Racket programming -- 4
Budjetti $10-30 USD
Simulate the publish-subscribe communication pattern in Go. Your solution should have at least two publishers and three subscribers, all implemented as goroutines. The publishers will send messages on specific topics at random intervals to all subscribers on those topics. The subscribers will subscribe to topics and will display the messages received on the console.
Get the initial code from: [login to view URL]
Example
To illustrate, consider the following messages on two different topics: “bees” and “Colorado.”
“bees” messages:
"bees are pollinators,"
"bees produce honey,"
"all worker bees are female,"
"bees have 5 eyes," and
"bees fly about 20mph."
“Colorado” messages:
"Colfax in Denver is the longest continuous street in America,"
"Colorado has the highest mean altitude of all the states," and
"Colorado state flower is the columbine."
Your simulation should create two publishers, one for each set of topic messages. You should also create at least three subscribers. Let’s say “John” wants to subscribe to “bees” type of messages, while “Mary” wants to subscribe to not only “bees” but also “Colorado” type of messages.
A typical output of this simulation would look like the following:
Mary received: Colfax in Denver is the longest continuous street in America
Mary received: bees produce honey
John received: bees produce honey
Mary received: Colorado has the highest mean altitude of all the states
John received: all worker bees are female
Mary received: all worker bees are female
Mary received: bees have 5 eyes
John received: bees have 5 eyes
Mary received: Colorado state flower is the columbine
Mary received: bees fly about 20mph
John received: bees fly about 20mph
The picture below gives a high-level visual of the scenario to help your comprehension.
Implementation
Although it is up to you how to implement this project, we suggest using the following struct:
type PubSub struct {
mu [login to view URL]
topics map[string][]chan string
}
PubSub has a semaphore named “mu” to control access to the map of communication channels (note that the map’s key is a string with the topic name). The idea is to create a new channel for each new subscriber of a particular topic. The publisher will send the message to ALL the channels associated with a particular topic.
We suggest the following methods associated with the PubSub struct:
Method
Description
(ps PubSub) subscribe (topic string) chan string
creates and returns a new channel on a given topic, updating the PubSub struct
(ps PubSub) publish (topic string, msg string)
writes the given message on all the channels associated with the given topic
For the goroutines we suggest the following functions:
Function
Description
publisher(ps PubSub, topic string, msgs[]string)
sends messages taken from a given array of message, one at a time and at random intervals, to all topic subscribers
subscriber(ps PubSub, name string, topic string)
reads and displays all messages received from a particular topic
If you are implementing your own solution, make sure you fulfill the following requirements:
each publisher runs as a goroutine;
each subscriber runs as a goroutine;
publishers and subscribers communicate using channels;
there shouldn't be a limit on the number of messages, publishers, and subscribers;
the solution should be thread-safe so any shared object must have its access properly synchronized; and
you should be able to reproduce a similar output as the given example.
2 freelanceria on tarjonnut keskimäärin $75 tähän työhön
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