Default thread pool in tomcat of a spring boot application

Question

In a spring boot application or in generally, does tomcat has a default thread pool configured?

If we do not configure anything, the tomcat will initiate new threads for each request and the thread gets destroy once the request finish?

And if a thread pool configured, particular thread would serve many requests when ever container pick that thread from pool?

Answer 1

Here is the configs of the embed Tomcat in springboot

server.tomcat.accept-count=100 # Maximum queue length for incoming connection requests when all possible request processing threads are in use.
server.tomcat.accesslog.buffered=true # Whether to buffer output such that it is flushed only periodically.
server.tomcat.accesslog.directory=logs # Directory in which log files are created. Can be absolute or relative to the Tomcat base dir.
server.tomcat.accesslog.enabled=false # Enable access log.
server.tomcat.accesslog.file-date-format=.yyyy-MM-dd # Date format to place in the log file name.
server.tomcat.accesslog.pattern=common # Format pattern for access logs.
server.tomcat.accesslog.prefix=access_log # Log file name prefix.
server.tomcat.accesslog.rename-on-rotate=false # Whether to defer inclusion of the date stamp in the file name until rotate time.
server.tomcat.accesslog.request-attributes-enabled=false # Set request attributes for the IP address, Hostname, protocol, and port used for the request.
server.tomcat.accesslog.rotate=true # Whether to enable access log rotation.
server.tomcat.accesslog.suffix=.log # Log file name suffix.
server.tomcat.additional-tld-skip-patterns= # Comma-separated list of additional patterns that match jars to ignore for TLD scanning.
server.tomcat.background-processor-delay=10s # Delay between the invocation of backgroundProcess methods. If a duration suffix is not specified, seconds will be used.
server.tomcat.basedir= # Tomcat base directory. If not specified, a temporary directory is used.
server.tomcat.internal-proxies=10\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
        192\\.168\\.\\d{1,3}\\.\\d{1,3}|\\
        169\\.254\\.\\d{1,3}\\.\\d{1,3}|\\
        127\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.1[6-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.2[0-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
        172\\.3[0-1]{1}\\.\\d{1,3}\\.\\d{1,3}\\
        0:0:0:0:0:0:0:1\\
        ::1 # Regular expression that matches proxies that are to be trusted.
server.tomcat.max-connections=10000 # Maximum number of connections that the server accepts and processes at any given time.
server.tomcat.max-http-header-size=0 # Maximum size in bytes of the HTTP message header.
server.tomcat.max-http-post-size=2097152 # Maximum size in bytes of the HTTP post content.
server.tomcat.max-threads=200 # Maximum amount of worker threads.
server.tomcat.min-spare-threads=10 # Minimum amount of worker threads.
server.tomcat.port-header=X-Forwarded-Port # Name of the HTTP header used to override the original port value.
server.tomcat.protocol-header= # Header that holds the incoming protocol, usually named "X-Forwarded-Proto".
server.tomcat.protocol-header-https-value=https # Value of the protocol header indicating whether the incoming request uses SSL.
server.tomcat.redirect-context-root=true # Whether requests to the context root should be redirected by appending a / to the path.
server.tomcat.remote-ip-header= # Name of the HTTP header from which the remote IP is extracted. For instance, `X-FORWARDED-FOR`.
server.tomcat.resource.cache-ttl= # Time-to-live of the static resource cache.
server.tomcat.uri-encoding=UTF-8 # Character encoding to use to decode the URI.
server.tomcat.use-relative-redirects= # Whether HTTP 1.1 and later location headers generated by a call to sendRedirect will use relative or absolute redirects.

As you can see for the default value, the minimum amount of worker threads is 10, and the maximum amount of worker threads is 200, and the maximum queue length for incoming connection requests when all possible request processing threads are in use is 100.

Answer 2

Yes spring boot uses Embeded tomcat server, you can modify some of its configs in application.yml or application.properties By default it has 200 threads spring-docs

# EMBEDDED SERVER CONFIGURATION (ServerProperties)
server.port=8080
server.address= # bind to a specific NIC
server.session-timeout= # session timeout in seconds
server.context-path= # the context path, defaults to '/'
server.servlet-path= # the servlet path, defaults to '/'
server.tomcat.access-log-pattern= # log pattern of the access log
server.tomcat.access-log-enabled=false # is access logging enabled
server.tomcat.protocol-header=x-forwarded-proto # ssl forward headers
server.tomcat.remote-ip-header=x-forwarded-for
server.tomcat.basedir=/tmp # base dir (usually not needed, defaults to tmp)
server.tomcat.background-processor-delay=30; # in seconds
server.tomcat.max-threads = 0 # number of threads in protocol handler
server.tomcat.uri-encoding = UTF-8 # character encoding to use for URL decoding