Adds the ability to track the lag of a consumer group (CG), that is, the number
of entries yet-to-be-delivered from the stream.
The proposed constant-time solution is in the spirit of "best-effort."
Partially addresses #8737.
## Description of approach
We add a new "entries_added" property to the stream. This starts at 0 for a new
stream and is incremented by 1 with every `XADD`. It is essentially an all-time
counter of the entries added to the stream.
Given the stream's length and this counter value, we can trivially find the logical
"entries_added" counter of the first ID if and only if the stream is contiguous.
A fragmented stream contains one or more tombstones generated by `XDEL`s.
The new "xdel_max_id" stream property tracks the latest tombstone.
The CG also tracks its last delivered ID's as an "entries_read" counter and
increments it independently when delivering new messages, unless the this
read counter is invalid (-1 means invalid offset). When the CG's counter is
available, the reported lag is the difference between added and read counters.
Lastly, this also adds a "first_id" field to the stream structure in order to make
looking it up cheaper in most cases.
## Limitations
There are two cases in which the mechanism isn't able to track the lag.
In these cases, `XINFO` replies with `null` in the "lag" field.
The first case is when a CG is created with an arbitrary last delivered ID,
that isn't "0-0", nor the first or the last entries of the stream. In this case,
it is impossible to obtain a valid read counter (short of an O(N) operation).
The second case is when there are one or more tombstones fragmenting
the stream's entries range.
In both cases, given enough time and assuming that the consumers are
active (reading and lacking) and advancing, the CG should be able to
catch up with the tip of the stream and report zero lag.
Once that's achieved, lag tracking would resume as normal (until the
next tombstone is set).
## API changes
* `XGROUP CREATE` added with the optional named argument `[ENTRIESREAD entries-read]`
for explicitly specifying the new CG's counter.
* `XGROUP SETID` added with an optional positional argument `[ENTRIESREAD entries-read]`
for specifying the CG's counter.
* `XINFO` reports the maximal tombstone ID, the recorded first entry ID, and total
number of entries added to the stream.
* `XINFO` reports the current lag and logical read counter of CGs.
* `XSETID` is an internal command that's used in replication/aof. It has been added with
the optional positional arguments `[ENTRIESADDED entries-added] [MAXDELETEDID max-deleted-entry-id]`
for propagating the CG's offset and maximal tombstone ID of the stream.
## The generic unsolved problem
The current stream implementation doesn't provide an efficient way to obtain the
approximate/exact size of a range of entries. While it could've been nice to have
that ability (#5813) in general, let alone specifically in the context of CGs, the risk
and complexities involved in such implementation are in all likelihood prohibitive.
## A refactoring note
The `streamGetEdgeID` has been refactored to accommodate both the existing seek
of any entry as well as seeking non-deleted entries (the addition of the `skip_tombstones`
argument). Furthermore, this refactoring also migrated the seek logic to use the
`streamIterator` (rather than `raxIterator`) that was, in turn, extended with the
`skip_tombstones` Boolean struct field to control the emission of these.
Co-authored-by: Guy Benoish <guy.benoish@redislabs.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
Adds the ability to autogenerate the sequence part of the millisecond-only explicit ID specified for `XADD`. This is useful in case added entries have an externally-provided timestamp without sub-millisecond resolution.
Fixes:
- When a consumer is created as a side effect, redis didn't issue a keyspace notification,
nor incremented the server.dirty (affects periodic snapshots).
this was a bug in XREADGROUP, XCLAIM, and XAUTOCLAIM.
- When attempting to delete a non-existent consumer, don't issue a keyspace notification
and don't increment server.dirty
this was a bug in XGROUP DELCONSUMER
Other changes:
- Changed streamLookupConsumer() to always only do lookup consumer (never do implicit creation),
Its last seen time is updated unless the SLC_NO_REFRESH flag is specified.
- Added streamCreateConsumer() to create a new consumer. When the creation is successful,
it will notify and dirty++ unless the SCC_NO_NOTIFY or SCC_NO_DIRTIFY flags is specified.
- Changed streamDelConsumer() to always only do delete consumer.
- Added keyspace notifications tests about stream events.
This PR adds a spell checker CI action that will fail future PRs if they introduce typos and spelling mistakes.
This spell checker is based on blacklist of common spelling mistakes, so it will not catch everything,
but at least it is also unlikely to cause false positives.
Besides that, the PR also fixes many spelling mistakes and types, not all are a result of the spell checker we use.
Here's a summary of other changes:
1. Scanned the entire source code and fixes all sorts of typos and spelling mistakes (including missing or extra spaces).
2. Outdated function / variable / argument names in comments
3. Fix outdated keyspace masks error log when we check `config.notify-keyspace-events` in loadServerConfigFromString.
4. Trim the white space at the end of line in `module.c`. Check: https://github.com/redis/redis/pull/7751
5. Some outdated https link URLs.
6. Fix some outdated comment. Such as:
- In README: about the rdb, we used to said create a `thread`, change to `process`
- dbRandomKey function coment (about the dictGetRandomKey, change to dictGetFairRandomKey)
- notifyKeyspaceEvent fucntion comment (add type arg)
- Some others minor fix in comment (Most of them are incorrectly quoted by variable names)
7. Modified the error log so that users can easily distinguish between TCP and TLS in `changeBindAddr`
APIs added for these stream operations: add, delete, iterate and
trim (by ID or maxlength). The functions are prefixed by RM_Stream.
* RM_StreamAdd
* RM_StreamDelete
* RM_StreamIteratorStart
* RM_StreamIteratorStop
* RM_StreamIteratorNextID
* RM_StreamIteratorNextField
* RM_StreamIteratorDelete
* RM_StreamTrimByLength
* RM_StreamTrimByID
The type RedisModuleStreamID is added and functions for converting
from and to RedisModuleString.
* RM_CreateStringFromStreamID
* RM_StringToStreamID
Whenever the stream functions return REDISMODULE_ERR, errno is set to
provide additional error information.
Refactoring: The zset iterator fields in the RedisModuleKey struct
are wrapped in a union, to allow the same space to be used for type-
specific info for streams and allow future use for other key types.
When loading an encoded payload we will at least do a shallow validation to
check that the size that's encoded in the payload matches the size of the
allocation.
This let's us later use this encoded size to make sure the various offsets
inside encoded payload don't reach outside the allocation, if they do, we'll
assert/panic, but at least we won't segfault or smear memory.
We can also do 'deep' validation which runs on all the records of the encoded
payload and validates that they don't contain invalid offsets. This lets us
detect corruptions early and reject a RESTORE command rather than accepting
it and asserting (crashing) later when accessing that payload via some command.
configuration:
- adding ACL flag skip-sanitize-payload
- adding config sanitize-dump-payload [yes/no/clients]
For now, we don't have a good way to ensure MIGRATE in cluster resharding isn't
being slowed down by these sanitation, so i'm setting the default value to `no`,
but later on it should be set to `clients` by default.
changes:
- changing rdbReportError not to `exit` in RESTORE command
- adding a new stat to be able to later check if cluster MIGRATE isn't being
slowed down by sanitation.
Syntax:
COPY <key> <new-key> [DB <dest-db>] [REPLACE]
No support for module keys yet.
Co-authored-by: tmgauss
Co-authored-by: Itamar Haber <itamar@redislabs.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
XREADGROUP auto-creates the consumer inside the consumer group the
first time it saw it.
When XREADGROUP is being used with NOACK option, the message will not
be added into the client's PEL and XGROUP SETID would be propagated.
When the replica gets the XGROUP SETID it will only update the last delivered
id of the group, but will not create the consumer.
So, in this commit XGROUP CREATECONSUMER is being added.
Command pattern: XGROUP CREATECONSUMER <key> <group> <consumer>.
When NOACK option is being used, createconsumer command would be
propagated as well.
In case of AOFREWRITE, consumer with an empty PEL would be saved with
XGROUP CREATECONSUMER whereas consumer with pending entries would be
saved with XCLAIM
This commit solves several edge cases that are related to
exhausting the streamID limits: We should correctly calculate
the succeeding streamID instead of blindly incrementing 'seq'
This affects both XREAD and XADD.
Other (unrelated) changes:
Reply with a better error message when trying to add an entry
to a stream that has exhausted last_id
Fixes GitHub issue #6492
Added stream support in RM_KeyType and RM_ValueLength.
Also moduleDelKeyIfEmpty was updated, even though it has
no effect now (It will be relevant when stream type direct
API will be coded - i.e. RM_StreamAdd)
now that replica can read rdb directly from the socket, it should avoid exiting
on short read and instead try to re-sync.
this commit tries to have minimal effects on non-diskless rdb reading.
and includes a test that tries to trigger this scenario on various read cases.
The approach used is to set a fixed header at the start of every
listpack blob (that contains many entries). The header contains a
"master" ID and fields, that are initially just obtained from the first
entry inserted in the listpack, so that the first enty is always well
compressed. Later every new entry is checked against these fields, and
if it matches, the SAMEFIELD flag is set in the entry so that we know to
just use the master entry flags. The IDs are always delta-encoded
against the first entry. This approach avoids cascading effects in which
entries are encoded depending on the previous entries, in order to avoid
complexity and rewritings of the data when data is removed in the middle
(which is a planned feature).
