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11.5.2. Request Header
When using Hot Rod to access Red Hat JBoss Data Grid, the contents of the request header consist of the following:
| Field Name | Data Type/Size | Details |
|---|---|---|
| Magic | 1 byte | Indicates whether the header is a request header or response header. |
| Message ID | vLong | Contains the message ID. Responses use this unique ID when responding to a request. This allows Hot Rod clients to implement the protocol in an asynchronous manner. |
| Version | 1 byte | Contains the Hot Rod server version. |
| Opcode | 1 byte | Contains the relevant operation code. In a request header, opcode can only contain the request operation codes. |
| Cache Name Length | vInt | Stores the length of the cache name. If Cache Name Length is set to 0 and no value is supplied for Cache Name, the operation interacts with the default cache. |
| Cache Name | string | Stores the name of the target cache for the specified operation. This name must match the name of a predefined cache in the cache configuration file. |
| Flags | vInt | Contains a numeric value of variable length that represents flags passed to the system. Each bit represents a flag, except the most significant bit, which is used to determine whether more bytes must be read. Using a bit to represent each flag facilitates the representation of flag combinations in a condensed manner. |
| Client Intelligence | 1 byte | Contains a value that indicates the client capabilities to the server. |
| Topology ID | vInt | Contains the last known view ID in the client. Basic clients supply the value 0 for this field. Clients that support topology or hash information supply the value 0 until the server responds with the current view ID, which is subsequently used until a new view ID is returned by the server to replace the current view ID. |
| Transaction Type | 1 byte | Contains a value that represents one of two known transaction types. Currently, the only supported value is 0. |
| Transaction ID | byte-array | Contains a byte array that uniquely identifies the transaction associated with the call. The transaction type determines the length of this byte array. If the value for Transaction Type was set to 0, no Transaction ID is present. |
