change: avoided running any init_by_lua* code inside signaller process and when testing Nginx configuration.

[spacewander]

Previously, when Nginx is run as a signaller like nginx -p . -s stop, the code in init_by_lua* will be executed. Now this probably unexpected behavior is avoided.

I hereby granted the copyright of the changes in this pull request
to the authors of this lua-nginx-module project.

[thibaultcha]

It should be doable to write a test for this behaviour with Test::Nginx (e.g. some side-effect triggered by init_by_lua*)? At least for the sake of preventing a future regression.

Food for thought:

Executing init_by_lua* in signaller processes has caused us some pain, so I am all in for this change. However, I can't help but think of:

1. some application out there that depends on this behaviour for some reason,
2. this behaviour actually being desired in the future to run Lua in signaller processes

We could address 1. with a new directive to optionally run the handler in signaller processes (lua_run_init_in_signaller on;). And 2. could be addressed with a new handler altogether, if we don't have the init_in_signaller on/off directive (e.g. signal_by_lua).

[spacewander]

@thibaultcha
IMHO, people could run their Lua code via resty before calling nginx -s, so there is always an alternative.

Now tests are added, and I also disable running init_by_lua* when testing Nginx configuration in the new commits.

[thibaultcha]

@spacewander Good call on -t and tests look fine to me 👍

[thibaultcha]

@spacewander Mind renaming this test suite to 159-disable-init-by-lua.t? See #1394 which already deals with 2 test suites named 157-*.t.

[spacewander]

@thibaultcha
Test file renamed.

[thibaultcha]

I have pushed a new commit which fixes the false positive found in the first test case. It is less fancy, but more robust and simpler.

[Lekensteyn]

For future reference:
This issue can only be reproduced with (1) nginx -t, or (2) nginx -s ... when a block is not using lua_shared_dict:

lua-nginx-module/src/ngx_http_lua_module.c

Line 798 in b687530

if (!lmcf->requires_shm && lmcf->init_handler) {

When lua_shared_dict is enabled, the init handler will not be called at that point and will be processed at a later stage. This oversight was also the cause for a crash with nginx -t (#1462) which was fixed by #1463.

[thibaultcha]

@Lekensteyn yes, I also have it on my TODO list already to fix a few other edge-cases that I believe aren' addressed yet. PRs welcome!