Errata

Figure 10-2 is the wrong image, and 9-2 has incorrect labels.

Note from the Author or Editor:
Thank you. These have been fixed for the next release.

Below command did not execute and threw error. I made change to --address to -addr 0.0.0.0:8080 resolve the issue

docker run --pid=container:${APP_ID} \
-p 8080:8080 \
brendanburns/topz:db0fa58 \
/server --address=0.0.0.0:8080

flag provided but not defined: -address
Usage of /server:
-addr string
The address to serve on (default "localhost:8080")

Following change resolved the issue.

docker run --pid=container:ms -p 8080:8080 brendanburns/topz:db0fa58 /server -addr 0.0.0.0:8080

Note from the Author or Editor:
Confirmed and fixed in the Atlas repo.

Missing name for configmap, it should be:

`kubectl create configmap twem-config --from-file=./nutcracker.yaml`

Note from the Author or Editor:
Confirmed and fixed in the book's repository.

The commands array for the pod should be listed as a string array instead of a YAML array. i.e.:
`command: ["nutcracker", "-c", "/etc/config/nutcracker.yaml", "-v", "7", "-s", "6222"]`

Note from the Author or Editor:
Fixed in the books source repo.

Missing configmap name, it should be:

`kubectl create configmap experiment-config --from-file=nginx.conf`

Note from the Author or Editor:
The reporter is correct. I fixed this in the original source for future versions.

The compareAndSwap implementation on page 96 appears to be incorrect. There are a few issues:

1. Updating an existing key with non-empty current value will always return false and an error
2. Updating an existing key with empty current value always succeeds
3. Updating a missing key with a non-empty current value will not result in an error
4. Etc...

I think the root cause of all of this, is a missing '!':

```
if _, found := store[key]; found {
```

Should be:

```
if _, found := store[key]; !found {
```

I wonder if this idea could be expressed without some of the Go complexity that may not make sense to non-Go programmers:

```
func compareAndSwap(key, nextValue, currentValue string) (bool, error) {
lock.Lock()
defer lock.Unlock()
v := store[key]
if v == currentValue {
store[key] = nextValue
return true, nil
}
if v == "" {
return false, fmt.Errorf("Expected value %s for key %s, but found empty", currentValue, key)
}
return false, nil
}
```

Not that it matters, but this also covers the case where a key is updated with an empty value.

As a side note, I felt it might be worth noting that though the example is logically relevant, compare-and-swap is typically implemented in hardware?

Thanks for the great read and for the interesting distraction!

Note from the Author or Editor:
The reporter is correct. I fixed the error in the original repository in atlas.

There is "In the first image" but second image does not exist.

Second image will be similar to the image in Figure 9-2 but "owner" in Lockserver should be "shard1.cluster.internal".

Note from the Author or Editor:
Confirmed and fixed in the book's source repo.

I noticed figures 10-2 and 10-3 were exactly the same and Figure 10-2’s descriptions did not align with the actual graph. Please confirm whether Figure 10-2 is correct. The book is extremely helpful for those of us that are trying to construct the most well thought out architectural patterns. Thank for making this book available!

Note from the Author or Editor:
Confirmed, somehow the picture that should have been 10-2 was copied from 10-3...