Added loggers sample

loggers/srv/dummy.cds

@@ -0,0 +1,3 @@
+service Sue {
+  entity Dummy { key ID: UUID; title: String; }
+}

loggers/srv/loggers.cds

@@ -0,0 +1,20 @@
+@rest service LogService {
+
+  @readonly entity Loggers : Logger {};
+  entity Logger {
+    key id : String;
+    level  : String;
+  }
+
+  action format (
+    timestamp : Boolean,
+    level     : Boolean,
+    tenant    : Boolean,
+    reqid     : Boolean,
+    id        : Boolean,
+  );
+
+  action debug (logger : String) returns Logger;
+  action reset (logger : String) returns Logger;
+
+}

loggers/srv/loggers.js

@@ -0,0 +1,56 @@
+const cds = require ('@sap/cds/lib')
+const LOG = cds.log('cds.log')
+
+module.exports = class LogService extends cds.Service {
+  init(){
+
+    this.on('GET','Loggers', (req)=>{
+      let loggers = Object.values(cds.log.loggers).map (_logger)
+      let {$search} = req._.req.query
+      if ($search) {
+        const re = RegExp($search,'i')
+        loggers = loggers.filter (l => re.test(l.id) || re.test(l.level))
+      }
+      return loggers
+    })
+
+    this.on('PUT','Logger', (req)=>{
+      const {id} = req.params[0] || req.data
+      if (!id) return req.reject('No logger id specified in request')
+      return _logger (cds.log (id, req.data))
+    })
+
+    this.on('debug', (req)=>{
+      const {logger:id} = req.params[0] || req.data
+      if (!id) return req.reject('No logger id specified in request')
+      return _logger (cds.log (id, {level:'debug'}))
+    })
+
+    this.on('reset', (req)=>{
+      const {logger:id} = req.params[0] || req.data
+      if (!id) return req.reject('No logger id specified in request')
+      return _logger (cds.log (id, {level:'info'}))
+    })
+
+    this.on('format', (req)=>{
+      const $ = req.data; LOG.info('format:',$)
+      // Set format for new loggers constructed subsequently
+      cds.log.format = (id, level, ...args) => {
+        const fmt = []
+        if ($.timestamp) fmt.push ('|', (new Date).toISOString())
+        if ($.level) fmt.push ('|', _levels[level].padEnd(5))
+        if ($.tenant) fmt.push ('|', cds.context && cds.context.tenant)
+        if ($.reqid) fmt.push ('|', cds.context && cds.context.id)
+        if ($.id) fmt.push ('|', id)
+        fmt[0] = '[', fmt.push ('] -', ...args)
+        return fmt
+      }
+      // Apply this format to all existing loggers
+      Object.values(cds.log.loggers).forEach (l => l.setFormat (cds.log.format))
+    })
+  }
+
+}
+
+const _logger = ({id,level}) => ({id, level:_levels[level] })
+const _levels = [ 'SILENT', 'ERROR', 'WARN', 'INFO', 'DEBUG', 'TRACE' ]