Thread safety#

Most functions and classes are thread safe. Notable exceptions are documented here.

Not thread safe	Comment
`enable_verbose_debug_messages()`	This function modifies global state.
`AbstractFetcher.fetch_all()`	When `selective_fetch_all=True` (default), a temporary `Mapper` instance may be used. All built-in fetchers (e.g. the `SqlFetcher`) inherit from this class.
`Fetcher.initialize_sources()`	Invoked implicitly before all translation tasks. Results are cached when using a `MultiFetcher` or `AbstractFetcher` subtype, after which `initialize_sources` is thread-safe for these types.
`Translator.translated_names()`	Reflects the most recent `Translator.translate()` call on the instance. The `translate` call itself is thread safe (when `copy=True`), but the recorded names are not. Use `Translator.map()` in multi-threaded contexts.
`Translator.initialize_sources()`	Delegates to `Fetcher.initialize_sources` above, so the same “first call is not thread safe” caveat applies. The first call also registers fetcher-provided transformers (see `Fetcher.get_transformer()`), mutating the `Translator` itself. `translate()` triggers this implicitly on its own first call and inherits the same caveat.
`Translator.go_offline()`	Performs `Fetcher` teardown. Once offline, the `Translator` is safe to share.

Transformers#

The Translator.transformers are reused for all translation tasks. Bundled Transformer types are thread safe. Transformers are inherited by any TranslationMap instances created by the Translator, including the Translator.cache created by Translator.go_offline(). Note that Translator.register_transformer() mutates shared state (including the cache), so the safe-to-share guarantee above assumes no registrations are made after going offline. See the registration window for details.

Fetchers#

Some thread-unsafe Fetcher operations emit a ConcurrentOperationWarning on a best-effort basis when entered from multiple threads at once. This detection is cheap and lock-free, so it may miss races; absence of a warning does not prove correctness.