Switch to fork of sarama without zstd dependency

[danielnelson]

The newer sarama library uses CGO for it's zstd compression. Telegraf does not support enabling zstd compression currently, so it is safe to remove. This avoids the build requiring GLIBC_2.14, but we may want to make further changes to the build to avoid linking newer symbol versions.

Changes against sarama 1.23.1: https://github.com/influxdata/sarama/commit/b12709e6ca29240128c89fe0b30b6a76be42b457

closes #6344

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[andig]

Unfortunately, that commit b12709e6ca29240128c89fe0b30b6a76be42b457 does not seem to exist. Currently that breaks moving to go modules.

Should use latest commit https://github.com/influxdata/sarama/commit/d6c39e51b1aa805d23878ebe101a30675dc17866 instead?

[glinton]

Looks like it exists on the without-zstd branch - https://github.com/influxdata/sarama/commit/b12709e6ca29240128c89fe0b30b6a76be42b457 if that helps

[andig]

Looks like it exists on the without-zstd branch - influxdata/sarama@b12709e if that helps

Got it- for some reason github search doesn't find that commit, opened a ticket.

Working on #6118 I still can't get modules to work for sarama (posting here as the forked sarama repo doesn't support issues). My go.mod has:

replace github.com/Shopify/sarama v1.19.0 => github.com/influxdata/sarama v1.23.2-0.20190904202538-b12709e6ca29

yet:

❯ go run cmd/telegraf/telegraf.go -debug -sample-config
go: github.com/influxdata/sarama@v1.23.2-0.20190904202538-b12709e6ca29: parsing go.mod:
        module declares its path as: github.com/Shopify/sarama
                but was required as: github.com/influxdata/sarama

I think that the fork needs to have an updated module name in go.mod that matches its url.

Does that make sense? The I'd be happy to open a PR.