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Table of Contents
Protocol negotiation
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| title | Protocol Negotiation |
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Protocol Field Definitions
It is advised to read the Protocol Field Definitions page before reading this document to understand the data types referenced.
Message Definition
A message is a series of bytes which contains the request or response. If the message is large, then we will have provision to divide the message into small messages. In that case, client/server needs to collect all messages to parse the request/response.
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In order to consistently define messages the Extended Backus–Naur form grammar will be used.
Usage | Notation |
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| definition | = |
| alterationalternation | | |
| optional | [ ... ] |
| repetition | { ... } |
| Groupinggrouping | ( ... ) |
Generic Message definition
Every message will message (except for connection initializing handshakes, which are necessarily insulated from future changes to the message structure) will adhere to the following generic message definition. A Message will comprise of a MessageHeader and either a Request or Response component.
| Message = MessageHeader (Request | Response) | Description | |||
|---|---|---|---|---|
| type = MessageHeader | The MessageHeader corresponding to this Message. | Request | type = Request | This field will contain the Request component. |
| Response | type = Response
| This field will contain the Response component. | ||
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The Message header is a fixed size header which contains the size of a message, boolean flag to indicates whether a message is partial, and correlation id for that request message. The correlation id is used for the dual purpose here.
- If a message is sent in multiple sub-messages, then it will be used for combining the whole message.
- It will be used for correlating the request to its response.
| MessageHeader = Size CorrelationId isPartialMessage hasMetaData | Description | ||||
|---|---|---|---|---|---|
| Size | type = int32 | Size of request or response (not including this header) | |||
| CorrelationId | type = int32 | The correlationID used to match a request to its corresponding response. This will be important if/when we allow for out-of-order messages in the future. | isPartialMessage | type = boolean | Is this a partial message? The exact semantics of partial messages is to be determined. |
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The request contains optional metadata and the will contain an operation specific request structure itself.
Notes | Description | |||
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| optional, type = MetaData | This field is optional and will be populated if the MessageHeader.hasMeta is true | RequestAPI | type = variable | The specific Request message. Here are some examples of Request messages. PutRequest | GetRequest | PutAllRequest | GetAllRequest |ServerConfigRequest | ClientConfigRequest | AuthRequest |
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The response contains optional metadata and the return valuethe response object corresponding to the request, or an error response object.
Response = [MetaData] APIResponse | Description | MetaData | optional, type = MetaData|
|---|---|---|---|
| This field is optional and will be populated if the MessageHeader.hasMeta is true | APIResponse | type = variable | The Api specific Reponse message. Here are some examples of Response messages PutResponse | GetResponse | PutAllResponse | GetAllResponse | ServerConfigResposneServerConfigResponse | ClientConfigResponse | AuthResponse | ErrorResponse |
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The server will raise an error when it failed to execute API request from the client. The error response wraps an error object detailing the failure.
| ErrorResponse = Error | Description | |
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| error | type = Error | The error message |
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The server will raise the error when it failed to execute API request from the client. The error code and message should help the client to diagnose the issue.
| ErrorResponse = errorMessageerrorCode message | Description | |
|---|---|---|
| errorCode | type = int | Numeric code referencing the type of failure |
| messageerrorMessage | type = String | The error message |
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Some data being sent between the client and server, for the most part these rely on protobuf for proper serialization, except for CustomEncodedValues
| EncodedValue = (one of the below) | Description |
|---|---|
| intResult | 32-bit signed integer |
| longResult | 64-bit signed integer |
| shortResult | 16-bit signed integer |
| byteResult | 8-bit signed integer |
| booleanResult | True or False. |
| doubleResult | 64-bit floating point number. |
| floatResult | 32-bit floating point number. |
| binaryResult | A binary blob to be stored in the region. |
| stringResult | Character string |
| customEncodedValue | Data which doesn't use protobuf serialization |
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EncodedValue represents a serialized value in a format that Geode can understand. It is used for both keys and values in database requests.
| Value = { ValueHeader value} | Description | |
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| encodingType | type = int8 (encoding type) EncodingType | The encoding type of the following bytes. |
| value | type = bytes | Serialized Value Object which Geode can understand |
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EncodingType
Currently supported types are:
| Name | Description |
|---|---|
| Int | 32-bit signed integer, big-endian encoded |
| Long | 64-bit signed integer, big-endian encoded |
| Short | 16-bit signed integer, big-endian encoded |
| Byte | 8-bit signed integer, big-endian encoded |
| Boolean | True or False.|
| String | UTF-8 encoded string. (whether it can contain nulls is TBD) |
| Binary | A binary blob to be stored in the region. |
| JSON | UTF-8 encoded string, containing a JSON document that will be deserialized in the same way as the REST API. |
| Float | 32-bit floating point number. |
| Double | 64-bit floating point number. |
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The purpose of a metadata to pass defined key value pair with request and response. That will be optional for a client. If there is any metadata associated with request or response, then need to set "hasMetadata" flag to "true" in request or response header. After that send metadata in the following format.
| MetaData = NumberOfMetadata { MetadataKeyId MetadataKeyValue} | Description | |
|---|---|---|
| NumberOfMetadata | type = int16 | The number of MetaDataKeyId : MetaDataKeyValue combinations |
| MetadataKeyId | type = int16 | Supported MetaDataKeyId's can be found in the table "Supported MetaData - MetaData KeyId" |
| MetadataKeyValue | type = variable | The MetaData value for the KeyId. The supported dataType can be found in the table "Supported MetaData - MetaData Value Type" |
Supported MetaData
We would have following pre-defined key and value for a metadata. Note this list will grow over time.
MetaData for Requests
Request MetaData Key | MetaData KeyId | MetaData Value example | MetaData Value Type | Description |
|---|---|---|---|---|
| JSON_KEY | 1 | true | type = boolean | Geode will expect key as JSON string(or bytes) and it will convert that string into PDX key. If the response requires a key, then it will convert the PDX key to JSON string(or bytes) back. |
| JSON_VALUE | 2
| true | type = boolean | Geode will expect Value as JSON string(or bytes) and it will convert that string into PDX value. If the response requires a value, then it will convert PDX value to JSON string(or bytes) back. |
| EVENT_ID | 3
| EventId { uniqueId: type = String ThreadId:type=int64 SequenceId: type=int64 } | type = bytes | The eventid is used to identify same region event in Geode. Geode keeps map of "uniqueId + threadId" Vs "SequenceId" to know whether region event has been already seen or not.
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MetaData for Responses
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Response MetaData Key
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MetaData KeyId
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MetaData Value example
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MetaData Value Type
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Description
Entry
This structure represents a pair of data corresponding to a key and associated value.
| Entry = EncodedValue Error | Description | |
|---|---|---|
| key | type = EncodedValue | Data referencing the corresponding value |
| value | type = EncodedValue | Data associated to the corresponding key |
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Some responses may contain multiple errors keyed to different inputs. This object enables this behavior.
| KeyedError = EncodedValue Error | Description | |
|---|---|---|
| key | type = EncodedValue | Key corresponding to this error |
| error | type = Error | Details about the failure |
Request and Response Definitions
The request and response messages are further broken down by category and can be found on the following pages.
Connection API
Initial operations for correctly setting up a connection can be found here
Region API
Operations for getting, creating, and modifying data regions can be found here
Locator API
Connections to locators behave a bit differently from normal cache server connections. For more details and information about locator operations, visit this page.
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type = boolean
[optional]The server accepted and forwarded the request to the appropriate
node holding the affected cache entry. A smart client should refresh its partitioned
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