Use bucket based on placeholder

Signed-off-by: rmontenegroo <[email protected]>

Author: rmontenegroo

lib/fluent/plugin/out_s3.rb

@@ -298,6 +298,35 @@ def write(chunk)
                    else
                      @time_slice_with_tz.call(metadata.timekey)
                    end
+      
+      bucket_name = nil
+
+      if @s3_bucket =~ /\$\{.*\}/
+        @s3_bucket.scan(/\$\{([^\$\{\}]+)\}/) do |placeholder|
+          placeholder = placeholder.join
+          if (not chunk.metadata.variables) or (not chunk.metadata.variables.keys.include?(placeholder.to_sym))
+            log.warn "There is no placeholder '#{placeholder}'" 
+            if @s3_bucket_fallback
+              bucket_name = @s3_bucket_fallback
+              log.warn "Using @s3_bucket_fallback ('#{@s3_bucket_fallback}') as a fallback bucket name."
+              break
+            else
+              raise "It was possible to extract placeholder '#{placeholder}' from chunk and @s3_bucket_fallback is not set."
+            end
+          end
+        end
+
+        if not bucket_name
+          bucket_name = extract_placeholders(@s3_bucket, chunk)
+        end
+
+        bucket = @s3.bucket(bucket_name)
+        check_apikeys(bucket) if @check_apikey_on_start
+        ensure_bucket(bucket) if @check_bucket
+        ensure_bucket_lifecycle(bucket)
+      else
+        bucket = @bucket
+      end
 
       bucket = @bucket ? @bucket : nil