The Gatekeeper, or a project gating system
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zuul/doc/source/zuul.rst

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Zuul

Zuul

Configuration

Zuul has three configuration files:

zuul.conf

Connection information for Gerrit and Gearman, locations of the other config files. (required)

layout.yaml

Project and pipeline configuration -- what Zuul does. (required)

logging.conf

Python logging config. (optional)

Examples of each of the three files can be found in the etc/ directory of the source distribution.

zuul.conf

Zuul will look for /etc/zuul/zuul.conf or ~/zuul.conf to bootstrap its configuration. Alternately, you may specify -c /path/to/zuul.conf on the command line.

Gerrit and Gearman connection information are each described in a section of zuul.conf. The location of the other two configuration files (as well as the location of the PID file when running Zuul as a server) are specified in a third section.

The three sections of this config and their options are documented below. You can also find an example zuul.conf file in the git repository

gearman

Client connection information for gearman. If using Zuul's builtin gearmand server just set server to 127.0.0.1.

server

Hostname or IP address of the Gearman server. server=gearman.example.com (required)

port

Port on which the Gearman server is listening. port=4730 (optional)

gearman_server

The builtin gearman server. Zuul can fork a gearman process from itself rather than connecting to an external one.

start

Whether to start the internal Gearman server (default: False). start=true

listen_address

IP address or domain name on which to listen (default: all addresses). listen_address=127.0.0.1

log_config

Path to log config file for internal Gearman server. log_config=/etc/zuul/gearman-logging.yaml

webapp

listen_address

IP address or domain name on which to listen (default: 0.0.0.0). listen_address=127.0.0.1

port

Port on which the webapp is listening (default: 8001). port=8008

zuul

Zuul's main configuration section. At minimum zuul must be able to find layout.yaml to be useful.

Note

Must be provided when running zuul-server

layout_config

Path to layout config file. Used by zuul-server only. layout_config=/etc/zuul/layout.yaml

log_config

Path to log config file. Used by zuul-server only. log_config=/etc/zuul/logging.yaml

pidfile

Path to PID lock file. Used by zuul-server only. pidfile=/var/run/zuul/zuul.pid

state_dir

Path to directory that Zuul should save state to. Used by all Zuul commands. state_dir=/var/lib/zuul

jobroot_dir

Path to directory that Zuul should store temporary job files. jobroot_dir=/tmp

report_times

Boolean value (true or false) that determines if Zuul should include elapsed times for each job in the textual report. Used by zuul-server only. report_times=true

status_url

URL that will be posted in Zuul comments made to Gerrit changes when starting jobs for a change. Used by zuul-server only. status_url=https://zuul.example.com/status

status_expiry

Zuul will cache the status.json file for this many seconds. This is an optional value and 1 is used by default. status_expiry=1

job_name_in_report

Boolean value (true or false) that indicates whether the job name should be included in the report (normally only the URL is included). Defaults to false. Used by zuul-server only. job_name_in_report=true

merger

The zuul-merger process configuration. Detailed documentation on this process can be found on the merger page.

Note

Must be provided when running zuul-merger. Both services may share the same configuration (and even host) or otherwise have an individual zuul.conf.

git_dir

Directory that Zuul should clone local git repositories to. git_dir=/var/lib/zuul/git

git_user_email

Optional: Value to pass to git config user.email. git_user_email=zuul@example.com

git_user_name

Optional: Value to pass to git config user.name. git_user_name=zuul

zuul_url

URL of this merger's git repos, accessible to test workers. Usually "http://zuul.example.com/p" or "http://zuul-merger01.example.com/p" depending on whether the merger is co-located with the Zuul server.

log_config

Path to log config file for the merger process. log_config=/etc/zuul/logging.yaml

pidfile

Path to PID lock file for the merger process. pidfile=/var/run/zuul-merger/merger.pid

connection ArbitraryName

A connection can be listed with any arbitrary name. The required parameters are specified in the connections documentation depending on what driver you are using.

layout.yaml

This is the main configuration file for Zuul, where all of the pipelines and projects are defined, what tests should be run, and what actions Zuul should perform. There are three sections: pipelines, jobs, and projects.

Pipelines

Zuul can have any number of independent pipelines. Whenever a matching Gerrit event is found for a pipeline, that event is added to the pipeline, and the jobs specified for that pipeline are run. When all jobs specified for the pipeline that were triggered by an event are completed, Zuul reports back to Gerrit the results.

There are no pre-defined pipelines in Zuul, rather you can define whatever pipelines you need in the layout file. This is a very flexible system that can accommodate many kinds of workflows.

Here is a quick example of a pipeline definition followed by an explanation of each of the parameters:

- name: check
  manager: IndependentPipelineManager
  source: my_gerrit
  trigger:
    my_gerrit:
      - event: patchset-created
  success:
    my_gerrit:
      verified: 1
  failure:
    my_gerrit
      verified: -1
name

This is used later in the project definition to indicate what jobs should be run for events in the pipeline.

description

This is an optional field that may be used to provide a textual description of the pipeline.

source

A required field that specifies a connection that provides access to the change objects that this pipeline operates on. The name of the connection as per the zuul.conf should be specified. The driver used for the connection named will be the source. Currently only gerrit drivers are supported.

success-message

An optional field that supplies the introductory text in message reported back to Gerrit when all the voting builds are successful. Defaults to "Build successful."

failure-message

An optional field that supplies the introductory text in message reported back to Gerrit when at least one voting build fails. Defaults to "Build failed."

merge-failure-message

An optional field that supplies the introductory text in message reported back to Gerrit when a change fails to merge with the current state of the repository. Defaults to "Merge failed."

footer-message

An optional field to supply additional information after test results. Useful for adding information about the CI system such as debugging and contact details.

manager

There are currently two schemes for managing pipelines:

IndependentPipelineManager

Every event in this pipeline should be treated as independent of other events in the pipeline. This is appropriate when the order of events in the pipeline doesn't matter because the results of the actions this pipeline performs can not affect other events in the pipeline. For example, when a change is first uploaded for review, you may want to run tests on that change to provide early feedback to reviewers. At the end of the tests, the change is not going to be merged, so it is safe to run these tests in parallel without regard to any other changes in the pipeline. They are independent.

Another type of pipeline that is independent is a post-merge pipeline. In that case, the changes have already merged, so the results can not affect any other events in the pipeline.

DependentPipelineManager

The dependent pipeline manager is designed for gating. It ensures that every change is tested exactly as it is going to be merged into the repository. An ideal gating system would test one change at a time, applied to the tip of the repository, and only if that change passed tests would it be merged. Then the next change in line would be tested the same way. In order to achieve parallel testing of changes, the dependent pipeline manager performs speculative execution on changes. It orders changes based on their entry into the pipeline. It begins testing all changes in parallel, assuming that each change ahead in the pipeline will pass its tests. If they all succeed, all the changes can be tested and merged in parallel. If a change near the front of the pipeline fails its tests, each change behind it ignores whatever tests have been completed and are tested again without the change in front. This way gate tests may run in parallel but still be tested correctly, exactly as they will appear in the repository when merged.

One important characteristic of the DependentPipelineManager is that it analyzes the jobs that are triggered by different projects, and if those projects have jobs in common, it treats those projects as related, and they share a single virtual queue of changes. Thus, if there is a job that performs integration testing on two projects, those two projects will automatically share a virtual change queue. If a third project does not invoke that job, it will be part of a separate virtual change queue, and changes to it will not depend on changes to the first two jobs.

For more detail on the theory and operation of Zuul's DependentPipelineManager, see: gating.

trigger

At least one trigger source must be supplied for each pipeline. Triggers are not exclusive -- matching events may be placed in multiple pipelines, and they will behave independently in each of the pipelines they match.

Triggers are loaded from their connection name. The driver type of the connection will dictate which options are available. See triggers.

require

If this section is present, it established pre-requisites for any kind of item entering the Pipeline. Regardless of how the item is to be enqueued (via any trigger or automatic dependency resolution), the conditions specified here must be met or the item will not be enqueued.

approval This requires that a certain kind of approval be present for the current patchset of the change (the approval could be added by the event in question). It takes several sub-parameters, all of which are optional and are combined together so that there must be an approval matching all specified requirements.

username If present, an approval from this username is required. It is treated as a regular expression.

email If present, an approval with this email address is required. It is treated as a regular expression.

email-filter (deprecated) A deprecated alternate spelling of email. Only one of email or email_filter should be used.

older-than If present, the approval must be older than this amount of time to match. Provide a time interval as a number with a suffix of "w" (weeks), "d" (days), "h" (hours), "m" (minutes), "s" (seconds). Example 48h or 2d.

newer-than If present, the approval must be newer than this amount of time to match. Same format as "older-than".

Any other field is interpreted as a review category and value pair. For example verified: 1 would require that the approval be for a +1 vote in the "Verified" column. The value may either be a single value or a list: verified: [1, 2] would match either a +1 or +2 vote.

open A boolean value (true or false) that indicates whether the change must be open or closed in order to be enqueued.

current-patchset A boolean value (true or false) that indicates whether the change must be the current patchset in order to be enqueued.

status A string value that corresponds with the status of the change reported by the trigger. For example, when using the Gerrit trigger, status values such as NEW or MERGED may be useful.

reject

If this section is present, it establishes pre-requisites that can block an item from being enqueued. It can be considered a negative version of require.

approval This takes a list of approvals. If an approval matches the provided criteria the change can not be entered into the pipeline. It follows the same syntax as the "require approval" pipeline above <pipeline-require-approval>.

Example to reject a change with any negative vote:

reject:
  approval:
    - code-review: [-1, -2]
dequeue-on-new-patchset

Normally, if a new patchset is uploaded to a change that is in a pipeline, the existing entry in the pipeline will be removed (with jobs canceled and any dependent changes that can no longer merge as well. To suppress this behavior (and allow jobs to continue running), set this to false. Default: true.

ignore-dependencies

In any kind of pipeline (dependent or independent), Zuul will attempt to enqueue all dependencies ahead of the current change so that they are tested together (independent pipelines report the results of each change regardless of the results of changes ahead). To ignore dependencies completely in an independent pipeline, set this to true. This option is ignored by dependent pipelines. The default is: false.

success

Describes where Zuul should report to if all the jobs complete successfully. This section is optional; if it is omitted, Zuul will run jobs and do nothing on success; it will not even report a message to Gerrit. If the section is present, the listed reporter plugins will be asked to report on the jobs. The reporters are listed by their connection name. The options available depend on the driver for the supplied connection. See reporters for more details.

failure

Uses the same syntax as success, but describes what Zuul should do if at least one job fails.

merge-failure

Uses the same syntax as success, but describes what Zuul should do if it is unable to merge in the patchset. If no merge-failure reporters are listed then the failure reporters will be used to notify of unsuccessful merges.

start

Uses the same syntax as success, but describes what Zuul should do when a change is added to the pipeline manager. This can be used, for example, to reset the value of the Verified review category.

disabled

Uses the same syntax as success, but describes what Zuul should do when a pipeline is disabled. See disable-after-consecutive-failures.

disable-after-consecutive-failures

If set, a pipeline can enter a ''disabled'' state if too many changes in a row fail. When this value is exceeded the pipeline will stop reporting to any of the success, failure or merge-failure reporters and instead only report to the disabled reporters. (No start reports are made when a pipeline is disabled).

precedence

Indicates how the build scheduler should prioritize jobs for different pipelines. Each pipeline may have one precedence, jobs for pipelines with a higher precedence will be run before ones with lower. The value should be one of high, normal, or low. Default: normal.

window

DependentPipelineManagers only. Zuul can rate limit DependentPipelineManagers in a manner similar to TCP flow control. Jobs are only started for changes in the queue if they sit in the actionable window for the pipeline. The initial length of this window is configurable with this value. The value given should be a positive integer value. A value of 0 disables rate limiting on the DependentPipelineManager. Default: 20.

window-floor

DependentPipelineManagers only. This is the minimum value for the window described above. Should be a positive non zero integer value. Default: 3.

window-increase-type

DependentPipelineManagers only. This value describes how the window should grow when changes are successfully merged by zuul. A value of linear indicates that window-increase-factor should be added to the previous window value. A value of exponential indicates that window-increase-factor should be multiplied against the previous window value and the result will become the window size. Default: linear.

window-increase-factor

DependentPipelineManagers only. The value to be added or multiplied against the previous window value to determine the new window after successful change merges. Default: 1.

window-decrease-type

DependentPipelineManagers only. This value describes how the window should shrink when changes are not able to be merged by Zuul. A value of linear indicates that window-decrease-factor should be subtracted from the previous window value. A value of exponential indicates that window-decrease-factor should be divided against the previous window value and the result will become the window size. Default: exponential.

window-decrease-factor

DependentPipelineManagers only. The value to be subtracted or divided against the previous window value to determine the new window after unsuccessful change merges. Default: 2.

Some example pipeline configurations are included in the sample layout file. The first is called a check pipeline:

- name: check
  manager: IndependentPipelineManager
  trigger:
    my_gerrit:
      - event: patchset-created
  success:
    my_gerrit:
      verified: 1
  failure:
    my_gerrit:
      verified: -1

This will trigger jobs each time a new patchset (or change) is uploaded to Gerrit, and report +/-1 values to Gerrit in the verified review category. :

- name: gate
  manager: DependentPipelineManager
  trigger:
    my_gerrit:
      - event: comment-added
        approval:
          - approved: 1
  success:
    my_gerrit:
      verified: 2
      submit: true
  failure:
    my_gerrit:
      verified: -2

This will trigger jobs whenever a reviewer leaves a vote of 1 in the approved review category in Gerrit (a non-standard category). Changes will be tested in such a way as to guarantee that they will be merged exactly as tested, though that will happen in parallel by creating a virtual queue of dependent changes and performing speculative execution of jobs. :

- name: post
  manager: IndependentPipelineManager
  trigger:
    my_gerrit:
      - event: ref-updated
        ref: ^(?!refs/).*$

This will trigger jobs whenever a change is merged to a named branch (e.g., master). No output will be reported to Gerrit. This is useful for side effects such as creating per-commit tarballs. :

- name: silent
  manager: IndependentPipelineManager
  trigger:
    my_gerrit:
      - event: patchset-created

This also triggers jobs when changes are uploaded to Gerrit, but no results are reported to Gerrit. This is useful for jobs that are in development and not yet ready to be presented to developers. :

pipelines:
  - name: post-merge
    manager: IndependentPipelineManager
    trigger:
      my_gerrit:
        - event: change-merged
    success:
      my_gerrit:
        force-message: True
    failure:
      my_gerrit:
        force-message: True

The change-merged events happen when a change has been merged in the git repository. The change is thus closed and Gerrit will not accept modifications to the review scoring such as code-review or verified. By using the force-message: True parameter, Zuul will pass --force-message to the gerrit review command, thus making sure the message is actually sent back to Gerrit regardless of approval scores. That kind of pipeline is nice to run regression or performance tests.

Note

The change-merged event does not include the commit sha1 which can be hazardous, it would let you report back to Gerrit though. If you were to build a tarball for a specific commit, you should consider instead using the ref-updated event which does include the commit sha1 (but lacks the Gerrit change number).

Jobs

The jobs section is optional, and can be used to set attributes of jobs that are independent of their association with a project. For example, if a job should return a customized message on failure, that may be specified here. Otherwise, Zuul does not need to be told about each job as it builds a list from the project specification.

name

The name of the job. This field is treated as a regular expression and will be applied to each job that matches.

queue-name (optional)

Zuul will automatically combine projects that share a job into shared change queues for dependent pipeline managers. In order to report statistics about these queues, it is convenient for them to have names. Zuul can automatically name change queues, however these can grow quite long and are prone to changing as projects in the queue change. If you assign a queue-name to a job, Zuul will use that as the name for the shared change queue that contains that job instead of the automatically generated one. It is an error for a shared change queue to have more than one job with a queue-name if they are not the same.

failure-message (optional)

The message that should be reported to Gerrit if the job fails.

success-message (optional)

The message that should be reported to Gerrit if the job fails.

failure-pattern (optional)

The URL that should be reported to Gerrit if the job fails. Defaults to the build URL or the url_pattern configured in zuul.conf. May be supplied as a string pattern with substitutions as described in url_pattern in zuulconf.

success-pattern (optional)

The URL that should be reported to Gerrit if the job succeeds. Defaults to the build URL or the url_pattern configured in zuul.conf. May be supplied as a string pattern with substitutions as described in url_pattern in zuulconf.

hold-following-changes (optional)

This is a boolean that indicates that changes that follow this change in a dependent change pipeline should wait until this job succeeds before executing. If this is applied to a very short job that can predict whether longer jobs will fail early, this can be used to reduce the number of jobs that Zuul will execute and ultimately have to cancel. In that case, a small amount of parallelization of jobs is traded for more efficient use of testing resources. On the other hand, to apply this to a long running job would largely defeat the parallelization of dependent change testing that is the main feature of Zuul. Default: false.

semaphore (optional)

This is a string that names a semaphore that should be observed by this job. The semaphore defines how many jobs which reference that semaphore can be enqueued at a time. This applies across all pipelines in the same tenant. The max value of the semaphore can be specified in the config repositories and defaults to 1.

branch (optional)

This job should only be run on matching branches. This field is treated as a regular expression and multiple branches may be listed.

files (optional)

This job should only be run if at least one of the files involved in the change (added, deleted, or modified) matches at least one of the file patterns listed here. This field is treated as a regular expression and multiple expressions may be listed.

skip-if (optional)

This job should not be run if all the patterns specified by the optional fields listed below match on their targets. When multiple sets of parameters are provided, this job will be skipped if any set matches. For example: :

jobs:
  - name: check-tempest-dsvm-neutron
    skip-if:
      - project: ^openstack/neutron$
        branch: ^stable/juno$
        all-files-match-any:
          - ^neutron/tests/.*$
          - ^tools/.*$
      - all-files-match-any:
          - ^doc/.*$
          - ^.*\.rst$

With this configuration, the job would be skipped for a neutron patchset for the stable/juno branch provided that every file in the change matched at least one of the specified file regexes. The job will also be skipped for any patchset that modified only the doc tree or rst files.

project (optional)

The regular expression to match against the project of the change.

branch (optional)

The regular expression to match against the branch or ref of the change.

all-files-match-any (optional)

A list of regular expressions intended to match the files involved in the change. This parameter will be considered matching a change only if all files in a change match at least one of these expressions.

The pattern for '/COMMIT_MSG' is always matched on and does not have to be included. Exception is merge commits (without modified files), in this case '/COMMIT_MSG' is not matched, and job is not skipped. In case of merge commits it's assumed that list of modified files isn't predictible and CI should be run.

voting (optional)

Boolean value (true or false) that indicates whatever a job is voting or not. Default: true.

attempts (optional)

Number of attempts zuul will execute a job. Once reached, zuul will report RETRY_LIMIT as the job result. Defaults to 3.

tags (optional)

A list of arbitrary strings which will be associated with the job.

Here is an example of setting the failure message for jobs that check whether a change merges cleanly:

- name: ^.*-merge$
  failure-message: This change or one of its cross-repo dependencies
  was unable to be automatically merged with the current state of
  its repository. Please rebase the change and upload a new
  patchset.

Projects

The projects section indicates what jobs should be run in each pipeline for events associated with each project. It contains a list of projects. Here is an example:

- name: example/project
  check:
    - project-merge:
      - project-unittest
      - project-pep8
      - project-pyflakes
  gate:
    - project-merge:
      - project-unittest
      - project-pep8
      - project-pyflakes
  post:
    - project-publish
name

The name of the project (as known by Gerrit).

merge-mode (optional)

An optional value that indicates what strategy should be used to merge changes to this project. Supported values are:

** merge-resolve ** Equivalent to 'git merge -s resolve'. This corresponds closely to what Gerrit performs (using JGit) for a project if the "Merge if necessary" merge mode is selected and "Automatically resolve conflicts" is checked. This is the default.

** merge ** Equivalent to 'git merge'.

** cherry-pick ** Equivalent to 'git cherry-pick'.

This is followed by a section for each of the pipelines defined above. Pipelines may be omitted if no jobs should run for this project in a given pipeline. Within the pipeline section, the jobs that should be executed are listed. If a job is entered as a dictionary key, then jobs contained within that key are only executed if the key job succeeds. In the above example, project-unittest, project-pep8, and project-pyflakes are only executed if project-merge succeeds. Furthermore, project-finaltest is executed only if project-unittest, project-pep8 and project-pyflakes all succeed. This can help avoid running unnecessary jobs while maximizing parallelism. It is also useful when distributing results between jobs.

The special job named noop is internal to Zuul and will always return SUCCESS immediately. This can be useful if you require that all changes be processed by a pipeline but a project has no jobs that can be run on it.

The OpenStack Zuul configuration for a comprehensive example: https://git.openstack.org/cgit/openstack-infra/project-config/tree/zuul/layout.yaml

Project Templates

Whenever you have lot of similar projects (such as plugins for a project) you will most probably want to use the same pipeline configurations. The project templates let you define pipelines and job name templates to trigger. One can then just apply the template on its project which make it easier to update several similar projects. As an example:

project-templates:
  # Name of the template
  - name: plugin-triggering
    # Definition of pipelines just like for a `project`
    check:
     - '{jobprefix}-merge':
       - '{jobprefix}-pep8'
       - '{jobprefix}-pyflakes'
    gate:
     - '{jobprefix}-merge':
       - '{jobprefix}-unittest'
       - '{jobprefix}-pep8'
       - '{jobprefix}-pyflakes'

In your projects definition, you will then apply the template using the template key:

projects:
 - name: plugin/foobar
   template:
    - name: plugin-triggering
      jobprefix: plugin-foobar

You can pass several parameters to a template. A parameter value will be used for expansion of {parameter} in the template strings. The parameter name will be automatically provided and will contain the short name of the project, that is the portion of the project name after the last / character.

Multiple templates can be combined in a project, and the jobs from all of those templates will be added to the project. Individual jobs may also be added:

projects:
 - name: plugin/foobar
   template:
    - name: plugin-triggering
      jobprefix: plugin-foobar
    - name: plugin-extras
      jobprefix: plugin-foobar
   check:
    - foobar-extra-special-job

Individual jobs may optionally be added to pipelines (e.g. check, gate, et cetera) for a project, in addition to those provided by templates.

The order of the jobs listed in the project (which only affects the order of jobs listed on the report) will be the jobs from each template in the order listed, followed by any jobs individually listed for the project.

Note that if multiple templates are used for a project and one template specifies a job that is also specified in another template, or specified in the project itself, the configuration defined by either the last template or the project itself will take priority.

Semaphores

When using semaphores the maximum value of each one can be specified in their respective config repositories. Unspecified semaphores default to 1:

- semaphore:
    name: semaphore-foo
    max: 5
- semaphore:
    name: semaphore-bar
    max: 3

logging.conf

This file is optional. If provided, it should be a standard logging.config module configuration file. If not present, Zuul will output all log messages of DEBUG level or higher to the console.

Starting Zuul

To start Zuul, run zuul-server:

usage: zuul-server [-h] [-c CONFIG] [-l LAYOUT] [-d] [-t] [--version]

Project gating system.

optional arguments:
  -h, --help  show this help message and exit
  -c CONFIG   specify the config file
  -l LAYOUT   specify the layout file
  -d          do not run as a daemon
  -t          validate layout file syntax
  --version   show zuul version

You may want to use the -d argument while you are initially setting up Zuul so you can detect any configuration errors quickly. Under normal operation, omit -d and let Zuul run as a daemon.

If you send signal 1 (SIGHUP) to the zuul-server process, Zuul will stop executing new jobs, wait until all executing jobs are finished, reload its layout.yaml, and resume. Changes to any connections or the PID file will be ignored until Zuul is restarted.

If you send a SIGUSR1 to the zuul-server process, Zuul will stop executing new jobs, wait until all executing jobs are finished, then exit. While waiting to exit Zuul will queue Gerrit events and save these events prior to exiting. When Zuul starts again it will read these saved events and act on them.

If you need to abort Zuul and intend to manually requeue changes for jobs which were running in its pipelines, prior to terminating you can use the zuul-changes.py tool script to simplify the process. For example, this would give you a list of zuul-enqueue commands to requeue changes for the gate and check pipelines respectively:

./tools/zuul-changes.py http://zuul.openstack.org/ gate
./tools/zuul-changes.py http://zuul.openstack.org/ check

If you send a SIGUSR2 to the zuul-server process, or the forked process that runs the Gearman daemon, Zuul will dump a stack trace for each running thread into its debug log. It is written under the log bucket zuul.stack_dump. This is useful for tracking down deadlock or otherwise slow threads.

When yappi (Yet Another Python Profiler) is available, additional functions' and threads' stats are emitted as well. The first SIGUSR2 will enable yappi, on the second SIGUSR2 it dumps the information collected, resets all yappi state and stops profiling. This is to minimize the impact of yappi on a running system.