Previously, `docker logs` (and by extension, `docker service logs`) had
an error in the way they returned errors that occurred after a stream
had already been started. Specifically, the errors were added verbatim
to the HTTP response, which caused StdCopy to fail with an esoteric
error. This change updates StdCopy to accept errors from the source
stream and then return those errors when copying to the destination
stream.
Signed-off-by: Drew Erny <drew.erny@docker.com>
Avoids allocations and copying by using a buffer pool for intermediate
writes.
```
benchmark old ns/op new ns/op delta
BenchmarkWrite-8 996 175 -82.43%
benchmark old MB/s new MB/s speedup
BenchmarkWrite-8 4414.48 25069.46 5.68x
benchmark old allocs new allocs delta
BenchmarkWrite-8 2 0 -100.00%
benchmark old bytes new bytes delta
BenchmarkWrite-8 4616 0 -100.00%
```
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Stop using global variables as prefixes to inject the writer header.
That can cause issues when two writers set the length of the buffer in
the same header concurrently.
Stop Writing to the internal buffer twice for each write. This could
mess up with the ordering information is written.
Signed-off-by: David Calavera <david.calavera@gmail.com>
