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Update stateful section

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Jerome Petazzoni
2016-09-19 11:23:23 -07:00
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@@ -105,7 +105,7 @@ Docker <br/> Orchestration <br/> Workshop
AJ ([@s0ulshake](https://twitter.com/s0ulshake))
Jerome ([@jpetazzo](https://twitter.com/jpetazzo))
Jérôme ([@jpetazzo](https://twitter.com/jpetazzo))
Shawn ([@drizzt51](https://twitter.com/drizzt51))
@@ -199,6 +199,8 @@ grep '^# ' index.html | grep -v '<br' | tr '#' '-'
## Chapter 4: deeper in Swarm
(Additional/optional/bonus content!)
- Dealing with stateful services
- Scripting image building and pushing
- Distributed Application Bundles
@@ -801,6 +803,7 @@ class: title
## SwarmKit features
- Highly-available, distributed store based on Raft
<br/>(more on next slide)
- *Services* managed with a *declarative API*
<br/>(implementing *desired state* and *reconciliation loop*)
@@ -2390,7 +2393,10 @@ By default, SwarmKit does a rolling upgrade, one instance at a time.
]
(Remove `-v` if you don't like verbose things!)
Remove `-v` if you don't like verbose things.
Shameless promo: for more Go and Docker love, check
[this blog post](http://jpetazzo.github.io/2016/09/09/go-docker/)!
---
@@ -2554,7 +2560,7 @@ What we will do:
- We could author a custom image bundling this configuration
- We can also pass the configuration on the command line
- We can also pass the [configuration](https://github.com/jpetazzo/orchestration-workshop/blob/master/elk/logstash.conf) on the command line
.exercise[
@@ -2912,13 +2918,17 @@ class: title
redis get foo
```
- Adding a constraint caused the service to be restarted, *even if it didn't have to move*:
- Adding a constraint caused the service to be redeployed:
```bash
docker service ps stateful
```
]
Note: even if the constraint ends up being a no-op (i.e. not
moving the service), the service gets redeployed.
This ensures consistent behavior.
---
## Setting the key again
@@ -2941,117 +2951,67 @@ class: title
---
## Making sure that Redis correctly persists data
- Before going further, we need to make sure that Redis correctly saves to disk
.exercise[
- Restart the container:
```bash
CID=$(docker ps -q --filter label=com.docker.swarm.service.name=stateful)
docker restart $CID
```
- Check the `foo` key:
```bash
redis get foo
```
]
--
(╯°□°）╯︵ ┻━┻)
---
## Instructing Redis to save data on restarts
- The default configuration that comes with the `redis` image doesn't save on shutdown
(See [this issue](https://github.com/docker-library/redis/issues/4) for some hints about what's happening)
- Let's add an extra flag to enable AOF persistence
.exercise[
- Add `--appendonly yes` to Redis starting flags:
```bash
docker service update stateful --args "--appendonly yes"
```
]
Note: we can achieve the same result by enabling RDB snapshots instead.
<br/>
See http://redis.io/topics/persistence for more details about Redis persistence.
---
## Checking persistence across container restarts
.exercise[
- Set the `foo` key once again:
```bash
redis set foo bar
```
- Restart the container:
```bash
CID=$(docker ps -q --filter label=com.docker.swarm.service.name=stateful)
docker restart $CID
```
- Check that `foo` is still there:
```bash
redis get foo
```
]
---
## Service updates cause containers to be replaced
- Let's try to make a trivial update to the service and see what happens
.exercise[
- Set a memory limit to our Redis service:
```bash
docker service update stateful --limit-memory 100M
```
- Try to get the `foo` key one more time:
```bash
redis get foo
```
]
The key is blank again!
---
## Service volumes are ephemeral by default
- Let's highlight what's going on with volumes!
.exercise[
- Check the current list of volumes:
```bash
docker volume ls
```
- Set a memory limit to our Redis service:
- Carry a minor update to our Redis service:
```bash
docker service update stateful --limit-memory 100M
docker service update stateful --limit-memory 200M
```
]
Note: all changes trigger the creation of a new task, and therefore a replacement of the existing container;
Again: all changes trigger the creation of a new task, and therefore a replacement of the existing container;
even when it is not strictly technically necessary.
---
## Services volumes are ephemeral
## The data is gone again
- What happened to our data?
.exercise[
- The `foo` key is (once again) gone:
```bash
redis get foo
```
- The volume has been recycled, too:
- The list of volumes is slightly different:
```bash
docker volume ls
```
- And as you can expect, the `foo` key is gone:
```bash
redis get foo
```
]
---
@@ -3088,9 +3048,9 @@ Note: the `local` volume driver automatically creates volumes.
redis set foo barbar
```
- Update the service with another trivial change:
- Update the service with yet another trivial change:
```bash
docker service update stateful --limit-memory 200M
docker service update stateful --limit-memory 300M
```
- Check that `foo` is still set:
@@ -3104,7 +3064,7 @@ Note: the `local` volume driver automatically creates volumes.
## Recap
- The service must commit its state to disk when being shutdown
- The service must commit its state to disk when being shutdown.red[*]
(Shutdown = being sent a `TERM` signal)
@@ -3116,6 +3076,9 @@ Note: the `local` volume driver automatically creates volumes.
(And losing that node means losing the data, unless there are other backups)
.footnote[<br/>.red[*]Until recently, the Redis image didn't automatically
persist data. Beware!]
---
## Cleaning up
@@ -3505,7 +3468,15 @@ class: title
# Thanks! <br/> Questions?
<!--
## [@jpetazzo](https://twitter.com/jpetazzo) <br/> [@docker](https://twitter.com/docker)
-->
## AJ ([@s0ulshake](https://twitter.com/s0ulshake)) — Jérôme ([@jpetazzo](https://twitter.com/jpetazzo)) <br/> Shawn ([@drizzt51](https://twitter.com/drizzt51)) — Tiffany ([@tiffanyfayj](https://twitter.com/tiffanyfayj))
### Reminder 1: lunch will be in "Rhinelander", same floor as the tutorials.
### Reminder 2: Shawn is doing a [4-hour version of this](http://sched.co/8Gfp) at #cdatx ([Container Days Austin](http://www.containerdaysaustin.com/2016/), October 14-15)
</textarea>
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