v2.2.0

Listener batch size handling

• Fail config validation if listener batch size is greater than
  1MB. NATS will only accept messages of up to 1MB in size.
• Ensure the listener will never send a batch to NATS that is bigger
  than the 1MB which NATS will accept. This was previously possible
  under some circumstances.

InfluxDB HTTP basic auth support

influx-spout writers can now authenticate to InfluxDB backends if
required. The username and password are read from two environment
variables (INFLUXDB_USER and INFLUXDB_PASS).

Write retries

influx-spout writers will now retry failed writes for a configurable
number of times. Retries are configured by the following new options:

• writer_retry_batches: The maximum number of batches that failed to
  write to InfluxDB to track for retry at any given time. The oldest retry batch will be
  discarded if necessary to keep the set of batches being retried within this
  limit. Default is 1. Set to 0 to disable write retries.
• writer_retry_interval: The amount of time between write retry
  attempts. Default is "10s".
• writer_retry_timeout: The maximum amount of time to keep retrying
  a given batch. Default is "1m"

Enforce maximum writer batch size

When writing a batch to InfluxDB it is possible for the batch size to
exceed the maximum batch size because incoming lines are unlikely to
exactly fit inside the desired batch size. A BatchSplitter is now used
to ensure that the configured batch size is never exceeded.

This is important because InfluxDB has a maximum body size that it will accept.

Other

• Fixed escape handling bugs in downsampler component.
• The Prometheus metrics published by each influx-spout component is
  now documented in README.md.
• InfluxDB Line Protocol unescaping is now about 4% faster.
• Batches recevied by the listener component will now have a newline
  added if it is missing.
• Fixed incorrect accounting of received batches for the UDP listener.
• Fix potential issues with batch memory growth. Batch buffers now
  grow by at least the maximum UDP packet size to ensure that there is
  always sufficient memory available.