Garnet API

The IGarnetApi interface contains the operators exposed to the public API, which ultimately perform operations over the keys stored in Garnet. It inherits from IGarnetReadApi (read-only commands interface) and IGarnetAdvancedApi (advanced API calls).

For adding an new operator or command to the API, add a new method signature to the IGarnetReadApi interface in case the command performs read-only operations, or IGarnetApi otherwise.

Adding a new command to Garnet

If you are trying to add a command for your specific Garnet server instance, see Custom Commands

To add a new command to Garnet, follow these steps:

1. If your command operates on an object (i.e. List, SortedSet etc.), add a new enum value to the [ObjectName]Operation enum in Garnet.server/Objects/[ObjectName]/[ObjectName]Object.cs
   Otherwise, add a new enum value to the RespCommand enum in Garnet.server/Resp/RespCommand.cs.
2. Add the parsing logic of the new command name to Garnet.server/Resp/RespCommand.cs. If the command has a fixed number of arguments, add parsing logic to the FastParseCommand method. Otherwise, add parsing logic to the FastParseArrayCommand method.
3. Add a new method signature to IGarnetReadApi, in case the command performs read-only operations, or to IGarnetApi otherwise (Garnet.server/API/IGarnetAPI.cs).
4. Add a new method to the RespServerSession class. This method will parse the command from the network buffer, call the storage layer API (method declared in step #3) and write the RESP formatted response back to the network buffer (note that the RespServerSession class is divided across several .cs files, object-specific commands will reside under Garnet.server/Resp/Objects/[ObjectName]Commands.cs, while others will reside under Garnet.server/Resp/[Admin|Array|Basic|etc...]Commands.cs, depending on the command type).
5. Back in Garnet.server/Resp/RespCommand.cs, add the new command case to the ProcessBasicCommands or ProcessArrayCommands method respectively, calling the method that was added in step #4.
6. Add a new method to the StorageSession class. This method is part of the storage layer. This storage API ONLY performs the RMW or Read operation calls, and it wraps the Tsavorite API. (note that the StorageSession class is divided across several .cs files, object store operations will reside under Garnet.server/Storage/Session/ObjectStore/[ObjectName]Ops.cs, while main store operations will mainly reside under Garnet.server/Storage/Session/MainStore/MainStoreOps.cs, with some exceptions).
   To implement the storage-level logic of the new command, follow these guidelines according to the new command type:
   • Single-key object store command: If you are adding a command that operates on a single object, the implementation of this method will simply be a call [Read|RMW]ObjectStoreOperation[WithOutput], which in turn will call the Operate method in Garnet.server/Objects/[ObjectName]/[ObjectName]Object.cs, where you will have to add a new case for the command and and the object-specific command implementation in Garnet.server/Objects/[ObjectName]/[ObjectName]ObjectImpl.cs
   • Multi-key object store command: If you are adding a command that operates on multiple objects, you may need to create a transaction in which you will appropriately lock the keys (using the TransactionManager instance). You can then operate on multiple objects (for instance using the GET & SET operations).
   • Main-store command: If you are adding a command that operates on the main store, you'll need to call Tsavorite's Read or RMW methods. If you are calling RMW, you will need to implement the initialization and in-place / copy update functionality of the new command in Garnet.server/Storage/Functions/MainStore/RMWMethods.cs.
7. If the command supports being called in a transaction context, add a new case for the command in the TransactionManager.GetKeys method and return the appropriate key locks required by the command (Garnet.server/Transaction/TxnKeyManager.cs).
8. Add tests that run the command and check its output under valid and invalid conditions, test using both SE.Redis and LightClient, if applicable. For object commands, add tests to Garnet.test/Resp[ObjectName]Tests.cs. For other commands, add to Garnet.test/RespTests.cs or Garnet.test/Resp[AdminCommands|etc...]Tests.cs, depending on the command type.
9. Add newly supported command documentation to the appropriate markdown file under website/docs/commands/, and specify the command as supported in website/docs/commands/api-compatibility.md.
10. Add command info by following the next section

tip

Before you start implementing your command logic, add a basic test that calls the new command, it will be easier to debug and implement missing logic as you go along.

Adding command info

Each supported RESP command in Garnet should have an entry in Garnet.server/Resp/RespCommandsInfo.json, specifying the command's info.
A command's info can be added manually, but we recommend using the CommandInfoUpdater tool to update the JSON file (can be found under playground/).

The CommandInfoUpdater tool calculates the difference between existing commands in Garnet.server/Resp/RespCommandsInfo.json and commands specified in CommandInfoUpdater/SupportedCommands.cs. It then attempts to add / remove commands' info as necessary.
Info for Garnet-only commands is retrieved from CommandInfoUpdater/GarnetCommandsInfo.json, and info for other RESP commands is retrieved from an external RESP server (which you will need to run locally / have access to in order to run this tool).

To add command info to Garnet, follow these steps:

1. Add the supported command and its supported sub-commands (if applicable) to CommandInfoUpdater/SupportedCommands.cs.
2. If you are adding a Garnet-specific command, add its info to CommandInfoUpdater/GarnetCommandsInfo.json.
3. Build & run the tool (for syntax help run the tool with -h or --help).