- 21 Jun, 2012 1 commit
-
-
antirez authored
The way we compared the authentication password using strcmp() allowed an attacker to gain information about the password using a well known class of attacks called "timing attacks". The bug appears to be practically not exploitable in most modern systems running Redis since even using multiple bytes of differences in the input at a time instead of one the difference in running time in in the order of 10 nanoseconds, making it hard to exploit even on LAN. However attacks always get better so we are providing a fix ASAP. The new implementation uses two fixed length buffers and a constant time comparison function, with the goal of: 1) Completely avoid leaking information about the content of the password, since the comparison is always performed between 512 characters and without conditionals. 2) Partially avoid leaking information about the length of the password. About "2" we still have a stage in the code where the real password and the user provided password are copied in the static buffers, we also run two strlen() operations against the two inputs, so the running time of the comparison is a fixed amount plus a time proportional to LENGTH(A)+LENGTH(B). This means that the absolute time of the operation performed is still related to the length of the password in some way, but there is no way to change the input in order to get a difference in the execution time in the comparison that is not just proportional to the string provided by the user (because the password length is fixed). Thus in practical terms the user should try to discover LENGTH(PASSWORD) looking at the whole execution time of the AUTH command and trying to guess a proportionality between the whole execution time and the password length: this appears to be mostly unfeasible in the real world. Also protecting from this attack is not very useful in the case of Redis as a brute force attack is anyway feasible if the password is too short, while with a long password makes it not an issue that the attacker knows the length.
-
- 25 May, 2012 1 commit
-
-
antirez authored
The 'persistence' section of INFO output now contains additional four fields related to RDB and AOF persistence: rdb_last_bgsave_time_sec Duration of latest BGSAVE in sec. rdb_current_bgsave_time_sec Duration of current BGSAVE in sec. aof_last_rewrite_time_sec Duration of latest AOF rewrite in sec. aof_current_rewrite_time_sec Duration of current AOF rewrite in sec. The 'current' fields are set to -1 if a BGSAVE / AOF rewrite is not in progress. The 'last' fileds are set to -1 if no previous BGSAVE / AOF rewrites were performed. Additionally a few fields in the persistence section were renamed for consistency: changes_since_last_save -> rdb_changes_since_last_save bgsave_in_progress -> rdb_bgsave_in_progress last_save_time -> rdb_last_save_time last_bgsave_status -> rdb_last_bgsave_status bgrewriteaof_in_progress -> aof_rewrite_in_progress bgrewriteaof_scheduled -> aof_rewrite_scheduled After the renaming, fields in the persistence section start with rdb_ or aof_ prefix depending on the persistence method they describe. The field 'loading' and related fields are not prefixed because they are unique for both the persistence methods.
-
- 24 May, 2012 3 commits
-
-
antirez authored
The motivation for this new commands is to be search in the usage of Redis for real time statistics. See the article "Fast real time metrics using Redis". http://blog.getspool.com/2011/11/29/fast-easy-realtime-metrics-using-redis-bitmaps/ In general Redis strings when used as bitmaps using the SETBIT/GETBIT command provide a very space-efficient and fast way to store statistics. For instance in a web application with users, every user can be associated with a key that shows every day in which the user visited the web service. This information can be really valuable to extract user behaviour information. With Redis bitmaps doing this is very simple just saying that a given day is 0 (the data the service was put online) and all the next days are 1, 2, 3, and so forth. So with SETBIT it is possible to set the bit corresponding to the current day every time the user visits the site. It is possible to take the count of the bit sets on the run, this is extremely easy using a Lua script. However a fast bit count native operation can be useful, especially if it can operate on ranges, or when the string is small like in the case of days (even if you consider many years it is still extremely little data). For this reason BITOP was introduced. The command counts the number of bits set to 1 in a string, with optional range: BITCOUNT key [start end] The start/end parameters are similar to GETRANGE. If omitted the whole string is tested. Population counting is more useful when bit-level operations like AND, OR and XOR are avaialble. For instance I can test multiple users to see the number of days three users visited the site at the same time. To do this we can take the AND of all the bitmaps, and then count the set bits. For this reason the BITOP command was introduced: BITOP [AND|OR|XOR|NOT] dest_key src_key1 src_key2 src_key3 ... src_keyN In the special case of NOT (that inverts the bits) only one source key can be passed. The judicious use of BITCOUNT and BITOP combined can lead to interesting use cases with very space efficient representation of data. The implementation provided is still not tested and optimized for speed, next commits will introduce unit tests. Later the implementation will be profiled to see if it is possible to gain an important amount of speed without making the code much more complex.
-
antirez authored
The INFO output, persistence section, already contained the field describing the size of the current AOF buffer to flush on disk. However the other AOF buffer, used to accumulate changes during an AOF rewrite, was not mentioned in the INFO output. This commit introduces a new field called aof_rewrite_buffer_length with the length of the rewrite buffer.
-
antirez authored
During the AOF rewrite process, the parent process needs to accumulate the new writes in an in-memory buffer: when the child will terminate the AOF rewriting process this buffer (that ist the difference between the dataset when the rewrite was started, and the current dataset) is flushed to the new AOF file. We used to implement this buffer using an sds.c string, but sds.c has a 2GB limit. Sometimes the dataset can be big enough, the amount of writes so high, and the rewrite process slow enough that we overflow the 2GB limit, causing a crash, documented on github by issue #504. In order to prevent this from happening, this commit introduces a new system to accumulate writes, implemented by a linked list of blocks of 10 MB each, so that we also avoid paying the reallocation cost. Note that theoretically modern operating systems may implement realloc() simply as a remaping of the old pages, thus with very good performances, see for instance the mremap() syscall on Linux. However this is not always true, and jemalloc by default avoids doing this because there are issues with the current implementation of mremap(). For this reason we are using a linked list of blocks instead of a single block that gets reallocated again and again. The changes in this commit lacks testing, that will be performed before merging into the unstable branch. This fix will not enter 2.4 because it is too invasive. However 2.4 will log a warning when the AOF rewrite buffer is near to the 2GB limit.
-
- 14 May, 2012 3 commits
-
-
antirez authored
activeExpireCycle() can consume no more than a few milliseconds per iteration. This commit improves the precision of the check for the time elapsed in two ways: 1) We check every 16 iterations instead of the main loop instead of 256. 2) We reset iterations at the start of the function and not every time we switch to the next database, so the check is correctly performed every 16 iterations.
-
antirez authored
A previous commit introduced REDIS_HZ define that changes the frequency of calls to the serverCron() Redis function. This commit improves different related things: 1) Software watchdog: now the minimal period can be set according to REDIS_HZ. The minimal period is two times the timer period, that is: (1000/REDIS_HZ)*2 milliseconds 2) The incremental rehashing is now performed in the expires dictionary as well. 3) The activeExpireCycle() function was improved in different ways: - Now it checks if it already used too much time using microseconds instead of milliseconds for better precision. - The time limit is now calculated correctly, in the previous version the division was performed before of the multiplication resulting in a timelimit of 0 if HZ was big enough. - Databases with less than 1% of buckets fill in the hash table are skipped, because getting random keys is too expensive in this condition. 4) tryResizeHashTables() is now called at every timer call, we need to match the number of calls we do to the expired keys colleciton cycle. 5) REDIS_HZ was raised to 100.
-
antirez authored
Redis uses a function called serverCron() that is very similar to the timer interrupt of an operating system. This function is used to handle a number of asynchronous things, like active expired keys collection, clients timeouts, update of statistics, things related to the cluster and replication, triggering of BGSAVE and AOF rewrite process, and so forth. In the past the timer was called 1 time per second. At some point it was raised to 10 times per second, but it still was fixed and could not be changed even at compile time, because different functions called from serverCron() assumed a given fixed frequency. This commmit makes the frequency configurable, so that it is simpler to pick a good tradeoff between overhead of this function (that is usually very small) and the responsiveness of Redis during a few critical circumstances where a lot of work is done inside the timer. An example of such a critical condition is mass-expire of a lot of keys in the same second. Up to a given percentage of CPU time is used to perform expired keys collection per expire cylce. Now changing the REDIS_HZ macro it is possible to do less work but more times per second in order to block the server for less time. If this patch will work well in our tests it will enter Redis 2.6-final.
-
- 12 May, 2012 2 commits
-
-
antirez authored
-
antirez authored
If a large amonut of keys are all expiring about at the same time, the "active" expired keys collection cycle used to block as far as the percentage of already expired keys was >= 25% of the total population of keys with an expire set. This could block the server even for many seconds in order to reclaim memory ASAP. The new algorithm uses at max a small amount of milliseconds per cycle, even if this means reclaiming the memory less promptly it also means a more responsive server.
-
- 02 May, 2012 1 commit
-
-
antirez authored
We used to reply -ERR ... message ..., now the reply is instead -MASTERDOWN ... message ... so that it can be distinguished easily by the other error conditions.
-
- 27 Apr, 2012 1 commit
-
-
antirez authored
This commit reverts most of c5757662, in order to use back main stack for signal handling. The main reason is that otherwise it is completely pointless that we do a lot of efforts to print the stack trace on crash, and the content of the stack and registers as well. Using an alternate stack broken this feature completely.
-
- 19 Apr, 2012 1 commit
-
-
antirez authored
-
- 18 Apr, 2012 1 commit
-
-
antirez authored
1) Don't accept maxclients set to < 0 2) Allow maxclients < 1024, it is useful for testing.
-
- 13 Apr, 2012 3 commits
-
-
antirez authored
After considering the interaction between ability to delcare globals in scripts using the 'global' function, and the complexities related to hanlding replication and AOF in a sane way with globals AND ability to turn protection On and Off, we reconsidered the design. The new design makes clear that there is only one good way to write Redis scripts, that is not using globals. In the rare cases state must be retained across calls a Redis key can be used.
-
antirez authored
-
antirez authored
-
- 10 Apr, 2012 2 commits
- 08 Apr, 2012 1 commit
-
-
antirez authored
-
- 06 Apr, 2012 1 commit
-
-
antirez authored
-
- 05 Apr, 2012 1 commit
-
-
Premysl Hruby authored
-
- 04 Apr, 2012 4 commits
-
-
antirez authored
Structure field controlling the INFO field master_link_down_since_seconds initialized correctly to avoid strange INFO output at startup when a slave has yet to connect to its master.
-
antirez authored
-
antirez authored
-
antirez authored
Print milliseconds of the current second in log lines timestamps. Sometimes precise timing is very important for debugging.
-
- 03 Apr, 2012 1 commit
-
-
antirez authored
When the user-provided 'maxclients' value is too big for the max number of files we can open, at least try to search the max the OS is allowing (in steps of 256 filedes).
-
- 30 Mar, 2012 1 commit
-
-
Joseph Jang authored
occurs when two or more dbs are replicated and at least one of them is >db10
-
- 28 Mar, 2012 3 commits
- 27 Mar, 2012 1 commit
-
-
Premysl Hruby authored
-
- 25 Mar, 2012 1 commit
-
-
antirez authored
This new field counts all the times Redis is configured with AOF enabled and fsync policy 'everysec', but the previous fsync performed by the background thread was not able to complete within two seconds, forcing Redis to perform a write against the AOF file while the fsync is still in progress (likely a blocking operation).
-
- 24 Mar, 2012 1 commit
-
-
antirez authored
-
- 22 Mar, 2012 3 commits
-
-
antirez authored
-
antirez authored
DEBUG should not be flagged as w otherwise we can not call DEBUG DIGEST and other commands against read only slaves.
-
antirez authored
This commit introduces support for read only slaves via redis.conf and CONFIG GET/SET commands. Also various semantical fixes are implemented here: 1) MULTI/EXEC with only read commands now work where the server is into a state where writes (or commands increasing memory usage) are not allowed. Before this patch everything inside a transaction would fail in this conditions. 2) Scripts just calling read-only commands will work against read only slaves, when the server is out of memory, or when persistence is into an error condition. Before the patch EVAL always failed in this condition.
-
- 19 Mar, 2012 1 commit
-
-
antirez authored
-
- 18 Mar, 2012 2 commits