#Directions & Examples Each machine should in your distributed system should have Golang installed. Make sure every machine in your distributed system is running the server program.

Use the following command to start the server. The program needs the path of the log file and the ip address of the machine where it is running.

go run server.go LOG_FILE_PATH IP_ADDRESS_OF_THE_MACHINE

Now, on any machine, to query for certain key-value pairs in log files, you must run the program 'grepClient.go'. To query every machine in your system, the client program uses a 'masterlist.txt' file located in the directory where grep client is located. This file contains a list of the IP addresses of each machine in the system.

To run properly, the client program asks for two arguments, the first argument being the pattern matching for the key and the second argument for the value. Ex: 'go run grepClient.go '

Note: to ignore any particular pattern in the key or value, use a wildcard statement in the respective argument. Don't use '.' as the '.' and the '' symbol in the first position of an argument breaks all other arguments in Golang. As a replacement, use '^.*' as the wildcard statement, as this works well with our program.

When you run the client program with the arguments, the client will query the servers, and the response will be printed out on console.

Example queries=

go run grepClient.go helloworld
go run grepClient.go ^ERROR$ ^.*Hi.*$
go run grepClient.go FAIL ^.*

Example output=

machine.1
JOIN: 127.0.0.1 joined the system
machine.2
no matching patterns found.

#Underlying Architecture

Our distributed logging system allows you to run system grep calls through all the machines in our system and returns the relevant matches back to the user. Grep is executed on each machine's log separately. The machines are independent in the sense that they do not wait for each other to complete. The client receives the response as soon as a machine completes executing grep on its log. As the machines are not waiting for each other there is no blocking in the execution process.

The machine where we are querying from has a masterlist.txt that contains the ip addresses of all the machines we will query including itself. When we want to add a new machine we have to update the masterlist.txt. Similarly, when we want to remove a machine from the system we just delete the ip address of the machine from masterlist.txt.

In order to make sure that our system is fault-tolerant we ignore machines that are down. Therefore, as soon as we observe that a machine in our system is down the whole system does not break down. In the worst case (where all machines are down), we return results from the machine that is invoking the grepClient.go.

#Average query latency We tested our system which contained 4 different machines containing a log file of size 137 MB each. This is how the results look like ###Rare (Query results appear in individual log files 3.85%)

1. 624.354182 ms

2. 623.701059 ms

3. 614.587465 ms

4. 615.16865 ms

5. 633.258762 ms

Average latency: 622.2140236 ms

###Frequent (Query results appear in individual log files 19.23%)

1. 9.465099 s

2. 9.436086196 s

3. 9.506596702 s

4. 9.401853494 s

5. 9.480838906 s

Average latency: 9.4580948596 s

#Authors ###Irtefa, Mohd ###Lee, Stephen