config: handle box.cfg's TT_* env vars

[Totktonada]

There may be some confusion, so let's start with a background information.

There are TT_* environment variables introduced in commit 1b33012 ("box: set box.cfg options via environment variables"). They're interpreted by the box.cfg() call.

There are TT_* environment variables introduced in commit 82b0cff ("config: introduce env source"). They're interpreted by the declarative configuration logic, when tarantool starts with the --name <...> CLI option.

box.cfg's env variables have names deduced from box.cfg option names, while config's env variable names are deduced from the config schema.

Some options have the same names here and there, for example TT_REPLICATION_ANON (from box.cfg.replication_anon and replication.anon). However, there are ones that have different names, for example TT_LISTEN and TT_IPROTO_LISTEN.

Moreover, the declarative configuration has its own restrictions on the configuration data. For example, TT_IPROTO_LISTEN is always a list of URIs (like [{"uri": <...>, "params": {<...>}}]), not a single URI, not a string, not a number. The declarative configuration has a certain shape and doesn't allow polymorphic values.

Next, handling of box.cfg's variables by the old code in load_cfg.lua doesn't work well with the declarative configuration flow.

The main reason is that the new configuration flow calls box.cfg() with all the box.cfg values set, including default ones. If a user removes an option from its config, it applies its default. On the same time it instructs box.cfg() to don't read the corresponding environment variables.

This commit offers a partial solution: it adds support of the most of the box.cfg environment variables. The values are added into the configuration data with the lowest priority: if the same value is set in, for example, a file configuration, the file's value is preferred.

The following box.cfg's environment variables are not handled in this commit.

• TT_LOG
• TT_METRICS
• TT_INSTANCE_NAME
• TT_REPLICASET_NAME
• TT_CLUSTER_NAME
• TT_FORCE_RECOVERY,
• TT_READ_ONLY
• TT_BOOTSTRAP_LEADER
• TT_REPLICATION
• TT_REPLICATION_CONNECT_QUORUM

Fixes #9485

[coveralls]

coverage: 86.842% (+0.02%) from 86.818%
when pulling cd0a95b on Totktonada:gh-9485-handle-old-boxcfg-env-vars
into dde7342
on tarantool:master.

[ImeevMA]

Thanks for the patch!

[Totktonada]

@ImeevMA I've significantly changed the code and the test (see my comments in the pull request above). So, I would appreciate if you'll do a second look. Sorry for the false start.

[ImeevMA]

Thank you for the changes! Now it looks more complete. LGTM.

[Totktonada]

I'm going to rebase it on top of the recently pushed PR #9544 and add two test cases with the key=value,key=value mapping syntax in TT_LISTEN.

The added test cases.

diff --git a/test/config-luatest/box_cfg_env_test.lua b/test/config-luatest/box_cfg_env_test.lua
index 16ee08ca1c..16282aaf33 100644
--- a/test/config-luatest/box_cfg_env_test.lua
+++ b/test/config-luatest/box_cfg_env_test.lua
@@ -152,6 +152,19 @@ g.test_more = helpers.run_as_script(function()
                 {uri = 'localhost:3302', params = {transport = 'plain'}},
             }}},
         },
+        -- TT_LISTEN: mapping.
+        {
+            env = {['TT_LISTEN'] = 'uri=3301'},
+            config = {iproto = {listen = {
+                {uri = '3301'},
+            }}},
+        },
+        {
+            env = {['TT_LISTEN'] = 'uri=localhost:3301'},
+            config = {iproto = {listen = {
+                {uri = 'localhost:3301'},
+            }}},
+        },
         -- TT_LISTEN: JSON object.
         {
             env = {['TT_LISTEN'] = '{"uri": "3301"}'},