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# Configuring gevent

See also

`gevent.setswitchinterval()` For additional runtime configuration.

class Config

  Bases: `object`

  Global configuration for gevent.

  There is one instance of this object at `gevent.config`. If you are going to make changes in code, instead of using the documented environment variables, you need to make the changes before using any parts of gevent that might need those settings. For example:

      >>> from gevent import config
      >>> config.fileobject = 'thread'

      >>> from gevent import fileobject
      >>> fileobject.FileObject.__name__
      'FileObjectThread'

  Added in version 1.3a2.

  property ares_servers

    A list of strings giving the IP addresses of nameservers for the ares resolver.

    In the environment variable, these strings are separated by commas.

    Deprecated since version 1.3a2: Prefer the `resolver_nameservers` setting. If both are set, the results are not defined.

    The default value is `None`

    The environment variable `GEVENTARES_SERVERS` can be used to control this.

  property ares_timeout

    Deprecated since version 1.3a2: Prefer the `resolver_timeout` setting. If both are set, the results are not defined.

    The default value is `None`

    The environment variable `GEVENTARES_TIMEOUT` can be used to control this.

  property disable_watch_children

    Should we not watch children with the event loop watchers?

    This is an advanced setting.

    See `gevent.os` for a detailed description.

    This is a boolean value.

    In the environment variable, it may be given as `1`, `true`, `on` or `yes` for `True`, or `0`, `false`, `off`, or `no` for `False`.

    The default value is `False`

    The environment variable `GEVENT_NOWAITPID` can be used to control this.

  property fileobject

    The kind of `FileObject` we will use.

    See `gevent.fileobject` for a detailed description.

    This is an importable value. It can be given as a string naming an importable object, or a list of strings in preference order and the first successfully importable object will be used. (Separate values in the environment variable with commas.) It can also be given as the callable object itself (in code). Shorthand names for default objects are [‘thread’, ‘posix’, ‘block’]

    The default value is `['posix', 'thread']`

    The environment variable `GEVENT_FILE` can be used to control this.

  property format_context

    This is an importable value. It can be given as a string naming an importable object, or a list of strings in preference order and the first successfully importable object will be used. (Separate values in the environment variable with commas.) It can also be given as the callable object itself (in code).

    The default value is `pprint.saferepr`

    The environment variable `GEVENT_FORMAT_CONTEXT` can be used to control this.

  property libev_backend

    The backend for libev, such as ‘select’

    The default value is `None`

    The environment variable `GEVENT_BACKEND` can be used to control this.

  property loop

    The kind of the loop we use.

    On Windows, this defaults to libuv, while on other platforms it defaults to libev.

    This is an importable value. It can be given as a string naming an importable object, or a list of strings in preference order and the first successfully importable object will be used. (Separate values in the environment variable with commas.) It can also be given as the callable object itself (in code). Shorthand names for default objects are [‘libev-cext’, ‘libev-cffi’, ‘libuv-cffi’, ‘libuv’]

    The default value is `['libev-cext', 'libev-cffi', 'libuv-cffi']`

    The environment variable `GEVENT_LOOP` can be used to control this.

  property max_blocking_time

    If the `monitor_thread` is enabled, this is approximately how long (in seconds) the event loop will be allowed to block before a warning is issued.

    This function depends on using `greenlet.settrace`, so installing your own trace function after starting the monitoring thread will cause this feature to misbehave unless you call the function returned by `greenlet.settrace`. If you install a tracing function before the monitoring thread is started, it will still be called.

    Note

    In the unlikely event of creating and using multiple different gevent hubs in the same native thread in a short period of time, especially without destroying the hubs, false positives may be reported.

    Added in version 1.3b1.

    The default value is `0.1`

    The environment variable `GEVENT_MAX_BLOCKING_TIME` can be used to control this.

  property max_memory_usage

    If `monitor_thread` is enabled, then if memory usage exceeds this amount (in bytes), events will be emitted. See `gevent.events`. In the environment variable, you can use a suffix of ‘kb’, ‘mb’ or ‘gb’ to specify the value in kilobytes, megabytes or gigibytes.

    There is no default value for this setting. If you wish to cap memory usage, you must choose a value.

    The default value is `None`

    The environment variable `GEVENT_MONITOR_MEMORY_MAX` can be used to control this.

  property memory_monitor_period

    If `monitor_thread` is enabled, this is approximately how long (in seconds) we will go between checking the processes memory usage.

    Checking the memory usage is relatively expensive on some operating systems, so this should not be too low. gevent will place a floor value on it.

    The default value is `5`

    The environment variable `GEVENT_MONITOR_MEMORY_PERIOD` can be used to control this.

  property monitor_thread

    Should each hub start a native OS thread to monitor for problems?

    Such a thread will periodically check to see if the event loop is blocked for longer than `max_blocking_time`, producing output on the hub’s exception stream (stderr by default) if it detects this condition.

    If this setting is true, then this thread will be created the first time the hub is switched to, or you can call `gevent.hub.Hub.start_periodic_monitoring_thread()` at any time to create it (from the same thread that will run the hub). That function will return an instance of `gevent.events.IPeriodicMonitorThread` to which you can add your own monitoring functions. That function also emits an event of `gevent.events.PeriodicMonitorThreadStartedEvent`.

    See also

    `max_blocking_time`

    Added in version 1.3b1.

    This is a boolean value.

    In the environment variable, it may be given as `1`, `true`, `on` or `yes` for `True`, or `0`, `false`, `off`, or `no` for `False`.

    The default value is `False`

    The environment variable `GEVENT_MONITOR_THREAD_ENABLE` can be used to control this.

  property resolver

    The callable that will be used to create `gevent.hub.Hub.resolver`.

    See Name Resolution (DNS) for more information.

    This is an importable value. It can be given as a string naming an importable object, or a list of strings in preference order and the first successfully importable object will be used. (Separate values in the environment variable with commas.) It can also be given as the callable object itself (in code). Shorthand names for default objects are [‘ares’, ‘thread’, ‘block’, ‘dnspython’]

    The default value is `['thread', 'dnspython', 'ares', 'block']`

    The environment variable `GEVENT_RESOLVER` can be used to control this.

  property resolver_nameservers

    A list of strings giving the IP addresses of nameservers for the (non-system) resolver.

    In the environment variable, these strings are separated by commas.

    Resolver Behaviour

    - blocking

      Ignored

    - Threaded

      Ignored

    - dnspython

      If this setting is not given, the dnspython resolver will load nameservers to use from `/etc/resolv.conf` or the Windows registry. This setting replaces any nameservers read from those means. Note that the file and registry are still read for other settings.

      Caution

      dnspython does not validate the members of the list. An improper address (such as a hostname instead of IP) has undefined results, including hanging the process.

    - ares

      Similar to dnspython, but with more platform and compile-time options. ares validates that the members of the list are valid addresses.

    The default value is `None`

    The environment variable `GEVENT_RESOLVER_NAMESERVERS` can be used to control this.

  property resolver_timeout

    The total amount of time that the DNS resolver will spend making queries.

    Only the ares and dnspython resolvers support this.

    Added in version 1.3a2.

    The default value is `None`

    The environment variable `GEVENT_RESOLVER_TIMEOUT` can be used to control this.

  property threadpool

    The kind of threadpool we use.

    This is an importable value. It can be given as a string naming an importable object, or a list of strings in preference order and the first successfully importable object will be used. (Separate values in the environment variable with commas.) It can also be given as the callable object itself (in code).

    The default value is `gevent.threadpool.ThreadPool`

    The environment variable `GEVENT_THREADPOOL` can be used to control this.

  property threadpool_idle_task_timeout

    How long threads in the default threadpool (used for DNS by default) are allowed to be idle before exiting.

    Use -1 for no timeout.

    Added in version 22.08.0.

    The default value is `5.0`

    The environment variable `GEVENT_THREADPOOL_IDLE_TASK_TIMEOUT` can be used to control this.

  property trace_malloc

    Should FFI objects track their allocation?

    This is only useful for low-level debugging.

    On Python 3, this environment variable is built in to the interpreter, and it may also be set with the `-X tracemalloc` command line argument.

    On Python 2, gevent interprets this argument and adds extra tracking information for FFI objects.

    The default value is `False`

    The environment variable `PYTHONTRACEMALLOC` can be used to control this.

  property track_greenlet_tree

    Should `Greenlet` objects track their spawning tree?

    Setting this to a false value will make spawning `Greenlet` objects and using `spawn_raw` faster, but the `spawning_greenlet`, `spawn_tree_locals` and `spawning_stack` will not be captured. Setting this to a false value can also reduce memory usage because capturing the stack captures some information about Python frames.

    Added in version 1.3b1.

    This is a boolean value.

    In the environment variable, it may be given as `1`, `true`, `on` or `yes` for `True`, or `0`, `false`, `off`, or `no` for `False`.

    The default value is `True`

    The environment variable `GEVENT_TRACK_GREENLET_TREE` can be used to control this.