6.28 Configuring the HTTP Server - 6.28.1 Configuring Server Thread Pools - 《Micronaut v2.2.3 Documentation》

6.28.1 Configuring Server Thread Pools
- Blocking Operations

6.28.1 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.netty.event-loops.default.

The event loop configuration under micronaut.server.netty.worker will only be used if the event-loop-group is set to a name and that name doesn’t correspond to any micronaut.netty.event-loops configuration. This behavior is deprecated and will be removed in a future version. Use micronaut.netty.event-loops.* for any event loop group configuration beyond setting the name through event-loop-group. This does not apply to the parent event loop configuration (micronaut.server.netty.parent).

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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
`micronaut.server.netty.worker.shutdown-quiet-period`	java.time.Duration	Set the shutdown quiet period
`micronaut.server.netty.worker.shutdown-timeout`	java.time.Duration	Set the shutdown timeout (must be >= shutdownQuietPeriod)

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
`micronaut.netty.event-loops..shutdown-quiet-period`	java.time.Duration
`micronaut.netty.event-loops..shutdown-timeout`	java.time.Duration

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.