fix: report error when pm2 flush targets a nonexistent process

When pm2 flush is called with an app name or id that does not match
any running process, it previously printed "Logs flushed" even though
nothing was actually flushed. This is misleading.

Now it prints an error and returns an error callback when the
specified process is not found. Also adds tests for pm_id-based
flushing and the not-found error case.

Closes #4553

Author: YoanWai

lib/API/LogManagement.js

@@ -28,8 +28,12 @@ module.exports = function(CLI) {
         Common.printError(err);
         return cb ? cb(Common.retErr(err)) : that.exitCli(cst.ERROR_EXIT);
       }
+
+      var found = false;
+
       list.forEach(function(l) {
         if (typeof api == 'undefined') {
+          found = true;
           Common.printOut(cst.PREFIX_MSG + 'Flushing:');
           Common.printOut(cst.PREFIX_MSG + l.pm2_env.pm_out_log_path);
           Common.printOut(cst.PREFIX_MSG + l.pm2_env.pm_err_log_path);
@@ -42,6 +46,7 @@ module.exports = function(CLI) {
           fs.closeSync(fs.openSync(l.pm2_env.pm_err_log_path, 'w'));
         }
         else if (l.pm2_env.pm_id == api || l.pm2_env.name === api) {
+          found = true;
           Common.printOut(cst.PREFIX_MSG + 'Flushing:');
 
           if (l.pm2_env.pm_log_path && fs.existsSync(l.pm2_env.pm_log_path)) {
@@ -61,7 +66,12 @@ module.exports = function(CLI) {
         }
       });
 
-      Common.printOut(cst.PREFIX_MSG + 'Logs flushed');
+      if (found) {
+        Common.printOut(cst.PREFIX_MSG + 'Logs flushed');
+      } else if (typeof api !== 'undefined') {
+        Common.printError(cst.PREFIX_MSG_ERR + 'No process found with name or id \'' + api + '\'');
+        return cb ? cb(Common.retErr('process not found')) : that.exitCli(cst.ERROR_EXIT);
+      }
       return cb ? cb(null, list) : that.exitCli(cst.SUCCESS_EXIT);
     });
   };

test/programmatic/flush.mocha.js

@@ -77,5 +77,50 @@ describe('Programmatic flush feature test', function() {
         });
       });
     });
+    it('flush logs by pm_id', function(done) {
+      pm2.start({
+        script: './echo.js',
+        name: 'first',
+        error_file : 'error-first.log',
+        out_file   : 'out-first.log',
+        merge_logs: false
+      }, function(err, procs) {
+        should(err).be.null();
+        var out_file = procs[0].pm2_env.pm_out_log_path;
+        var err_file = procs[0].pm2_env.pm_err_log_path;
+        var pm_id = String(procs[0].pm2_env.pm_id);
+        pm2.start({
+            script: './001-test.js',
+            name: 'second',
+            error_file : 'error-second.log',
+            out_file   : 'out-second.log',
+            merge_logs: false
+          }, function(err, procs) {
+            should(err).be.null();
+            var out_file1 = procs[0].pm2_env.pm_out_log_path;
+            var err_file1 = procs[0].pm2_env.pm_err_log_path;
+            pm2.flush(pm_id, function(){
+              fs.readFileSync(out_file, "utf8").toString().should.be.empty();
+              fs.readFileSync(err_file, "utf8").toString().should.be.empty();
+              fs.readFileSync(out_file1, "utf8").toString().should.not.be.empty();
+              fs.readFileSync(err_file1, "utf8").toString().should.not.be.empty();
+              done();
+        });
+        });
+      });
+    });
+    it('should return error when process not found', function(done) {
+      pm2.start({
+        script: './echo.js',
+        name: 'myapp',
+        merge_logs: false
+      }, function(err) {
+        should(err).be.null();
+        pm2.flush('nonexistent', function(err) {
+          should(err).not.be.null();
+          done();
+        });
+      });
+    });
   });
 });