Change insert node output

[smyrman]

This is suggested as an extension to #36.

We might consider to change the node output to not contain raw requests, but an aggregate of the msg.ack field.

Suggestion:

• Output 1: the aggregated content of msg.ack for data updates on success.
• Output 2: the aggregated content of msg.ack for meta data updates on success.

I.e. consider the following messages:

{
  _msgid: 1,
  ack: ["a1", "a1-2"],
  payload: {...}
}
{
  _msgid: 2,
  // ack undefined
  payload: {...},
  signal: {...}
}
{
  _msgid: 3,
  ack: ["a3"],
  payload: {...},
  signal: {...}
}
{
  _msgid: 4,
  ack: ["a4"],
  signal: {...}
}

The aggregated output 1 on success is:

• {msgs: [1,2,3], ack:["a1","a1-2","a3"]} // all messages with data.

The aggregated output 2 on success is:

• {msgs:[3,4], ack: ["a3", "a4"]} // all messages with meta data.

Errors, are logged, while the detailed response is discarded both on success and on error.

[khtufteland]

I like the main idea of this proposal, but it makes a quite big assumption: it assumes that most source system is Pub/Sub (or similar with acknowledging mechanics) which is the case for our existing integrations using Telegraf, via Google Pub/Sub to Node-RED. But this a legacy strategy, all new integrations are implemented in Node-RED directly. And whenever existing integrations require an update, I will always consider migrating the integrations to Node-RED.

[smyrman]

We should definitively adapt, evolve this.

There seam to be some "ack" nodes in node-red:

• https://flows.nodered.org/node/node-red-contrib-ack
• https://flows.nodered.org/node/node-red-contrib-amqp-ack

We could have a look at what they are doning, and which message fields they are inspecting.

[smyrman]

Somehow related (if splitting a message!)

• https://nodered.org/docs/user-guide/messages#message-sequences

[smyrman]

I think it would be OK to ignore split messages (sequences) in the initial version. That is, for a split message to be acked correctly, it must be joined before it's passed to the input node.