Motivation:
as nfs4j api is not stable yet, breaking changes have to be documented.

Modification:
add API-changes.md as well as warning in the README.md

Result:
library users are better informed.

Acked-by: Paul Millar
Acked-by: Lea Morschel
Acked-by: Olufemi Adeyemi
Target: master

Motivation:
When client want's to inform metadata server about errors or statistics
in its interactions with the layout, then LAYOUTERROR and LAYOUTSTATS
operations are called. This information have to be propagated to the pnfs
device manager.

Modification:
Add NFSv41DeviceManager#layoutError and NFSv41DeviceManager#layoutStats
methods. Update corresponding operations to pass requests to device manager.

Result:
Layout usage errors and statistics available to the pnfs device manager.

Acked-by: Paul Millar
Target: master

Acked-by: Paul Millar
Acked-by: Lea Morschel
Target: master

Acked-by: Paul Millar
Acked-by: Lea Morschel
Target: master

Acked-by: Paul Millar
Target: master

Acked-by: Paul Millar
Target: master

stats mode field must contain file system object type

Acked-by: Paul Millar
Target: master

Motivation:
improve test coverage

Modification:
Add OperationLAYOUTCOMMITTest to test leyout commit with read-only open
state.

Result:
better code coverage.

Acked-by: Paul Millar
Target: master

Acked-by: Paul Millar
Target: master

Motivation:
Current implementation of layout commit operation assumes that
only action that have to be done is updating file size. However,
the back-end system may perform other actions as well if required.

Modification:
Introduce NFSv41DeviceManager#layoutCommit method. The driver
implementation should take care to update file size, if required. The
sanity check of a valid state it is sill performed as a part of genetic
request processing.

Result:
The layout driver gets possibility to handle commit operation.

Acked-by: Albert Rossi
Acked-by: Paul Millar
Target: master

Motivation:
as findbugs is dead move to the successor

https://mailman.cs.umd.edu/pipermail/findbugs-discuss/2017-September/004383.html

Modification:
enable spotbugs plugin that can be activated by:
```
mvn spotbugs:spotbugs
```

Result:
use up-to-date static code analysis tool

Target: master
Acked-By: Paul Millar

Acked-by: Paul Millar
Acked-by: Lea Morschel
Target: master

Motivation:
pNFS operations have usually have multiple arguments. This require that
corresponding methods as well accept multiple arguments, which makes
code looks a bit messy.

Modification:
re-factor NFSv41DeviceManager interface to accept corresponding XDR
arguments without extracting each field.

Result:
simple code.

Acked-by: Paul Millar
Target: master

Acked-by: Lea Morschel
Target: master, 0.18

Motivation:
The NFSv4OperationFactory interface provides only a method to retrieve
nfs operation for a given request. The request execution is done by nfs
server itself. Though a different factories can be provided, the way
how requests are executed can't be changed. The example of such desired
change can be execution metrics, fault injection, notifications.

Modification:
Introduce OperationExecutor interface. Introduce AbstractOperationExecutor
that provides a generic implementation of request execution, but sill
allows subclasses to control which requests are supported. Removed
RequestExecutionTimeGauges and OperationFactoryMXBeanImpl as they can be
added by subclassing/wrapping an instance of OperationExecutor.

Though this is a breaking change, code migration should be easy:

MDSOperationFactory -> MDSOperationExecutor

        NFSServerV41 nfs4 = new NFSServerV41.Builder()
                .withExportTable(exportFile)
                .withVfs(vfs)
                .withOperationExecutor(new MDSOperationExecutor())
                .build();

Result:
A way to inject different strategies for request execution

Acked-by: Paul Millar
Target: master

deprecate NFSServerV41Factory#setExportFile in favor for new method

Acked-by: Paul Millar
Target: master

Modified V3 Components to Use ExportTable

Signed-off-by: Adam Marcionek <amarcionek@seven10storage.com>

Signed-off-by: Adam Marcionek <amarcionek@seven10storage.com>

Signed-off-by: Adam Marcionek <amarcionek@seven10storage.com>

isPesudoInode -> isPseudoInode

Reported-by: David Kocher <dkocher@iterate.ch>
Acked-by: Lea Morschel
Acked-by: Paul Millar
Target: master

Acked-by: Paul Millar
Target: master

improve code coverage

Acked-by: Paul Millar
Target: master

Motivation:
current code have some issues:

  - the pseudo file systems directory cookie starts with zero,
    which is not allowed.

  - listing in pseudo file system ignores provided cookie.

Modification:

update listPseudoDirectory to generate cookies stargin from 3,
as 0, 1 and 2 are reserved values. Return tail of listing started from
cookie, if provided.

Result:
fixed directory listing in pseudo file system with non zero initial
cookie.

Acked-by: Paul Millar
Target: master, 0.18

Acked-by: Paul Millar
Target: master

Motivation:
To build more complicated test cases without mocking all world a timple
file system suitable test is required.

Modification:
Adjust local file system based vfs implementation

https://github.com/kofemann/simple-nfs/blob/master/src/main/java/org/dcache/simplenfs/LocalFileSystem.java

to work with jimfs (Google's file system for testing).

Update existing PseudoFsTest to to use DummyVFS.

Result:
More complicated tests can be created.

Acked-by: Paul Millar
Target: master

Motivation:
NFSv4.2 have introduced some new operations including LAYOUTSTATS and
LAYOUTERROR. Tough those operations are not supported, we return error
illegal.

Modification:
Add dummy OperationLAYOUTERROR and OperationLAYOUTSTATS that returns
NFSERR_NOTSUPP.

Result:
client receives NFSERR_NOTSUPP instead of NFSERR_ILLEGAL. First building
block to add support for LAYOUTSTATS and LAYOUTERROR.

Acked-by: Paul Millar
Target: master

ensure, that readdir behind last entry returns empty directory listing.

Acked-by: Paul Millar
Target: master

Motivation:
latest version of hamcrest test suite to write more sophisticated test
cases.

Modification:
Update dependency in the pom file. Update test to avoid usage of
deprecated API.

Result:
up-to-date test infrastructure to enhance tests.

Acked-by: Paul Millar
Target: master

up-to-date version with java11 support

Acked-by: Paul Millar
Target: master

Acked-by: Paul Millar
Target: master

Motivation:
 - Benchmark IP matcher that used for processed of any NFS request.
 - enhancing JMH knowledge

Modification:
Add benchmark for ip address matcher.

Result:

Benchmark                                      (client)                 (template)   Mode  Cnt          Score         Error  Units
IpMatcherBenchmark.benchmark                192.168.1.1                192.168.1.1  thrpt   25  156536643.166 ± 3114973.363  ops/s
IpMatcherBenchmark.benchmark                192.168.1.1             192.168.1.0/24  thrpt   25  154687994.062 ± 5716679.866  ops/s
IpMatcherBenchmark.benchmark                192.168.1.1  fe80::9cef:10f5:f2ae:1aa1  thrpt   25  269111251.883 ± 6734146.251  ops/s
IpMatcherBenchmark.benchmark                192.168.5.1                192.168.1.1  thrpt   25  158110904.503 ± 1620381.437  ops/s
IpMatcherBenchmark.benchmark                192.168.5.1             192.168.1.0/24  thrpt   25  158561449.487 ± 1235704.889  ops/s
IpMatcherB...

Motivation:
When layout stats are reported, then consumer misses client information,
which is not the expected behavior.

Modification:
Update LayoutDriver#acceptLayoutReturnData to accept compound context.

Result:
Request information is available when layout stats are processed.

Acked-by: Paul Millar
Target: master

Motivation:
make FsExport usable for collections

Modification:
add hashCode and equals to FsExport and InerAddressMatcher

Result:
FsExport can be used in java collections.

Acked-by: Albert Rossi
Target: master

Motivation:
traditionally, nfs exports table is implemented as a export file. However,
nfs server interested only in the content of the export table. Moreover,
Some deployments,for instance openstack shared file system interface, may
require more dynamic ways to manipulate export table, which is not optimal
for file based implementation.

Modification:
Introduce ExportTable interface that provide API required by nfs server
without exposing implementation details. Update methods to more generic
names. Update codebase to refer to ExportTable instead of ExportFile.
The ExportTable class is implementing ExportTable interface.

Result:
multiple implementation of ExportTable is possible without nfs code changes.

Acked-by: Albert Rossi
Target: master

Motivation:
as we must match most specific match first, the entries like

lab-*wn*.site.com
lab-cwn01.site.com
10.1.2.2
10.1.2.0/24

must be sorted as

10.1.2.2
lab-cwn01.site.com
10.1.2.0/24
lab-*wn*.site.com

Modification:
ensure that IP address has a higher priority then full host name.
Update comparator to always return desired order (IOW, no need for
reverse sorting).

Result:
The export entries evaluated in desired order.

Acked-by: Paul Millar
Target: master, 0.18, 0.17

Motivation:

 - performance benchmarking
 - getting in touch with JMH

Modification:
Add throughput test for lock manager. Introduce a dedicated profile to
run benchmark tests.

```
$ mvn clean verify -Pbenchmark

....

Result "org.dcache.nfs.benchmarks.ConcurrentLockManagerBenchmark.benchmarkConcurrentLocking":
  1574556.068 ±(99.9%) 98632.233 ops/s [Average]
  (min, avg, max) = (1078256.296, 1574556.068, 1735655.142), stdev = 131671.209
  CI (99.9%): [1475923.835, 1673188.301] (assumes normal distribution)

$
```

Result:
automated performance monitoring can be integrated into CI.

Acked-by: Albert Rossi
Target: master

fixes: 7aee3bc6

Motivation:
as FATTR4_RDATTR_ERROR must be used in a context of READDIR operation
only, the VERIFY/NVERIFY operations must check that FATTR4_RDATTR_ERROR is
not set.

Modification:
check for invalid attribute prior VERIFY/NFERIVY operations start to
compare attributes.

Result:
better spec compliance.

Acked-by: Paul Millar
Target: master, 0.18