Docker, a kind of lightweight virtualization technology which has the characteristics of resource isolation, rapid deployment and low cost, is widely used in the construction of the cloud services. Dockerbased containers has become the important basis of core cloud businesses. In order to manage the large-scale cloud cluster and enforce the quality of cloud services for consumers, monitoring mechanism for the containerbased clouds are indispensable. In this paper, we design and implement a cloud monitoring system - PLMSys based on cluster performance and container logs. It provides the following functions: i) Multi-dimensional resources monitoring. PLMSys can monitor the running states of the cluster hosts and containers, including the utilization of CPU, memory, disk and other resources. ii) Container log collection. PLMSys can centrally collect the logs generated by all containers of the cluster. iii) Rulebased exception alerts. PLMSys allows users to define the abnormal state of the hosts and containers by creating rules, and provides multiple alerting methods. iv) Workload analysis and prediction. PLMSys extracts the descriptive statistics from the cluster workloads and uses the time series models to predict the future workloads. v) Data monitoring visualization. The system uses rich visual charts to reflect the running states of cluster hosts and containers. By using PLMSys, users can better manage cluster hosts and containers.