fix(elasticsearch sink): Elasticsearch sink with api_version set to "…

…auto"

  does not recognize the API version of ES6 as V6 (vectordotdev#17226)

src/sinks/elasticsearch/common.rs

@@ -160,7 +160,7 @@ impl ElasticsearchCommon {
                                    %assumed_version,
                                    %config.suppress_type_name
                             );
-                            warn!(message = "Failed to determine Elasticsearch version from `/_cluster/state/version`. Please fix the reported error or set an API version explicitly via `api_version`.",
+                            warn!(message = "Failed to determine Elasticsearch version. Please fix the reported error or set an API version explicitly via `api_version`.",
                                   %assumed_version,
                                   %error
                             );
@@ -276,29 +276,35 @@ async fn get_version(
     tls_settings: &TlsSettings,
     proxy_config: &ProxyConfig,
 ) -> crate::Result<usize> {
+    #[derive(Deserialize)]
+    struct Version {
+        number: Option<String>,
+    }
     #[derive(Deserialize)]
     struct ClusterState {
-        version: Option<usize>,
+        version: Option<Version>,
     }
 
     let client = HttpClient::new(tls_settings.clone(), proxy_config)?;
-    let response = get(
-        base_url,
-        http_auth,
-        aws_auth,
-        region,
-        request,
-        client,
-        "/_cluster/state/version",
-    )
-    .await
-    .map_err(|error| format!("Failed to get Elasticsearch API version: {}", error))?;
+    let response = get(base_url, http_auth, aws_auth, region, request, client, "/")
+        .await
+        .map_err(|error| format!("Failed to get Elasticsearch API version: {}", error))?;
 
     let (_, body) = response.into_parts();
     let mut body = body::aggregate(body).await?;
     let body = body.copy_to_bytes(body.remaining());
     let ClusterState { version } = serde_json::from_slice(&body)?;
-    version.ok_or_else(||"Unexpected response from Elasticsearch endpoint `/_cluster/state/version`. Missing `version`. Consider setting `api_version` option.".into())
+    if let Some(version) = version {
+        if let Some(number) = version.number {
+            let v: Vec<&str> = number.split('.').collect();
+            if v.len() > 0 {
+                if let Ok(major_version) = v[0].parse::<usize>() {
+                    return Ok(major_version);
+                }
+            }
+        }
+    }
+    return Err("Unexpected response from Elasticsearch endpoint `/`. Consider setting `api_version` option.".into());
 }
 
 async fn get(