
Ensure that a given client is not able to access service resources more than the assigned limit.
## Explanation
Real world example
> A large multinational corporation offers API to its customers. The API is rate-limited and each customer can only make certain amount of calls per second.
> A large multinational corporation offers API to its customers. The API is rate-limited and each
> customer can only make certain amount of calls per second.
In plain words
@ -23,7 +26,9 @@ In plain words
[Microsoft documentation](https://docs.microsoft.com/en-us/azure/architecture/patterns/throttling) says
> Control the consumption of resources used by an instance of an application, an individual tenant, or an entire service. This can allow the system to continue to function and meet service level agreements, even when an increase in demand places an extreme load on resources.
> Control the consumption of resources used by an instance of an application, an individual tenant,
> or an entire service. This can allow the system to continue to function and meet service level
> agreements, even when an increase in demand places an extreme load on resources.
**Programmatic Example**
@ -77,7 +82,8 @@ public final class CallsCount {
}
```
Next we introduce the service that the tenants are calling. To track the call count we use the throttler timer.
Next we introduce the service that the tenants are calling. To track the call count we use the
throttler timer.
```java
public interface Throttler {
@ -134,7 +140,8 @@ class B2BService {
}
```
Now we are ready to see the full example in action. Tenant Adidas is rate-limited to 5 calls per second and Nike to 6.
Now we are ready to see the full example in action. Tenant Adidas is rate-limited to 5 calls per
second and Nike to 6.
```java
public static void main(String[] args) {
@ -171,9 +178,11 @@ Now we are ready to see the full example in action. Tenant Adidas is rate-limite
## Class diagram
![alt text](./etc/throttling-pattern.png "Throttling pattern class diagram")
![alt text](./etc/throttling_urm.png "Throttling pattern class diagram")
## Applicability
The Throttling pattern should be used:
* When a service access needs to be restricted to not have high impacts on the performance of the service.

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throttling/etc/throttling-pattern.ucls
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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.2.2" icons="true" always-add-relationships="false" generalizations="true" realizations="true"
associations="true" dependencies="false" nesting-relationships="true" router="FAN">
<class id="1" language="java" name="com.iluwatar.throttling.CallsCount" project="throttling"
file="/throttling/src/main/java/com/iluwatar/throttling/CallsCount.java" binary="false" corner="BOTTOM_RIGHT">
<position height="211" width="256" x="656" y="228"/>
<display autosize="false" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="2" language="java" name="com.iluwatar.throttling.Tenant" project="throttling"
file="/throttling/src/main/java/com/iluwatar/throttling/Tenant.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="465" y="524"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="3" language="java" name="com.iluwatar.throttling.B2BService" project="throttling"
file="/throttling/src/main/java/com/iluwatar/throttling/B2BService.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="464" y="192"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="4" language="java" name="com.iluwatar.throttling.timer.Throttler" project="throttling"
file="/throttling/src/main/java/com/iluwatar/throttling/timer/Throttler.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="167" y="174"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<class id="5" language="java" name="com.iluwatar.throttling.timer.ThrottleTimerImpl" project="throttling"
file="/throttling/src/main/java/com/iluwatar/throttling/timer/ThrottleTimerImpl.java" binary="false"
corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="166" y="396"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<association id="6">
<end type="SOURCE" refId="3" navigable="false">
<attribute id="7" name="callsCount"/>
<multiplicity id="8" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="1" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<dependency id="9">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="4"/>
</dependency>
<dependency id="10">
<end type="SOURCE" refId="3"/>
<end type="TARGET" refId="2"/>
</dependency>
<association id="11">
<end type="SOURCE" refId="5" navigable="false">
<attribute id="12" name="callsCount"/>
<multiplicity id="13" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="1" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<dependency id="14">
<end type="SOURCE" refId="2"/>
<end type="TARGET" refId="1"/>
</dependency>
<realization id="15">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="4"/>
</realization>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

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throttling/src/main/java/com/iluwatar/throttling/CallsCount.java
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@ -24,7 +24,6 @@
package com.iluwatar.throttling;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;
import org.slf4j.Logger;