# Google Cloud PubSub Input Plugin

The GCP PubSub plugin ingests metrics from [Google Cloud PubSub][pubsub]
and creates metrics using one of the supported [input data formats][].


### Configuration

This section contains the default TOML to configure the plugin.  You can
generate it using `telegraf --usage pubsub`.

```toml
[[inputs.pubsub]]
## Required. Name of Google Cloud Platform (GCP) Project that owns
  ## the given PubSub subscription.
  project = "my-project"

  ## Required. Name of PubSub subscription to ingest metrics from.
  subscription = "my-subscription"

  ## Required. Data format to consume.
  ## Each data format has its own unique set of configuration options.
  ## Read more about them here:
  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
  data_format = "influx"

  ## Optional. Filepath for GCP credentials JSON file to authorize calls to 
  ## PubSub APIs. If not set explicitly, Telegraf will attempt to use 
  ## Application Default Credentials, which is preferred. 
  # credentials_file = "path/to/my/creds.json"

  ## Optional. Maximum byte length of a message to consume. 
  ## Larger messages are dropped with an error. If less than 0 or unspecified, 
  ## treated as no limit.
  # max_message_len = 1000000

  ## Optional. Maximum messages to read from PubSub that have not been written 
  ## to an output. Defaults to %d.
  ## For best throughput set based on the number of metrics within
  ## each message and the size of the output's metric_batch_size.
  ##
  ## For example, if each message contains 10 metrics and the output 
  ## metric_batch_size is 1000, setting this to 100 will ensure that a
  ## full batch is collected and the write is triggered immediately without
  ## waiting until the next flush_interval.
  # max_undelivered_messages = 1000

  ## The following are optional Subscription ReceiveSettings in PubSub.
  ## Read more about these values:
  ## https://godoc.org/cloud.google.com/go/pubsub#ReceiveSettings
  
  ## Optional. Maximum number of seconds for which a PubSub subscription
  ## should auto-extend the PubSub ACK deadline for each message. If less than
  ## 0, auto-extension is disabled.
  # max_extension = 0

  ## Optional. Maximum number of unprocessed messages in PubSub 
  ## (unacknowledged but not yet expired in PubSub). 
  ## A value of 0 is treated as the default PubSub value. 
  ## Negative values will be treated as unlimited.
  # max_outstanding_messages = 0

  ## Optional. Maximum size in bytes of unprocessed messages in PubSub 
  ## (unacknowledged but not yet expired in PubSub). 
  ## A value of 0 is treated as the default PubSub value. 
  ## Negative values will be treated as unlimited.
  # max_outstanding_bytes = 0

  ## Optional. Max number of goroutines a PubSub Subscription receiver can spawn 
  ## to pull messages from PubSub concurrently. This limit applies to each 
  ## subscription separately and is treated as the PubSub default if less than 
  ## 1. Note this setting does not limit the number of messages that can be 
  ## processed concurrently (use "max_outstanding_messages" instead).
  # max_receiver_go_routines = 0
```

### Multiple Subscriptions and Topics

This plugin assumes you have already created a PULL subscription for a given
PubSub topic. To learn how to do so, see [how to create a subscription][pubsub create sub].

Each plugin agent can listen to one subscription at a time, so you will 
need to run multiple instances of the plugin to pull messages from multiple
subscriptions/topics.



[pubsub]: https://cloud.google.com/pubsub
[pubsub create sub]: https://cloud.google.com/pubsub/docs/admin#create_a_pull_subscription
[input data formats]: /docs/DATA_FORMATS_INPUT.md