6.27 Configuring the HTTP Server - 6.27.1 Configuring Server Thread Pools - 《Micronaut v2.1.0 Documentation》

6.27.1 Configuring Server Thread Pools
- Blocking Operations

6.27.1 Configuring Server Thread Pools

The HTTP server is built on Netty which is designed as a non-blocking I/O toolkit in an event loop model.

The Netty worker event loop uses the “default” named event loop group. That event loop can be configured through micronaut.server.netty.worker, or micronaut.netty.event-loops.default, with the latter having precedence.

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Table 1. Configuration Properties for NettyHttpServerConfiguration$Worker
Property	Type	Description
`micronaut.server.netty.worker.event-loop-group`	java.lang.String	Sets the name to use.
`micronaut.server.netty.worker.threads`	int	Sets the number of threads for the event loop group.
`micronaut.server.netty.worker.io-ratio`	java.lang.Integer	Sets the I/O ratio.
`micronaut.server.netty.worker.executor`	java.lang.String	Sets the name of the executor.
`micronaut.server.netty.worker.prefer-native-transport`	boolean	Set whether to prefer the native transport if available

The parent event loop can be configured with micronaut.server.netty.parent with the same configuration options.

The server can also be configured to use a different named worker event loop:

Using a different event loop for the server

micronaut:
    server:
        netty:
            worker:
                event-loop-group: other
    netty:
        event-loops:
            other:
                num-threads: 10

The default value for the number of threads is the value of the system property io.netty.eventLoopThreads, or if not specified, the available processors x 2.

See the following table for configuring event loops:

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Table 2. Configuration Properties for DefaultEventLoopGroupConfiguration
Property	Type	Description
`micronaut.netty.event-loops..num-threads`	int
`micronaut.netty.event-loops..io-ratio`	java.lang.Integer
`micronaut.netty.event-loops..prefer-native-transport`	boolean
`micronaut.netty.event-loops..executor`	java.lang.String

Blocking Operations

When dealing with blocking operations, Micronaut will shift the blocking operations to an unbound, caching I/O thread pool by default. You can configure the I/O thread pool using the ExecutorConfiguration named io. For example:

Configuring the Server I/O Thread Pool

micronaut:
    executors:
        io:
           type: fixed
           nThreads: 75

The above configuration will create a fixed thread pool with 75 threads.