in_nginx_exporter_metrics: add missing release function

[nokute78]

This patch is to add missing releasing function.

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• [N/A] Example configuration file for the change
• [N/A] Debug log output from testing the change

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

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• [N/A] Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[edsiper]

@nokute78 thanks for this patch.

I see that the context is registered right after creation here:

fluent-bit/plugins/in_nginx_exporter_metrics/nginx.c

Line 1600 in 4d7fad2

flb_input_set_context(ins, ctx);

but if the plugin cannot be initialized, in theory, it should be released, have you checked with Valgrind if is there a real leak ?

[nokute78]

@edsiper I tested 2 cases.
Valgrind reported struct nginx_ctx is leaked.

1. After flb_input_set_context

I added following patch for v2.1.8 branch.

diff --git a/plugins/in_nginx_exporter_metrics/nginx.c b/plugins/in_nginx_exporter_metrics/nginx.c
index 9645fca8e..e5f985cfd 100644
--- a/plugins/in_nginx_exporter_metrics/nginx.c
+++ b/plugins/in_nginx_exporter_metrics/nginx.c
@@ -1595,6 +1595,8 @@ static int nginx_init(struct flb_input_instance *ins,
 
     flb_input_set_context(ins, ctx);
 
+    return -1;
+
     if (ctx->is_nginx_plus == FLB_FALSE) {
         /* These metrics follow the same format as those define here:
          * https://github.com/nginxinc/nginx-prometheus-exporter#metrics-for-nginx-oss

Valgrind output is

$ valgrind --leak-check=full bin/fluent-bit -i nginx_metrics -o stdout
==15380== Memcheck, a memory error detector
==15380== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==15380== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==15380== Command: bin/fluent-bit -i nginx_metrics -o stdout
==15380== 
Fluent Bit v2.1.8
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/09/02 07:29:59] [ info] [fluent bit] version=2.1.8, commit=1d83649441, pid=15380
[2023/09/02 07:29:59] [ info] [storage] ver=1.2.0, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/09/02 07:29:59] [ info] [cmetrics] version=0.6.3
[2023/09/02 07:29:59] [ info] [ctraces ] version=0.3.1
[2023/09/02 07:29:59] [ info] [input:nginx_metrics:nginx_metrics.0] initializing
[2023/09/02 07:29:59] [ info] [input:nginx_metrics:nginx_metrics.0] storage_strategy='memory' (memory only)
[2023/09/02 07:29:59] [error] failed initialize input nginx_metrics.0
[2023/09/02 07:29:59] [error] [engine] input initialization failed
[2023/09/02 07:29:59] [error] [lib] backend failed
==15380== 
==15380== HEAP SUMMARY:
==15380==     in use at exit: 713 bytes in 8 blocks
==15380==   total heap usage: 1,185 allocs, 1,177 frees, 222,107 bytes allocated
==15380== 
==15380== 7 bytes in 1 blocks are definitely lost in loss record 1 of 8
==15380==    at 0x4848899: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==15380==    by 0x1C3E60: flb_malloc (flb_mem.h:80)
==15380==    by 0x1C414A: flb_strndup (flb_str.h:34)
==15380==    by 0x1C41B1: flb_strdup (flb_str.h:46)
==15380==    by 0x1C681C: flb_main (fluent-bit.c:928)
==15380==    by 0x1C7593: main (fluent-bit.c:1358)
==15380== 
==15380== 706 (192 direct, 514 indirect) bytes in 1 blocks are definitely lost in loss record 8 of 8
==15380==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==15380==    by 0x4D89F9: flb_calloc (flb_mem.h:95)
==15380==    by 0x4E3D3D: nginx_ctx_init (nginx.c:1519)
==15380==    by 0x4E401E: nginx_init (nginx.c:1590)
==15380==    by 0x1FD551: flb_input_instance_init (flb_input.c:1189)
==15380==    by 0x1FD714: flb_input_init_all (flb_input.c:1248)
==15380==    by 0x242B41: flb_engine_start (flb_engine.c:770)
==15380==    by 0x1DD944: flb_lib_worker (flb_lib.c:638)
==15380==    by 0x4FF3B42: start_thread (pthread_create.c:442)
==15380==    by 0x5084BB3: clone (clone.S:100)
==15380== 
==15380== LEAK SUMMARY:
==15380==    definitely lost: 199 bytes in 2 blocks
==15380==    indirectly lost: 514 bytes in 6 blocks
==15380==      possibly lost: 0 bytes in 0 blocks
==15380==    still reachable: 0 bytes in 0 blocks
==15380==         suppressed: 0 bytes in 0 blocks
==15380== 
==15380== For lists of detected and suppressed errors, rerun with: -s
==15380== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

2. Failed at nginx_ctx_init

I added following patch for v2.1.8 branch.

diff --git a/plugins/in_nginx_exporter_metrics/nginx.c b/plugins/in_nginx_exporter_metrics/nginx.c
index 9645fca8e..57d49d2e4 100644
--- a/plugins/in_nginx_exporter_metrics/nginx.c
+++ b/plugins/in_nginx_exporter_metrics/nginx.c
@@ -1547,6 +1547,8 @@ struct nginx_ctx *nginx_ctx_init(struct flb_input_instance *ins,
 
     upstream = flb_upstream_create(config, ins->host.name, ins->host.port,
                                    upstream_flags, ins->tls);
+    flb_upstream_destroy(upstream);
+    return NULL;
 
     if (!upstream) {
         flb_plg_error(ins, "upstream initialization error");

Valgrind output is

$ valgrind --leak-check=full bin/fluent-bit -i nginx_metrics -o stdout
==18193== Memcheck, a memory error detector
==18193== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==18193== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==18193== Command: bin/fluent-bit -i nginx_metrics -o stdout
==18193== 
Fluent Bit v2.1.8
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/09/02 07:43:04] [ info] [fluent bit] version=2.1.8, commit=1d83649441, pid=18193
[2023/09/02 07:43:04] [ info] [storage] ver=1.2.0, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2023/09/02 07:43:04] [ info] [cmetrics] version=0.6.3
[2023/09/02 07:43:04] [ info] [ctraces ] version=0.3.1
[2023/09/02 07:43:04] [ info] [input:nginx_metrics:nginx_metrics.0] initializing
[2023/09/02 07:43:04] [ info] [input:nginx_metrics:nginx_metrics.0] storage_strategy='memory' (memory only)
[2023/09/02 07:43:04] [error] failed initialize input nginx_metrics.0
[2023/09/02 07:43:04] [error] [engine] input initialization failed
[2023/09/02 07:43:04] [error] [lib] backend failed
==18193== 
==18193== HEAP SUMMARY:
==18193==     in use at exit: 383 bytes in 6 blocks
==18193==   total heap usage: 1,185 allocs, 1,179 frees, 222,107 bytes allocated
==18193== 
==18193== 7 bytes in 1 blocks are definitely lost in loss record 1 of 6
==18193==    at 0x4848899: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==18193==    by 0x1C3E60: flb_malloc (flb_mem.h:80)
==18193==    by 0x1C414A: flb_strndup (flb_str.h:34)
==18193==    by 0x1C41B1: flb_strdup (flb_str.h:46)
==18193==    by 0x1C681C: flb_main (fluent-bit.c:928)
==18193==    by 0x1C7593: main (fluent-bit.c:1358)
==18193== 
==18193== 376 (192 direct, 184 indirect) bytes in 1 blocks are definitely lost in loss record 6 of 6
==18193==    at 0x484DA83: calloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==18193==    by 0x4D89F9: flb_calloc (flb_mem.h:95)
==18193==    by 0x4E3D3D: nginx_ctx_init (nginx.c:1519)
==18193==    by 0x4E3F9A: nginx_init (nginx.c:1592)
==18193==    by 0x1FD551: flb_input_instance_init (flb_input.c:1189)
==18193==    by 0x1FD714: flb_input_init_all (flb_input.c:1248)
==18193==    by 0x242B41: flb_engine_start (flb_engine.c:770)
==18193==    by 0x1DD944: flb_lib_worker (flb_lib.c:638)
==18193==    by 0x4FF3B42: start_thread (pthread_create.c:442)
==18193==    by 0x5084BB3: clone (clone.S:100)
==18193== 
==18193== LEAK SUMMARY:
==18193==    definitely lost: 199 bytes in 2 blocks
==18193==    indirectly lost: 184 bytes in 4 blocks
==18193==      possibly lost: 0 bytes in 0 blocks
==18193==    still reachable: 0 bytes in 0 blocks
==18193==         suppressed: 0 bytes in 0 blocks
==18193== 
==18193== For lists of detected and suppressed errors, rerun with: -s
==18193== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

[edsiper]

thank you