1. 28 Dec, 2021 1 commit
    • guybe7's avatar
      Remove incomplete fix of a broader problem (#10013) · 266d9506
      guybe7 authored
      Preventing COFIG SET maxmemory from propagating is just the tip of the iceberg.
      Module that performs a write operation in a notification can cause any
      command to be propagated, based on server.dirty
      
      We need to come up with a better solution.
      266d9506
  2. 27 Dec, 2021 1 commit
    • guybe7's avatar
      Fix race in propagation test (#10012) · 0f15e025
      guybe7 authored
      There's a race between testing DBSIZE and the thread starting.
      If the thread hadn't started by the time we checked DBISZE, no
      keys will have been evicted.
      The correct way is to check the evicted_keys stat.
      0f15e025
  3. 22 Dec, 2021 1 commit
    • guybe7's avatar
      Sort out mess around propagation and MULTI/EXEC (#9890) · 7ac21307
      guybe7 authored
      The mess:
      Some parts use alsoPropagate for late propagation, others using an immediate one (propagate()),
      causing edge cases, ugly/hacky code, and the tendency for bugs
      
      The basic idea is that all commands are propagated via alsoPropagate (i.e. added to a list) and the
      top-most call() is responsible for going over that list and actually propagating them (and wrapping
      them in MULTI/EXEC if there's more than one command). This is done in the new function,
      propagatePendingCommands.
      
      Callers to propagatePendingCommands:
      1. top-most call() (we want all nested call()s to add to the also_propagate array and just the top-most
         one to propagate them) - via `afterCommand`
      2. handleClientsBlockedOnKeys: it is out of call() context and it may propagate stuff - via `afterCommand`. 
      3. handleClientsBlockedOnKeys edge case: if the looked-up key is already expired, we will propagate the
         expire but will not unblock any client so `afterCommand` isn't called. in that case, we have to propagate
         the deletion explicitly.
      4. cron stuff: active-expire and eviction may also propagate stuff
      5. modules: the module API allows to propagate stuff from just about anywhere (timers, keyspace notifications,
         threads). I could have tried to catch all the out-of-call-context places but it seemed easier to handle it in one
         place: when we free the context. in the spirit of what was done in call(), only the top-most freeing of a module
         context may cause propagation.
      6. modules: when using a thread-safe ctx it's not clear when/if the ctx will be freed. we do know that the module
         must lock the GIL before calling RM_Replicate/RM_Call so we propagate the pending commands when
         releasing the GIL.
      
      A "known limitation", which were actually a bug, was fixed because of this commit (see propagate.tcl):
         When using a mix of RM_Call with `!` and RM_Replicate, the command would propagate out-of-order:
         first all the commands from RM_Call, and then the ones from RM_Replicate
      
      Another thing worth mentioning is that if, in the past, a client would issue a MULTI/EXEC with just one
      write command the server would blindly propagate the MULTI/EXEC too, even though it's redundant.
      not anymore.
      
      This commit renames propagate() to propagateNow() in order to cause conflicts in pending PRs.
      propagatePendingCommands is the only caller of propagateNow, which is now a static, internal helper function.
      
      Optimizations:
      1. alsoPropagate will not add stuff to also_propagate if there's no AOF and replicas
      2. alsoPropagate reallocs also_propagagte exponentially, to save calls to memmove
      
      Bugfixes:
      1. CONFIG SET can create evictions, sending notifications which can cause to dirty++ with modules.
         we need to prevent it from propagating to AOF/replicas
      2. We need to set current_client in RM_Call. buggy scenario:
         - CONFIG SET maxmemory, eviction notifications, module hook calls RM_Call
         - assertion in lookupKey crashes, because current_client has CONFIG SET, which isn't CMD_WRITE
      3. minor: in eviction, call propagateDeletion after notification, like active-expire and all commands
         (we always send a notification before propagating the command)
      7ac21307
  4. 19 Apr, 2021 1 commit
    • guybe7's avatar
      Modules: Replicate lazy-expire even if replication is not allowed (#8816) · f40ca9cb
      guybe7 authored
      Before this commit using RM_Call without "!" could cause the master
      to lazy-expire a key (delete it) but without replicating to replicas.
      This could cause the replica's memory usage to gradually grow and
      could also cause consistency issues if the master and replica have
      a clock diff.
      This bug was introduced in #8617
      
      Added a test which demonstrates that scenario.
      f40ca9cb
  5. 15 Mar, 2021 1 commit
    • guybe7's avatar
      Missing EXEC on modules propagation after failed EVAL execution (#8654) · dba33a94
      guybe7 authored
      1. moduleReplicateMultiIfNeeded should use server.in_eval like
         moduleHandlePropagationAfterCommandCallback
      2. server.in_eval could have been set to 1 and not reset back
         to 0 (a lot of missed early-exits after in_eval is already 1)
      
      Note: The new assertions in processCommand cover (2) and I added
      two module tests to cover (1)
      
      Implications:
      If an EVAL that failed (and thus left server.in_eval=1) runs before a module
      command that replicates, the replication stream will contain MULTI (because
      moduleReplicateMultiIfNeeded used to check server.lua_caller which is NULL
      at this point) but not EXEC (because server.in_eval==1)
      This only affects modules as module.c the only user of server.in_eval.
      
      Affects versions 6.2.0, 6.2.1
      dba33a94
  6. 10 Mar, 2021 1 commit
    • guybe7's avatar
      Fix some issues with modules and MULTI/EXEC (#8617) · 3d0b427c
      guybe7 authored
      Bug 1:
      When a module ctx is freed moduleHandlePropagationAfterCommandCallback
      is called and handles propagation. We want to prevent it from propagating
      commands that were not replicated by the same context. Example:
      1. module1.foo does: RM_Replicate(cmd1); RM_Call(cmd2); RM_Replicate(cmd3)
      2. RM_Replicate(cmd1) propagates MULTI and adds cmd1 to also_propagagte
      3. RM_Call(cmd2) create a new ctx, calls call() and destroys the ctx.
      4. moduleHandlePropagationAfterCommandCallback is called, calling
         alsoPropagates EXEC (Note: EXEC is still not written to socket),
         setting server.in_trnsaction = 0
      5. RM_Replicate(cmd3) is called, propagagting yet another MULTI (now
         we have nested MULTI calls, which is no good) and then cmd3
      
      We must prevent RM_Call(cmd2) from resetting server.in_transaction.
      REDISMODULE_CTX_MULTI_EMITTED was revived for that purpose.
      
      Bug 2:
      Fix issues with nested RM_Call where some have '!' and some don't.
      Example:
      1. module1.foo does RM_Call of module2.bar without replication (i.e. no '!')
      2. module2.bar internally calls RM_Call of INCR with '!'
      3. at the end of module1.foo we call RM_ReplicateVerbatim
      
      We want the replica/AOF to see only module1.foo and not the INCR from module2.bar
      
      Introduced a global replication_allowed flag inside RM_Call to determine
      whether we need to replicate or not (even if '!' was specified)
      
      Other changes:
      Split beforePropagateMultiOrExec to beforePropagateMulti afterPropagateExec
      just for better readability
      3d0b427c
  7. 22 Dec, 2020 1 commit
    • Oran Agra's avatar
      Remove read-only flag from non-keyspace cmds, different approach for EXEC to... · 411c18bb
      Oran Agra authored
      Remove read-only flag from non-keyspace cmds, different approach for EXEC to propagate MULTI (#8216)
      
      In the distant history there was only the read flag for commands, and whatever
      command that didn't have the read flag was a write one.
      Then we added the write flag, but some portions of the code still used !read
      Also some commands that don't work on the keyspace at all, still have the read
      flag.
      
      Changes in this commit:
      1. remove the read-only flag from TIME, ECHO, ROLE and LASTSAVE
      
      2. EXEC command used to decides if it should propagate a MULTI by looking at
         the command flags (!read & !admin).
         When i was about to change it to look at the write flag instead, i realized
         that this would cause it not to propagate a MULTI for PUBLISH, EVAL, and
         SCRIPT, all 3 are not marked as either a read command or a write one (as
         they should), but all 3 are calling forceCommandPropagation.
      
         So instead of introducing a new flag to denote a command that "writes" but
         not into the keyspace, and still needs propagation, i decided to rely on
         the forceCommandPropagation, and just fix the code to propagate MULTI when
         needed rather than depending on the command flags at all.
      
         The implication of my change then is that now it won't decide to propagate
         MULTI when it sees one of these: SELECT, PING, INFO, COMMAND, TIME and
         other commands which are neither read nor write.
      
      3. Changing getNodeByQuery and clusterRedirectBlockedClientIfNeeded in
         cluster.c to look at !write rather than read flag.
         This should have no implications, since these code paths are only reachable
         for commands which access keys, and these are always marked as either read
         or write.
      
      This commit improve MULTI propagation tests, for modules and a bunch of
      other special cases, all of which used to pass already before that commit.
      the only one that test change that uncovered a change of behavior is the
      one that DELs a non-existing key, it used to propagate an empty
      multi-exec block, and no longer does.
      411c18bb
  8. 31 Mar, 2020 2 commits
  9. 03 Oct, 2019 1 commit