Advice on dealing with exceeding high watermark

[Greg Fast]

Hi Cassandra C++ driver experets,

While using the Cassandra driver (version 2.7) in my product I keep hitting the following error:

(Here's a snippet from my product's logs)

Jun 27 11:12:05.273 [ATCS|CASS] WARN (00007f352a5e2700) Exceeded write bytes water mark (current: 65754 water mark: 65536) on connection to host 127.0.0.2
Jun 27 11:12:05.274 [ATCS|CASS] WARN (00007f352a5e2700) Exceeded write bytes water mark (current: 65541 water mark: 65536) on connection to host 127.0.0.2
Jun 27 11:12:10.270 [ATCS|CASS] WARN (00007f352a5e2700) Exceeded write bytes water mark (current: 65561 water mark: 65536) on connection to host 127.0.0.2

My first instinct is to increase the high watermark with CassCluster's cass_cluster_set_write_bytes_low_water_mark()

However, I noticed from the documents that in the latest driver version (2.9) the watermark settings are deprecated and ignored.

(This doc: https://docs.datastax.com/en/developer/cpp-driver/2.9/api/struct.CassCluster/#function-cass_cluster_set_write_bytes_high_water_mark)

So my questions:
- Is this a problem I can upgrade out of?
- If I upgrade to 2.9, will I hit a different limit? If so, is there a setting for the that limit?

Thanks in advance, I really appreciate the help.

-Greg Fast

[Michael Penick]

On Wed, Jun 27, 2018 at 11:27 AM Greg Fast <gfa...@gmail.com> wrote:

Hi Cassandra C++ driver experets,

While using the Cassandra driver (version 2.7) in my product I keep hitting the following error:

(Here's a snippet from my product's logs)

Jun 27 11:12:05.273 [ATCS|CASS] WARN  (00007f352a5e2700) Exceeded write bytes water mark (current: 65754 water mark: 65536) on connection to host 127.0.0.2
Jun 27 11:12:05.274 [ATCS|CASS] WARN  (00007f352a5e2700) Exceeded write bytes water mark (current: 65541 water mark: 65536) on connection to host 127.0.0.2
Jun 27 11:12:10.270 [ATCS|CASS] WARN  (00007f352a5e2700) Exceeded write bytes water mark (current: 65561 water mark: 65536) on connection to host 127.0.0.2


My first instinct is to increase the high watermark with CassCluster's cass_cluster_set_write_bytes_low_water_mark()

However, I noticed from the documents that in the latest driver version (2.9) the watermark settings are deprecated and ignored.

(This doc: https://docs.datastax.com/en/developer/cpp-driver/2.9/api/struct.CassCluster/#function-cass_cluster_set_write_bytes_high_water_mark)


So my questions:
- Is this a problem I can upgrade out of?

You could upgraded or just set the high water mark arbitrarily high to have the same effect. You might want to set the pending request mark water mark higher too if you don't upgrade.

 

- If I upgrade to 2.9, will I hit a different limit? If so, is there a setting for the that limit?

It's not likely, but if you have extremely high throughput you might hit the I/O queue limit. That can be increased by using `cass_cluster_set_queue_size_io()`.

 

Thanks in advance, I really appreciate the help.

-Greg Fast

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[Greg Fast]

Thanks Michael, that's super helpful!