tahoe-lafs/trac-2024-07-25
2
0
Issues 1.1k Wiki

fix the definition of needs-rebalancing #2105

New Issue
Closed
opened 2013-11-14 17:41:38 +00:00 by daira · 13 comments
daira commented 2013-11-14 17:41:38 +00:00
Owner
Copy Link

Split from #1784 (also see /tahoe-lafs/trac-2024-07-25/issues/6177#comment:27):

The value of needs-rebalancing is computed inconsistently between checker.py and filenode.py. In checker.py it is computed as:

# The file needs rebalancing if the set of servers that have at least
# one share is less than the number of uniquely-numbered shares
# available.
# TODO: this may be wrong, see ticket #1115 comment:27 and ticket #1784.
needs_rebalancing = bool(good_share_hosts < len(verifiedshares))

In filenode.py it is computed as

# TODO: this may be wrong, see ticket #1115 comment:27 and ticket #1784.
needs_rebalancing = bool(len(sm) >= verifycap.total_shares)

where len(sm) is equal to count-shares-good. I don't understand this latter definition at all, it looks completely wrong. The definition in checker.py is more subtly wrong because it credits servers that only have duplicated shares as contributing to existing balance. The correct definition should be something like 'iff the happiness count is less than the number of uniquely-numbered good shares available'.

I propose to change filenode.py and checker.py to be consistent, and to both use the happiness-based definition above.

Split from #1784 (also see [/tahoe-lafs/trac-2024-07-25/issues/6177](/tahoe-lafs/trac-2024-07-25/issues/6177)#comment:27): The value of `needs-rebalancing` is computed inconsistently between `checker.py` and `filenode.py`. In `checker.py` it is computed as: ``` # The file needs rebalancing if the set of servers that have at least # one share is less than the number of uniquely-numbered shares # available. # TODO: this may be wrong, see ticket #1115 comment:27 and ticket #1784. needs_rebalancing = bool(good_share_hosts < len(verifiedshares)) ``` In `filenode.py` it is computed as ``` # TODO: this may be wrong, see ticket #1115 comment:27 and ticket #1784. needs_rebalancing = bool(len(sm) >= verifycap.total_shares) ``` where `len(sm)` is equal to `count-shares-good`. I don't understand this latter definition at all, it looks completely wrong. The definition in `checker.py` is more subtly wrong because it credits servers that only have duplicated shares as contributing to existing balance. The correct definition should be something like 'iff the happiness count is less than the number of uniquely-numbered good shares available'. I propose to change `filenode.py` and `checker.py` to be consistent, and to both use the happiness-based definition above.
tahoe-lafs added the
unknown
normal
defect
1.10.0
 labels 2013-11-14 17:41:38 +00:00
tahoe-lafs added this to the undecided milestone 2013-11-14 17:41:38 +00:00
tahoe-lafs added
code-frontend-web
 and removed
unknown
 labels 2013-11-14 17:42:46 +00:00
tahoe-lafs modified the milestone from undecided to 1.11.0 2013-11-14 17:42:46 +00:00
daira commented 2013-11-14 17:49:05 +00:00
Author
Owner
Copy Link

"comments and a caveat in webapi.rst indicating that the needs-rebalancing field may be computed incorrectly" were added in b06f8cd8d03a6239/trunk.

"comments and a caveat in webapi.rst indicating that the needs-rebalancing field may be computed incorrectly" were added in b06f8cd8d03a6239/trunk.
tahoe-lafs added
1.9.1
 and removed
1.10.0
 labels 2013-11-14 17:50:32 +00:00
zooko commented 2013-11-18 04:31:12 +00:00
Copy Link

I think this ticket is actually about "needs-repair" rather than about "needs-rebalancing". I'm not 100% sure of the definition of "needs-rebalancing", but I think of it as something like "The file doesn't need repair (i.e. its Happiness level is already above the requirement), but it would be better to move some of the shares around to other servers.

Possible reasons that moving shares might be useful even when it doesn't improve Happiness:

  • to optimize for faster-finding of the shares by moving them to servers earlier in the permuted ring, or
  • to move shares from servers that are full to servers that are mostly empty (load-balancing total storage)
I think this ticket is actually about "needs-repair" rather than about "needs-rebalancing". I'm not 100% sure of the definition of "needs-rebalancing", but I think of it as something like "The file *doesn't* need repair (i.e. its Happiness level is already above the requirement), but it would be better to move some of the shares around to other servers. Possible reasons that moving shares might be useful even when it doesn't improve Happiness: * to optimize for faster-finding of the shares by moving them to servers earlier in the permuted ring, or * to move shares from servers that are full to servers that are mostly empty (load-balancing total storage)
daira commented 2013-12-05 15:53:29 +00:00
Author
Owner
Copy Link

Replying to zooko:

I think this ticket is actually about "needs-repair" rather than about "needs-rebalancing". I'm not 100% sure of the definition of "needs-rebalancing", but I think of it as something like "The file doesn't need repair (i.e. its Happiness level is already above the requirement), but it would be better to move some of the shares around to other servers.

From source:docs/frontends/webapi.rst@0bebbe32#debugging-and-testing-features:

  needs-rebalancing: (bool) This field is intended to be True iff
                     reliability could be improved for this file by
                     rebalancing, i.e. by moving some shares to other
                     servers. It may be incorrect in some cases for
                     Tahoe-LAFS up to and including v1.10, and its
                     precise definition is expected to change.

Reliability can be improved when the shares-of-happiness count is less than shares.total. (In some cases, adding more servers may be necessary for an improvement, but I think that's fine.)

Replying to [zooko](/tahoe-lafs/trac-2024-07-25/issues/2105#issuecomment-93890): > I think this ticket is actually about "needs-repair" rather than about "needs-rebalancing". I'm not 100% sure of the definition of "needs-rebalancing", but I think of it as something like "The file *doesn't* need repair (i.e. its Happiness level is already above the requirement), but it would be better to move some of the shares around to other servers. From source:docs/frontends/webapi.rst@0bebbe32#debugging-and-testing-features: ``` needs-rebalancing: (bool) This field is intended to be True iff reliability could be improved for this file by rebalancing, i.e. by moving some shares to other servers. It may be incorrect in some cases for Tahoe-LAFS up to and including v1.10, and its precise definition is expected to change. ``` Reliability can be improved when the shares-of-happiness count is less than `shares.total`. (In some cases, adding more servers may be necessary for an improvement, but I think that's fine.)
daira commented 2013-12-05 16:33:08 +00:00
Author
Owner
Copy Link

We decided to remove needs-rebalancing for 1.11.

We decided to remove `needs-rebalancing` for 1.11.
daira commented 2013-12-05 18:31:29 +00:00
Author
Owner
Copy Link

https://github.com/tahoe-lafs/tahoe-lafs/pull/74 implements this ticket (i.e. removes need-rebalancing) and #1784.

<https://github.com/tahoe-lafs/tahoe-lafs/pull/74> implements this ticket (i.e. removes `need-rebalancing`) and #1784.
remyroy commented 2014-03-19 16:35:18 +00:00
Author
Owner
Copy Link

I'll review this patch/pull request.

I'll review this patch/pull request.
remyroy commented 2014-03-20 15:32:54 +00:00
Author
Owner
Copy Link

Review:

Everything seems great except for the use of the somewhat confusing "Happiness Count" expression. Count is fine for something countable like the number of good shares but it seems wrong for this. I think it would be preferable to use something like "Happiness Level", "Happiness Metric" or "Servers-of-Happiness Level".

Reassigning to daira for patch changes.

Review: Everything seems great except for the use of the somewhat confusing "Happiness Count" expression. Count is fine for something countable like the number of good shares but it seems wrong for this. I think it would be preferable to use something like "Happiness Level", "Happiness Metric" or "Servers-of-Happiness Level". Reassigning to daira for patch changes.
daira commented 2014-03-20 16:08:48 +00:00
Author
Owner
Copy Link

Zooko convinced me in the Tahoe hack hour to use "Happiness Level" (because it goes well with "happiness threshold").

Zooko convinced me in the Tahoe hack hour to use "Happiness Level" (because it goes well with "happiness threshold").
Daira Hopwood <daira@jacaranda.org> commented 2014-03-20 16:21:14 +00:00
Author
Owner
Copy Link

In /tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80:

Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
In [/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80](/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80): ``` Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105 Signed-off-by: Daira Hopwood <daira@jacaranda.org> ```
tahoe-lafs added the
fixed
 label 2014-03-20 16:21:14 +00:00
Daira Hopwood <daira@jacaranda.org> closed this issue 2014-03-20 16:21:14 +00:00
Daira Hopwood <daira@jacaranda.org> commented 2014-03-27 22:15:02 +00:00
Author
Owner
Copy Link

In /tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80:

Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
In [/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80](/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80): ``` Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105 Signed-off-by: Daira Hopwood <daira@jacaranda.org> ```
Daira Hopwood <daira@jacaranda.org> commented 2014-03-29 00:19:00 +00:00
Author
Owner
Copy Link

In /tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80:

Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
In [/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80](/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80): ``` Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105 Signed-off-by: Daira Hopwood <daira@jacaranda.org> ```
Daira Hopwood <daira@jacaranda.org> commented 2014-03-29 00:43:09 +00:00
Author
Owner
Copy Link

In /tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80:

Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
In [/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80](/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80): ``` Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105 Signed-off-by: Daira Hopwood <daira@jacaranda.org> ```
Daira Hopwood <daira@jacaranda.org> commented 2014-03-29 00:56:06 +00:00
Author
Owner
Copy Link

In /tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80:

Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
In [/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80](/tahoe-lafs/trac-2024-07-25/commit/0ef593947755a8b81edc73d033219724268faf80): ``` Remove 'needs-rebalancing' and add 'count-happiness' to checker reports; repair tests. fixes #1784, #2105 Signed-off-by: Daira Hopwood <daira@jacaranda.org> ```
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels   
0.2.0

   
0.3.0

   
0.4.0

   
0.5.0

   
0.5.1

   
0.6.0

   
0.6.1

   
0.7.0

   
0.8.0

   
0.9.0

   
1.0.0

   
1.1.0

   
1.10.0

   
1.10.1

   
1.10.2

   
1.10a2

   
1.11.0

   
1.12.0

   
1.12.1

   
1.13.0

   
1.14.0

   
1.15.0

   
1.15.1

   
1.2.0

   
1.3.0

   
1.4.1

   
1.5.0

   
1.6.0

   
1.6.1

   
1.7.0

   
1.7.1

   
1.7β

   
1.8.0

   
1.8.1

   
1.8.2

   
1.8.3

   
1.8β

   
1.9.0

   
1.9.0-s3branch

   
1.9.0a1

   
1.9.0a2

   
1.9.0b1

   
1.9.1

   
1.9.2

   
1.9.2a1

   
LeastAuthority.com automation

   
blocker

   
cannot reproduce

   
cloud-branch

   
code

catch-all for anything that can be fixed by writing code but isn't classified better

  
code-dirnodes

anything involving tahoe directories

  
code-encoding

immutable-file encoding format/layout, cap format, encoding/decoding algorithms

  
code-frontend

general frontend things: new user-facing interfaces, FTP/SFTP servers, FUSE-like interfaces

  
code-frontend-cli

CLI tools

  
code-frontend-ftp-sftp

   
code-frontend-magic-folder

   
code-frontend-web

webapi interfaces, user-facing "WUI" interfaces

  
code-mutable

anything involving mutable files: encoding/decoding, share format

  
code-network

Introducer, locating storage servers, establishing/maintaining connections to them

  
code-nodeadmin

node startup/shutdown, tools to create nodes, logging tools, management/monitoring tools, manhole, disk-space-limiting tools

  
code-peerselection

server selection/sorting algorithm, rebalancing code, allocation policy, swarming-download

  
code-storage

storage-server implementation, share-storage directory layout, client-to-server share transfer protocol

  
contrib

problems with non-core things that live in the source:contrib/ directory

  
critical

   
defect

   
dev-infrastructure

things that help us build Tahoe: buildbot, automated speed/memory/code-coverage tests and results-displayers, IRC channels, mailing lists, this Trac instance

  
documentation

docs items. Also use 'docs' keyword on tickets in more specific components.

  
duplicate

   
enhancement

   
fixed

   
invalid

   
major

   
minor

   
n/a

   
normal

   
operational

things involved in running a tahoe grid, external tools to monitor/maintain a grid (like "nodeadmin" but larger-scale). Was also used for issues with the allmydata.com grid.

  
packaging

setup.py script, library dependencies, binary packages, licensing, installation instructions

  
somebody else's problem

   
supercritical

   
task

   
trivial

   
unknown

Uncategorized. All tickets default to this component until someone updates it.

  
was already fixed

   
website

things about the tahoe-lafs.org website (and sometimes this Trac instance, shared with 'dev-infrastructure')

  
wontfix

   
worksforme
No Label
0.2.0
0.3.0
0.4.0
0.5.0
0.5.1
0.6.0
0.6.1
0.7.0
0.8.0
0.9.0
1.0.0
1.1.0
1.10.0
1.10.1
1.10.2
1.10a2
1.11.0
1.12.0
1.12.1
1.13.0
1.14.0
1.15.0
1.15.1
1.2.0
1.3.0
1.4.1
1.5.0
1.6.0
1.6.1
1.7.0
1.7.1
1.7β
1.8.0
1.8.1
1.8.2
1.8.3
1.8β
1.9.0
1.9.0-s3branch
1.9.0a1
1.9.0a2
1.9.0b1
1.9.1
1.9.2
1.9.2a1
LeastAuthority.com automation
blocker
cannot reproduce
cloud-branch
code
code-dirnodes
code-encoding
code-frontend
code-frontend-cli
code-frontend-ftp-sftp
code-frontend-magic-folder
code-frontend-web
code-mutable
code-network
code-nodeadmin
code-peerselection
code-storage
contrib
critical
defect
dev-infrastructure
documentation
duplicate
enhancement
fixed
invalid
major
minor
n/a
normal
operational
packaging
somebody else's problem
supercritical
task
trivial
unknown
was already fixed
website
wontfix
worksforme
Milestone
Clear milestone
No items
No Milestone
1.10.1
Assignees
Clear assignees
No Assignees
2 Participants
Notifications
Due Date
The due date is invalid or out of range. Please use the format 'yyyy-mm-dd'.

No due date set.

Reference: tahoe-lafs/trac-2024-07-25#2105
No description provided.
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?