Sorry for the clickbaity title. This is about static method
ConnectionTimeouts::getHTTPTimeouts(). It was be declared in header
IO/ConnectionTimeouts.h, and defined in header
IO/ConnectionTimeoutsContext.h (!). This is weird and caused issues with
linking on s390x (##45520). There was an attempt to fix some
inconsistencies (#45848) but neither did @Algunenano nor me at first
really understand why the definition is in the header.
Turns out that ConnectionTimeoutsContext.h is only #include'd from
source files which are part of the normal server build BUT NOT part of
the keeper standalone build (which must be enabled via CMake
-DBUILD_STANDALONE_KEEPER=1). This dependency was not documented and as
a result, some misguided workarounds were introduced earlier, e.g.
0341c6c54b
The deeper cause was that getHTTPTimeouts() is passed a "Context". This
class is part of the "dbms" libary which is deliberately not linked by
the standalone build of clickhouse-keeper. The context is only used to
read the settings and the "Settings" class is part of the
clickhouse_common library which is linked by clickhouse-keeper already.
To resolve this mess, this PR
- creates source file IO/ConnectionTimeouts.cpp and moves all
ConnectionTimeouts definitions into it, including getHTTPTimeouts().
- breaks the wrong dependency by passing "Settings" instead of "Context"
into getHTTPTimeouts().
- resolves the previous hacks
- When catboost will be added into library-bridge later on, a lot of
code will need to be duplicated.
- Avoid that by factorizing stuff which is not specific to external
dictionaries for reuse into a common base class.
- This is a refactoring without semantic change.
- ExternalDictionaryLibraryBridgeHelper provides the server-side
interface to access the dictionary part of the library bridge.
- In a later commit, CatBoostLibraryBridgeHelper will be added to access
the catboost part of the library bridge from the server.
Wall of text, sorry, but I also had to document some stuff for myself:
There are three ways to communicate data using HTTP:
- the HTTP verb: for our purposes, PUT and GET,
- the HTTP path: '/ping', '/request' etc.,
- the HTTP URL parameter(s), e.g. 'method=libNew&dictionary_id=1234'
The bridge will use different handlers for communication with the
external dictionary library and for communication with the catboost
library. Handlers are created based on a combination of the HTTP verb
and the HTTP method. More specifically, there will be combinations
- GET + '/extdict_ping'
- PUT + '/extdict_request'
- GET + '/catboost_ping'
- PUT + '/catboost_request'.
For each combination, the bridge expects a certain set of URL
parameters, e.g. for the first combination parameter "dictionary_id" is
expected.
Starting with this commit, the library-bridge creates handlers based on
the first two combinations (the latter two combinations will be added
later). This makes the handler creation mechanism consistent with it's
counterpart in xdbc-bridge.
For that, it was necessary to make both IBridgeHelper methods
"getMainURI()" and "getPingURI()" pure virtual so that derived classes
(LibraryBridgeHelper and XDBCBridgeHelper) must provide custom URLs with
custom paths.
Side note 1: Previously, LibraryBridgeHelper sent HTTP URL parameter
"method=ping" during handshake (PING) but the library-bridge ignored
that parameter. We now omit this parameter, i.e.
LibraryBridgeHelper::PING was removed. Again, this makes things
consistent with xdbc-bridge.
Side note 2: xdbc-bridge is unchanged in this commit. Therefore,
XDBCBridgeHelper now uses the HTTP paths previously in the base class.
For funny reason, XDBCBridgeHelper did not use
IBridgeHelper::getMainURI() - it generates the URLs by itself. I kept it
that way for now but provided an implementation of getMainURI() anyways.
- 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.
