class ThreadSafe::MriCacheBackend
Constants
- WRITE_LOCK
We can get away with a single global write lock (instead of a per-instance one) because of the GVL/green threads.
The previous implementation used `Thread.critical` on 1.8 MRI to implement the 4 composed atomic operations (`put_if_absent`, `replace_pair`, `replace_if_exists`, `delete_pair`) this however doesn't work for `compute_if_absent` because on 1.8 the Mutex class is itself implemented via `Thread.critical` and a call to `Mutex#lock` does not restore the previous `Thread.critical` value (thus any synchronisation clears the `Thread.critical` flag and we loose control). This poses a problem as the provided block might use synchronisation on its own.
NOTE: a neat idea of writing a c-ext to manually perform atomic put_if_absent, while relying on Ruby not releasing a GVL while calling a c-ext will not work because of the potentially Ruby implemented `#hash` and `#eql?` key methods.
Public Instance Methods
# File lib/thread_safe/mri_cache_backend.rb, line 14 def []=(key, value) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 58 def clear WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 30 def compute(key) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 18 def compute_if_absent(key) if stored_value = _get(key) # fast non-blocking path for the most likely case stored_value else WRITE_LOCK.synchronize { super } end end
# File lib/thread_safe/mri_cache_backend.rb, line 26 def compute_if_present(key) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 50 def delete(key) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 54 def delete_pair(key, value) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 46 def get_and_set(key, value) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 34 def merge_pair(key, value) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 42 def replace_if_exists(key, new_value) WRITE_LOCK.synchronize { super } end
# File lib/thread_safe/mri_cache_backend.rb, line 38 def replace_pair(key, old_value, new_value) WRITE_LOCK.synchronize { super } end