out_s3: add store_dir_limit_size to limit S3 disk usage

plugins/out_s3/s3.c

@@ -506,7 +506,6 @@ static int cb_s3_init(struct flb_output_instance *ins,
     int ret;
     flb_sds_t tmp_sds;
     int async_flags;
-    int len;
     char *role_arn = NULL;
     char *session_name;
     const char *tmp;
@@ -540,6 +539,15 @@ static int cb_s3_init(struct flb_output_instance *ins,
         return -1;
     }
 
+    /* the check against -1 is works here because size_t is unsigned
+     * and (int) -1 == unsigned max value
+     * Fluent Bit uses -1 (which becomes max value) to indicate undefined
+     */
+    if (ctx->ins->total_limit_size != -1) {
+        flb_plg_warn(ctx->ins, "Please use 'store_dir_limit_size' with s3 output instead of 'storage.total_limit_size'. "
+                     "S3 has its own buffer files located in the store_dir.");
+    }
+
     /* Date key */
     ctx->date_key = ctx->json_date_key;
     tmp = flb_output_get_property("json_date_key", ins);
@@ -570,15 +578,6 @@ static int cb_s3_init(struct flb_output_instance *ins,
         return -1;
     }
 
-    tmp = flb_output_get_property("chunk_buffer_dir", ins);
-    if (tmp) {
-        len = strlen(tmp);
-        if (tmp[len - 1] == '/' || tmp[len - 1] == '\\') {
-            flb_plg_error(ctx->ins, "'chunk_buffer_dir' can not end in a / or \\");
-            return -1;
-        }
-    }
-
     /*
      * store_dir is the user input, buffer_dir is what the code uses
      * We append the bucket name to the dir, to support multiple instances
@@ -2363,6 +2362,15 @@ static struct flb_config_map config_map[] = {
      " data will be locally buffered at any given point in time."
     },
 
+    {
+     FLB_CONFIG_MAP_SIZE, "store_dir_limit_size", (char *) NULL,
+     0, FLB_TRUE, offsetof(struct flb_s3, store_dir_limit_size),
+     "S3 plugin has its own buffering system with files in the `store_dir`. "
+     "Use the `store_dir_limit_size` to limit the amount of data S3 buffers in "
+     "the `store_dir` to limit disk usage. If the limit is reached, "
+     "data will be discarded. Default is 0 which means unlimited."
+    },
+
     {
      FLB_CONFIG_MAP_STR, "s3_key_format", "/fluent-bit-logs/$TAG/%Y/%m/%d/%H/%M/%S",
      0, FLB_TRUE, offsetof(struct flb_s3, s3_key_format),

plugins/out_s3/s3.h

@@ -120,6 +120,10 @@ struct flb_s3 {
     int compression;
     int port;
     int insecure;
+    size_t store_dir_limit_size;
+
+    /* track the total amount of buffered data */
+    size_t current_buffer_size;
 
     struct flb_aws_provider *provider;
     struct flb_aws_provider *base_provider;

plugins/out_s3/s3_store.c

@@ -130,6 +130,13 @@ int s3_store_buffer_put(struct flb_s3 *ctx, struct s3_file *s3_file,
     int ret;
     flb_sds_t name;
     struct flb_fstore_file *fsf;
+    size_t space_remaining;
+
+    if (ctx->store_dir_limit_size > 0 && ctx->current_buffer_size + bytes >= ctx->store_dir_limit_size) {
+        flb_plg_error(ctx->ins, "Buffer is full: current_buffer_size=%zu, new_data=%zu, store_dir_limit_size=%zu bytes",
+                    ctx->current_buffer_size, bytes, ctx->store_dir_limit_size);
+        return -1;
+    }
 
     /* If no target file was found, create a new one */
     if (!s3_file) {
@@ -184,6 +191,17 @@ int s3_store_buffer_put(struct flb_s3 *ctx, struct s3_file *s3_file,
         return -1;
     }
     s3_file->size += bytes;
+    ctx->current_buffer_size += bytes;
+
+    /* if buffer is 95% full, warn user */
+    if (ctx->store_dir_limit_size > 0) {
+        space_remaining = ctx->store_dir_limit_size - ctx->current_buffer_size;
+        if ((space_remaining * 20) < ctx->store_dir_limit_size) {
+            flb_plg_warn(ctx->ins, "Buffer is almost full: current_buffer_size=%zu, store_dir_limit_size=%zu bytes",
+                        ctx->current_buffer_size, ctx->store_dir_limit_size);
+            return -1;
+        }
+    }
 
     return 0;
 }
@@ -397,6 +415,7 @@ int s3_store_file_delete(struct flb_s3 *ctx, struct s3_file *s3_file)
     struct flb_fstore_file *fsf;
 
     fsf = s3_file->fsf;
+    ctx->current_buffer_size -= s3_file->size;
 
     /* permanent deletion */
     flb_fstore_file_delete(ctx->fs, fsf);