From b3f092bc435ddd9d0c3b9d76cc4b257611690143 Mon Sep 17 00:00:00 2001
From: Hiroshi Hatake <hatake@calyptia.com>
Date: Wed, 18 Oct 2023 19:18:04 +0900
Subject: [PATCH] engine: output: Add metrics for displaying the available
 capacity of chunks as percent

Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>
---
 include/fluent-bit/flb_output.h |  2 ++
 src/flb_engine.c                | 25 +++++++++++++++++++++++++
 src/flb_output.c                | 12 ++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/include/fluent-bit/flb_output.h b/include/fluent-bit/flb_output.h
index 5978c285679..5dc2bf286b2 100644
--- a/include/fluent-bit/flb_output.h
+++ b/include/fluent-bit/flb_output.h
@@ -370,6 +370,8 @@ struct flb_output_instance {
     struct cmt_gauge   *cmt_upstream_total_connections;
     /* m: output_upstream_busy_connections */
     struct cmt_gauge   *cmt_upstream_busy_connections;
+    /* m: output_chunk_available_capacity_percent */
+    struct cmt_gauge   *cmt_chunk_available_capacity_percent;
 
     /* OLD Metrics API */
 #ifdef FLB_HAVE_METRICS
diff --git a/src/flb_engine.c b/src/flb_engine.c
index 78be8d5ec8d..5e4fb5d04b4 100644
--- a/src/flb_engine.c
+++ b/src/flb_engine.c
@@ -312,6 +312,11 @@ static inline int handle_output_event(uint64_t ts,
                      flb_output_name(ins), out_id);
         }
 
+        cmt_gauge_set(ins->cmt_chunk_available_capacity_percent, ts,
+                      (100 * (1.0 - (ins->fs_backlog_chunks_size + ins->fs_chunks_size)/
+                              ((double)ins->total_limit_size))),
+                      1, (char *[]) {name});
+
         flb_task_retry_clean(task, ins);
         flb_task_users_dec(task, FLB_TRUE);
     }
@@ -321,6 +326,11 @@ static inline int handle_output_event(uint64_t ts,
             cmt_counter_add(ins->cmt_dropped_records, ts, task->records,
                             1, (char *[]) {name});
 
+            cmt_gauge_set(ins->cmt_chunk_available_capacity_percent, ts,
+                          (100 * (1.0 - (ins->fs_backlog_chunks_size + ins->fs_chunks_size)/
+                                  ((double)ins->total_limit_size))),
+                          1, (char *[]) {name});
+
             /* OLD metrics API */
 #ifdef FLB_HAVE_METRICS
             flb_metrics_sum(FLB_METRIC_OUT_DROPPED_RECORDS, task->records, ins->metrics);
@@ -353,6 +363,11 @@ static inline int handle_output_event(uint64_t ts,
             cmt_counter_add(ins->cmt_dropped_records, ts, task->records,
                             1, (char *[]) {name});
 
+            cmt_gauge_set(ins->cmt_chunk_available_capacity_percent, ts,
+                          (100 * (1.0 - (ins->fs_backlog_chunks_size + ins->fs_chunks_size)/
+                                  ((double)ins->total_limit_size))),
+                          1, (char *[]) {name});
+
             /* OLD metrics API */
 #ifdef FLB_HAVE_METRICS
             flb_metrics_sum(FLB_METRIC_OUT_RETRY_FAILED, 1, ins->metrics);
@@ -409,6 +424,11 @@ static inline int handle_output_event(uint64_t ts,
             cmt_counter_add(ins->cmt_retried_records, ts, task->records,
                             1, (char *[]) {name});
 
+            cmt_gauge_set(ins->cmt_chunk_available_capacity_percent, ts,
+                          (100 * (1.0 - (ins->fs_backlog_chunks_size + ins->fs_chunks_size)/
+                                  ((double)ins->total_limit_size))),
+                          1, (char *[]) {name});
+
             /* OLD metrics API: update the metrics since a new retry is coming */
 #ifdef FLB_HAVE_METRICS
             flb_metrics_sum(FLB_METRIC_OUT_RETRY, 1, ins->metrics);
@@ -422,6 +442,11 @@ static inline int handle_output_event(uint64_t ts,
         cmt_counter_add(ins->cmt_dropped_records, ts, task->records,
                         1, (char *[]) {name});
 
+        cmt_gauge_set(ins->cmt_chunk_available_capacity_percent, ts,
+                      (100 * (1.0 - (ins->fs_backlog_chunks_size + ins->fs_chunks_size)/
+                              ((double)ins->total_limit_size))),
+                      1, (char *[]) {name});
+
         /* OLD API */
 #ifdef FLB_HAVE_METRICS
         flb_metrics_sum(FLB_METRIC_OUT_ERROR, 1, ins->metrics);
diff --git a/src/flb_output.c b/src/flb_output.c
index ee50ed80a2a..15daa6c09d4 100644
--- a/src/flb_output.c
+++ b/src/flb_output.c
@@ -1200,6 +1200,18 @@ int flb_output_init_all(struct flb_config *config)
                       0,
                       1, (char *[]) {name});
 
+        /* output_chunk_available_capacity_percent */
+        ins->cmt_chunk_available_capacity_percent = cmt_gauge_create(ins->cmt,
+                                                        "fluentbit",
+                                                        "output",
+                                                        "chunk_available_capacity_percent",
+                                                        "Available chunk capacity (percent)",
+                                                        1, (char *[]) {"name"});
+        cmt_gauge_set(ins->cmt_chunk_available_capacity_percent,
+                      ts,
+                      100.0,
+                      1, (char *[]) {name});
+
         /* old API */
         ins->metrics = flb_metrics_create(name);
         if (ins->metrics) {