feat: enable L4 stream logging (#5768)

apisix/cli/ngx_tpl.lua

@@ -84,6 +84,13 @@ stream {
     lua_ssl_trusted_certificate {* ssl.ssl_trusted_certificate *};
     {% end %}
 
+    # for stream logs, off by default
+    {% if stream.enable_access_log == true then %}
+    log_format main escape={* stream.access_log_format_escape *} '{* stream.access_log_format *}';
+
+    access_log {* stream.access_log *} main buffer=16384 flush=3;
+    {% end %}
+
     # stream configuration snippet starts
     {% if stream_configuration_snippet then %}
     {* stream_configuration_snippet *}

conf/config-default.yaml

@@ -174,6 +174,11 @@ nginx_config:                     # config for render the template to generate n
   #  - TEST_ENV
 
   stream:
+    enable_access_log: false         # enable access log or not, default false
+    access_log: logs/access_stream.log
+    access_log_format: "$remote_addr [$time_local] $protocol $status $bytes_sent $bytes_received $session_time"
+                                            # create your custom log format by visiting http://nginx.org/en/docs/varindex.html
+    access_log_format_escape: default       # allows setting json or default characters escaping in variables
     lua_shared_dict:
       etcd-cluster-health-check-stream: 10m
       lrucache-lock-stream: 10m

t/cli/test_access_log.sh

@@ -224,3 +224,40 @@ fi
 
 make stop
 echo "passed: should find upstream scheme"
+
+# check stream logs
+echo '
+apisix:
+    stream_proxy:                  # UDP proxy
+     udp:
+       - "127.0.0.1:9200"
+
+nginx_config:
+  stream:
+    enable_access_log: true
+    access_log_format: "$remote_addr $protocol test_stream_access_log_format"
+' > conf/config.yaml
+
+make init
+
+grep "test_stream_access_log_format" conf/nginx.conf > /dev/null
+if [ ! $? -eq 0 ]; then
+    echo "failed: stream access_log_format in nginx.conf doesn't change"
+    exit 1
+fi
+echo "passed: stream access_log_format in nginx.conf is ok"
+
+# check if logs are being written
+make run
+sleep 0.1
+# sending single udp packet
+echo -n "hello" | nc -4u -w0 localhost 9200
+sleep 4
+tail -n 1 logs/access_stream.log > output.log
+
+if ! grep '127.0.0.1 UDP test_stream_access_log_format' output.log; then
+    echo "failed: should have found udp log entry"
+    cat output.log
+    exit 1
+fi
+echo "passed: logs are being dumped for stream proxy"