Context Object

The acknowledgment, filter, and transformer functions all have access to a context object. This object can be used to retrieve variable getters and setters that can be used to pass data between flows. Also in this context, you will find a logger function and the absolute unique message id. The context object can be defined as:

export interface IMessageContext {
  messageId: string
  logger: (log: string, logLevel?: 'debug' | 'info' | 'warn' | 'error') => void
  setGlobalVar: <V>(varName: string, varValue: V) => void
  getGlobalVar: <V>(varName: string) => V | undefined
  setChannelVar: <V>(varName: string, varValue: V) => void
  getChannelVar: <V>(varName: string) => V | undefined
  setRouteVar?: <V>(varName: string, varValue: V) => void
  getRouteVar?: <V>(varName: string) => V | undefined
  setMsgVar: <V>(varName: string, varValue: V) => void
  getMsgVar: <V>(varName: string) => V | undefined
}
export interface IAckContext extends IMessageContext {
  filtered: boolean
}

I assume most of these are self-explanatory, but let’s go over a few details just in case.

The variable getters and setters can be passed a generic type to strongly type the variable. It is recommended to use this to prevent any type of errors. 4 different types of variables can be set and retrieved. The Global variables are set and retrieved from the global context. The Channel variables are set and retrieved from the channel context. The Route variables are set and retrieved from the route context. The Route getters and setters may be undefined if not within the context of a route. The Msg variables are set and retrieved from the message context. After the processing of the message, the Msg variables are cleared to free up memory.

The set functions will create the variable if it does not exist, and the get functions will return undefined if the variable does not exist.

The filtered property of the AckContext is a boolean that is set to true if the message was filtered. This can be used to determine if the message was filtered or not in the ingestion flow before the acknowledgment config. Note, this is ignored if a queue is used in the Source.