add Subscription#setOptions()

[stephenplusplus]

From @tonila on November 5, 2017 6:40

We are upgrading pubsub from 0.13.x to 0.14.x and current API documentation does not seem to answer our questions.

Documentation states that "subscription options do not persist across multiple instances".

With current knowledge, I assume it means, that subscription, that you see at cloud console does not store subscription options, so you need to set them for each instance you receive from the cloud.

But how do you set options, since subscription does not seem to have function for that?

Currently we are just always using topic.createSubscription() for new and existing subscriptions and it seems to work fine, but I am wondering, what is the intended way of doing this?

Copied from original issue: googleapis/google-cloud-node#2723

[stephenplusplus]

You can set the options at the time of creating the Subscription reference object.

topic.createSubscription('name', { /* options */ })
// or...
var subscription = topic.subscription('name', { /* options */ })

You do bring up a good question-- how can you set the options when you get a Subscription from topic.getSubscriptions()? @callmehiphop ?

[stephenplusplus]

From @callmehiphop on November 5, 2017 19:46

You currently can't, sounds like maybe we need to make a setter.

[callmehiphop]

We have a release coming up that will allow you to set options via setOptions method. We've also made some changes/additions to the available subscription options. Below is an example of using the setter with all the available options and their default values

subscription.setOptions({
  ackDeadline: 10,
  batching: {
    callOptions: {}, // gax call options
    maxMessages: 3000,
    maxMilliseconds: 100,
  },
  flowControl: {
    allowExcessMessages: true,
    maxBytes: os.freem() * 0.2,
    maxExtension: Infinity,
    maxMessages: 100
  },
  streamingOptions: {
    highWaterMark: 0,
    maxStreams: 5, // formerly known as maxConnections
    timeout: 60000 * 5, // 5 minutes
  }
});