Change-Id: I7c44e3603df2dd368cb7c0ba0072413b887b6903
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This makes the intended use of the classes more clear. It also
simplifies generic functions that write reftables: they only need a
ReftableWriter as argument, as the stream is carried within the
ReftableWriter.

Change-Id: Idbb06f89ae33100f0c0b562cc38e5b3b026d5181
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Move the implementation of the static equals() method to a new method
and suppress the error. Deprecate the old method to signal that we
intend to remove it in the next major release.

See https://errorprone.info/bugpattern/AmbiguousMethodReference

Change-Id: I5e29c97f4db3e11770be589a6ccd785e2c9ac7f2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Callers of getAllRefs that only iterate over the `values()` of the
returned map can be trivially fixed to call getRefDatabase().getRefs()
instead.

Only fix those where the calling method is already declared to throw
IOException, to avoid potential API changes.

Change-Id: I2b05f785077a1713953cfd42df7bf915f889f90b
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

A tombstone will prevent a delayed reference update from resurrecting the
deleted reference.

Change-Id: Id9f4df43d435a299ff16cef614821439edef9b11
Signed-off-by: Minh Thai <mthai@google.com>

This ensure DfsReftableDatabase is tested by the same test suites that
use/test InMemoryRepository. It also simplifies the logic of
InMemoryRepository and brings its compatibility story closer to any
other DFS repository that uses reftables for its reference storage.

Change-Id: I881469fd77ed11a9239b477633510b8c482a19ca
Signed-off-by: Minh Thai <mthai@google.com>
Signed-off-by: Terry Parker <tparker@google.com>

If a ReftableConfig has been supplied by the caller, write out a
reftable as a sibling of the the GC pack, alongside the heads.

To bootstrap from a non-reftable system, the refs are read from the
DfsRefDatabase if no GC reftables are present.  Its assumed the
references are fully current, and do not need to be merged with any
other reftables.  Any non-GC reftables will be pruned at the end of
the GC cycle, just like any packs that were replaced.

If a GC reftable is present, all existing reftables are compacted, and
references from DfsRefDatabase are only used to seed the packer.  Its
assumed these are consistent with each other.

Change-Id: Ie397eb58aaaefb6865c816d9b39de3ac12998019

If set, "singlePack" will create a single GC pack file for all
objects reachable from refs/*. If not set, the GC pack will contain
object reachable from refs/heads/* and refs/tags/*, and the GC_REST
pack will contain all other reachable objects.

Change-Id: I56bcb6a9da2c10a0909c2f940c025db6f3acebcb
Signed-off-by: Terry Parker <tparker@google.com>

Necessary if a DFS implementation wants to override close()
to record DfsReaderIoStats.

Change-Id: I144575f9bf1abf2c1fd72030550c4f0795fcf44d

Delete the condition to check whether the garbage pack creation time
is older than the last GC operation, because it's not possible to
find the last GC operation time when there is no GC pack.

Add additional tests to make sure the contents of the expired garbage
packs are considered during the GC operation and any actively
referenced objects from the garbage packs are copied successfully
into the GC pack before deleting the garbage pack.

Change-Id: I09e8b2656de8ba7f9b996724ad1961d908e937b6
Signed-off-by: Thirumala Reddy Mutchukota <thirumala@google.com>

In 8ac65d33ed PackWriter changed its
behavior to always prefer the last object representation presented
to it by the ObjectReuseAsIs implementation. This was a fix to avoid
delta chain cycles.

Unfortunately it can lead to suboptimal compression when concurrent
GCs are run on the same repository. One case is automatic GC running
(with default settings) in parallel to a manual GC that has disabled
delta reuse in order to generate new smaller deltas for the entire
history of the repository.

Running GC with no-reuse generally requires more CPU time, which
also translates to a longer running time.  This can lead to a race
where the automatic GC completes before the no-reuse GC, leaving
the repository in a state such as:

  no-reuse GC:   size 1 GiB, mtime = 18:45
  auto GC:       size 8 GiB, mtime = 17:30

With the default sort ordering, the smaller no-reuse GC pack is
sorted earlier in the pack list, due to its more recent mtime.

During object reuse in a future GC, these smaller representations
are considered first by PackWriter, but are all discarded when the
auto GC file from 17:30 is examined second (due to its older mtime).

Work around this in two ways.

Well formed DFS repositories should have at most 1 GC pack. If
2 or more GC packs exist, break the sorting tie by selecting the
smaller file earlier in the pack list. This allows all normal read
code paths to favor the smaller file, which places less pressure
on the DfsBlockCache. If any GC race happens, readers serving clone
requests will prefer the file that is smaller.

During object reuse, flip this ordering so that the smaller file is
last. This allows PackWriter to see smaller deltas last, replacing
larger representations that were previously considered from other
pack files.

Change-Id: I0b7dc8bb9711c82abd6bd16643f518cfccc6d31a

Disabling the garbage pack coalescing when garbageTtl > 0 can result in
lot of garbage packs if they are created within the garbageTtl time.

To avoid a large number of garbage packs, re-introducing garbage pack
coalescing for the packs that are created within a single calendar day
when the garbageTtl is more than one day or one third of the garbageTtl.

Change-Id: If969716aeb55fb4fd0ff71d75f41a07638cd5a69
Signed-off-by: Thirumala Reddy Mutchukota <thirumala@google.com>

The Compacter and Garbage Collector will record the estimated size of
the newly going to be created compact, gc or garbage packs. This
information can be used by the clients to better make a call on how to
actually store the pack based on the approximated expected size.

Added a new protected method DfsObjDatabase.newPack(PackSource
packSource, long estimatedPackSize), so that the clients can override
this method to make use of the estimatedPackSize while creating a new
PackDescription object. The default implementation of this method is
equivalent to
newPack(packSource).setEstimatedPackSize(estimatedPackSize). I didn't
make it abstract because that would force all the existing sub classes
of DfsObjDatabase to implement this method. Due to this default
implementation, the estimatedPackSize is added to DfsPackDescription
using a setter instead of a constructor parameter (even though
constructor parameter would be a better choice as this value is set only
during the object creation).

Change-Id: Iade1122633ea774c2e842178a6a6cbb4a57b598b
Signed-off-by: Thirumala Reddy Mutchukota <thirumala@google.com>

DfsGarbageCollector will now enforce a maximum time to live (TTL) for
UNREACHABLE_GARBAGE packs.  The default TTL is 1 day, which should be
enough time to avoid races with other processes that are inserting
data into the repository.

Change-Id: Id719e6e2a03cfc9a0c0aef8ed71d261dda14bd0c
Signed-off-by: Mike Williams <miwilliams@google.com>