Joshua Boniface
31f252ad9b
Implements the ability for a client to watch almost-live domain
console logs from the hypervisors. It does this using a deque-based
"tail -f" mechanism (with a configurable buffer per-VM) that watches
the domain console logfile in the (configurable) directory every
half-second. It then stores the current buffer in Zookeeper when
changed, where a client can then request it, either as a static piece
of text in the `less` pager, or via a similar "tail -f" functionality
implemented using fixed line splitting and comparison to provide a
generally-seamless output.
Enabling this feature requires each guest VM to implement a Libvirt
serial log and write its (text) console to it, for example using the
default logging directory:
```
<serial type='pty'>
<log file='/var/log/libvirt/vmname.log' append='off'/>
<serial>
```
The append mode can be either on or off; on grows files unbounded,
off causes the log (and hence the PVC log data) to be truncated on
initial VM startup from offline. The administrator must choose how
they best want to handle this until Libvirt implements their own
clog-type logging format.
95 lines
2.8 KiB
Python
95 lines
2.8 KiB
Python
#!/usr/bin/env python3
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# zkhandler.py - Secure versioned ZooKeeper updates
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# Part of the Parallel Virtual Cluster (PVC) system
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#
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# Copyright (C) 2018 Joshua M. Boniface <joshua@boniface.me>
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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#
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###############################################################################
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import kazoo.client
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import uuid
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#import pvcd.log as log
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# Child list function
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def listchildren(zk_conn, key):
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children = zk_conn.get_children(key)
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return children
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# Key deletion function
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def deletekey(zk_conn, key, recursive=True):
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zk_conn.delete(key, recursive=recursive)
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# Data read function
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def readdata(zk_conn, key):
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data_raw = zk_conn.get(key)
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data = data_raw[0].decode('utf8')
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meta = data_raw[1]
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return data
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# Data write function
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def writedata(zk_conn, kv):
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# Start up a transaction
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zk_transaction = zk_conn.transaction()
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# Proceed one KV pair at a time
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for key in sorted(kv):
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data = kv[key]
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if not data:
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data = ''
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# Check if this key already exists or not
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if not zk_conn.exists(key):
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# We're creating a new key
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zk_transaction.create(key, str(data).encode('utf8'))
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else:
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# We're updating a key with version validation
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orig_data = zk_conn.get(key)
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version = orig_data[1].version
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# Set what we expect the new version to be
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new_version = version + 1
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# Update the data
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zk_transaction.set_data(key, str(data).encode('utf8'))
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# Set up the check
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try:
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zk_transaction.check(key, new_version)
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except TypeError:
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print('Zookeeper key "{}" does not match expected version'.format(key))
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return False
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# Commit the transaction
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try:
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zk_transaction.commit()
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return True
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except Exception:
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return False
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# Write lock function
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def writelock(zk_conn, key):
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lock_id = str(uuid.uuid1())
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lock = zk_conn.WriteLock('{}'.format(key), lock_id)
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return lock
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# Read lock function
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def readlock(zk_conn, key):
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lock_id = str(uuid.uuid1())
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lock = zk_conn.ReadLock('{}'.format(key), lock_id)
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return lock
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