How Do I Troubleshoot an Unresponsive Website Hosted on My ECS?

Symptom

Websites running on an ECS might become unreachable for multiple reasons. Check whether the configurations of network, port, firewall, or security group of the ECS are correct.

Fault Locating

If an error is displayed when you access a website, identify possible causes based on the error message.

Identify possible causes based on error code description in Returned Values for General Requests.

If the error message cannot help you locate the fault, record the resource details and fault occurred time. Then, choose Service Tickets > Create Service Ticket in the upper right corner of the management console to submit a ticket.

You can also locate the fault based on the following possible causes which are listed in order of their probability.

If the fault persists after you have ruled out one cause, move on to the next one.

Figure 1 Fault locating

Checking Port Communication

Ensure that service processes and ports are in LISTEN state. Table 2 lists the common TCP statuses.

• Linux

  Run the netstat -antpu command to check whether the port used by the target website is in LISTEN status,

  for example, netstat -antpu |grep sshd.

  Figure 2 Checking port listening status
  

  • If the port status is LISTEN, go to Checking Security Group Rules.
  • If the port status is not LISTEN, check whether the web service process has been started and correctly configured.
• Windows

  Perform the following operations to check port communication:

  1. Run cmd.exe.
  2. Run the netstat -ano | findstr "Port number" command to obtain the port number used by the process.
     For example, run netstat -ano | findstr "80".

     Figure 3 Checking port listening status
     

     • If the port is in LISTENING state, go to Checking Security Group Rules.
     • If the port is not in LISTENING state, check whether the web service process has been started and correctly configured.

Checking Security Group Rules

Checking the Firewall Configuration

• Linux ECS
  The following uses port 80 and CentOS 6.8 as an example.

  1. Run the iptables -nvL --line-number command to obtain firewall policies.
  2. Run the following commands to allow access to port 80:

     iptables -A INPUT -p tcp --dport 80 -j ACCEPT

     iptables -A OUTPUT -p tcp --sport 80 -j ACCEPT

  3. Run the service iptables save command to save the added rules.
  4. Run the service iptables restart command to restart iptables.
  5. Run the iptables -nvL --line-number command to check whether the added rules have taken effect.
  6. Disable the firewall and try again.
• Windows ECS
  1. Log in to the Windows ECS.
  2. Click the Windows icon in the lower left corner of the desktop and choose Control Panel > Windows Firewall.

     

  3. Click Turn Windows Firewall on or off.

     View and set the firewall status.

     

  4. Disable the firewall and try again.

Checking the ECS Route Configuration

• Linux ECS
  1. Run the route command to check the routing policy. Ensure that the default route of 0.0.0.0 is destined for the gateway and that the IP address and the gateway are in the same network segment, as shown in the first and third lines in the following figure.

     

  2. Run the ifconfig or ip addr command to obtain the ECS IP address.
     Figure 4 ifconfig command output
     
     Figure 5 ip addr command output
     
  3. Run the route -n command to obtain the gateway in the routing table.
     The following is an example just for reference.

     Figure 6 route -n command output
     

Checking the Local Network

Try another hotspot or network for access.

If the access is successful, the fault may occur in the local carrier network. In such a case, rectify the local network fault and try again.

Checking the CPU usage

If the bandwidth or vCPU usage of an ECS is too high, website access failures may occur. If you have created an alarm rule in Cloud Eye, the system automatically sends an alarm to you when the bandwidth or CPU usage reaches the threshold specified in the rule.

1. Identify the processes leading to a high bandwidth or vCPU usage.
   • Windows

     Windows offers multiple tools to locate faults, including Task Manager, Performance Monitor, Resource Monitor, Process Explorer, Xperf (supported by versions later than Windows Server 2008), and full memory dump analysis.

   • Linux

     Run the top command to check the OS running status.

2. Check whether the processes are malicious and handle the issue accordingly.
   • If the processes are normal, optimize them or modify ECS configurations by referring to General OperationsGeneral Operations for Modifying ECS Specifications.
   • If the processes are malicious, stop these processes manually or use a third-party tool to stop them automatically.