Revert "Instrument read_multi".

Reevaluating the log output generated from this instrumentation,
we've found that it wasn't all that useful in practice.

```
Caches multi read:
- views/david/2/4184ab71db6849621a4d8820fcd2c0ad
- views/david/2/4184ab71db6849621a4d8820fcd2c0ad
- views/david/3/4184ab71db6849621a4d8820fcd2c0ad
- views/david/3/4184ab71db6849621a4d8820fcd2c0ad
```

If rendering many templates the output is inscrutable, and it's impossible
to see how many cache misses there were.

Revert ca6aba7f30 and implement a better way later.

1 files changed, 10 insertions, 23 deletions

diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 610105f41c..1c63e8a93f 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -333,21 +333,19 @@ module ActiveSupport
         options = names.extract_options!
         options = merged_options(options)
 
-        instrument_multi(:read, names, options) do |payload|
-          results = {}
-          names.each do |name|
-            key = normalize_key(name, options)
-            entry = read_entry(key, options)
-            if entry
-              if entry.expired?
-                delete_entry(key, options)
-              else
-                results[name] = entry.value
-              end
+        results = {}
+        names.each do |name|
+          key = normalize_key(name, options)
+          entry = read_entry(key, options)
+          if entry
+            if entry.expired?
+              delete_entry(key, options)
+            else
+              results[name] = entry.value
             end
           end
-          results
         end
+        results
       end
 
       # Fetches data from the cache, using the given keys. If there is data in
@@ -555,17 +553,6 @@ module ActiveSupport
           ActiveSupport::Notifications.instrument("cache_#{operation}.active_support", payload){ yield(payload) }
         end
 
-        def instrument_multi(operation, keys, options = nil)
-          log do
-            formatted_keys = keys.map { |k| "- #{k}" }.join("\n")
-            "Caches multi #{operation}:\n#{formatted_keys}#{options.blank? ? "" : " (#{options.inspect})"}"
-          end
-
-          payload = { key: keys }
-          payload.merge!(options) if options.is_a?(Hash)
-          ActiveSupport::Notifications.instrument("cache_#{operation}_multi.active_support", payload) { yield(payload) }
-        end
-
         def log
           return unless logger && logger.debug? && !silence?
           logger.debug(yield)