Watchman looks for configuration files in two places:
- The global configuration file
- The root specific configuration file
When watching a root, if a valid JSON file named
.watchmanconfig is present in
the root directory, watchman will load it and use it as a source of
configuration information specific to that root.
The global configuration path can be changed by passing the
option to configure when you build watchman. This documentation refers to it as
/etc/watchman.json throughout, just be aware that your particular installation
may locate it elsewhere. In addition, the environmental variable
$WATCHMAN_CONFIG_FILE will override the default location.
If the global configuration file does not exist, Watchman will fall back on that path with ".default" appended (e.g. /etc/watchman.json.default). This allows the Watchman system package to provide different configuration defaults, like setting enforce_root_files to true.
Changes to the
/etc/watchman.json files are not picked up
automatically; you will need to remove and re-add the watch (for
.watchmanconfig) or restart watchman (for
/etc/watchman.json) for those
changes to take effect.
Resolution / Scoping
There are three configuration scopes:
- local - the option value is read from the
.watchmanconfigfile in the associated root.
- global - the option value is read from the
- fallback - the option value is read from the
.watchmanconfigfile. If the option was not present in the
.watchmanconfigfile, then read it from the
This table shows the scoping and availability of the various options:
|global||deprecated in 3.1|
Specifies the settle period in milliseconds. This controls how long the filesystem should be idle before dispatching triggers. The default value is 20 milliseconds.
Specifies a list of files that, if present in a directory, identify that directory as the root of a project.
If left unspecified, to aid in transitioning between versions, watchman will use the value of the now deprecated root_restrict_files configuration setting.
root_restrict_files is specified in the
configuration, watchman will use a default value consisting of:
Watchman will add
.watchmanconfig to whatever value is specified for this
configuration value if it is not present.
This example causes only
.watchmanconfig to be considered as a project root
See the watch-project command for more information.
This is a boolean option that defaults to
false. If it is set to
the watch command will only succeed if the requested directory
contains one of the files listed by the root_files configuration
option, and the watch-project command will only succeed
if a valid project root is found.
If left unspecified, to aid in transitioning between versions, watchman will
check to see if the now deprecated root_restrict_files
configuration setting is present. If it is found then the effective value of
enforce_root_files is set to
Deprecated starting in version 3.1; use root_files and enforce_root_files to effect the same behavior.
Specifies a list of files, at least one of which should be present in a directory for watchman to add it as a root. By default there are no restrictions.
"root_restrict_files": [".git", ".hg"]
will allow watches only in the top level of Git or Mercurial repositories.
Specifies a list of filesystem types that watchman is prohibited to attempt to
watch. Watchman will determine the filesystem type of the root of a watch; if
the typename is present in the
illegal_fstypes list, the watch will be
prohibited. You may also specify
illegal_fstypes_advice as a string with
additional advice to your user. The purpose of this configuration option is
largely to prevent the use of Watchman on network mounted filesystems. On Linux
systems, Watchman may not be able to determine the precise type name of a
mounted filesystem. If the filesystem type is not known to watchman, it will be
"illegal_fstypes": ["nfs", "cifs", "smb"],
"illegal_fstypes_advice": "use a local directory"
will prevent watching dirs mounted on network filesystems and provide the advice
to use a local directory. You may omit the
illegal_fstypes_advice setting to
use a default suggestion to relocate the directory to local disk.
Apply special VCS ignore logic to the set of named dirs. This option has a
default value of
[".git", ".hg", ".svn"]. Dirs that match this option are
observed and watched using special shallow logic. The shallow watch allows
watchman to mildly abuse the version control directories to store its query
cookie files and to observe VCS locking activity without having to watch the
entire set of VCS data for large trees.
Dirs that match are completely ignored by watchman. This is useful to ignore a directory that contains only build products and where file change notifications are unwanted because of the sheer volume of files.
would ignore the
build directory at the top level of the watched tree, and
everything below it. It will never appear in the watchman query results for the
On Linux systems,
ignore_dirs is respected at the OS level; the kernel simply
will not tell watchman about changes to ignored dirs. macOS and Windows have
limited or no support for this, so watchman needs to process and ignore this
class of change.
For large trees or especially busy build dirs, it is recommended that you move the busy build dirs out of the tree for more optimal performance.
Since version 2.9.9, if you list a dir in
ignore_dirs that is also listed in
ignore_dirs placement will take precedence. This may not
sound like a big deal, but since
ignore_vcs is used as a hint to for the
placement of cookie files, having these two options overlap in
earlier versions would break watchman queries.
On macOS the first 8 items listed in
ignore_dirs can be accelerated at the OS
level. This means that changes to those paths are not even communicated to the
watchman service. Entries beyond the first 8 are processed and ignored by
watchman. If your workload is prone to recrawl events you will want to
ignore_dirs list so that the most busy ignored locations
occupy the first 8 positions in this list.
Deleted files (and dirs) older than this are periodically pruned from the
internal view of the filesystem. Until they are pruned, they will be visible to
queries but will have their
exists field set to
false. Once they are pruned,
watchman will remember the most recent clock value of the pruned nodes. Any
since queries based on a clock prior to the last prune clock will be treated as
a fresh instance query. This allows a client to detect and choose how to handle
the case where they have missed changes. See
is_fresh_instance elsewhere in
this document for more information. The default for this is
43200 (12 hours).
How often to check for, and prune out, deleted nodes per the
option description above. The default for this is
86400 (24 hours). Set this
0 to disable the periodic pruning operation.
Controls the latency parameter that is passed to
FSEventStreamCreate on macOS.
The value is measured in seconds. The fixed value of this parameter prior to
version 3.2 of watchman was
0.0001 seconds. Starting in version 3.2 of
watchman, the default is now
0.01 seconds and can be controlled on a per-root
If you observe problems with
kFSEventStreamEventFlagUserDropped increasing the
latency parameter will allow the system to batch more change notifications
together and operate more efficiently.
This is macOS specific.
false. If set to
true, if a watch receives a
kFSEventStreamEventFlagUserDropped event, attempt to resync from the
fsevents journal if it is available. The journal may not be available if one
or more volumes are mounted read-only, if the administrator has purged the
journal, or if the
fsevents id numbers have rolled over.
This resync operation is advantageous because it effectively allows rewinding and replaying the event stream from a known point in time and avoids the need to recrawl the entire watch.
If this option is set to
false, or if the journal is not available, the
original strategy of recrawling the watched directory tree is used instead.
The default changed to
true. In addition, this resync strategy is now also
Since December 2021.
The default changed to
false. There are possible undiagnosed correctness
issues with this setting.
This is macOS specific.
false. If set to
true, Watchman will use several FSEvents
streams to watch a directory hierarchy instead of a single stream. This has been
shown to significantly reduce the number of
events for workflows issuing heavy writes to a top-level directory that is
listed in ignore_dirs.
How many seconds a watch can remain idle before becoming a candidate for
reaping, measured in seconds. The default for this is
432000 (5 days). Set
0 to prevent reaping.
A watch is considered to be idle when it has had no commands that operate on it
idle_reap_age_seconds. If an idle watch has no triggers and no
subscriptions then it will be cancelled, releasing the associated operating
system resources, and removed from the state file.
Used to pre-size hash tables used to track files per directory. This is most impactful during the initial crawl of the filesystem. Setting this too small will increase the chance of a hash insert having a collision and drive up the cost of the insert and subsequent gets.
Prior to version 3.9 of watchman this value was fixed at
2. Starting in
version 3.9 the default value is
64 and can be configured via this setting in
.watchmanconfig or the global
/etc/watchman.json configuration file.
Setting this value very large increases the memory overhead per directory in the tree; the value is rounded up to the next power of two and pre-allocated in an array of pointers. On a 64-bit system multiply that number by 8 to arrive at the number of bytes of overhead (halve this on a 32-bit system). The overhead is doubled when using a case insensitive filesystem.
The ideal size from a time complexity perspective is the number of files in your largest directory. From a space complexity perspective, the ideal size is 1; you would pay the cost of the collisions during the initial crawl and have a more optimal memory usage. Since watchman is primarily employed as an accelerator, we'd recommend biasing towards using more memory and taking less time to run.
Used to pre-size hash tables that are used to track the total set of files in the entire watched tree. The default value for this is 131072.
The optimal size is a power-of-two larger than the number of directories in your
find . -type d | wc -l will tell you the number that you have.
Making this number too large is potentially wasteful of memory. Making this number too small results in increased latency during crawling while the hash tables are rebuilt.
When set to
true, watchman will not produce recrawl related warning fields in
the response PDUs of various requests. The default is
false; the intent is
that someone in your organization should be aware of recrawls and be able to
manage the configuration and workload. Some sites employ an alternative
mechanism for sampling and reporting this to the right set of people and wish to
disable the warning so that it doesn't appear in front of users that are unable
to make the appropriate configuration changes for themselves.
This is specific to the EdenFS watcher
When set to a non-zero value, Watchman will return a fresh instance to since queries/subscriptions if the number of changed files exceeds the configured value. In particular, during large updates of the working copies, a lot of files may have changed forcing both Watchman and EdenFS to fetch a significant amount of metadata to answer these queries.
This behavior is only enabled if the query specifies the
empty_on_fresh_instance option or when this config is set to
0. Default to