From 22d3d60ba1185d646f46f51e589d49412e6de585 Mon Sep 17 00:00:00 2001
From: Mitsuo HEIJO <mitsuo.heijo@gmail.com>
Date: Sat, 12 Jul 2025 17:25:54 +0900
Subject: [PATCH] out_prometheus_remote_write: support zstd compression

Signed-off-by: Mitsuo HEIJO <mitsuo.heijo@gmail.com>
---
 plugins/out_prometheus_remote_write/remote_write.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/plugins/out_prometheus_remote_write/remote_write.c b/plugins/out_prometheus_remote_write/remote_write.c
index 85cfe9840cb..459f60dbd01 100644
--- a/plugins/out_prometheus_remote_write/remote_write.c
+++ b/plugins/out_prometheus_remote_write/remote_write.c
@@ -20,6 +20,7 @@
 #include <fluent-bit/flb_output_plugin.h>
 #include <fluent-bit/flb_snappy.h>
 #include <fluent-bit/flb_gzip.h>
+#include <fluent-bit/flb_zstd.h>
 #include <fluent-bit/flb_metrics.h>
 #include <fluent-bit/flb_kv.h>
 
@@ -71,6 +72,10 @@ static int http_post(struct prometheus_remote_write_context *ctx,
         ret = flb_gzip_compress((void *) body, body_len,
                                 &payload_buf, &payload_size);
     }
+    else if (strcasecmp(ctx->compression, "zstd") == 0) {
+        ret = flb_zstd_compress((void *) body, body_len,
+                                &payload_buf, &payload_size);
+    }
     else {
         payload_buf = (void *) body;
         payload_size = body_len;
@@ -134,6 +139,13 @@ static int http_post(struct prometheus_remote_write_context *ctx,
                             "gzip",
                             strlen("gzip"));
     }
+    else if (strcasecmp(ctx->compression, "zstd") == 0) {
+        flb_http_add_header(c,
+                            "Content-Encoding",
+                            strlen("Content-Encoding"),
+                            "zstd",
+                            strlen("zstd"));
+    }
 
     /* Basic Auth headers */
     if (ctx->http_user && ctx->http_passwd) {
@@ -415,7 +427,7 @@ static struct flb_config_map config_map[] = {
     {
      FLB_CONFIG_MAP_STR, "compression", "snappy",
      0, FLB_TRUE, offsetof(struct prometheus_remote_write_context, compression),
-     "Compress the payload with either snappy, gzip if set"
+     "Compress the payload with either snappy, gzip, zstd if set"
     },
 
 #ifdef FLB_HAVE_SIGNV4