def execute(self, action, actionargs=None, vs=None, rs=None):
"""
Execute an action.
"""
if action not in [
"enable", "disable", "operenable", "operdisable", "enableall",
"disableall"
]:
yield None
return
v, httpclass, rip, port = self.parse(vs, rs)
if rip is None:
yield {}
return
orip = ip2oid(rip)
if action == "enableall" or action == "disableall":
d = defer.waitForDeferred(
self.proxy.set(
(self.oids['ltmNodeAddrNewSessionEnable'], orip),
(action == "enableall") and 2 or 1))
yield d
d.getResult()
yield True
return
# Get pool
ov = str2oid(v)
if httpclass is None:
p = defer.waitForDeferred(
self.cache_or_get(('ltmVirtualServDefaultPool', ov)))
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(
self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
op = str2oid(p)
d = defer.waitForDeferred(
self.proxy.set(
(self.oids['ltmPoolMemberNewSessionEnable'], op, orip, port),
action.endswith("enable") and 2 or 1))
yield d
d.getResult()
yield True
return
def execute(self, action, actionargs=None, vs=None, rs=None):
"""
Execute an action.
"""
if action not in ["enable", "disable", "operenable", "operdisable",
"enableall", "disableall"]:
yield None
return
v, httpclass, rip, port = self.parse(vs, rs)
if rip is None:
yield {}
return
orip = ip2oid(rip)
if action == "enableall" or action == "disableall":
d = defer.waitForDeferred(
self.proxy.set((self.oids['ltmNodeAddrNewSessionEnable'], orip),
(action == "enableall") and 2 or 1))
yield d
d.getResult()
yield True
return
# Get pool
ov = str2oid(v)
if httpclass is None:
p = defer.waitForDeferred(self.cache_or_get(('ltmVirtualServDefaultPool', ov)))
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
op = str2oid(p)
d = defer.waitForDeferred(
self.proxy.set((self.oids['ltmPoolMemberNewSessionEnable'],
op, orip, port),
action.endswith("enable") and 2 or 1))
yield d
d.getResult()
yield True
return
def process_rs(self, owner, content, service, backup=False):
"""
Process data for a given virtual server and real server.
@param service: service name
@param backup: C{False} or a string representing backup position
C{None} is we don't know if it is a backup or not
@return: a deferred C{IRealServer} or None
"""
oservice = str2oid(service)
# Retrieve some data if needed:
oids = []
for o in self.oids:
if o.startswith("apSvc"):
oids.append((o, oservice))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# Is it a backup?
if backup is None:
oowner = str2oid(owner)
ocontent = str2oid(content)
for b in ["primary", "second"]:
s = defer.waitForDeferred(
self.cache_or_get(('apCnt%sSorryServer' % b.capitalize(),
oowner, ocontent)))
yield s
s = s.getResult()
if s and s == service:
backup = b
break
if backup is None:
backup = False
# Build the real server
rip = self.cache(('apSvcIPAddress', oservice))
rport = self.cache(('apSvcPort', oservice))
protocol = self.protocols[
self.cache(('apSvcIPProtocol', oservice))]
state = self.states[
self.cache(('apSvcState', oservice))]
if not backup:
weight = self.cache(('apSvcWeight', oservice))
rs = RealServer(service, rip, rport, protocol, weight, state)
else:
rs = SorryServer(service, rip, rport, protocol, state)
rs.extra["backup type"] = backup
rs.extra["KAL type"] = self.kals[
self.cache(('apSvcKALType', oservice))]
for key, oid in [
('KAL frequency', 'apSvcKALFrequency'),
('KAL max failure', 'apSvcKALMaxFailure'),
('KAL retry period', 'apSvcKALRetryPeriod'),
('KAL URI', 'apSvcKALUri'),
('KAL port', 'apSvcKALPort')
]:
try:
rs.extra[key] = self.cache((oid, oservice))
except KeyError:
pass
yield rs
return
def process_vs(self, owner, content):
"""
Process data for a given virtual server when no real server is provided
@param owner: owner of the content
@param content: content name
@return: a deferred C{IVirtualServer} or None
"""
oowner = str2oid(owner)
ocontent = str2oid(content)
# Retrieve some data if needed
oids = []
for o in self.oids:
if o.startswith("apCnt") and not o.startswith("apCntsvc"):
oids.append((o, oowner, ocontent))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# Let's build our virtual server
vip = "%s:%d" % tuple(self.cache(('apCntIPAddress', oowner, ocontent),
('apCntPort', oowner, ocontent)))
protocol = self.protocols[self.cache(('apCntIPProtocol', oowner, ocontent))]
mode = self.modes[self.cache(('apCntBalance', oowner, ocontent))]
vs = VirtualServer(content, vip, protocol, mode)
# Add some extra information
vs.extra["URL"] = self.cache(('apCntUrl', oowner, ocontent))
vs.extra["sticky"] = self.sticky[
self.cache(('apCntSticky', oowner, ocontent))]
vs.extra["virtual server status"] = self.status[
self.cache(('apCntEnable', oowner, ocontent))] and "up" or "down"
vs.extra["persistence"] = self.status[
self.cache(('apCntPersistence', oowner, ocontent))] and "enabled" or "disabled"
vs.extra["content type"] = self.contents[
self.cache(('apCntContentType', oowner, ocontent))]
# Find and attach real servers
if not self.is_cached(('apCntsvcSvcName', oowner, ocontent)):
services = defer.waitForDeferred(
self.proxy.walk("%s.%s.%s" % (self.oids['apCntsvcSvcName'],
oowner, ocontent)))
yield services
services.getResult()
for r in self.cache(('apCntsvcSvcName', oowner, ocontent)):
service = oid2str(r)
rs = defer.waitForDeferred(self.process_rs(owner, content, service))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers[service] = rs
# Add backups
for backup in ["primary", "second"]:
service = self.cache(('apCnt%sSorryServer' % backup.capitalize(),
oowner, ocontent))
if not service: continue
rs = defer.waitForDeferred(self.process_rs(owner, content, service, backup))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers[service] = rs
yield vs
return
def process_rs(self, v, httpclass, rip, port):
"""
Process data for a given virtual server and real server.
@param v: virtual server
@param httpclass: HTTP class (or C{None} for default pool)
@param rip: real IP
@param port: port
"""
# Retrieve some data if needed:
ov = str2oid(v)
orip = ip2oid(rip)
if httpclass is None:
p = defer.waitForDeferred(self.cache_or_get(('ltmVirtualServDefaultPool', ov)))
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
op = str2oid(p)
oids = []
for o in self.oids:
if o.startswith("ltmPoolMbr") or o.startswith("ltmPoolMember"):
oids.append((o, op, orip, port))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
oids = []
for o in self.oids:
if o.startswith("ltmNodeAddr"):
oids.append((o, orip))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
name = self.cache(('ltmNodeAddrScreenName', orip))
protocol = defer.waitForDeferred(self.get_protocol(ov))
yield protocol
protocol = protocol.getResult()
weight = self.cache(('ltmPoolMemberWeight', op, orip, port))
avail, enabled, session = self.cache(
('ltmPoolMbrStatusAvailState', op, orip, port),
('ltmPoolMbrStatusEnabledState', op, orip, port),
('ltmPoolMemberSessionStatus', op, orip, port))
if session != 1 or self.enabledstates[enabled] != "enabled":
state = "disabled"
else:
state = self.availstates[avail]
rs = RealServer(name, rip, port, protocol, weight, state)
rs.extra["detailed reason"] = self.cache(('ltmPoolMbrStatusDetailReason',
op, orip, port))
rs.extra["monitor rule"] = self.cache(('ltmPoolMemberMonitorRule',
op, orip, port))
# Actions
if self.proxy.writable:
# ltmPoolMemberNewSessionEnable == 1 means user disabled
if self.cache(('ltmPoolMemberNewSessionEnable', op, orip, port)) != 1:
rs.actions['disable'] = 'Disable (permanent)'
else:
rs.actions['enable'] = 'Enable (permanent)'
if self.cache(('ltmNodeAddrNewSessionEnable', orip)) != 1:
rs.actions['disableall'] = 'Disable globally (permanent)'
else:
rs.actions['enableall'] = 'Enable globally (permanent)'
yield rs
return
def process_vs(self, v, httpclass):
"""
Process data for a given virtual server when no real server is provided
@param v: virtual server
@param httpclass: HTTP class to use (or C{None} for default pool) to select pool
@return: a maybe deferred C{IVirtualServer}
"""
ov = str2oid(v)
# Retrieve some data if needed
oids = []
for o in self.oids:
if o.startswith("ltmVirtualServ") or o.startswith("ltmVs"):
if not o.startswith("ltmVirtualServProfile"):
oids.append((o, ov))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# IPv6 or IPv4 virtual server
if self.cache(('ltmVirtualServAddrType', ov)) not in [1, 2]:
log.msg("In %r, unknown address type for virtual server %s, skip it" % (self.lb.name, v))
yield None
return
# Get pool
if httpclass is None:
p = self.cache(('ltmVirtualServDefaultPool', ov))
if not p:
log.msg("In %r, no pool for %s, skip it" % (self.lb.name, v))
yield None
return
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
if not p:
log.msg("In %r, no pool for %s (class %s), skip it" % (self.lb.name, v, httpclass))
yield None
return
op = str2oid(p)
oids = []
for o in self.oids:
if o.startswith("ltmPool") and not o.startswith("ltmPoolMbr") and \
not o.startswith("ltmPoolMember"):
oids.append((o, op))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
if self.cache(('ltmVirtualServAddrType', ov)) == 1:
vip = "%s:%d" % (socket.inet_ntop(socket.AF_INET,
self.cache(('ltmVirtualServAddr', ov))),
self.cache(('ltmVirtualServPort', ov)))
else:
vip = "[%s]:%d" % (socket.inet_ntop(socket.AF_INET6,
self.cache(('ltmVirtualServAddr', ov))),
self.cache(('ltmVirtualServPort', ov)))
protocol = defer.waitForDeferred(self.get_protocol(ov))
yield protocol
protocol = protocol.getResult()
mode = self.modes[self.cache(('ltmPoolLbMode', op))]
vs = VirtualServer(httpclass is None and v or ("%s;%s" % (v, httpclass)),
vip, protocol, mode)
if httpclass:
vs.extra["http class"] = httpclass
vs.extra["vs availability state"] = \
self.availstates[self.cache(('ltmVsStatusAvailState', ov))]
vs.extra["vs enabled state"] = \
self.enabledstates[self.cache(('ltmVsStatusEnabledState', ov))]
vs.extra["virtual server detailed reason"] = \
self.cache(('ltmVsStatusDetailReason', ov))
vs.extra["address translation"] = \
self.cache(('ltmVirtualServTranslateAddr', ov)) == 1 and "enabled" or "disabled"
vs.extra["pool name"] = p
vs.extra["pool availability state"] = \
self.availstates[self.cache(('ltmPoolStatusAvailState', op))]
vs.extra["pool enabled state"] = \
self.enabledstates[self.cache(('ltmPoolStatusEnabledState', op))]
vs.extra["pool detailed reason"] = \
self.cache(('ltmPoolStatusDetailReason', op))
# Find and attach real servers
if not self.is_cached(('ltmPoolMbrStatusAvailState', op)):
for o in self.oids:
if o.startswith('ltmPoolMbr') or o.startswith('ltmPoolMember'):
# F5 is buggy here, we need to walk all pool members
# pm = defer.waitForDeferred(
# self.proxy.walk("%s.%s" % (self.oids[o], op)))
pm = defer.waitForDeferred(
self.proxy.walk(self.oids[o]))
yield pm
pm.getResult()
if not self.is_cached(('ltmPoolMbrStatusAvailState', op)):
print "pool %s is empty..." % p
yield None
return
for r in self.cache(('ltmPoolMbrStatusAvailState', op)):
rip = socket.inet_ntop(r[0] == 1 and socket.AF_INET or socket.AF_INET6,
struct.pack("B"*r[1], *r[-(r[1]+1):-1]))
port = r[-1]
rs = defer.waitForDeferred(self.process_rs(v, httpclass, rip, port))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers["%s,%d" % (rip, port)] = rs
yield vs
return
def process_rs(self, owner, content, service, backup=False):
"""
Process data for a given virtual server and real server.
@param service: service name
@param backup: C{False} or a string representing backup position
C{None} is we don't know if it is a backup or not
@return: a deferred C{IRealServer} or None
"""
oservice = str2oid(service)
# Retrieve some data if needed:
oids = []
for o in self.oids:
if o.startswith("apSvc"):
oids.append((o, oservice))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# Is it a backup?
if backup is None:
oowner = str2oid(owner)
ocontent = str2oid(content)
for b in ["primary", "second"]:
s = defer.waitForDeferred(
self.cache_or_get(('apCnt%sSorryServer' % b.capitalize(),
oowner, ocontent)))
yield s
s = s.getResult()
if s and s == service:
backup = b
break
if backup is None:
backup = False
# Build the real server
rip = self.cache(('apSvcIPAddress', oservice))
rport = self.cache(('apSvcPort', oservice))
protocol = self.protocols[self.cache(('apSvcIPProtocol', oservice))]
state = self.states[self.cache(('apSvcState', oservice))]
if not backup:
weight = self.cache(('apSvcWeight', oservice))
rs = RealServer(service, rip, rport, protocol, weight, state)
else:
rs = SorryServer(service, rip, rport, protocol, state)
rs.extra["backup type"] = backup
rs.extra["KAL type"] = self.kals[self.cache(
('apSvcKALType', oservice))]
for key, oid in [('KAL frequency', 'apSvcKALFrequency'),
('KAL max failure', 'apSvcKALMaxFailure'),
('KAL retry period', 'apSvcKALRetryPeriod'),
('KAL URI', 'apSvcKALUri'),
('KAL port', 'apSvcKALPort')]:
try:
rs.extra[key] = self.cache((oid, oservice))
except KeyError:
pass
yield rs
return
def process_vs(self, owner, content):
"""
Process data for a given virtual server when no real server is provided
@param owner: owner of the content
@param content: content name
@return: a deferred C{IVirtualServer} or None
"""
oowner = str2oid(owner)
ocontent = str2oid(content)
# Retrieve some data if needed
oids = []
for o in self.oids:
if o.startswith("apCnt") and not o.startswith("apCntsvc"):
oids.append((o, oowner, ocontent))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# Let's build our virtual server
vip = "%s:%d" % tuple(
self.cache(('apCntIPAddress', oowner, ocontent),
('apCntPort', oowner, ocontent)))
protocol = self.protocols[self.cache(
('apCntIPProtocol', oowner, ocontent))]
mode = self.modes[self.cache(('apCntBalance', oowner, ocontent))]
vs = VirtualServer(content, vip, protocol, mode)
# Add some extra information
vs.extra["URL"] = self.cache(('apCntUrl', oowner, ocontent))
vs.extra["sticky"] = self.sticky[self.cache(
('apCntSticky', oowner, ocontent))]
vs.extra["virtual server status"] = self.status[self.cache(
('apCntEnable', oowner, ocontent))] and "up" or "down"
vs.extra["persistence"] = self.status[self.cache(
('apCntPersistence', oowner,
ocontent))] and "enabled" or "disabled"
vs.extra["content type"] = self.contents[self.cache(
('apCntContentType', oowner, ocontent))]
# Find and attach real servers
if not self.is_cached(('apCntsvcSvcName', oowner, ocontent)):
services = defer.waitForDeferred(
self.proxy.walk(
"%s.%s.%s" %
(self.oids['apCntsvcSvcName'], oowner, ocontent)))
yield services
services.getResult()
for r in self.cache(('apCntsvcSvcName', oowner, ocontent)):
service = oid2str(r)
rs = defer.waitForDeferred(self.process_rs(owner, content,
service))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers[service] = rs
# Add backups
for backup in ["primary", "second"]:
service = self.cache(
('apCnt%sSorryServer' % backup.capitalize(), oowner, ocontent))
if not service: continue
rs = defer.waitForDeferred(
self.process_rs(owner, content, service, backup))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers[service] = rs
yield vs
return
def process_rs(self, v, httpclass, rip, port):
"""
Process data for a given virtual server and real server.
@param v: virtual server
@param httpclass: HTTP class (or C{None} for default pool)
@param rip: real IP
@param port: port
"""
# Retrieve some data if needed:
ov = str2oid(v)
orip = ip2oid(rip)
if httpclass is None:
p = defer.waitForDeferred(
self.cache_or_get(('ltmVirtualServDefaultPool', ov)))
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(
self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
op = str2oid(p)
oids = []
for o in self.oids:
if o.startswith("ltmPoolMbr") or o.startswith("ltmPoolMember"):
oids.append((o, op, orip, port))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
oids = []
for o in self.oids:
if o.startswith("ltmNodeAddr"):
oids.append((o, orip))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
name = self.cache(('ltmNodeAddrScreenName', orip))
protocol = defer.waitForDeferred(self.get_protocol(ov))
yield protocol
protocol = protocol.getResult()
weight = self.cache(('ltmPoolMemberWeight', op, orip, port))
avail, enabled, session = self.cache(
('ltmPoolMbrStatusAvailState', op, orip, port),
('ltmPoolMbrStatusEnabledState', op, orip, port),
('ltmPoolMemberSessionStatus', op, orip, port))
if session != 1 or self.enabledstates[enabled] != "enabled":
state = "disabled"
else:
state = self.availstates[avail]
rs = RealServer(name, rip, port, protocol, weight, state)
rs.extra["detailed reason"] = self.cache(
('ltmPoolMbrStatusDetailReason', op, orip, port))
rs.extra["monitor rule"] = self.cache(
('ltmPoolMemberMonitorRule', op, orip, port))
# Actions
if self.proxy.writable:
# ltmPoolMemberNewSessionEnable == 1 means user disabled
if self.cache(
('ltmPoolMemberNewSessionEnable', op, orip, port)) != 1:
rs.actions['disable'] = 'Disable (permanent)'
else:
rs.actions['enable'] = 'Enable (permanent)'
if self.cache(('ltmNodeAddrNewSessionEnable', orip)) != 1:
rs.actions['disableall'] = 'Disable globally (permanent)'
else:
rs.actions['enableall'] = 'Enable globally (permanent)'
yield rs
return
def process_vs(self, v, httpclass):
"""
Process data for a given virtual server when no real server is provided
@param v: virtual server
@param httpclass: HTTP class to use (or C{None} for default pool) to select pool
@return: a maybe deferred C{IVirtualServer}
"""
ov = str2oid(v)
# Retrieve some data if needed
oids = []
for o in self.oids:
if o.startswith("ltmVirtualServ") or o.startswith("ltmVs"):
if not o.startswith("ltmVirtualServProfile"):
oids.append((o, ov))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
# IPv6 or IPv4 virtual server
if self.cache(('ltmVirtualServAddrType', ov)) not in [1, 2]:
log.msg(
"In %r, unknown address type for virtual server %s, skip it" %
(self.lb.name, v))
yield None
return
# Get pool
if httpclass is None:
p = self.cache(('ltmVirtualServDefaultPool', ov))
if not p:
log.msg("In %r, no pool for %s, skip it" % (self.lb.name, v))
yield None
return
else:
oc = str2oid(httpclass)
p = defer.waitForDeferred(
self.cache_or_get(('ltmHttpClassPoolName', oc)))
yield p
p = p.getResult()
if not p:
log.msg("In %r, no pool for %s (class %s), skip it" %
(self.lb.name, v, httpclass))
yield None
return
op = str2oid(p)
oids = []
for o in self.oids:
if o.startswith("ltmPool") and not o.startswith("ltmPoolMbr") and \
not o.startswith("ltmPoolMember"):
oids.append((o, op))
oids = tuple(oids)
c = defer.waitForDeferred(self.cache_or_get(*oids))
yield c
c.getResult()
if self.cache(('ltmVirtualServAddrType', ov)) == 1:
vip = "%s:%d" % (socket.inet_ntop(
socket.AF_INET, self.cache(('ltmVirtualServAddr', ov))),
self.cache(('ltmVirtualServPort', ov)))
else:
vip = "[%s]:%d" % (socket.inet_ntop(
socket.AF_INET6, self.cache(('ltmVirtualServAddr', ov))),
self.cache(('ltmVirtualServPort', ov)))
protocol = defer.waitForDeferred(self.get_protocol(ov))
yield protocol
protocol = protocol.getResult()
mode = self.modes[self.cache(('ltmPoolLbMode', op))]
vs = VirtualServer(
httpclass is None and v or ("%s;%s" % (v, httpclass)), vip,
protocol, mode)
if httpclass:
vs.extra["http class"] = httpclass
vs.extra["vs availability state"] = \
self.availstates[self.cache(('ltmVsStatusAvailState', ov))]
vs.extra["vs enabled state"] = \
self.enabledstates[self.cache(('ltmVsStatusEnabledState', ov))]
vs.extra["virtual server detailed reason"] = \
self.cache(('ltmVsStatusDetailReason', ov))
vs.extra["address translation"] = \
self.cache(('ltmVirtualServTranslateAddr', ov)) == 1 and "enabled" or "disabled"
vs.extra["pool name"] = p
vs.extra["pool availability state"] = \
self.availstates[self.cache(('ltmPoolStatusAvailState', op))]
vs.extra["pool enabled state"] = \
self.enabledstates[self.cache(('ltmPoolStatusEnabledState', op))]
vs.extra["pool detailed reason"] = \
self.cache(('ltmPoolStatusDetailReason', op))
# Find and attach real servers
if not self.is_cached(('ltmPoolMbrStatusAvailState', op)):
for o in self.oids:
if o.startswith('ltmPoolMbr') or o.startswith('ltmPoolMember'):
# F5 is buggy here, we need to walk all pool members
# pm = defer.waitForDeferred(
# self.proxy.walk("%s.%s" % (self.oids[o], op)))
pm = defer.waitForDeferred(self.proxy.walk(self.oids[o]))
yield pm
pm.getResult()
if not self.is_cached(('ltmPoolMbrStatusAvailState', op)):
print "pool %s is empty..." % p
yield None
return
for r in self.cache(('ltmPoolMbrStatusAvailState', op)):
rip = socket.inet_ntop(
r[0] == 1 and socket.AF_INET or socket.AF_INET6,
struct.pack("B" * r[1], *r[-(r[1] + 1):-1]))
port = r[-1]
rs = defer.waitForDeferred(self.process_rs(v, httpclass, rip,
port))
yield rs
rs = rs.getResult()
if rs is not None:
vs.realservers["%s,%d" % (rip, port)] = rs
yield vs
return
