It uses heartbeat interval and election timeout to estimate the
expected request timeout.
This PR helps etcd survive under high roundtrip-time environment,
e.g., globally-deployed cluster.
This solves the problem that etcd may fatal because its critical path
cannot get file descriptor resource when the number of clients is too
big. The PR lets the client listener close client connections
immediately after they are accepted when
the file descriptor usage in the process reaches some pre-set limit, so
it ensures that the internal critical path could always get file
descriptor when it needs.
When there are tons to clients connecting to the server, the original
behavior is like this:
```
2015/08/4 16:42:08 etcdserver: cannot monitor file descriptor usage
(open /proc/self/fd: too many open files)
2015/08/4 16:42:33 etcdserver: failed to purge snap file open
default2.etcd/member/snap: too many open files
[halted]
```
Current behavior is like this:
```
2015/08/6 19:05:25 transport: accept error: closing connection,
exceed file descriptor usage limitation (fd limit=874)
2015/08/6 19:05:25 transport: accept error: closing connection,
exceed file descriptor usage limitation (fd limit=874)
2015/08/6 19:05:26 transport: accept error: closing connection,
exceed file descriptor usage limitation (fd limit=874)
2015/08/6 19:05:27 transport: accept error: closing connection,
exceed file descriptor usage limitation (fd limit=874)
2015/08/6 19:05:28 transport: accept error: closing connection,
exceed file descriptor usage limitation (fd limit=874)
2015/08/6 19:05:28 etcdserver: 80% of the file descriptor limit is
used [used = 873, limit = 1024]
```
It is available at linux system today because pkg/runtime only has linux
support.
If the user sets TLS info, this implies that he wants to listen on TLS.
If etcd finds that urls to listen is still HTTP schema, it prints out
warning to notify user about possible wrong setting.
This PR set maxIdleConnsPerHost to 128 to let proxy handle 128 concurrent
requests in long term smoothly.
If the number of concurrent requests is bigger than this value,
proxy needs to create one new connection when handling each request in
the delta, which is bad because the creation consumes resource and may
eat up your ephemeral port.
After this PR, only cluster's interface Cluster is exposed, which makes
code much cleaner. And it avoids external packages to rely on cluster
struct in the future.
The PR extracts types.Cluster from etcdserver.Cluster. types.Cluster
is used for flag parsing and etcdserver config.
There is no need to expose etcdserver.Cluster public, which contains
lots of etcdserver internal details and methods. This is the first step
for it.
Before this PR, people can set listen-client-urls without setting
advertise-client-urls, and leaves advertise-client-urls as default
localhost value. The client libraries which sync the cluster info
fetch wrong advertise-client-urls and cannot connect to the cluster.
This PR avoids this case and provides better UX.
On the other hand, this change is safe because people always want to set
advertise-client-urls if listen-client-urls is set. The default localhost
advertise url cannot be accessed from the outside, and should always be
set except that etcd is bootstrapped with no flag.
Currently this doesn't work if a user wants to try out a single machine
cluster but change the name for whatever reason. This is because the
name is always "default" and the
```
./bin/etcd -name 'baz'
```
This solves our problem on CoreOS where the default is `ETCD_NAME=%m`.
Dial timeout is set shorter because
1. etcd is supposed to work in good environment, and the new value is long
enough
2. shorter dial timeout makes dial fail faster, which is good for
performance
The functionality in pkg/osutil ensures that all interrupt handlers finish
and the process kills itself with the proper signal.
Test for interrupt handling added.
The server shutsdown gracefully by stopping on interrupt (Issue #2277.)
