The instance health diagnosis feature is a self-service diagnostic tool that provides a comprehensive diagnosis of computing services, storage services, networking services, configuration management, and related configurations of the instance's operating system. This feature helps you understand the health of your instance and promptly identify and resolve common issues. This topic describes the diagnostic items that Simple Application Server supports, their diagnostic scopes, and recommended actions.
Diagnostic items
The following table lists the diagnostic items supported by the instance health diagnosis feature.
Diagnostic Item Classification | Description |
Diagnoses the underlying resources and hypervisor of Simple Application Server instances to ensure that the underlying services are running correctly. | |
Checks whether the disks of an instance are running as expected. | |
Checks the status of network components in an instance and identifies exceptions in the external network environment. | |
Checks whether an operation prevents an instance from starting or running correctly. | |
Diagnostics of related configurations in the instance OS (Linux) | Checks whether system files, critical processes, and the firewall status in the instance's operating system are normal. |
Diagnostics of related configurations in the instance OS (Windows) | Checks whether the usage of common service ports and the firewall status in the instance's operating system are normal. |
Exceptions discovered by the health diagnostics for computing, networking, storage, and configuration management services are not reported in real time. The diagnostic results show historical exceptions that occurred within the last 48 hours. These issues may not require immediate action.
Health diagnostics of computing services
The following table lists the health diagnostic items of computing services.
Diagnostic item | Description | Diagnostic scope and recommended operation |
Instance Virtualization Exceptions | The instance crashes or is unexpectedly paused during runtime. | Check whether exceptions exist in the core services at the underlying hypervisor of the instance. If exceptions exist, the instance may not respond or may be unexpectedly stopped. You can restart the instance for recovery. |
Instance OS Exceptions | A fault such as a kernel panic, out-of-memory (OOM) exception, or internal breakdown occurs in the instance system. | Check whether faults such as kernel panics, OOM exceptions, or internal breakdowns exist in the operating system of the instance. These faults may be caused by improper configurations of the instance or user programs in the operating system of the instance. You can restart the instance for recovery. |
Alerts for Instance Host | Alerts are triggered on the physical device that hosts the instance. | Check whether faults exist in the underlying physical server that hosts the instance. If faults exist in the underlying physical server, the status or performance of the instance may be affected. You can restart the instance for recovery. |
Health diagnostics of networking services
The following table lists the health diagnostic items of networking services.
Diagnostic item | Description | Diagnostic scope and recommended operation |
Network Connection Exceptions | The network interface card cannot establish sessions, or the number of sessions exceeds the limit. | Checks whether sessions can be established on the network interface card of the instance. If connections cannot be established on the NIC or if the maximum number of connections on the NIC is reached, the network connectivity or throughput of the instance is affected. For example, you cannot connect to the instance, or the network speed is slow. You can restart the instance for recovery. |
Exceptions on Protection Against DDoS Attacks | Checks whether the public IP address of the instance is under a DDoS attack and checks the protection status. | Checks whether the IP address of the instance is under a DDoS attack. The free Anti-DDoS service provided by Alibaba Cloud can scrub a certain amount of attack traffic and mitigate unavailability caused by DDoS attacks. However, if the attack traffic exceeds the mitigation capabilities of the instance, the instance may become unavailable and inaccessible. For more information about DDoS attacks, see What is a DDoS attack?. If needed, you can purchase other Anti-DDoS products to defend against DDoS attacks. For more information, see Alibaba Cloud Anti-DDoS product overview. To urgently unblock your instance, you can also request the free emergency service for DDoS attacks. For information about the best practices for preventing DDoS attacks on Alibaba Cloud, see Best practices for mitigating DDoS attacks. |
Health diagnostics of storage services
The following table lists the health diagnostic items of storage services.
Diagnostic item | Description | Diagnostic scope and recommended operation |
Ineffective Disk Extension | After the disk of a Linux instance is scaled out in the console, checks whether you need to run more scale-out commands. | Checks whether the disk scale-out has taken effect after you scale out the disk of the instance in the console. If the scale-out operation is complete in the console but has not taken effect, you must manually run commands to scale out the partition and file system. For more information, see Scale out a data disk. |
Disk Resizing Exceptions | The operating system fails to adjust the size of the file system after the disk is resized. | Checks whether the file system on the disk is also resized after the system disk of the instance is scaled out. If the file system is not resized, the disk failed to scale out due to insufficient resources or other reasons. The newly added disk space cannot be used. You must initiate the scale-out operation again. For more information, see Scale out a data disk. |
Disk I/O Hang | A disk I/O hang occurs, which makes the disk unreadable or unwritable. | Checks whether an I/O hang occurs on the system disk of the instance. An I/O hang means that the file system on the disk has a high read and write I/O latency, which causes the system to become unstable or stop responding. If an I/O hang occurs, the disk cannot be read or written. You can view the performance metrics of the disk. For more information, see View disk read and write metrics. If you use the Alibaba Cloud Linux 2 operating system, see Detect I/O hangs of file systems and block layers for information about how to detect I/O hangs. |
Disk Loading Exceptions | An error occurs when you create or attach a disk. | Checks whether the disk can be attached when the instance is starting. If the disk fails to attach, the instance cannot start. To resolve this issue, you can stop the instance and then start it again, or re-attach the disk. For more information about how to attach a disk, see Attach a data disk and Partition and format a data disk. |
Disk Read/Write Limited | The disk I/O latency is too long, or the disk I/O has reached the limit for the disk type. | Checks for latency in the read and write I/O of the instance system disk and whether the read and write IOPS exceeds the IOPS limit of the disk. If the read and write IOPS of the disk exceeds the limit, read and write operations on the disk are throttled. For information about how to view disk metrics, see View disk monitoring information. To prevent this issue from recurring, you can reduce the read and write frequency of the disk or upgrade the disk to a higher-performance type. For information about the read and write performance metrics of different disk types, see Elastic Block Storage performance. |
Diagnostics of instance configuration management
The following table lists the diagnostic items of instance configuration management.
Diagnostic item | Description | Diagnostic scope and recommended operation |
Core Operation Exceptions | The management operation that you performed on the instance failed. | Check whether the management operations that you recently performed on the instance, such as starting, stopping, and upgrading the instance, were successful. If the operations fail, you must perform the operations again. |
Image Loading Exceptions | The image used by the instance cannot be loaded. | Check whether the image used by the instance can be loaded on startup. The image may fail to be loaded due to system or image issues. You can restart the instance for recovery. |
Instance Startup Exceptions | The instance cannot be started by the management system. | Check whether the boot operation of the instance can be loaded. If you cannot perform the boot operation on the instance, you must create another instance. |
Diagnostics of related configurations in the instance OS (Linux)
The following table lists the diagnostic items for related configurations in the OS of a Linux instance.
Diagnostic item (console) | Description | Diagnostic scope and recommended operation |
High total CPU usage | The current CPU usage of the instance exceeds 80% (based on data from the top command). | Checks the total CPU usage of the instance. If the CPU utilization is high, you can identify the processes that use large amounts of CPU resources and determine whether these processes are normal. For more information, see How do I query CPU load and analyze cases on a Linux instance?. |
Disk inode check | Checks whether the disk has enough inodes. | Checks the inode usage of the instance disk. If the usage is too high, you may not be able to create new files on the disk. If needed, you can scale out the disk. For more information, see Scale out a data disk and Attach a data disk. |
System firewall status check | Checks whether the system firewall is enabled. | Checks the firewall of the instance. If the firewall is enabled and has rules that block external access, you may not be able to remotely connect to the instance. For more information about how to enable or disable the firewall, see Enable or disable the system firewall on a Linux instance. |
Common service port listener status check | Checks whether common service ports, such as 22 and 3389, are in the listening state. | Checks the common service ports of the instance. If a port is not in a listening state, applications on the instance may be inaccessible. For information about how to check and modify common service ports, see Start common services and query port listening status on a Linux instance. |
Processes with CPU usage over 50% | The CPU utilization of the instance has exceeded 50%, as reported by the top command. | Checks the CPU usage of processes in the instance. If some processes have high CPU usage, you must determine whether they are running as expected. For more information about how to check CPU usage, see Query and analyze the CPU load of a Linux system and Troubleshoot and resolve high CPU usage or high CPU load on ECS instances that run Linux. |
SELinux status check | Checks whether SELinux is enabled. | Checks whether the SELinux service is enabled on the instance. If the SELinux service is enabled, an error may occur when you use SSH to remotely connect to the instance. If needed, you can temporarily or permanently disable the SELinux service. For more information about how to disable the SELinux service, see An SSH remote connection to a Linux instance fails because the SELinux service is enabled. |
SSH access permissions check | Checks whether the SSH access permissions are correctly configured. | Checks the SSH access permission configuration of the instance. If the SSH access permissions are incorrectly configured, you may be unable to connect to the instance. For more information about how to modify SSH access permissions, see Remote connection to a Linux instance fails due to SSH access permission issues. |
SSH critical file check | Checks whether the critical files or directories required for SSH access exist. | Checks the critical files or directories required for the SSH service in the instance. If the critical files or directories required for the SSH service do not exist, you may fail to log on to the instance using SSH. For more information about how to restore the critical files or directories required for the SSH service, see Check whether the required files or directories for the SSH service exist on a Linux instance. |
SSH root logon check | Checks whether the SSH configuration allows the root user to connect. | Checks whether the SSH configuration allows the root user to connect. If the root user is not allowed to log on to the instance, the "Permission denied, please try again" error is returned when you try to log on as the root user. For more information about how to fix this error, see How do I fix the "Permission denied, please try again" error when I use the root user to log on to a Linux instance over SSH?. |
Diagnostics of related configurations in the instance OS (Windows)
The following table lists the diagnostic items for related configurations in the OS of a Windows instance.
Diagnostic item (console) | Description | Diagnostic scope and recommended operation |
Windows operating system version check | Microsoft no longer maintains Windows Server 2008 and earlier versions. | Checks the Windows version of the instance. Alibaba Cloud and Microsoft no longer maintain Windows Server 2008 and earlier versions. If needed, you can reinstall a later version of Windows. For more information, see Reset simple application server. |
High total CPU usage | Checks whether the total CPU usage of Windows exceeds 85%. | Checks the CPU usage of the instance. If the total CPU usage is too high, you can identify the processes that consume a large amount of CPU resources and determine if they are running as expected. For more information about how to check CPU usage, see Troubleshoot and resolve high CPU usage on Windows instances. |
High memory usage | Checks whether the memory usage of the Windows system exceeds 80%. | Checks whether the memory usage exceeds 80%. If the current total memory usage of the instance exceeds 80%, the top five processes with the highest memory usage are listed. You must check whether these processes are running as expected. For more information about how to analyze high memory usage in Windows, see Introduction to Windows memory analysis tools. |
Windows common service port usage check | Checks whether port 3389 of the Windows system is open. | Checks port 3389 of the instance. If port 3389 is disabled, the instance cannot be accessed using RDP. For more information, see Enable the RDP service for a Windows instance. |
Disk capacity check | Checks whether the free space of the system disk (C:) is less than 1 GB. | Checks the free space of the system disk (C:) of the instance. If the free space is less than 1 GB, the system may run slowly or the instance may fail to start. If needed, you can upgrade the disk. For more information, see Upgrade configurations. |
Windows firewall status check | Checks whether the Windows firewall is enabled. | Checks the firewall status of the instance. If the firewall is enabled, you may not be able to access services on the instance. If needed, you can adjust the firewall policy configuration. For more information about how to configure a firewall policy, see Methods for configuring firewall policies for Windows Server instances. |
Administrator account check | Checks whether the Administrator account exists. | Checks whether the Administrator account exists. If an Administrator account does not exist, the service may be inaccessible. You can decide whether to create an Administrator account based on your business needs. For instructions on how to create an account on a Windows system, see How to Add or Remove an Administrator by Using the Management Console. |