telemetry: increment .count when deduping telemetry logs (#5001)

packages/dd-trace/src/telemetry/logs/log-collector.js

@@ -3,7 +3,7 @@
 const log = require('../../log')
 const { calculateDDBasePath } = require('../../util')
 
-const logs = new Map()
+const logs = new Map() // hash -> log
 
 // NOTE: Is this a reasonable number?
 let maxEntries = 10000
@@ -79,8 +79,10 @@ const logCollector = {
       }
       const hash = createHash(logEntry)
       if (!logs.has(hash)) {
-        logs.set(hash, logEntry)
+        logs.set(hash, errorCopy(logEntry))
         return true
+      } else {
+        logs.get(hash).count++
       }
     } catch (e) {
       log.error('Unable to add log to logCollector: %s', e.message)
@@ -120,6 +122,19 @@ const logCollector = {
   }
 }
 
+// clone an Error object to later serialize and transmit
+// { ...error } doesn't work
+// also users can add arbitrary fields to an error
+function errorCopy (error) {
+  const keys = Object.getOwnPropertyNames(error)
+  const obj = {}
+  for (const key of keys) {
+    obj[key] = error[key]
+  }
+  obj.count = 1
+  return obj
+}
+
 logCollector.reset()
 
 module.exports = logCollector

packages/dd-trace/src/util.js

@@ -66,6 +66,8 @@ function globMatch (pattern, subject) {
   return true
 }
 
+// TODO: this adds stack traces relative to packages/
+// shouldn't paths be relative to the root of dd-trace?
 function calculateDDBasePath (dirname) {
   const dirSteps = dirname.split(path.sep)
   const packagesIndex = dirSteps.lastIndexOf('packages')

packages/dd-trace/test/telemetry/logs/log-collector.spec.js

@@ -126,5 +126,24 @@ describe('telemetry log collector', () => {
       expect(logs.length).to.be.equal(4)
       expect(logs[3]).to.deep.eq({ message: 'Omitted 2 entries due to overflowing', level: 'ERROR' })
     })
+
+    it('duplicated errors should send incremented count values', () => {
+      const err1 = new Error('oh no')
+      err1.level = 'ERROR'
+
+      const err2 = new Error('foo buzz')
+      err2.level = 'ERROR'
+
+      logCollector.add(err1)
+      logCollector.add(err2)
+      logCollector.add(err1)
+      logCollector.add(err2)
+      logCollector.add(err1)
+
+      const drainedErrors = logCollector.drain()
+      expect(drainedErrors.length).to.be.equal(2)
+      expect(drainedErrors[0].count).to.be.equal(3)
+      expect(drainedErrors[1].count).to.be.equal(2)
+    })
   })
 })