feat: migrate logging log -> tracing

[CommanderStorm]

Lets split this up into two PRs

• one changing the interface, tests and dependencys
• one adding additional configuration options to martin AND documenting them

Alternatively, we can keep this PR open and I am going to get back to this sometime on the weekend

Resolves #836

we should continue using the RUST_LOG env var for all the configuration, with the possible addition of CLI and Config params

• RUST_LOG
• custom env variables MARTIN_LOG_FORMAT, MARTIN_LOG_LEVEL, ...
• deduplicating code
• CLI
• Config
• Writing docs (🦖)

[nyurik]

needs a few cleanups, but this might be ok... We should probably run some perf tests (we have that using oha in the justfile iirc) - to see if there are any significant slowdowns due to the switch

[CommanderStorm]

So I ran the performance benchmarks..
Seems like there is a supprising performance difference..

Will investigate where this is coming from.. I have some theories, such as my terminal not being the best at printing formatted output and such => will test them and report back and update the table below

experiment
baseline/log + with terminal output via ssh
log + no terminal output
tracing + with terminal output via ssh
tracing + no terminal output
tracing+ with terminal output via ssh + MARTIN_LOG_FORMAT=json
tracing+ with terminal output via ssh + NO request logging via actix-tracing, but via actix-middleware + MARTIN_LOG_FORMAT=json
tracing+ with terminal output via ssh + request logging via actix-tracing, but NOT via actix-middleware + MARTIN_LOG_FORMAT=json
tracing + with terminal output via ssh + request logging via actix-tracing, but NOT via actix-middleware + MARTIN_LOG_FORMAT=json + interest cache in tracing_log
tracing + no terminal output + request logging via actix-tracing, but NOT via actix-middleware + interest cache in tracing_log

[CommanderStorm]

Okay.. So I got performance up there again. Was a good call to do benchmarks 😅

I think there are severe performance issues with my ssh-terminal and rendering special characters => I am going to discount the initial and only consider MARTIN_LOG_FORMAT=json
I don't think on a server, this is reasonably a problem.

The rqs went down on some of these, but 170k -> 130k is likely not something that users will see in reality.
Will look further into what is causing the slowdown there

[CommanderStorm]

So apparently some of our dependencys log via tracing (switch on the trace level to see it.. that is a lot).
There is the expected change from not having so much semi-const stuff.. I think the ~relatively small change is fine..

=> I think performance is not a bottleneck anymore. Will investigate configurability next

[nyurik]

WOW! This is a very thorough job you did there! Thank you!

Ideally, we should continue using the RUST_LOG env var for all the configuration, with the possible addition of CLI and Config params. If we need more values like output format (vs output filtering), that may go into separate params too.

When doing performance, stdout + term + ssh is almost always a bad choice - there might be locking and syscall issues affecting it. Best to redirect it to /dev/null to avoid additional uncertainty, or perhaps dump to a file (but that might also be less than stable).

[CommanderStorm]

Bit unsure about the API/naming here..

I tried to make it less "magic", but unsure if this is the best way to handle it.

[CommanderStorm]

This SHOULD work, but for some reason it does only locally.. no clue why..

This also just SOMETIMES does this.. so weird

Will have to look further into the code what is overriding this being active...

[Copilot]

Pull Request Overview

This PR migrates the logging functionality from the log crate to tracing throughout Martin’s codebase and updates the corresponding CLI help and documentation.

• Replace log imports with tracing equivalents in multiple modules
• Update CLI text and configuration documentation to reference tracing-subscriber instead of env_logger
• Add a new martin-observability-utils package for improved observability support

Reviewed Changes

Copilot reviewed 71 out of 71 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
martin/src/pg/pg_source.rs	Updated log::debug to tracing::debug
martin/src/pg/config_table.rs	Replaced log macros with tracing macros
martin/src/pg/config.rs	Replaced log::warn with tracing::warn
martin/src/pg/builder.rs	Replaced log macros with tracing macros
martin/src/mbtiles/mod.rs	Replaced log::trace with tracing::trace
martin/src/fonts/mod.rs	Replaced log macros with tracing macros
martin/src/file_config.rs	Replaced log macros with tracing macros
martin/src/config.rs	Updated log::info to tracing::info
martin/src/cog/source.rs	Reordered imports and replaced log::warn with tracing::warn
martin/src/args/srv.rs	Updated use and derived order; added new CLI options for logging
martin/src/args/root.rs	Updated after_help text with tracing-subscriber docs reference
martin/src/args/pg.rs	Replaced log macros with tracing macros
martin/src/args/environment.rs	Replaced log::warn with tracing::warn
martin/Cargo.toml	Removed env_logger and log; added tracing dependencies
martin-observability-utils/src/lib.rs	Introduced tracing-based observability utilities
martin-observability-utils/README.md	Added initial README for logging utilities
martin-observability-utils/Cargo.toml	Added package manifest for the observability utilities package
docs/src/env-vars.md	Updated logging env var details to reference tracing-subscriber docs
docs/src/config-file.md	Updated configuration examples to use tracing-based logging
Cargo.toml	Updated workspace members and dependencies to include tracing-based crates

Comments suppressed due to low confidence (1)

martin-observability-utils/src/lib.rs:51

• Consider clarifying this error message to more explicitly state that setting the global subscriber failed because a subscriber has already been set. For example, use: "Failed to set global subscriber: global subscriber already set."

        .expect("since martin has not set the global_default, no global default is set");