commit 0021eafa47500a008367d98d6fa6e599eeb8e952
author Edwin Kempin <ekempin@google.com> Wed Apr 21 10:06:20 2021 +0200
committer Edwin Kempin <ekempin@google.com> Wed Apr 21 10:06:33 2021 +0200
tree 5cdd5457ae0010558dcab855edacc756e12fa058
parent 5feb3fd01007e0d9f66fc14759df0e71c7690de6

Cache all parsed config values to avoid reparsing them

The code-owners plugin has quite a lot of configuration parameters that
are accessed frequently. If reading config parameters is slow, this can
sum up to a significant amount of latency.

What we have done so far is that CodeOwnersPluginConfigSnapshot which
reads the project specific plugin configuration is cached for the time
of the request (see change If541bc329). This avoids loading the
code-owners.config file from this project and the parent projects again
and again. However whenever a config parameter is needed, we still
reparse it each time. Parsing a config parameter means inspecting the
Config that was read from the code-owners.config files and if necessary
fall-back to inspecting the Config that was read from gerrit.config.
With this change we do the parsing only once and cache the result in
CodeOwnersPluginConfigSnapshot.

In addition to project specific configuration parameters that are
handled by CodeOwnersPluginConfigSnapshot there are also a couple of
global configuration parameters that are handled in
CodeOwnersPluginConfiguration. For the global parameters we have the
same problem that they are reparsed on each access. E.g. the allowed
email domains are parsed each time a code owner email is resolved to an
account. This can be the reason why the step that resolves code owner
emails to accounts is rather slow. To address this we follow the example
of CodeOwnersPluginConfigSnapshot and add a
CodeOwnersPluginGlobalConfigSnapshot class that handles the reading of
the global config parameters. Same as CodeOwnersPluginConfigSnapshot it
is cached for the request time and internally it caches the parsed
config values so that they need to parsed only once.

To make it clearer that CodeOwnersPluginConfigSnapshot is about reading
project-specific configuration parameters, it is renamed to
CodeOwnersPluginProjectConfigSnapshot.

Change-Id: I6e4c608133717b598d356d1ce76246eb19b08c4b
Signed-off-by: Edwin Kempin <ekempin@google.com>