output: Fix "placeholder chunk_id not replaced" warnings

On some setup, Fluentd warns about "chunk_id" being not found in `@chunk_keys`. This warning is misguided. `${chunk_id}` is a special field that Fluentd should automatically fill it with `chunk.unique_id`. It should never try to look up the key in `@chunk_keys`. This patch fixes the warning by adjusting the evaluation order, extending the preceding work f18640b by Brian Atkinson. Signed-off-by: Fujimoto Seiji <[email protected]>
fluent · Apr 20, 2021 · 3e6180c · 3e6180c
1 parent 8c7d674
commit 3e6180c
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Showing 2 changed files with 13 additions and 11 deletions.
diff --git a/lib/fluent/plugin/output.rb b/lib/fluent/plugin/output.rb
@@ -754,7 +754,17 @@ def extract_placeholders(str, chunk)
               log.warn "tag placeholder '#{$1}' not replaced. tag:#{metadata.tag}, template:#{str}"
             end
           end
-          # ${a_chunk_key}, ...
+
+          # First we replace ${chunk_id} with chunk.unique_id (hexlified).
+          rvalue = rvalue.sub(CHUNK_ID_PLACEHOLDER_PATTERN) {
+            if chunk_passed
+              dump_unique_id_hex(chunk.unique_id)
+            else
+              log.warn "${chunk_id} is not allowed in this plugin. Pass Chunk instead of metadata in extract_placeholders's 2nd argument"
+            end
+          }
+
+          # Then, replace other ${chunk_key}s.
           if !@chunk_keys.empty? && metadata.variables
             hash = {'${tag}' => '${tag}'} # not to erase this wrongly
             @chunk_keys.each do |key|
@@ -769,14 +779,6 @@ def extract_placeholders(str, chunk)
             end
           end
 
-          rvalue = rvalue.sub(CHUNK_ID_PLACEHOLDER_PATTERN) {
-            if chunk_passed
-              dump_unique_id_hex(chunk.unique_id)
-            else
-              log.warn "${chunk_id} is not allowed in this plugin. Pass Chunk instead of metadata in extract_placeholders's 2nd argument"
-            end
-          }
-
           if rvalue =~ CHUNK_KEY_PLACEHOLDER_PATTERN
             log.warn "chunk key placeholder '#{$1}' not replaced. template:#{str}"
           end

diff --git a/test/plugin/test_output.rb b/test/plugin/test_output.rb
@@ -379,8 +379,8 @@ def waiting(seconds)
     end
 
     test '#extract_placeholders does not log for ${chunk_id} placeholder' do
-      @i.configure(config_element('ROOT', '', {}, [config_element('buffer', '')]))
-      tmpl = "/mypath/${chunk_id}/tail"
+      @i.configure(config_element('ROOT', '', {}, [config_element('buffer', 'key1')]))
+      tmpl = "/mypath/${chunk_id}/${key1}/tail"
       t = event_time('2016-04-11 20:30:00 +0900')
       v = {key1: "value1", key2: "value2"}
       c = create_chunk(timekey: t, tag: 'fluentd.test.output', variables: v)