- In general, it is expected that clickhouse-*-bridges and
clickhouse-server were build from the same source version (e.g. are
upgraded "atomically"). If that is not the case, we should at least
be able to detect the mismatch and abort.
- This commit adds a URL parameter "version", defined in a header shared
by the server and bridges. The bridge returns an error in case of
mismatch.
- The version is *not* send and checked for "ping" requests (used for
handshake), only for regular requests send after handshake. This is
because the internally thrown server-side exception due to HTTP
failure does not propagate the exact HTTP error (it only stores the
error as text), and as a result, the server-side handshake code
simply retries in case of error with exponential backoff and finally
fails with a "timeout error". This is reasonable as pings typically
fail due to time out. However, without a rework of HTTP exceptions,
version mismatch during ping would also appear as "timeout" which is
too misleading. The behavior may be changed later if needed.
- Note that introducing a version parameter does not represent a
protocol upgrade itself. Bridges older than the server will simply
ignore the field. Only servers older than the bridges receive an error
but such a situation should never occur in practice.
- Rename generic file and identifier names in library-bridge to
something more dictionary-specific. This is needed because later on,
catboost will be integrated into library-bridge.
- Also: Some smaller fixes like typos and un-inlining non-performance
critical code.
- The logic remains unchanged in this commit.
