common

Common Lib

This module consists of the data types used in all go modules.

Data Types

Stored in the data_type package. This package consists of various data types.

Queue

First in, First out queue. Available in data_type.Queue. The queue has a cap.

Database

Stored in the data_type/database package. It Consists of the SQL database interfaces that all databases must implement.

KeyValue

Stored in the data_type/key_value.KeyValue. The KeyValue is the wrapper around map[string]interface{}. The structure adds methods to extract the data with the validation.

The structure also can not contain the null parameters.

All the keys are string.

The values can be:

• NestedValue – nested KeyValue
• NestedListValue – list of KeyValue.
• Uint64 – any natural numbers and zero are converted into go's uint64 type. KeyValue negative numbers are represented as Float64.
• Float64 – the number is represented as a float of 64 bits.
• String – a string.
• Strings – a slice of string.
• BigNumber – the number of big.Int format.
• Bool – a boolean parameter.

KeyValueList

Stored in the data_type/key_value.List. The List is the KeyValue with two conditions: Keys are interface, not string. The key types must be identical. The value types must be identical.

The List has a cap.

If the first value that you set is the number key, and struct A value. Then all keys must be number, and all values must be struct A.

Message

The messages are the data that SDS uses for intercommunication. There are two types of the messages: Requests and Replies.

Internally, the SDS framework uses the interface: RequestInterface and ReplyInterface. Any message type must implement the interfaces.

Operations

All messages are grouped into the message.Operations. It's a structure with the function references. The SDS Framework accepts the message.Operations for a message manipulation.

• NewReq([]messages) (RequestInterface, error)
• NewReply([]messages) (ReplyInterface, error)
• EmptyReq() RepquestInterface
• EmptyReply() ReplyInterface

Built in message types

The SDS comes with two types of messages as well as their operations.

The default message is the JSON compatible Structure. The raw message is the represents the strings.

Default Message

The default message types are JSON compatible. The operations are defined as DefaultMessage in the message/request.go file.

The request format is defined in message.Request. The reply format is defined in message.Reply.

Raw Message

The messages are the wrappers around zeromq message envelopes. The SDS framework as a framework to write distributed systems uses zeromq internally.

The Raw messages are the wrappers around zeromq's messages. The wrapped messages are fully compatible with the SDS framework. Because raw messages implement RequestInterface and ReplyInterface.

Both request and replies are defined in message/raw.go file. The request format is defined in message.RawRequest. The reply format is defined in message.RawReply.

The operations are defined as message.RawMessage().

Todo Set an actual link to the documentation for usage of the messages in clients and handlers.

Refer to client-lib and handler-lib for changing default message format.

Trace

To make debugging easy in the distributed systems, the messages come with the traces. The message that was sent by a user to the service A, which then forwarded to service B must include the service information as a stack.

Therefore, there is an important rule:

The next request must from service A to service B must be defined through request.Next. The package that handled the message must include its stack with the information about the service, handler and a time.