class LoadBalancingServer(ValidateModelMixin, TimeStampedModel):
"""
A model representing a configured load-balancing server.
"""
objects = LoadBalancingServerManager()
domain = models.CharField(max_length=100, unique=True)
# The username used to ssh into the server
ssh_username = models.CharField(max_length=32)
# Whether new backends can be assigned to this load-balancing server
accepts_new_backends = models.BooleanField(default=True)
# A random postfix appended to the haproxy configuration file names to make collisions
# impossible.
fragment_name_postfix = models.CharField(max_length=8, blank=True)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.logger = ModelLoggerAdapter(logger, {'obj': self})
def set_field_defaults(self):
if not self.fragment_name_postfix:
# Set a unique fragment_name_postfix to avoid clashes between multiple instance
# managers sharing the same load balancer.
bits = self._meta.get_field("fragment_name_postfix").max_length * 4
self.fragment_name_postfix = format(random.getrandbits(bits), "x")
super().set_field_defaults()
def __str__(self):
return self.domain
def get_log_message_annotation(self):
"""
Annotate log messages for the load-balancing server.
"""
return "load_balancer={} ({!s:.15})".format(self.pk, self.domain)
def get_instances(self):
"""
Yield all instances configured to use this load balancer.
"""
# Local import due to avoid problems with circular dependencies.
from instance.models.mixins.load_balanced import LoadBalancedInstance
for field in self._meta.get_fields():
if field.one_to_many and issubclass(field.related_model, LoadBalancedInstance):
yield from getattr(self, field.get_accessor_name()).iterator()
def get_configuration(self, triggering_instance_id=None):
"""
Collect the backend maps and configuration fragments from all associated instances.
This function also appends fragment_name_postfix to all backend names to avoid name clashes
between multiple instance managers using the same load balancer (e.g. for the integration
tests).
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map = []
backend_conf = []
for instance in self.get_instances():
triggered_by_instance = instance.ref.pk == triggering_instance_id
map_entries, conf_entries = instance.get_load_balancer_configuration(
triggered_by_instance
)
backend_map.extend(
" ".join([domain.lower(), backend + self.fragment_name_postfix])
for domain, backend in map_entries
)
backend_conf.extend(
"backend {}\n{}\n".format(backend + self.fragment_name_postfix, conf)
for backend, conf in conf_entries
)
return "\n".join(backend_map), "\n".join(backend_conf)
def get_ansible_vars(self, triggering_instance_id=None):
"""
Render the configuration script to be executed on the load balancer.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map, backend_conf = self.get_configuration(triggering_instance_id)
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
return (
"FRAGMENT_NAME: {fragment_name}\n"
"BACKEND_CONFIG_FRAGMENT: |\n"
"{backend_conf}\n"
"BACKEND_MAP_FRAGMENT: |\n"
"{backend_map}\n"
).format(
fragment_name=fragment_name,
backend_conf=textwrap.indent(backend_conf, " "),
backend_map=textwrap.indent(backend_map, " "),
)
def run_playbook(self, ansible_vars):
"""
Run the playbook to perform the server reconfiguration.
This is factored out into a separate method so it can be mocked out in the tests.
"""
playbook_path = pathlib.Path(settings.SITE_ROOT) / "playbooks/load_balancer_conf/load_balancer_conf.yml"
with cache.lock("load_balancer_reconfigure:{}".format(self.domain), timeout=900):
returncode = ansible.capture_playbook_output(
requirements_path=str(playbook_path.parent / "requirements.txt"),
inventory_str=self.domain,
vars_str=ansible_vars,
playbook_path=str(playbook_path),
username=self.ssh_username,
logger_=self.logger,
)
if returncode != 0:
self.logger.error("Playbook to reconfigure load-balancing server %s failed.", self)
raise ReconfigurationFailed
def reconfigure(self, triggering_instance_id=None):
"""
Regenerate the configuration fragments on the load-balancing server.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
self.logger.info("Reconfiguring load-balancing server %s", self.domain)
self.run_playbook(self.get_ansible_vars(triggering_instance_id))
def deconfigure(self):
"""
Remove the configuration fragment from the load-balancing server.
"""
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
self.run_playbook(
"FRAGMENT_NAME: {fragment_name}\nREMOVE_FRAGMENT: True".format(fragment_name=fragment_name)
)
def delete(self, *args, **kwargs):
"""
Delete the LoadBalancingServer from the database.
"""
self.deconfigure()
super().delete(*args, **kwargs) # pylint: disable=no-member
class WatchedPullRequest(models.Model):
"""
Represents a single watched pull request; holds the ID of the Instance created for that PR,
if any
"""
# TODO: Remove 'ref_type' ?
# TODO: Remove parameters from 'update_instance_from_pr'; make it fetch PR details from the
# api (including the head commit sha hash, which does not require a separate API call as
# is currently used.)
branch_name = models.CharField(max_length=50, default='master')
ref_type = models.CharField(max_length=50, default='heads')
github_organization_name = models.CharField(max_length=200, db_index=True)
github_repository_name = models.CharField(max_length=200, db_index=True)
github_pr_url = models.URLField(blank=False)
instance = models.OneToOneField('instance.OpenEdXInstance', null=True, blank=True, on_delete=models.SET_NULL)
objects = WatchedPullRequestQuerySet.as_manager()
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.logger = ModelLoggerAdapter(logger, {'obj': self})
@property
def fork_name(self):
"""
Fork name (eg. 'open-craft/edx-platform')
"""
return '{0.github_organization_name}/{0.github_repository_name}'.format(self)
@property
def reference_name(self):
"""
A descriptive name for the PR, which includes meaningful attributes
"""
return '{0.github_organization_name}/{0.branch_name}'.format(self)
@property
def github_base_url(self):
"""
Base GitHub URL of the fork (eg. 'https://github.com/open-craft/edx-platform')
"""
return 'https://github.com/{0.fork_name}'.format(self)
@property
def github_branch_url(self):
"""
GitHub URL of the branch tree
"""
return '{0.github_base_url}/tree/{0.branch_name}'.format(self)
@property
def github_pr_number(self):
"""
Get the PR number from the URL of the PR.
"""
if not self.github_pr_url:
return None
return int(self.github_pr_url.split('/')[-1])
@property
def target_fork_name(self):
"""
Get the full name of the target repo/fork (e.g. 'edx/edx-platform')
"""
# Split up a URL like https://github.com/edx/edx-platform/pull/12345678
org, repo, pull, dummy = self.github_pr_url.split('/')[-4:]
assert pull == "pull"
return "{}/{}".format(org, repo)
@property
def repository_url(self):
"""
URL of the git repository (eg. 'https://github.com/open-craft/edx-platform.git')
"""
return '{0.github_base_url}.git'.format(self)
@property
def updates_feed(self):
"""
RSS/Atom feed of commits made on the repository/branch
"""
return '{0.github_base_url}/commits/{0.branch_name}.atom'.format(self)
def get_log_message_annotation(self):
"""
Format a log message annotation for this PR.
"""
if self.instance:
return self.instance.get_log_message_annotation()
return None
def get_branch_tip(self):
"""
Get the `commit_id` of the current tip of the branch
"""
self.logger.info('Fetching commit ID of the tip of branch %s', self.branch_name)
try:
new_commit_id = github.get_commit_id_from_ref(
self.fork_name,
self.branch_name,
ref_type=self.ref_type)
except github.ObjectDoesNotExist:
self.logger.error("Branch '%s' not found. Has it been deleted on GitHub?",
self.branch_name)
raise
return new_commit_id
def set_fork_name(self, fork_name):
"""
Set the organization and repository based on the GitHub fork name
"""
assert not self.github_organization_name
assert not self.github_repository_name
self.logger.info('Setting fork name: %s', fork_name)
fork_org, fork_repo = github.fork_name2tuple(fork_name)
self.github_organization_name = fork_org
self.github_repository_name = fork_repo
def update_instance_from_pr(self, pr):
"""
Update/create the associated sandbox instance with settings from the given pull request.
This will not spawn a new AppServer.
This method will automatically save this WatchedPullRequest's 'instance' field.
"""
# The following fields should never change:
assert self.github_pr_url == pr.github_pr_url
assert self.fork_name == pr.fork_name
assert self.branch_name == pr.branch_name
# Create an instance if necessary:
instance = self.instance or OpenEdXInstance()
instance.internal_lms_domain = generate_internal_lms_domain('pr{number}.sandbox'.format(number=pr.number))
instance.edx_platform_repository_url = self.repository_url
instance.edx_platform_commit = self.get_branch_tip()
instance.name = (
'PR#{pr.number}: {pr.truncated_title} ({pr.username}) - {i.reference_name} ({commit_short_id})'
.format(pr=pr, i=self, commit_short_id=instance.edx_platform_commit[:7])
)
instance.configuration_extra_settings = pr.extra_settings
instance.use_ephemeral_databases = pr.use_ephemeral_databases(instance.domain)
instance.configuration_source_repo_url = pr.get_extra_setting(
'edx_ansible_source_repo', default=instance.configuration_source_repo_url
)
instance.configuration_version = pr.get_extra_setting(
'configuration_version', default=instance.configuration_version
)
# Save atomically. (because if the instance gets created but self.instance failed to
# update, then any subsequent call to update_instance_from_pr() would try to create
# another instance, which would fail due to unique domain name constraints.)
with transaction.atomic():
instance.save()
if not self.instance:
self.instance = instance
self.save(update_fields=["instance"]) # pylint: disable=no-member
class WatchedPullRequest(models.Model):
"""
Represents a single watched pull request; holds the ID of the Instance created for that PR,
if any
"""
# TODO: Remove 'ref_type' ?
# TODO: Remove parameters from 'update_instance_from_pr'; make it fetch PR details from the
# api (including the head commit sha hash, which does not require a separate API call as
# is currently used.)
watched_fork = models.ForeignKey(WatchedFork,
blank=True,
null=True,
on_delete=models.CASCADE)
branch_name = models.CharField(max_length=255, default='master')
ref_type = models.CharField(max_length=50, default='heads')
github_organization_name = models.CharField(max_length=200, db_index=True)
github_repository_name = models.CharField(max_length=200, db_index=True)
github_pr_url = models.URLField(blank=False)
instance = models.OneToOneField('instance.OpenEdXInstance',
null=True,
blank=True,
on_delete=models.SET_NULL)
objects = WatchedPullRequestQuerySet.as_manager()
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.logger = ModelLoggerAdapter(logger, {'obj': self})
@property
def fork_name(self):
"""
Fork name (eg. 'open-craft/edx-platform')
"""
return '{0.github_organization_name}/{0.github_repository_name}'.format(
self)
@property
def reference_name(self):
"""
A descriptive name for the PR, which includes meaningful attributes
"""
return '{0.github_organization_name}/{0.branch_name}'.format(self)
@property
def github_base_url(self):
"""
Base GitHub URL of the fork (eg. 'https://github.com/open-craft/edx-platform')
"""
return 'https://github.com/{0.fork_name}'.format(self)
@property
def github_branch_url(self):
"""
GitHub URL of the branch tree
"""
return '{0.github_base_url}/tree/{0.branch_name}'.format(self)
@property
def github_pr_number(self):
"""
Get the PR number from the URL of the PR.
"""
if not self.github_pr_url:
return None
return int(self.github_pr_url.split('/')[-1])
@property
def target_fork_name(self):
"""
Get the full name of the target repo/fork (e.g. 'edx/edx-platform')
"""
# Split up a URL like https://github.com/edx/edx-platform/pull/12345678
org, repo, pull, dummy = self.github_pr_url.split('/')[-4:]
assert pull == "pull"
return "{}/{}".format(org, repo)
@property
def repository_url(self):
"""
URL of the git repository (eg. 'https://github.com/open-craft/edx-platform.git')
"""
return '{0.github_base_url}.git'.format(self)
@property
def updates_feed(self):
"""
RSS/Atom feed of commits made on the repository/branch
"""
return '{0.github_base_url}/commits/{0.branch_name}.atom'.format(self)
def get_log_message_annotation(self):
"""
Format a log message annotation for this PR.
"""
if self.instance:
return self.instance.get_log_message_annotation()
return None
def get_branch_tip(self):
"""
Get the `commit_id` of the current tip of the branch
"""
self.logger.info('Fetching commit ID of the tip of branch %s',
self.branch_name)
try:
new_commit_id = github.get_commit_id_from_ref(
self.fork_name, self.branch_name, ref_type=self.ref_type)
except github.ObjectDoesNotExist:
self.logger.error(
"Branch '%s' not found. Has it been deleted on GitHub?",
self.branch_name)
raise
return new_commit_id
def set_fork_name(self, fork_name):
"""
Set the organization and repository based on the GitHub fork name
"""
assert not self.github_organization_name
assert not self.github_repository_name
self.logger.info('Setting fork name: %s', fork_name)
fork_org, fork_repo = github.fork_name2tuple(fork_name)
self.github_organization_name = fork_org
self.github_repository_name = fork_repo
def update_instance_from_pr(self, pr):
"""
Update/create the associated sandbox instance with settings from the given pull request.
This will not spawn a new AppServer.
This method will automatically save this WatchedPullRequest's 'instance' field.
"""
# The following fields should never change:
assert self.github_pr_url == pr.github_pr_url
assert self.fork_name == pr.fork_name
assert self.branch_name == pr.branch_name
# Create an instance if necessary:
instance = self.instance or OpenEdXInstance()
is_external_pr = self.watched_fork is None
instance.internal_lms_domain = generate_internal_lms_domain(
'{prefix}pr{number}.sandbox'.format(
prefix='ext' if is_external_pr else '',
number=pr.number,
))
instance.edx_platform_repository_url = self.repository_url
instance.edx_platform_commit = self.get_branch_tip()
instance.name = (
'{prefix}PR#{pr.number}: {pr.truncated_title} ({pr.username}) - {i.reference_name} ({commit_short_id})'
.format(
pr=pr,
i=self,
commit_short_id=instance.edx_platform_commit[:7],
prefix='EXT' if is_external_pr else '',
))
if is_external_pr:
instance.configuration_extra_settings = pr.extra_settings
else:
instance.configuration_extra_settings = yaml_merge(
self.watched_fork.configuration_extra_settings,
pr.extra_settings)
if not instance.ref.creator or not instance.ref.owner:
try:
user = UserProfile.objects.get(github_username=pr.username)
instance.ref.creator = user
instance.ref.owner = user.organization
except UserProfile.DoesNotExist:
# PR is not associated with an Ocim user
pass
# Configuration repo and version and edx release follow this precedence:
# 1) PR settings. 2) WatchedFork settings. 3) instance model defaults
instance.configuration_source_repo_url = pr.get_extra_setting(
'edx_ansible_source_repo',
default=((self.watched_fork
and self.watched_fork.configuration_source_repo_url)
or instance.configuration_source_repo_url))
instance.configuration_version = pr.get_extra_setting(
'configuration_version',
default=((self.watched_fork
and self.watched_fork.configuration_version)
or instance.configuration_version))
instance.openedx_release = pr.get_extra_setting(
'openedx_release',
default=((self.watched_fork and self.watched_fork.openedx_release)
or instance.openedx_release))
# Save atomically. (because if the instance gets created but self.instance failed to
# update, then any subsequent call to update_instance_from_pr() would try to create
# another instance, which would fail due to unique domain name constraints.)
with transaction.atomic():
instance.save()
if not self.instance:
self.instance = instance
self.save(update_fields=["instance"])
class LoadBalancingServer(ValidateModelMixin, TimeStampedModel):
"""
A model representing a configured load-balancing server.
"""
objects = LoadBalancingServerManager()
domain = models.CharField(max_length=100, unique=True)
# The username used to ssh into the server
ssh_username = models.CharField(max_length=32)
# Whether new backends can be assigned to this load-balancing server
accepts_new_backends = models.BooleanField(default=True)
# A random postfix appended to the haproxy configuration file names to avoid clashes between
# multiple instance managers (or multiple concurrently running integration tests) sharing the
# same load balancer.
fragment_name_postfix = models.CharField(
max_length=8,
blank=True,
default=functools.partial(generate_fragment_name, length=8),
)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.logger = ModelLoggerAdapter(logger, {'obj': self})
def __str__(self):
return self.domain
def get_log_message_annotation(self):
"""
Annotate log messages for the load-balancing server.
"""
return "load_balancer={} ({!s:.15})".format(self.pk, self.domain)
def get_instances(self):
"""
Yield all instances configured to use this load balancer.
"""
# Local import due to avoid problems with circular dependencies.
from instance.models.mixins.load_balanced import LoadBalancedInstance
for field in self._meta.get_fields():
if field.one_to_many and issubclass(field.related_model, LoadBalancedInstance):
yield from getattr(self, field.get_accessor_name()).iterator()
def get_configuration(self, triggering_instance_id=None):
"""
Collect the backend maps and configuration fragments from all associated instances.
This function also appends fragment_name_postfix to all backend names to avoid name clashes
between multiple instance managers using the same load balancer (e.g. for the integration
tests).
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map = []
backend_conf = []
for instance in self.get_instances():
triggered_by_instance = instance.ref.pk == triggering_instance_id
map_entries, conf_entries = instance.get_load_balancer_configuration(
triggered_by_instance
)
backend_map.extend(
" ".join([domain.lower(), backend + self.fragment_name_postfix])
for domain, backend in map_entries
)
backend_conf.extend(
"backend {}\n{}\n".format(backend + self.fragment_name_postfix, conf)
for backend, conf in conf_entries
)
return "\n".join(backend_map), "\n".join(backend_conf)
def get_ansible_vars(self, triggering_instance_id=None):
"""
Render the configuration script to be executed on the load balancer.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map, backend_conf = self.get_configuration(triggering_instance_id)
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
return (
"FRAGMENT_NAME: {fragment_name}\n"
"BACKEND_CONFIG_FRAGMENT: |\n"
"{backend_conf}\n"
"BACKEND_MAP_FRAGMENT: |\n"
"{backend_map}\n"
).format(
fragment_name=fragment_name,
backend_conf=textwrap.indent(backend_conf, " "),
backend_map=textwrap.indent(backend_map, " "),
)
def run_playbook(self, ansible_vars):
"""
Run the playbook to perform the server reconfiguration.
This is factored out into a separate method so it can be mocked out in the tests.
"""
playbook_path = pathlib.Path(settings.SITE_ROOT) / "playbooks/load_balancer_conf/load_balancer_conf.yml"
returncode = ansible.capture_playbook_output(
requirements_path=str(playbook_path.parent / "requirements.txt"),
inventory_str=self.domain,
vars_str=ansible_vars,
playbook_path=str(playbook_path),
username=self.ssh_username,
logger_=self.logger,
)
if returncode != 0:
self.logger.error("Playbook to reconfigure load-balancing server %s failed.", self)
raise ReconfigurationFailed
def _configuration_lock(self):
"""
A Redis lock to protect reconfigurations of this load balancer instance.
"""
return cache.lock("load_balancer_reconfigure:{}".format(self.domain), timeout=900)
def reconfigure(self, triggering_instance_id=None):
"""
Regenerate the configuration fragments on the load-balancing server.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
self.logger.info("Reconfiguring load-balancing server %s", self.domain)
with self._configuration_lock():
self.run_playbook(self.get_ansible_vars(triggering_instance_id))
def deconfigure(self):
"""
Remove the configuration fragment from the load-balancing server.
"""
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
with self._configuration_lock():
self.run_playbook(
"FRAGMENT_NAME: {fragment_name}\nREMOVE_FRAGMENT: True".format(fragment_name=fragment_name)
)
def delete(self, *args, **kwargs):
"""
Delete the LoadBalancingServer from the database.
"""
self.deconfigure()
super().delete(*args, **kwargs)
class LoadBalancingServer(ValidateModelMixin, TimeStampedModel):
"""
A model representing a configured load-balancing server.
"""
objects = LoadBalancingServerManager()
domain = models.CharField(max_length=100, unique=True)
ssh_username = models.CharField(
max_length=32,
help_text='The username used to SSH into the server.'
)
accepts_new_backends = models.BooleanField(
default=False,
help_text='Whether new backends can be assigned to this load-balancing server.'
)
fragment_name_postfix = models.CharField(
max_length=8,
blank=True,
default=functools.partial(generate_fragment_name, length=8),
help_text=(
'A random postfix appended to the haproxy configuration file names to avoid clashes between '
'multiple instance managers (or multiple concurrently running integration tests) sharing the '
'same load balancer.'
)
)
configuration_version = models.PositiveIntegerField(
default=1,
help_text=(
'The current version of configuration for this load balancer. '
'The version value is the total number of requests ever made to reconfigure the load balancer.'
)
)
deployed_configuration_version = models.PositiveIntegerField(
default=1,
help_text=(
'The currently active configuration version of the load balancer. '
'If it is less than the configuration version, the load balancer is dirty. '
'If it is equal to it, then no new reconfiguration is currently required.'
)
)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.logger = ModelLoggerAdapter(logger, {'obj': self})
def __str__(self):
return self.domain
def get_log_message_annotation(self):
"""
Annotate log messages for the load-balancing server.
"""
return "load_balancer={} ({!s:.15})".format(self.pk, self.domain)
def get_instances(self):
"""
Yield all instances configured to use this load balancer.
"""
# Local import due to avoid problems with circular dependencies.
from instance.models.mixins.load_balanced import LoadBalancedInstance
for field in self._meta.get_fields():
if field.one_to_many and issubclass(field.related_model, LoadBalancedInstance):
yield from getattr(self, field.get_accessor_name()).iterator()
def get_configuration(self, triggering_instance_id=None):
"""
Collect the backend maps and configuration fragments from all associated instances.
This function also appends fragment_name_postfix to all backend names to avoid name clashes
between multiple instance managers using the same load balancer (e.g. for the integration
tests).
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map = []
backend_conf = []
for instance in self.get_instances():
triggered_by_instance = instance.ref.pk == triggering_instance_id
map_entries, conf_entries = instance.get_load_balancer_configuration(
triggered_by_instance
)
backend_map.extend(
" ".join([domain.lower(), backend + self.fragment_name_postfix])
for domain, backend in map_entries
)
backend_conf.extend(
"backend {}\n{}\n".format(backend + self.fragment_name_postfix, conf)
for backend, conf in conf_entries
)
return "\n".join(backend_map), "\n".join(backend_conf)
def get_ansible_vars(self, triggering_instance_id=None):
"""
Render the configuration script to be executed on the load balancer.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
"""
backend_map, backend_conf = self.get_configuration(triggering_instance_id)
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
return (
"FRAGMENT_NAME: {fragment_name}\n"
"BACKEND_CONFIG_FRAGMENT: |\n"
"{backend_conf}\n"
"BACKEND_MAP_FRAGMENT: |\n"
"{backend_map}\n"
).format(
fragment_name=fragment_name,
backend_conf=textwrap.indent(backend_conf, " "),
backend_map=textwrap.indent(backend_map, " "),
)
def run_playbook(self, ansible_vars):
"""
Run the playbook to perform the server reconfiguration.
This is factored out into a separate method so it can be mocked out in the tests.
"""
playbook_path = pathlib.Path(settings.SITE_ROOT) / "playbooks/load_balancer_conf/load_balancer_conf.yml"
returncode = ansible.capture_playbook_output(
requirements_path=str(playbook_path.parent / "requirements.txt"),
inventory_str=self.domain,
vars_str=ansible_vars,
playbook_path=str(playbook_path),
username=self.ssh_username,
logger_=self.logger,
)
if returncode != 0:
self.logger.error("Playbook to reconfigure load-balancing server %s failed.", self)
raise ReconfigurationFailed
def reconfigure(self, triggering_instance_id=None, mark_dirty=True):
"""
Regenerate the configuration fragments on the load-balancing server.
The triggering_instance_id indicates the id of the instance reference that initiated the
reconfiguration of the load balancer.
The mark_dirty flag indicates whether the LB configuration should be marked as dirty. If
this method is called because the configuration changed, the flag should be set to True (the
default). If this method is called because the LB was marked dirty earlier, the flag
should be set to False.
"""
if mark_dirty:
# We need to use an F expression here. The problem is not other processes trying to
# increase this counter concurrently – that wouldn't matter, since we don't care whether
# we increase this counter by one or by two, since both marks the LB as dirty. However, if
# another process is making a completely unrelated change to the LB object we might lose
# the increment altogether.
LoadBalancingServer.objects.filter(pk=self.pk).update(
configuration_version=models.F("configuration_version") + 1
)
try:
with self._configuration_lock(blocking=False):
# Memorize the configuration version, in case new threads change it.
self.refresh_from_db()
candidate_configuration_version = self.configuration_version
self.logger.info("Reconfiguring load-balancing server %s", self.domain)
self.run_playbook(self.get_ansible_vars(triggering_instance_id))
LoadBalancingServer.objects.filter(pk=self.pk).update(
deployed_configuration_version=candidate_configuration_version
)
self.refresh_from_db()
except OtherReconfigurationInProgress:
pass
def deconfigure(self):
"""
Remove the configuration fragment from the load-balancing server.
"""
self.logger.info("Deconfiguring load-balancing server %s", self.domain)
fragment_name = settings.LOAD_BALANCER_FRAGMENT_NAME_PREFIX + self.fragment_name_postfix
with self._configuration_lock():
self.run_playbook(
"FRAGMENT_NAME: {fragment_name}\nREMOVE_FRAGMENT: True".format(fragment_name=fragment_name)
)
def delete(self, *args, **kwargs):
"""
Delete the LoadBalancingServer from the database.
"""
self.deconfigure()
super().delete(*args, **kwargs)
@contextlib.contextmanager
def _configuration_lock(self, *, blocking=True):
"""
A Redis lock to protect reconfigurations of this load balancer instance.
"""
lock = cache.lock(
"load_balancer_reconfigure:{}".format(self.domain),
timeout=settings.REDIS_LOCK_TIMEOUT,
)
if not lock.acquire(blocking):
raise OtherReconfigurationInProgress
try:
yield lock
finally:
lock.release()