mirror of
https://codeberg.org/redict/redict.git
synced 2025-01-22 16:18:28 -05:00
d0da0a6a3f
Allow running blocking commands from within a module using `RM_Call`. Today, when `RM_Call` is used, the fake client that is used to run command is marked with `CLIENT_DENY_BLOCKING` flag. This flag tells the command that it is not allowed to block the client and in case it needs to block, it must fallback to some alternative (either return error or perform some default behavior). For example, `BLPOP` fallback to simple `LPOP` if it is not allowed to block. All the commands must respect the `CLIENT_DENY_BLOCKING` flag (including module commands). When the command invocation finished, Redis asserts that the client was not blocked. This PR introduces the ability to call blocking command using `RM_Call` by passing a callback that will be called when the client will get unblocked. In order to do that, the user must explicitly say that he allow to perform blocking command by passing a new format specifier argument, `K`, to the `RM_Call` function. This new flag will tell Redis that it is allow to run blocking command and block the client. In case the command got blocked, Redis will return a new type of call reply (`REDISMODULE_REPLY_PROMISE`). This call reply indicates that the command got blocked and the user can set the on_unblocked handler using `RM_CallReplyPromiseSetUnblockHandler`. When clients gets unblocked, it eventually reaches `processUnblockedClients` function. This is where we check if the client is a fake module client and if it is, we call the unblock callback instead of performing the usual unblock operations. **Notice**: `RM_CallReplyPromiseSetUnblockHandler` must be called atomically along side the command invocation (without releasing the Redis lock in between). In addition, unlike other CallReply types, the promise call reply must be released by the module when the Redis GIL is acquired. The module can abort the execution on the blocking command (if it was not yet executed) using `RM_CallReplyPromiseAbort`. the API will return `REDISMODULE_OK` on success and `REDISMODULE_ERR` if the operation is already executed. **Notice** that in case of misbehave module, Abort might finished successfully but the operation will not really be aborted. This can only happened if the module do not respect the disconnect callback of the blocked client. For pure Redis commands this can not happened. ### Atomicity Guarantees The API promise that the unblock handler will run atomically as an execution unit. This means that all the operation performed on the unblock handler will be wrapped with a multi exec transaction when replicated to the replica and AOF. The API **do not** grantee any other atomicity properties such as when the unblock handler will be called. This gives us the flexibility to strengthen the grantees (or not) in the future if we will decide that we need a better guarantees. That said, the implementation **does** provide a better guarantees when performing pure Redis blocking command like `BLPOP`. In this case the unblock handler will run atomically with the operation that got unblocked (for example, in case of `BLPOP`, the unblock handler will run atomically with the `LPOP` operation that run when the command got unblocked). This is an implementation detail that might be change in the future and the module writer should not count on that. ### Calling blocking commands while running on script mode (`S`) `RM_Call` script mode (`S`) was introduced on #0372. It is used for usecases where the command that was invoked on `RM_Call` comes from a user input and we want to make sure the user will not run dangerous commands like `shutdown`. Some command, such as `BLPOP`, are marked with `NO_SCRIPT` flag, which means they will not be allowed on script mode. Those commands are marked with `NO_SCRIPT` just because they are blocking commands and not because they are dangerous. Now that we can run blocking commands on RM_Call, there is no real reason not to allow such commands on script mode. The underline problem is that the `NO_SCRIPT` flag is abused to also mark some of the blocking commands (notice that those commands know not to block the client if it is not allowed to do so, and have a fallback logic to such cases. So even if those commands were not marked with `NO_SCRIPT` flag, it would not harm Redis, and today we can already run those commands within multi exec). In addition, not all blocking commands are marked with `NO_SCRIPT` flag, for example `blmpop` are not marked and can run from within a script. Those facts shows that there are some ambiguity about the meaning of the `NO_SCRIPT` flag, and its not fully clear where it should be use. The PR suggest that blocking commands should not be marked with `NO_SCRIPT` flag, those commands should handle `CLIENT_DENY_BLOCKING` flag and only block when it's safe (like they already does today). To achieve that, the PR removes the `NO_SCRIPT` flag from the following commands: * `blmove` * `blpop` * `brpop` * `brpoplpush` * `bzpopmax` * `bzpopmin` * `wait` This might be considered a breaking change as now, on scripts, instead of getting `command is not allowed from script` error, the user will get some fallback behavior base on the command implementation. That said, the change matches the behavior of scripts and multi exec with respect to those commands and allow running them on `RM_Call` even when script mode is used. ### Additional RedisModule API and changes * `RM_BlockClientSetPrivateData` - Set private data on the blocked client without the need to unblock the client. This allows up to set the promise CallReply as the private data of the blocked client and abort it if the client gets disconnected. * `RM_BlockClientGetPrivateData` - Return the current private data set on a blocked client. We need it so we will have access to this private data on the disconnect callback. * On RM_Call, the returned reply will be added to the auto memory context only if auto memory is enabled, this allows us to keep the call reply for longer time then the context lifetime and does not force an unneeded borrow relationship between the CallReply and the RedisModuleContext. |
||
|---|---|---|
| .. | ||
| assets | ||
| cluster | ||
| helpers | ||
| integration | ||
| modules | ||
| sentinel | ||
| support | ||
| tmp | ||
| unit | ||
| instances.tcl | ||
| README.md | ||
| test_helper.tcl | ||
Redis Test Suite
The normal execution mode of the test suite involves starting and manipulating
local redis-server instances, inspecting process state, log files, etc.
The test suite also supports execution against an external server, which is
enabled using the --host and --port parameters. When executing against an
external server, tests tagged external:skip are skipped.
There are additional runtime options that can further adjust the test suite to match different external server configurations:
| Option | Impact |
|---|---|
--singledb |
Only use database 0, don't assume others are supported. |
--ignore-encoding |
Skip all checks for specific encoding. |
--ignore-digest |
Skip key value digest validations. |
--cluster-mode |
Run in strict Redis Cluster compatibility mode. |
--large-memory |
Enables tests that consume more than 100mb |
Tags
Tags are applied to tests to classify them according to the subsystem they test, but also to indicate compatibility with different run modes and required capabilities.
Tags can be applied in different context levels:
start_servercontexttagscontext that bundles several tests together- A single test context.
The following compatibility and capability tags are currently used:
| Tag | Indicates |
|---|---|
external:skip |
Not compatible with external servers. |
cluster:skip |
Not compatible with --cluster-mode. |
large-memory |
Test that requires more than 100mb |
tls:skip |
Not compatible with --tls. |
needs:repl |
Uses replication and needs to be able to SYNC from server. |
needs:debug |
Uses the DEBUG command or other debugging focused commands (like OBJECT REFCOUNT). |
needs:pfdebug |
Uses the PFDEBUG command. |
needs:config-maxmemory |
Uses CONFIG SET to manipulate memory limit, eviction policies, etc. |
needs:config-resetstat |
Uses CONFIG RESETSTAT to reset statistics. |
needs:reset |
Uses RESET to reset client connections. |
needs:save |
Uses SAVE or BGSAVE to create an RDB file. |
When using an external server (--host and --port), filtering using the
external:skip tags is done automatically.
When using --cluster-mode, filtering using the cluster:skip tag is done
automatically.
When not using --large-memory, filtering using the largemem:skip tag is done
automatically.
In addition, it is possible to specify additional configuration. For example, to
run tests on a server that does not permit SYNC use:
./runtest --host <host> --port <port> --tags -needs:repl