Allow log sampling configuration from Caddyfile

caddyconfig/httpcaddyfile/builtins.go

@@ -981,6 +981,50 @@ func parseLogHelper(h Helper, globalLogNames map[string]struct{}) ([]ConfigValue
 			}
 			cl.WriterRaw = caddyconfig.JSONModuleObject(wo, "output", moduleName, h.warnings)
 
+		case "sampling":
+			d := h.Dispenser.NewFromNextSegment()
+			for d.NextArg() {
+				// consume any tokens on the same line, if any.
+			}
+
+			sampling := &caddy.LogSampling{}
+			for nesting := d.Nesting(); d.NextBlock(nesting); {
+				subdir := d.Val()
+				switch subdir {
+				case "interval":
+					if !d.NextArg() {
+						return nil, d.ArgErr()
+					}
+					interval, err := time.ParseDuration(d.Val() + "ns")
+					if err != nil {
+						return nil, d.Errf("failed to parse interval: %v", err)
+					}
+					sampling.Interval = interval
+				case "first":
+					if !d.NextArg() {
+						return nil, d.ArgErr()
+					}
+					first, err := strconv.Atoi(d.Val())
+					if err != nil {
+						return nil, d.Errf("failed to parse first: %v", err)
+					}
+					sampling.First = first
+				case "thereafter":
+					if !d.NextArg() {
+						return nil, d.ArgErr()
+					}
+					thereafter, err := strconv.Atoi(d.Val())
+					if err != nil {
+						return nil, d.Errf("failed to parse thereafter: %v", err)
+					}
+					sampling.Thereafter = thereafter
+				default:
+					return nil, d.Errf("unrecognized subdirective: %s", subdir)
+				}
+			}
+
+			cl.Sampling = sampling
+
 		case "core":
 			if !h.NextArg() {
 				return nil, h.ArgErr()

caddyconfig/httpcaddyfile/builtins_test.go

@@ -62,6 +62,20 @@ func TestLogDirectiveSyntax(t *testing.T) {
 			output:      `{"logging":{"logs":{"default":{"exclude":["http.log.access.name-override"]},"name-override":{"writer":{"filename":"foo.log","output":"file"},"core":{"module":"mock"},"include":["http.log.access.name-override"]}}},"apps":{"http":{"servers":{"srv0":{"listen":[":8080"],"logs":{"default_logger_name":"name-override"}}}}}}`,
 			expectError: false,
 		},
+		{
+			input: `:8080 {
+				log {
+					sampling {
+						interval 2
+						first 3
+						thereafter 4
+					}
+				}
+			}
+			`,
+			output:      `{"logging":{"logs":{"default":{"exclude":["http.log.access.log0"]},"log0":{"sampling":{"interval":2,"first":3,"thereafter":4},"include":["http.log.access.log0"]}}},"apps":{"http":{"servers":{"srv0":{"listen":[":8080"],"logs":{"default_logger_name":"log0"}}}}}}`,
+			expectError: false,
+		},
 	} {
 
 		adapter := caddyfile.Adapter{