Pause/resume Instance Operation Details-5 minutes a day to play OpenStack (34)

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This section analyzes Nova Pause/resume operations in detail through logs.

Sometimes you need to pause instance for a short time, and you can save the instance state to the host's memory through the pause operation. When recovery is required, perform a resume operation, read back the instance state from memory, and then continue running instance.

Here is the flowchart for pause instance

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1. Send a request to NOVA-API

2. Nova-api sending messages

3. Nova-compute Performing actions

Let's discuss each step in detail below.

send a request to Nova-api

The customer (which can be an OpenStack end user or another program) sends a request to the API (NOVA-API): "Help me to pause this Instance"

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View Log/opt/stack/logs/n-api.log

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Note: For the Pause operation, the log does not have the previous Start record so detailed.

For example, there is no log of the nova.api.openstack.compute.servers and NOVA.COMPUTE.API code modules, which may be because the logic of the operation is simple and the developer does not include the log when coding.

Nova-api sending Messages

Nova-api sent a message to Messaging (RabbitMQ): "Pause this Instance" to view the source code/opt/stack/nova/nova/compute/api.py by pausing.

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Nova-compute Performing Actions

View Log/opt/stack/logs/n-cpu.log

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After the pause operation executes successfully, the instance state changes to Paused

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resume operations is reserved for everyone to practice. Tip: The Resume operation here is actually a unpause operation, which can be used to locate the log through the keyword "unpause".

The above is a detailed analysis of Pause/resume, the next section we continue to analyze suspend/resume operations.
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Pause/resume Instance Operation Details-5 minutes a day to play OpenStack (34)