v2: Module documentation; refactor LoadModule(); new caddy struct tags (#2924)

This commit goes a long way toward making automated documentation of
Caddy config and Caddy modules possible. It's a broad, sweeping change,
but mostly internal. It allows us to automatically generate docs for all
Caddy modules (including future third-party ones) and make them viewable
on a web page; it also doubles as godoc comments.

As such, this commit makes significant progress in migrating the docs
from our temporary wiki page toward our new website which is still under
construction.

With this change, all host modules will use ctx.LoadModule() and pass in
both the struct pointer and the field name as a string. This allows the
reflect package to read the struct tag from that field so that it can
get the necessary information like the module namespace and the inline
key.

This has the nice side-effect of unifying the code and documentation. It
also simplifies module loading, and handles several variations on field
types for raw module fields (i.e. variations on json.RawMessage, such as
arrays and maps).

I also renamed ModuleInfo.Name -> ModuleInfo.ID, to make it clear that
the ID is the "full name" which includes both the module namespace and
the name. This clarity is helpful when describing module hierarchy.

As of this change, Caddy modules are no longer an experimental design.
I think the architecture is good enough to go forward.

1 files changed, 30 insertions, 10 deletions

diff --git a/modules/logging/filewriter.go b/modules/logging/filewriter.go
index 6957b6a..cc60c64 100644
--- a/modules/logging/filewriter.go
+++ b/modules/logging/filewriter.go
@@ -28,22 +28,42 @@ func init() {
 	caddy.RegisterModule(FileWriter{})
 }
 
-// FileWriter can write logs to files.
+// FileWriter can write logs to files. By default, log files
+// are rotated ("rolled") when they get large, and old log
+// files get deleted, to ensure that the process does not
+// exhaust disk space.
 type FileWriter struct {
-	Filename      string `json:"filename,omitempty"`
-	Roll          *bool  `json:"roll,omitempty"`
-	RollSizeMB    int    `json:"roll_size_mb,omitempty"`
-	RollCompress  *bool  `json:"roll_gzip,omitempty"`
-	RollLocalTime bool   `json:"roll_local_time,omitempty"`
-	RollKeep      int    `json:"roll_keep,omitempty"`
-	RollKeepDays  int    `json:"roll_keep_days,omitempty"`
+	// Filename is the name of the file to write.
+	Filename string `json:"filename,omitempty"`
+
+	// Roll toggles log rolling or rotation, which is
+	// enabled by default.
+	Roll *bool `json:"roll,omitempty"`
+
+	// When a log file reaches approximately this size,
+	// it will be rotated.
+	RollSizeMB int `json:"roll_size_mb,omitempty"`
+
+	// Whether to compress rolled files. Default: true
+	RollCompress *bool `json:"roll_gzip,omitempty"`
+
+	// Whether to use local timestamps in rolled filenames.
+	// Default: false
+	RollLocalTime bool `json:"roll_local_time,omitempty"`
+
+	// The maximum number of rolled log files to keep.
+	// Default: 10
+	RollKeep int `json:"roll_keep,omitempty"`
+
+	// How many days to keep rolled log files. Default: 90
+	RollKeepDays int `json:"roll_keep_days,omitempty"`
 }
 
 // CaddyModule returns the Caddy module information.
 func (FileWriter) CaddyModule() caddy.ModuleInfo {
 	return caddy.ModuleInfo{
-		Name: "caddy.logging.writers.file",
-		New:  func() caddy.Module { return new(FileWriter) },
+		ID:  "caddy.logging.writers.file",
+		New: func() caddy.Module { return new(FileWriter) },
 	}
 }