├── MANIFEST.in ├── .gitignore ├── CHANGELOG.rst ├── setup.py ├── gilmsg.py ├── README.rst └── LICENSE /MANIFEST.in: -------------------------------------------------------------------------------- 1 | include LICENSE 2 | include README.rst 3 | include CHANGELOG.rst 4 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | build 2 | dist 3 | *.egg* 4 | *.pyc 5 | *.pyo 6 | *.swp 7 | *.pdf 8 | _build 9 | html-output 10 | htmldoc 11 | _tweet-real.py 12 | htmldocs 13 | .coverage 14 | fedmsg/tests/test_certs/gpg/random_seed 15 | html-docs 16 | status 17 | .tox 18 | -------------------------------------------------------------------------------- /CHANGELOG.rst: -------------------------------------------------------------------------------- 1 | Changelog 2 | ========= 3 | 4 | 0.1.2 5 | ----- 6 | 7 | - Add license fulltext. `f2c5e8d56 `_ 8 | - Ship that stuff to PyPI. `ba08429d4 `_ 9 | 10 | 0.1.1 11 | ----- 12 | 13 | - Adjust "split here". `2a77c2b17 `_ 14 | -------------------------------------------------------------------------------- /setup.py: -------------------------------------------------------------------------------- 1 | # This file is part of gilmsg. 2 | # Copyright (C) 2015 Red Hat, Inc. 3 | # 4 | # gilmsg is free software; you can redistribute it and/or 5 | # modify it under the terms of the GNU Lesser General Public 6 | # License as published by the Free Software Foundation; either 7 | # version 2.1 of the License, or (at your option) any later version. 8 | # 9 | # gilmsg is distributed in the hope that it will be useful, 10 | # but WITHOUT ANY WARRANTY; without even the implied warranty of 11 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 | # Lesser General Public License for more details. 13 | # 14 | # You should have received a copy of the GNU Lesser General Public 15 | # License along with gilmsg; if not, write to the Free Software 16 | # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 0.1.2.15.0 USA 17 | # 18 | # Authors: Ralph Bean 19 | # 20 | 21 | try: 22 | from setuptools import setup 23 | except ImportError: 24 | from ez_setup import use_setuptools 25 | use_setuptools() 26 | from setuptools import setup 27 | 28 | f = open('README.rst') 29 | long_description = f.read().strip() 30 | long_description = long_description.split('split here', 1)[-1] 31 | f.close() 32 | 33 | 34 | install_requires = [ 35 | 'fedmsg', 36 | 'fedmsg[crypto]', 37 | 'fedmsg[consumers]', 38 | 'fedmsg[commands]', 39 | ] 40 | 41 | setup( 42 | name='gilmsg', 43 | version='0.1.2', 44 | description="A reliability layer on top of fedmsg", 45 | long_description=long_description, 46 | author='Ralph Bean', 47 | author_email='rbean@redhat.com', 48 | url='https://github.com/fedora-infra/gilmsg/', 49 | license='LGPLv2+', 50 | install_requires=install_requires, 51 | py_modules=['gilmsg'], 52 | include_package_data=True, 53 | zip_safe=False, 54 | entry_points={ 55 | 'console_scripts': [ 56 | "gilmsg-logger=gilmsg:logger_cli", 57 | ], 58 | }, 59 | ) 60 | -------------------------------------------------------------------------------- /gilmsg.py: -------------------------------------------------------------------------------- 1 | """ gilmsg - A reliability layer on top of fedmsg. 2 | 3 | See the README for documentation. 4 | https://github.com/fedora-infra/gilmsg/ 5 | 6 | Author: Ralph Bean 7 | License: LGPLv2+ 8 | 9 | """ 10 | 11 | 12 | import threading 13 | import time 14 | 15 | import logging 16 | log = logging.getLogger("fedmsg") 17 | logging.basicConfig() 18 | 19 | import fedmsg 20 | import fedmsg.commands.logger 21 | import fedmsg.consumers 22 | import fedmsg.crypto 23 | 24 | 25 | import pkg_resources 26 | gilmsg_version = pkg_resources.get_distribution('gilmsg').version 27 | 28 | __all__ = ['init', 'publish', 'tail_messages', 'Timeout'] 29 | 30 | # Passthrough. Just here for API compat. 31 | init = fedmsg.init 32 | 33 | 34 | class Timeout(Exception): 35 | pass 36 | 37 | 38 | class AckListener(threading.Thread): 39 | c = None 40 | msg_id = None 41 | expectations = None 42 | results = [] 43 | time_is_up = False 44 | 45 | 46 | def set_config(self, config): 47 | self.c = config 48 | 49 | def set_msg_id(self, msg_id): 50 | self.msg_id = msg_id 51 | 52 | def set_expectations(self, expectations): 53 | self.expectations = expectations 54 | 55 | def sanity_check(self): 56 | if not self.msg_id: 57 | raise ValueError("thread starting before msg_id was set") 58 | if not self.expectations: 59 | raise ValueError("thread starting before expectations was set") 60 | if not self.c: 61 | raise ValueError("thread starting before config was set") 62 | 63 | def die(self): 64 | self.time_is_up = True 65 | 66 | def run(self): 67 | self.sanity_check() 68 | ack_topic = '.'.join([ 69 | self.c['topic_prefix'], 70 | self.c['environment'], 71 | 'gilmsg.ack', 72 | ]) 73 | 74 | # Go into a loop, receiving gilmsg ACK messages from the fedmsg bus 75 | for n, e, t, msg in fedmsg.tail_messages(**self.c): 76 | 77 | # Did we run out of time? 78 | if self.time_is_up: 79 | return 80 | 81 | # Throw away anything that's not an ACK produced by a consumer. 82 | if t != ack_topic: 83 | continue 84 | 85 | # We should only know about ACKs. Is this an ACK for *ours*? 86 | if not msg['msg']['ack_msg_id'] == self.msg_id: 87 | continue 88 | 89 | # We can declare that multiple other systems *must* receive our 90 | # message. Write down who is acking this one. 91 | for signer in self.expectations: 92 | if not fedmsg.crypto.validate_signed_by(msg, signer, **self.c): 93 | continue 94 | self.results.append(signer) 95 | 96 | # Check to see if we collected all the pokemon. 97 | # If all the people that we wanted to get the message have sent 98 | # us ACKs for this message_id, then hooray! If not, go back into 99 | # tail_messages to wait for more ACKs. The clock is ticking.... 100 | if set(self.results) == set(self.expectations): 101 | return 102 | 103 | 104 | def publish(topic=None, msg=None, modname=None, 105 | recipients=None, 106 | ack_timeout=0.25, 107 | **kw): 108 | if not recipients: 109 | log.warn("Why use gilmsg if no recipients are specified? " 110 | "Just use fedmsg instead.") 111 | return fedmsg.publish(topic=topic, msg=msg, modname=modname, **kw) 112 | 113 | listener = AckListener() 114 | listener.set_config(kw) 115 | listener.set_expectations(recipients) 116 | 117 | def pre_fire_hook(msg): 118 | msg['gilmsg_version'] = gilmsg_version 119 | listener.set_msg_id(msg['msg_id']) 120 | listener.start() 121 | # Give the listener a good head start... 122 | time.sleep(kw['post_init_sleep'] * 2) 123 | 124 | fedmsg.publish( 125 | topic=topic, 126 | msg=msg, 127 | modname=modname, 128 | pre_fire_hook=pre_fire_hook, 129 | **kw 130 | ) 131 | 132 | listener.join(timeout=ack_timeout) 133 | if listener.isAlive(): 134 | listener.die() 135 | # Then the timeout expired and we haven't received our ACKs yet. 136 | raise Timeout("Received %i acks from %i of %i systems in %d seconds" % ( 137 | len(listener.results), 138 | len(set(listener.results)), 139 | len(set(recipients)), 140 | ack_timeout, 141 | )) 142 | else: 143 | # Hopefully everything went well? 144 | assert len(set(listener.results)) == len(set(recipients)), listener.results 145 | 146 | 147 | def _acknowledge(message, **config): 148 | if 'gilmsg_version' not in message: 149 | return 150 | ack = dict(ack_msg_id=message['msg_id']) 151 | fedmsg.publish(topic="ack", msg=ack, **config) 152 | 153 | 154 | def tail_messages(topic="", passive=False, **kw): 155 | for n, e, t, m in fedmsg.tail_messages(topic=topic, passive=passive, **kw): 156 | # Only acknowledge gilmsg messages to avoid catastrophic spam storm 157 | _acknowledge(m, **kw) 158 | yield n, e, t, m 159 | 160 | 161 | class GilmsgConsumer(fedmsg.consumers.FedmsgConsumer): 162 | """ Extend this to make your own robust consumers. """ 163 | def pre_consume(self, m): 164 | super(GilmsgConsumer, self).pre_consume(m) 165 | _acknowledge(m, **self.hub.config) 166 | 167 | 168 | class LoggerCommand(fedmsg.commands.logger.LoggerCommand): 169 | extra_args = fedmsg.commands.logger.LoggerCommand.extra_args + [ 170 | (['--recipients'], { 171 | 'dest': 'recipients', 172 | 'metavar': 'SIGNER', 173 | 'nargs': '+', 174 | 'help': 'Names on the certificates of some required recipients', 175 | }), 176 | (['--ack-timeout'], { 177 | 'dest': 'ack_timeout', 178 | 'metavar': 'SECONDS', 179 | 'default': 0.25, 180 | 'type': float, 181 | 'help': 'Number of seconds to wait for acknowledgement.', 182 | }), 183 | ] 184 | 185 | def _log_message(self, kw, message): 186 | if not self.config['recipients']: 187 | raise ValueError("'--recipients' is required.") 188 | 189 | if kw['json_input']: 190 | msg = fedmsg.encoding.loads(message) 191 | else: 192 | msg = {'log': message} 193 | 194 | # Use our publish function, not fedmsg's 195 | publish( 196 | msg=msg, 197 | **self.config) 198 | 199 | 200 | def logger_cli(): 201 | return LoggerCommand().execute() 202 | -------------------------------------------------------------------------------- /README.rst: -------------------------------------------------------------------------------- 1 | gilmsg 2 | ====== 3 | 4 | A reliability layer on top of fedmsg. 5 | 6 | .. split here 7 | 8 | What is "Reliability"? 9 | ---------------------- 10 | 11 | Every few months, a discussion comes up about *fedmsg reliability*. 12 | Typically, a team somewhere in the Fedora Project will be looking into how they 13 | can streamline their workflows by either using data from or sending data to the 14 | bus. We end up having a lengthy discussion in IRC until the matter gets settled. 15 | But that conversation gets lost in the ether of freenode and the *next* time a 16 | different team has the same questions we have to have the conversation over 17 | again. 18 | 19 | `fedmsg `_ is a set of python tools (one part library, one 20 | part framework) that we use around Fedora Infrastructure to enable system 21 | processes to publish and listen for messages. We typically call it our 22 | "message bus", but that is bad nomenclature; it doesn't accurately describe 23 | what is going on. When a process wants to publish fedmsg messages, it invokes 24 | ``fedmsg.publish(...)`` which reads in some configuration from disk, binds a 25 | socket to a port if it hasn't already, and writes the message there. When 26 | another process wants to consume fedmsg messages, it invokes 27 | ``fedmsg.tail_messages()`` (or registers itself with an already listening 28 | ``fedmsg-hub`` daemon) which then *connects* a socket to the bound port of the 29 | other process to ``recv`` the message(s). 30 | 31 | A little more detail now: the call to ``fedmsg.publish`` doesn't manage the 32 | socket binding and sending itself. It hands things off to zeromq which in 33 | turn hands things off to a number of worker threads it manages. Zeromq keeps 34 | an internal queue of messages it has been asked to send, which it sends as 35 | fast as it can. A key takeaway here is that it is "fire-and-forget": a web 36 | application that has been enabled to publish fedmsg messages will ask the fedmsg 37 | library to do so, and then walk away to finish its database transactions or do 38 | whatever other work it is intended to do. fedmsg (really zeromq here) opaquely 39 | sends the message as soon as it has a spare moment. 40 | 41 | (As an aside, the process involves even more than that. Outgoing 42 | messages are signed using cryptographic certificates. Python data types are 43 | serialized. Incoming messages are validated and deserialized and checked 44 | against an authorization policy about who is allowed to sign what messages, 45 | etc.. We'll come back to this.) 46 | 47 | Let's quote `the zguide `_:: 48 | 49 | Most people who speak of "reliability" don't really know what they mean. We 50 | can only define reliability in terms of failure. That is, if we can handle 51 | a certain set of well-defined and understood failures, then we are reliable 52 | with respect to those failures. No more, no less. So let's look at the 53 | possible causes of failure in a distributed ZeroMQ application 54 | 55 | In practice, we do not "drop messages" in Fedora Infrastructure. We have run a 56 | number of experiments that demonstrate this to a degree sufficient 57 | to establish confidence with a number of other teams. 58 | 59 | In theory, though, there's a race condition here. You could start your 60 | publishing service and it could publish a message *before* anyone connects to 61 | listen for it. It would be lost. Again, in practice we have appropriate 62 | delays and reconnect intervals (with exponential backoff) configured to make 63 | this a non-issue. 64 | 65 | Still, there could be network partitions -- a listening service may suddenly 66 | find itself walled off from a publishing service by dead routers or a 67 | misconfigured firewall or a dead vpn or catastrophe, in all of such cases: 68 | messages will be lost. 69 | 70 | Designing Reliability 71 | --------------------- 72 | 73 | The zguide provides a good description of `how to think about and approach 74 | reliability for REQ-REP socket patterns 75 | `_. However, 76 | we've settled over the last few years on using *only* the PUB-SUB socket 77 | pattern for fedmsg. Adding another pattern (REQ-REP) alongside that smells 78 | wrong (it's currently so simple). 79 | 80 | The approach here in `gilmsg `_ is to 81 | layer a reliability check *on top of* the existing PUB-SUB fedmsg framework. 82 | 83 | Here's how it works broadly: 84 | 85 | - When ``gilmsg.publish(...)`` is invoked, you must declare a list of 86 | **required recipients**. 87 | - A background thread is started that listens for **ACK** messages on the whole 88 | bus. 89 | - If an **ACK** is not received from all ``recipients`` within a given timeout, 90 | then a ``Timeout`` exception is raised. 91 | 92 | Failure cases this addresses: 93 | 94 | - If an intended recipient is offline when the message is published, we'll 95 | raise an exception so that the originating process can fail and alert the 96 | operator. 97 | - If an intended recipient is online, but we're suffering from a network 98 | partition, the publisher will fail loudly. 99 | 100 | It is possible for us to have *False Negatives*: 101 | 102 | - If the intended recipient is online, but cannot publish the *ACK* back due to 103 | a one-way network failure or a misconfiguration, the publisher will fail 104 | loudly *even though* the consumer did receive the message. 105 | 106 | It is not possible for us to have *False Positives*. If the producer completes 107 | execution, we can be sure the consumer received the message. 108 | 109 | Some Details 110 | ------------ 111 | 112 | - We are sure that the ACKs comes from the ``recipients`` we declared because 113 | the ACKs are *cryptographically signed*. 114 | - We take care to distinguish between ACKs for *the message we published* and 115 | ACKs for *other messages we know nothing about*. 116 | - We start the ACK-listening socket on the producer in a thread **before** we 117 | publish the original message. This is necessary to avoid a race condition 118 | where we publish our original message but the ACK comes back before we get a 119 | chance to start listening for it. 120 | 121 | Why not use gilmsg? 122 | ------------------- 123 | 124 | fedmsg has worked very well. We have a `long list of integrated message 125 | producers in Fedora Infrastructure `_. 126 | The success is due in part to just how *dumb* fedmsg is. It has contributed to 127 | the rise of a *loosely coupled architecture*, which was the original aim. When 128 | some Fedora hacker gets an idea, then can hook onto the bus to consume messages 129 | without having to negotiate with anyone about it. They can produce messages 130 | without having to go to committee. 131 | 132 | As an example: you can stand up Bodhi2 web app on your local box, and it will 133 | "publish to fedmsg" without you having to start any additional services or 134 | anything like that. It will publish to fedmsg on your laptop, no one will 135 | be listening, and it won't care. 136 | 137 | In contrast, with gilmsg-enabled services: 138 | 139 | - Your producers will declare their required consumers. 140 | - As you add more consumers, you're going to have to patch your producers 141 | leading to an exponential number of code changes to get new things done. 142 | - You cannot run or test a gilmsg-enabled service on your own box without a 143 | replica of the whole production environment, since it will *require* that 144 | other services respond to it. 145 | - Your ensemble of production services becomes brittle -- prone to one dead 146 | service bringing the others down. 147 | 148 | gilmsg-enabled services are *tightly coupled*. 149 | 150 | ---- 151 | 152 | A cosmetic note: 153 | 154 | - The more gilmsg-enabled producer/consumer pairs you bring on line, the more 155 | spam you'll have on the bus. It can handle the throughput(!) but it will 156 | make the datagrepper logs less readable as you add more. 157 | 158 | Using gilmsg 159 | ------------ 160 | 161 | It is API backwards compatible with fedmsg core. So, write your script to use 162 | fedmsg first. If at some point in the future you decide that you *must* have 163 | the set of guarantees that gilmsg provides, then port to gilmsg. 164 | 165 | **Publishing** with ``.publish(..)`` from Python:: 166 | 167 | import gilmsg 168 | 169 | import fedmsg.config 170 | config = fedmsg.config.load_config() 171 | 172 | gilmsg.publish( 173 | topic="whatever", 174 | msg=dict(foo="bar"), 175 | recipients=( 176 | "bodhi-bodhi-backend01.phx2.fedoraproject.org", 177 | "shell-autocloud01.phx2.fedoraproject.org", 178 | ), 179 | ack_timeout=0.25, # 0.25 seconds 180 | **config) 181 | 182 | **Publishing** from the shell with ``gilmsg-logger`` with a timeout of 3 seconds:: 183 | 184 | echo testing | gilmsg-logger --recipients shell-value01.phx2.fedoraproject.org --ack-timeout 3 185 | 186 | Compare the above with `publishing with fedmsg alone 187 | `_. 188 | 189 | ---- 190 | 191 | **Consuming** with ``.tail_messages(..)`` in Python:: 192 | 193 | import gilmsg 194 | 195 | import fedmsg.config 196 | config = fedmsg.config.load_config() 197 | 198 | target = "org.fedoraproject.prod.compose.rawhide.complete" 199 | for name, ep, t, msg in gilmsg.tail_messages(topic=target, **config): 200 | # The ACK has already been sent at this point. 201 | print "Received", t, msg['msg_id'] 202 | 203 | **Consuming** with the "Hub-Consumer" approach:: 204 | 205 | import gilmsg 206 | 207 | class MyConsumer(gilmsg.GilmsgConsumer): 208 | topic = "org.fedoraproject.prod.compose.rawhide.complete" 209 | 210 | def consume(self, message): 211 | # The ACK has already been sent at this point. 212 | print "Received", message['topic'], message['msg_id'] 213 | 214 | Compare the above with `consuming with fedmsg alone 215 | `_. 216 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU LESSER GENERAL PUBLIC LICENSE 2 | Version 2.1, February 1999 3 | 4 | Copyright (C) 1991, 1999 Free Software Foundation, Inc. 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | [This is the first released version of the Lesser GPL. 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