Black Marlin: A light in-memory database as an alternative to Redis with a REST API interface for easy development and integration.

Black Marlin is an in-memory database for fast reading, writing and deleting cached data. Light, fast and easy to use with no need for third-party libraries.

Why does it have a REST API interface?

The interface was created with easy development in mind, instead of having to use some sort of third-party library or framework; meaning its no different from making requests to a REST API in your program.

Any other program can cache its data without having to worry about its own available space in memory (if running on another host), maintaining connections or manually reading the output of other processes. This also allows servers in an architecture that uses Load Balancing to share keys as they want with a fast, easy access to the same cache.

Features:

• The main library is covered by unit tests with catchv2;
• REST API interface for HTTP methods written on top of the main library with cpp-httplib;
• Integration tests are made to insure that every route is working as intended. This repository has a Postman collection with a really big JSON file you can use to test its performance;
• Allows custom response headers and port.

Usage:

The program runs on port 7000 by default. You can test it by making a GET request to "http://127.0.0.1:7000/count" with your program running, for example. It should return 200 - OK with 0 in the response body (assuming you didn't have any keys cached by Black Marlin prior to calling this route). The only thing you have to do to integrate it with your application is make HTTP requests and handle its responses.

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Configuring a custom port:

If you want Black Marlin to be available via a port of your choice, you can run the program from a CLI and pass in a number as an argument, like so:

./blackmarlin 8534

Note that if the port argument is an invalid value the program will not run and an error message will be written to STDOUT.

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How to set custom headers:

1. Create a file in the same directory as the program called "bm_response_headers.txt";
2. Inside the file, put the headers as "key-values", separated by a single whitespace " ", like so: Allow GET, POST, PUT, PATCH, DELETE;
3. Run the program. The headers will be loaded only once in memory during startup and will return in the response for every valid request. Note that if the file is updated while the program is running the headers won't be updated. The program has to be restarted so it can load the contents of the file into memory again.

This allows for custom configurations such as cache control, specifying unusual HTTP methods etc. depending on your use-case.

If there is no file with the name mentioned above, there will be no additional custom headers in the response and this step will be ignored.

If the file exists and does not have the exact configurations as mentioned above (key and value separated by one whitespace character and then next line for every response header), the program will not be able to run.

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How to set HTTPS with an SSL certificate:

1. Create a file in the same directory as the program called bm_cert_key_paths.txt;
2. Inside the file, there should be two lines:
   1. The first line should contain the path to the certificate file (the path can be absolute or relative);
   2. The second line should contain the path to the private key.

Inside your file there should be two lines like these:

path/to/cert/my_cert.crt

path/to/cert/my_private_key.key

Thats all. When you run the program again, your calls to the URL should now contain https.

To disable this behavior just delete/remove the file mentioned and the server will use http.

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For each route and method:

Any failed operation will return a 500 - Internal Server Error HTTP status code.

"/":

• GET accepts a key query parameter: http://127.0.0.1:7000/?key=

  • Call this to get the value of an existing key. Returns: 400 - Bad Request if no key is sent, 200 - OK if a key was found and 204 - No Content if a key was provided but not found.

• POST accepts a key query parameter (http://127.0.0.1:7000/?key=) and a body. The body can be sent in any format.

  • Call this to create a new key value pair. Returns 201 - Created if the key value pair was created successfully.
  • It accepts another query parameter called expiresin. This parameter should be an integer representing an amount of seconds: http://127.0.0.1:7000/?key=key&expiresin=900.
  • The expiresin parameter is optional, meaning that if you want a key that does not expire unless manually deleted, all you have to do is omit the parameter.
  • Even if a key has been set to expire, it can be deleted by calling the default route / with the DELETE method (or /flush) or have its value overwritten by the default route's PUT or PATCH.
  • An already existing key cannot be set to expire.
  • The expiresin parameter must be a value bigger than 0 (zero) and less than or equal to USHRT_MAX (65535) and cannot be an invalid string such as "abcd", otherwise it will return 400 - Bad Request.
  • In summary, returns 400 - Bad Request if:
    • No key parameter was sent;
    • No body was sent; or
    • The expiresin parameter was sent with an invalid value.

• PUT and PATCH: accepts a key query parameter (http://127.0.0.1:7000/?key=) and a body. The body can be sent in any format.

  • Call this to update an existing key's value. Returns: 400 - Bad Request if no key or body was sent in the request and 200 - OK if the key value pair was updated successfully.

• DELETE accepts a key query parameter: http://127.0.0.1:7000/?key=

  • Call this to delete a key value pair. Returns: 400 - Bad Request if no key is sent and 200 - OK if a key was provided. Even if the hash table does not have the provided key, no specific HTTP Status Code will return.

"/count":

• GET takes no parameters: http://127.0.0.1:7000/count
  • Call this to get the number of key value pairs in memory. Returns: 200 - OK if everthing went well. This number is a size_t value, so it can get as big as the max value of an unsigned long long.

"/exists":

• GET accepts a key query parameter: http://127.0.0.1:7000/exists?key=
  • Call this to check if a key exists. Returns: 400 - Bad Request if no key is sent, 200 - OK if a key is found and 204 - No Content if a key provided wasn't found.

"/flush":

• DELETE takes no parameters: http://127.0.0.1:7000/flush
  • Call this to erase all items in memory. Returns: 200 - OK if everything went well.

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Logs:

Everytime an error occurs it is written to a file called bm_logs.txt (it is created if it doesn't already exist in the same directory). Every log message will have the following format:

{Year}-{Month}-{Day} {Hour}:{Minute}:{Second} - {ErrorMessage}

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Current roadmap:

• Support for HTTP/2 calls.

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Sidenotes:

• This program does NOT officially support any other operating system except for GNU/Linux;
• The first official release is available!

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Contributions:

General:

Feel free to open issues and fork as you feel like it. I'll be happy to help in any case.

How to compile:

The program can be compiled in any way as long as it supports threads (expiring keys in the main library and cpphttplib), is targeting the C++17 standard and includes OpenSSL. The recommended way to compile the program is using CMake.

How to test:

cd to unittests directory and run the run_unittests.sh bash file. Any other modules to be tested have to be added to the mentioned file.

Guidelines:

• Please follow the code's pattern; keeping the code looking the same everywhere in the program makes it easier to change stuff.