Dive into sentry

Dive into Sentry
The modern error logging and aggregation platform
XTao
09.19.2015 Beijing

北京/上海/广州 0xFF Life's pathetic, go Pythonic!
徐涛
● @ 豆瓣
● (?:产品开发|运维)工程师
● (?:CODE|DevOps|Git|Python)
● 2014 PyConChina Beijing
● https://blog.xtao.me
❏ Douban: @xtaooooo
❏ Twitter: @xtao
❏ Github: @xtao

Sentry 概述
Sentry 毕业于 Disqus
https://engineering.disqus.com/
Sentry 历史
Sentry 是什么
DEMO

起源
● 2010
● http://disqus.com/
● django-db-log (祖父)
● tl;dr Sentry and Raven
are StarCraft 2（星际争
霸 2） units.
● driven-by-open-source
commit 3c2e87573d3bd16f61cf08fece0638cc47a4fc22
Author: David Cramer <dcramer@gmail.com>
Date: Mon May 12 16:26:19 2008 +0000
initial working code
djangodblog/__init__.py | 35
+++++++++++++++++++++++++++++++++++
djangodblog/models.py | 36
++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+)

Sentry 5
● 2012
● Protocol Version 3
● branch: 5.4.x-maint

Sentry 6
● 2013
● Alerts
● Filters

Sentry 7
● 2014
● Organizations
● TSDB
● Rules
● Web API
● BIGINT
● Help Pages

Senty 8
● 2015 ?
● Most of the
application has
been overhauled
and rewritten on
top of React and
our web API.
● beta

Sentry 是什么
● 一个错误记录和汇聚平台
○ Server: Sentry (The Sentry Open Source Server)
○ Client: The Raven Clients.

为什么要用 Sentry
● 详细的错误息
○ 某一行代码 (Python)
○ 某一个变量 (Python)
● 详细错误分类
○ Tag
● 提醒
● 合理的重复错误处理
● 支持多种语言
○ 对 Python 支持好
❏ 额外的收获
❏ 入门
❏ 一个很好的 Django 项目，如果你要
学习如何使用 Django 的话，可以读
一下 Sentry 的源码
❏ 进阶
❏ Sentry 应该算是一个中型 Web 项目
了，如果你缺少 Web 项目开发经
验，也可以从源码中获取一些经验
❏ 开源
❏ 一个 Python 开源 Web 应用的示
例，数据迁移还是靠谱的

Sentry - 服务端(7.x)
● Backend
○ Python
○ Django
○ Celery
● Frontend
○ JQuery
○ Backbone
○ Underscore
○ Bootstrap
○ Moment
● Database
○ MySQL
○ PostgreSQL
● KV
○ Cassandra
○ Riak
○ Redis
● Queue
○ Redis
○ RabbitMQ

Raven - 官方支持的 Client
● Python
● JavaScript
● Node.js
● PHP
● Ruby
● Objective-C
● Java
● C#
● Go

DEMO
1. Hosted Sentry
a. https://www.getsentry.
com/signup/
b. 14-day Free Trial
2. Sentry On Promise
a. https://docs.getsentry.
com/on-
premise/server/installati
on/
b. Sentry Internal

Sentry 使用
如何提交错误
Raven
DSN

Raven 101
pip install raven --upgrade
from raven import Client
client = Client('___DSN___')
try:
1 / 0
except ZeroDivisionError:
client.captureException()
def handle_request(request):
client.context.merge({'user': {
'email': request.user.email
}})
try:
...
finally:
client.context.clear()

Raven 102
● WSGI middleware
● raven/middleware.py
```
A WSGI middleware which will
attempt to capture any
uncaught exceptions and send
them to Sentry.
>>> from raven.base import Client
>>> application = Sentry
(application, Client())
```

DSN 101
'{PROTOCOL}://{PUBLIC_KEY}:{SECRET_KEY}@{HOST}/{PATH}{PROJECT_ID}'
http://c44a73655e50454581da995bbedd392a:
8d29447e0e8241b9a178fd726fb07190@onimaru.intra.douban.com/10
udp://c44a73655e50454581da995bbedd392a:
8d29447e0e8241b9a178fd726fb07190@onimaru-udp.intra.douban.com:
4008/10

Sentry 特性
(๑•̀ㅂ•́)‫✧و‬ (つд⊂)
Event
Group
Protocol
Interface
TSDB
Buffer
Cache

Event
● HTTP(DATA)
● UDP(DATA) ● EventManager ● Project
● Event
● Group
● EventMapping
○ event_id: uuid.uuid4().
hex
● UserReport
○ 用户反馈 Sentry 问题
● post_process_group.delay
● index_event.delay

Group
● hashes
○ checksum (provided by client)
○ fingerprint / (default + fingerprint)
○ default (first interface ordered by score)
● find group
○ find group at GroupHash by hash
○ first matched group
● sample event (count, time)
● regression (resolved event)

Protocol
● CLIENT_RESERVED_ATTRS = (
● 'project',
● 'event_id',
● 'message',
● 'checksum',
● 'culprit',
● 'fingerprint',
● 'level',
● 'time_spent',
● 'logger',
{
"event_id": "fc6d8c0c43fc4630ad850ee518f1b9d0",
"culprit": "my.module.function_name",
"timestamp": "2011-05-02T17:41:36",
"message": "SyntaxError: Wattttt!"
"sentry.interfaces.Exception": {
"type": "SyntaxError":
"value": "Wattttt!",
"module": "__builtins__"
}
}
● 'server_name',
● 'site',
● 'timestamp',
● 'extra',
● 'modules',
● 'tags',
● 'platform',
● 'release',
● )

UDP Protocol
"AUTHnnDATA"
● AUTH
○ "Sentry key=value, key=value, …"
● DATA
○ json string
○ zlib
○ base64

HTTP Protocol
● 用户认证跟 Web 复用了
● /api/store
● GET/POST DATA

Interface
An interface is a structured
representation of data, which may
render differently than the default
``extra`` metadata in an event.
● to_python
● get_api_context
● to_json
● get_path
● get_alias
● get_hash
● get_score
● ...

Interface - Exception
● 标准的 Python 异常
● type, value, module
● stacktrace == sentry.interfaces.
Stacktrace
>>> {
>>> "type": "ValueError",
>>> "value": "My exception value",
>>> "module": "__builtins__"
>>> "stacktrace": {
>>> # see sentry.interfaces.Stacktrace
>>> }
>>> }

Interface - Message
● message (<= 1000)
● params
>>> {
>>> "message": "My raw message
with interpreted strings like %s",
>>> "params": ["this"]
>>> }

Interface - HTTP
● 常用的 HTTP 参数 >>> {
>>> "url": "http://absolute.uri/foo",
>>> "method": "POST",
>>> "data": {
>>> "foo": "bar"
>>> },
>>> "query_string": "hello=world",
>>> "cookies": "foo=bar",
>>> "headers": {
>>> "Content-Type": "text/html"
>>> },
>>> "env": {
>>> "REMOTE_ADDR": "192.168.0.1"
>>> }
>>> }

Interface - Query
● 用于记录 SQL >>> {
>>> "query": "SELECT 1"
>>> "engine": "psycopg2"
>>> }

Interface - Template
● A rendered template (generally
used like a single frame in a
stacktrace).
● The attributes ``filename``,
``context_line``, and ``lineno`` are
required.
>>> {
>>> "abs_path": "/real/file/name.html"
>>> "filename": "file/name.html",
>>> "pre_context": [
>>> "line1",
>>> "line2"
>>> ],
>>> "context_line": "line3",
>>> "lineno": 3,
>>> "post_context": [
>>> "line4",
>>> "line5"
>>> ],
>>> }

Interface - User
● 定义一个用户 >>> {
>>> "id": "unique_id",
>>> "username": "my_user",
>>> "email": "foo@example.com"
>>> "ip_address": "127.0.0.1",
>>> "optional": "value"
>>> }

Interface - Stacktrace
● Python Frame
>>> {
>>> "frames": [{
>>> "abs_path": "/real/file/name.py"
>>> "filename": "file/name.py",
>>> "function": "myfunction",
>>> "vars": {
>>> "key": "value"
>>> },
>>> "pre_context": [
>>> "line1",
>>> "line2"
>>> ],
>>> "context_line": "line3",
>>> "lineno": 3,
>>> "in_app": true,
>>> "post_context": [
>>> "line4",
>>> "line5"
>>> ],
>>> }],
>>> "frames_omitted": [13, 56]
>>> }

TSDB - 时序数据库
● Dummy (none)
● InMemory (defaultdict)
● Redis (hashes)
Redis:
{
"TSDBModel:epoch:shard": {
"Key": Count
}
}
# rollups must be ordered from highest
granularity to lowest
SENTRY_TSDB_ROLLUPS = (
# (time in seconds, samples to keep)
(10, 360), # 60 minutes at 10 seconds
(3600, 24 * 7), # 7 days at 1 hour
(3600 * 24, 60), # 60 days at 1 day
)

NodeStore - KV 数据库
● riak
● cassandra
● django (node table)
● 用于和数据一起存储一些特殊信息(比如不
适合存在数据库里的大文本等)
● validate
● create
● delete
● delete_multi
● get
● get_multi
● set
● set_multi
● generate_id
● cleanup

Example
class Event(Model):
"""
An individual event.
"""
__core__ = False
...
time_spent = BoundedIntegerField(null=True)
data = NodeField(blank=True, null=True)

Cache
● django
○ filesystem
○ memcached
○ local memory
○ dummy
● redis
● set
● get
● delete
● redis:
○ from nydus.db import create_cluster
○ 支持 cluster
○ 重写了 rb，但还没有在已发布的版本里使用

Example
● Cache 与 Model
○ db/models/manager.py
○ class BaseManager(Manager)
● get_from_cache
● updated by signal
● deleted by signal

Buffer
This is useful in situations where a single event
might be happening so fast that the queue can't
keep up with the updates.
● InProcess (no buffer)
● Redis
● 降低 MySQL 数据的 QPS (写)
● 支持 Cluster Redis
● Redis 2.6.12 or newer

Buffer Internal
● 生产者
● incr
●
● 'b:k:%s:%s' (hashmap, key_expire = 60 * 60
# 1 hour)
○ 'm'
○ 'f'
○ 'l+%s'
○ 'e+%s'
● 'b:p' (Sorted sets)
● 消费者
● process pending
● process
'flush-buffers': {
'task': 'sentry.tasks.process_buffer.process_pending',
'schedule': timedelta(seconds=10),
'options': {
'expires': 10,
'queue': 'counters-0',
}
},

Membership
Roles
● Member *:read
● Admin *:write
● Owner *:delete
Scoping has access to all teams
● 跟 GitHub 类似的组织结构以及权限控制
● Organization - Owner, Admin, Member
● Team - (Role, Project)
● Project

Sensitive Data
● 'password',
● 'secret',
● 'passwd',
● 'authorization',
● 'api_key',
● 'apikey',
● 'access_token',
● DEFAULT_SCRUBBED_FIELDS

Notifications
● Rules
○ An event is first seen (the first event in a rollup)
○ An event changes state from resolved to unresolved
● State
○ Unresolved
○ Resolved
○ Muted
● Condition
● Action

Tagging Events
● Event 分类
● We’ll automatically index all tags
for an event, as well as the
frequency and the last time a
value has been seen.
● TagValue
● GroupTagValue
● Added by buffer

Rollups & Sampling
● Rollups
○ Raven.captureException(ex, {fingerprint: ['my', 'custom', 'fingerprint']})
○ Raven.captureException(ex, {fingerprint: ['{{ default }}', 'other', 'data']})
● Sampling
○ Count
○ Time

Web Profile
● ?prof=1
● DEBUG
● super user
● src/sentry/utils/debug.py
def can(self, request):
if 'prof' not in request.GET:
return False
if settings.DEBUG:
return True
if hasattr(request, 'user') and
request.user.is_superuser:
return True
return False

Sentry to Sentry
● 自举
● DISABLE_RAVEN
● default: project id == 1
● src/sentry/utils/raven.py

PostgreSQL & Gevent
● psycopg2
● src/sentry/utils/gevent.py
● Sentry 官方使用的应该是这个数据库，有非阻塞的 patch，支持异步

Sentry
@douban
有料
其中充斥着不少嘈点
问题
部署
监控
调优
Tips

“自己解决不了的
问题，不要指望工
具能帮你解决”
乔治@豆瓣

Monitor

豆瓣
● 应用
○ Python (大部分)
○ Javascript (前端)
○ Go (少部分)
○ C++/C/Java (少量)
● 错误
○ devtools (DIY, 已废弃)
○ Sentry

问题
● 已经部署了一套 Sentry
● 5.x 使用 UDP 协议
● 测试以及线上，有丢错误情况
● 且比较明显
● 但是这时还没有针对 Sentry 的监控
● 开始研究黑盒
● UDP Worker CPU 使用率比较高
● UDP 是用 DNS 做负载均衡
● DNS 因为 cache 问题，导致负载不平衡
● 使用 Random 改善了 cache 带来的隐患
● 查看 Worker 代码
● Gevent / Eventlet 使用错误，没有 Monkey
Patch
● 5.x 数据库压力较大，需要做合并写

升级
● 5.x-maint support UDP
● but 7.x not
● We have to backport UDP to 7.x
● 幸好原来的接口还在
❏ src/sentry/conf/server.py:
❏ #socket.setdefaulttimeout(5)
❏ src/sentry/coreapi.py:
❏ insert_data_to_database_sync (async to
sync，Redis 内存放大太厉害，因为 cache
原因)

Insert Queue
● insert_data_to_database - cache
● preprocess_event - queue
● save_event - queue
●
● insert_data_to_database_sync - queue

部署情况
● HTTP x 4 (默认 Sentry 是用 Gunicorn 管理 Worker 的)
● UDP x 4 (开启了 Gevent，收到包后，扔到队列)
● Celery x 4 (Task consumer, 默认是开启 CPU_NUM 个 Worker)
● Celery Beat x 1
● Cron：cleanup 21 (只保留 21 天的数据)
● HTTP 前面用 LVS + Nginx 做负载均衡
● UDP 用 DNS 做负载均衡

内部配置
● LDAP
○ 我们用的用户帐号系统
○ 配置一下 Sentry 即可
● MAIL
○ 配置 Sentry 邮件服务器
● IRC
○ sentry-irc
○ 因为我们使用了 ircbot，稍微改了一下这个插件代码

Why UDP
● 快
● 应用不需要关心 Sentry 服务是否正常
● 即使 Sentry 出问题，也不影响应用
● 可以观察系统 UDP 丢包情况，判断 UDP 服务是否正常

Celery
● 芹菜
● 还没有吃透

DBA
● Redis
○ Memory
○ QPS
○ CPU
○ Queue Size
● MySQL
○ QPS
■ update
■ insert
■ delete
■ select
○ thread

Sentry
● Statsd
○ celery worker cpu
○ udp worker cpu
○ http worker cpu
● App 内统计
○ task 执行时间
○ task 执行数量

UDP Received Packet (Sentry)
● udp worker
● 收包后记录
● d = sock.recvfrom(self.BUF_SIZE)
● statsd.increment(STATSD_KEY_RECV)

UDP Received Packet (Kernel)
● UDP Server 收到的包数 (by diamond)
● ~ $ sudo /sbin/iptables -t filter -I INPUT -i lan -p udp --dport 4008 -j ACCEPT
● ~ $ sudo /sbin/iptables -L INPUT 1 -nvx
● 52308183 414772916064 ACCEPT udp -- lan * 0.0.0.0/0
0.0.0.0/0 udp dpt:4008
● pkts (UDP 完整包数，底层已经处理了分包问题)
● bts

UDP Dropped Packets (Kernel)
● cat /proc/net/udp
● sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode ref pointer drops
● 41: 00000000:80CE 00000000:0000 07 00000000:00000000 00:00000000 00000000 6561 0 4110825944 2 ffff8809c23e5e40 0
● cat /proc/net/snmp
● Udp: InDatagrams NoPorts InErrors OutDatagrams RcvbufErrors SndbufErrors
● Udp: 5416706536 993028 290598311 22725578190 4662160 1318
● UdpLite: InDatagrams NoPorts InErrors OutDatagrams RcvbufErrors SndbufErrors
● UdpLite: 0 0 0 0 0 0

TIPS
● Webhooks:
○ 默认禁止访问内网 IP, 需要更改一下配置
● Timezone
○ SENTRY_DEFAULT_TIME_ZONE = 'Asia/Shanghai' 设置用户默认时区
● Public
○ SENTRY_PUBLIC = False 这个权限有点问题，不要开启
● Register
○ SENTRY_FEATURES['auth:register'] = False 禁止自己注册

下一步计划
● 项目错误统计(QPS，Sentry 提供的图还不能满足需求)
● Profile 工具，有助于分析 Worker 瓶颈 (Celery)
● 应对雪崩式错误的处理方案(压测 Sentry)
● 尝试一下 MySQL + Redis + Gevent

Jobs
● 2016 校招
● always 社招
● TO: ruby@douban.com
● 当然 python 也可以
● TO: python@douban.com
● 如果你想试试 js 也可以尝试
● TO: js@douban.com
● 详情: http://jobs.douban.com

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