Some optimizations for sending UDP messages

[dqminh]

This adds:

• benchmark for various cases writing UDP messages out
• improved performances in general cases witha bytes pool, and add support for sending uncompressed UDP messages with CompressionType=CompressNone
• add supports for RawExtra attributes in messages, for cases where all messages from a source share the same extra attributes, so we only need to encode once.

Following is the benchmark:

=> git rev-list --reverse 4f441fa..8b73a5c
Checking out: 8fa7145 add a benchmark test
=> git checkout --quiet 8fa7145f561628a942e8027ac75a3dec2ee8a846
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2       2000        599531 ns/op     1508341 B/op        185 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    1.306s
=> git reset --hard --quiet

Checking out: 9352186 use marshaljsonbuf
=> git checkout --quiet 93521869f558cb3c5884d4fae61a2e163e4b00c5
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2       2000        562657 ns/op     1508197 B/op        183 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    1.234s
=> git reset --hard --quiet

Checking out: 9f8a322 add bytes pool for json and gzip
=> git checkout --quiet 9f8a32256b3c0497981c9df03ad8ea34c72cbe36
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2       2000        582404 ns/op     1507220 B/op        179 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    1.271s
=> git reset --hard --quiet

Checking out: 4a04cd7 add a test for no compression
=> git checkout --quiet 4a04cd7c3b68827d89c3157dff28da8ac72e14cc
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2           2000        731160 ns/op     1507866 B/op        178 allocs/op
BenchmarkWriteNoCompression-2      20000         73277 ns/op      116671 B/op        128 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    3.755s
=> git reset --hard --quiet

Checking out: d80a2b2 add CompressNone support which disable compression with a magic 2 byte header
=> git checkout --quiet d80a2b2eaabf3d212d4ae674349d1480807adb11
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2                           2000        772494 ns/op     1508722 B/op        180 allocs/op
BenchmarkWriteNoCompression-2                      20000         57902 ns/op      113603 B/op        122 allocs/op
BenchmarkWriteDisableCompressionCompletely-2       50000         22889 ns/op        1853 B/op         23 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    5.668s
=> git reset --hard --quiet

Checking out: 67732da refactor MarshalJSONBuf to save 1 allocation
=> git checkout --quiet 67732da8fde0014412de32e0dc73547ced55e4e7
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2                           2000        641034 ns/op     1507898 B/op        178 allocs/op
BenchmarkWriteNoCompression-2                      20000         84399 ns/op      113152 B/op        122 allocs/op
BenchmarkWriteDisableCompressionCompletely-2       50000         25330 ns/op        1853 B/op         23 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    5.581s
=> git reset --hard --quiet

Checking out: 45fe8a5 add RawExtra for pre-encoded extra attributes
=> git checkout --quiet 45fe8a5e04d87902f13e0b273cf086f782769b69
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2                               2000        659069 ns/op     1507418 B/op        173 allocs/op
BenchmarkWriteNoCompression-2                          20000         68501 ns/op      114307 B/op        123 allocs/op
BenchmarkWriteDisableCompressionCompletely-2          100000         22870 ns/op        1625 B/op         21 allocs/op
BenchmarkWriteDisableCompressionAndPreencodeExtra-2   100000         15038 ns/op         836 B/op          7 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    7.648s
=> git reset --hard --quiet

Checking out: 8b73a5c refactor duplicated code for compressing gzip/zlip
=> git checkout --quiet 8b73a5c1c7fcb26e4e0d72f1ae9f4ef075569cd7
=> go test -benchmem -bench .
PASS
BenchmarkWriteBestSpeed-2                               2000        663248 ns/op     1507446 B/op        173 allocs/op
BenchmarkWriteNoCompression-2                          20000        201816 ns/op      116357 B/op        127 allocs/op
BenchmarkWriteDisableCompressionCompletely-2           50000         36753 ns/op        1613 B/op         21 allocs/op
BenchmarkWriteDisableCompressionAndPreencodeExtra-2   100000         15673 ns/op         836 B/op          7 allocs/op
ok      github.com/Graylog2/go-gelf/gelf    10.029s
=> git reset --hard --quiet
=> git checkout --quiet 8b73a5c
OK for all revisions!

[ashishgandhi]

👍

[mariussturm]

Awesome work, thanks a lot!