redict/tests/integration/psync2-master-restart.tcl

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start_server {tags {"psync2 external:skip"}} {
start_server {} {
start_server {} {
set master [srv 0 client]
set master_host [srv 0 host]
set master_port [srv 0 port]
set replica [srv -1 client]
set replica_host [srv -1 host]
set replica_port [srv -1 port]
set sub_replica [srv -2 client]
# Make sure the server saves an RDB on shutdown
$master config set save "3600 1"
# Because we will test partial resync later, we dont want a timeout to cause
# the master-replica disconnect, then the extra reconnections will break the
# sync_partial_ok stat test
$master config set repl-timeout 3600
$replica config set repl-timeout 3600
$sub_replica config set repl-timeout 3600
# Build replication chain
$replica replicaof $master_host $master_port
$sub_replica replicaof $replica_host $replica_port
wait_for_condition 50 100 {
[status $replica master_link_status] eq {up} &&
[status $sub_replica master_link_status] eq {up}
} else {
fail "Replication not started."
}
# Avoid PINGs
$master config set repl-ping-replica-period 3600
$master config rewrite
# Generate some data
createComplexDataset $master 1000
test "PSYNC2: Partial resync after Master restart using RDB aux fields" {
wait_for_condition 500 100 {
[status $master master_repl_offset] == [status $replica master_repl_offset] &&
[status $master master_repl_offset] == [status $sub_replica master_repl_offset]
} else {
fail "Replicas and master offsets were unable to match *exactly*."
}
set replid [status $master master_replid]
set offset [status $master master_repl_offset]
$replica config resetstat
catch {
Wait for replicas when shutting down (#9872) To avoid data loss, this commit adds a grace period for lagging replicas to catch up the replication offset. Done: * Wait for replicas when shutdown is triggered by SIGTERM and SIGINT. * Wait for replicas when shutdown is triggered by the SHUTDOWN command. A new blocked client type BLOCKED_SHUTDOWN is introduced, allowing multiple clients to call SHUTDOWN in parallel. Note that they don't expect a response unless an error happens and shutdown is aborted. * Log warning for each replica lagging behind when finishing shutdown. * CLIENT_PAUSE_WRITE while waiting for replicas. * Configurable grace period 'shutdown-timeout' in seconds (default 10). * New flags for the SHUTDOWN command: - NOW disables the grace period for lagging replicas. - FORCE ignores errors writing the RDB or AOF files which would normally prevent a shutdown. - ABORT cancels ongoing shutdown. Can't be combined with other flags. * New field in the output of the INFO command: 'shutdown_in_milliseconds'. The value is the remaining maximum time to wait for lagging replicas before finishing the shutdown. This field is present in the Server section **only** during shutdown. Not directly related: * When shutting down, if there is an AOF saving child, it is killed **even** if AOF is disabled. This can happen if BGREWRITEAOF is used when AOF is off. * Client pause now has end time and type (WRITE or ALL) per purpose. The different pause purposes are *CLIENT PAUSE command*, *failover* and *shutdown*. If clients are unpaused for one purpose, it doesn't affect client pause for other purposes. For example, the CLIENT UNPAUSE command doesn't affect client pause initiated by the failover or shutdown procedures. A completed failover or a failed shutdown doesn't unpause clients paused by the CLIENT PAUSE command. Notes: * DEBUG RESTART doesn't wait for replicas. * We already have a warning logged when a replica disconnects. This means that if any replica connection is lost during the shutdown, it is either logged as disconnected or as lagging at the time of exit. Co-authored-by: Oran Agra <oran@redislabs.com>
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# SHUTDOWN NOW ensures master doesn't send GETACK to replicas before
# shutting down which would affect the replication offset.
restart_server 0 true false true now
set master [srv 0 client]
}
wait_for_condition 50 1000 {
[status $replica master_link_status] eq {up} &&
[status $sub_replica master_link_status] eq {up}
} else {
fail "Replicas didn't sync after master restart"
}
# Make sure master restore replication info correctly
assert {[status $master master_replid] != $replid}
assert {[status $master master_repl_offset] == $offset}
assert {[status $master master_replid2] eq $replid}
assert {[status $master second_repl_offset] == [expr $offset+1]}
# Make sure master set replication backlog correctly
assert {[status $master repl_backlog_active] == 1}
assert {[status $master repl_backlog_first_byte_offset] == [expr $offset+1]}
assert {[status $master repl_backlog_histlen] == 0}
# Partial resync after Master restart
assert {[status $master sync_partial_ok] == 1}
assert {[status $replica sync_partial_ok] == 1}
}
test "PSYNC2: Partial resync after Master restart using RDB aux fields with expire" {
$master debug set-active-expire 0
for {set j 0} {$j < 1024} {incr j} {
$master select [expr $j%16]
$master set $j somevalue px 10
}
after 20
Wait for replicas when shutting down (#9872) To avoid data loss, this commit adds a grace period for lagging replicas to catch up the replication offset. Done: * Wait for replicas when shutdown is triggered by SIGTERM and SIGINT. * Wait for replicas when shutdown is triggered by the SHUTDOWN command. A new blocked client type BLOCKED_SHUTDOWN is introduced, allowing multiple clients to call SHUTDOWN in parallel. Note that they don't expect a response unless an error happens and shutdown is aborted. * Log warning for each replica lagging behind when finishing shutdown. * CLIENT_PAUSE_WRITE while waiting for replicas. * Configurable grace period 'shutdown-timeout' in seconds (default 10). * New flags for the SHUTDOWN command: - NOW disables the grace period for lagging replicas. - FORCE ignores errors writing the RDB or AOF files which would normally prevent a shutdown. - ABORT cancels ongoing shutdown. Can't be combined with other flags. * New field in the output of the INFO command: 'shutdown_in_milliseconds'. The value is the remaining maximum time to wait for lagging replicas before finishing the shutdown. This field is present in the Server section **only** during shutdown. Not directly related: * When shutting down, if there is an AOF saving child, it is killed **even** if AOF is disabled. This can happen if BGREWRITEAOF is used when AOF is off. * Client pause now has end time and type (WRITE or ALL) per purpose. The different pause purposes are *CLIENT PAUSE command*, *failover* and *shutdown*. If clients are unpaused for one purpose, it doesn't affect client pause for other purposes. For example, the CLIENT UNPAUSE command doesn't affect client pause initiated by the failover or shutdown procedures. A completed failover or a failed shutdown doesn't unpause clients paused by the CLIENT PAUSE command. Notes: * DEBUG RESTART doesn't wait for replicas. * We already have a warning logged when a replica disconnects. This means that if any replica connection is lost during the shutdown, it is either logged as disconnected or as lagging at the time of exit. Co-authored-by: Oran Agra <oran@redislabs.com>
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# Wait until master has received ACK from replica. If the master thinks
# that any replica is lagging when it shuts down, master would send
# GETACK to the replicas, affecting the replication offset.
set offset [status $master master_repl_offset]
wait_for_condition 500 100 {
Wait for replicas when shutting down (#9872) To avoid data loss, this commit adds a grace period for lagging replicas to catch up the replication offset. Done: * Wait for replicas when shutdown is triggered by SIGTERM and SIGINT. * Wait for replicas when shutdown is triggered by the SHUTDOWN command. A new blocked client type BLOCKED_SHUTDOWN is introduced, allowing multiple clients to call SHUTDOWN in parallel. Note that they don't expect a response unless an error happens and shutdown is aborted. * Log warning for each replica lagging behind when finishing shutdown. * CLIENT_PAUSE_WRITE while waiting for replicas. * Configurable grace period 'shutdown-timeout' in seconds (default 10). * New flags for the SHUTDOWN command: - NOW disables the grace period for lagging replicas. - FORCE ignores errors writing the RDB or AOF files which would normally prevent a shutdown. - ABORT cancels ongoing shutdown. Can't be combined with other flags. * New field in the output of the INFO command: 'shutdown_in_milliseconds'. The value is the remaining maximum time to wait for lagging replicas before finishing the shutdown. This field is present in the Server section **only** during shutdown. Not directly related: * When shutting down, if there is an AOF saving child, it is killed **even** if AOF is disabled. This can happen if BGREWRITEAOF is used when AOF is off. * Client pause now has end time and type (WRITE or ALL) per purpose. The different pause purposes are *CLIENT PAUSE command*, *failover* and *shutdown*. If clients are unpaused for one purpose, it doesn't affect client pause for other purposes. For example, the CLIENT UNPAUSE command doesn't affect client pause initiated by the failover or shutdown procedures. A completed failover or a failed shutdown doesn't unpause clients paused by the CLIENT PAUSE command. Notes: * DEBUG RESTART doesn't wait for replicas. * We already have a warning logged when a replica disconnects. This means that if any replica connection is lost during the shutdown, it is either logged as disconnected or as lagging at the time of exit. Co-authored-by: Oran Agra <oran@redislabs.com>
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[string match "*slave0:*,offset=$offset,*" [$master info replication]] &&
$offset == [status $replica master_repl_offset] &&
$offset == [status $sub_replica master_repl_offset]
} else {
show_cluster_status
fail "Replicas and master offsets were unable to match *exactly*."
}
set offset [status $master master_repl_offset]
$replica config resetstat
catch {
Wait for replicas when shutting down (#9872) To avoid data loss, this commit adds a grace period for lagging replicas to catch up the replication offset. Done: * Wait for replicas when shutdown is triggered by SIGTERM and SIGINT. * Wait for replicas when shutdown is triggered by the SHUTDOWN command. A new blocked client type BLOCKED_SHUTDOWN is introduced, allowing multiple clients to call SHUTDOWN in parallel. Note that they don't expect a response unless an error happens and shutdown is aborted. * Log warning for each replica lagging behind when finishing shutdown. * CLIENT_PAUSE_WRITE while waiting for replicas. * Configurable grace period 'shutdown-timeout' in seconds (default 10). * New flags for the SHUTDOWN command: - NOW disables the grace period for lagging replicas. - FORCE ignores errors writing the RDB or AOF files which would normally prevent a shutdown. - ABORT cancels ongoing shutdown. Can't be combined with other flags. * New field in the output of the INFO command: 'shutdown_in_milliseconds'. The value is the remaining maximum time to wait for lagging replicas before finishing the shutdown. This field is present in the Server section **only** during shutdown. Not directly related: * When shutting down, if there is an AOF saving child, it is killed **even** if AOF is disabled. This can happen if BGREWRITEAOF is used when AOF is off. * Client pause now has end time and type (WRITE or ALL) per purpose. The different pause purposes are *CLIENT PAUSE command*, *failover* and *shutdown*. If clients are unpaused for one purpose, it doesn't affect client pause for other purposes. For example, the CLIENT UNPAUSE command doesn't affect client pause initiated by the failover or shutdown procedures. A completed failover or a failed shutdown doesn't unpause clients paused by the CLIENT PAUSE command. Notes: * DEBUG RESTART doesn't wait for replicas. * We already have a warning logged when a replica disconnects. This means that if any replica connection is lost during the shutdown, it is either logged as disconnected or as lagging at the time of exit. Co-authored-by: Oran Agra <oran@redislabs.com>
2022-01-02 02:50:15 -05:00
# Unlike the test above, here we use SIGTERM, which behaves
# differently compared to SHUTDOWN NOW if there are lagging
# replicas. This is just to increase coverage and let each test use
# a different shutdown approach. In this case there are no lagging
# replicas though.
restart_server 0 true false
set master [srv 0 client]
}
wait_for_condition 50 1000 {
[status $replica master_link_status] eq {up} &&
[status $sub_replica master_link_status] eq {up}
} else {
fail "Replicas didn't sync after master restart"
}
set expired_offset [status $master repl_backlog_histlen]
# Stale keys expired and master_repl_offset grows correctly
assert {[status $master rdb_last_load_keys_expired] == 1024}
assert {[status $master master_repl_offset] == [expr $offset+$expired_offset]}
# Partial resync after Master restart
assert {[status $master sync_partial_ok] == 1}
assert {[status $replica sync_partial_ok] == 1}
set digest [$master debug digest]
assert {$digest eq [$replica debug digest]}
assert {$digest eq [$sub_replica debug digest]}
}
test "PSYNC2: Full resync after Master restart when too many key expired" {
$master config set repl-backlog-size 16384
$master config rewrite
$master debug set-active-expire 0
Replication backlog and replicas use one global shared replication buffer (#9166) ## Background For redis master, one replica uses one copy of replication buffer, that is a big waste of memory, more replicas more waste, and allocate/free memory for every reply list also cost much. If we set client-output-buffer-limit small and write traffic is heavy, master may disconnect with replicas and can't finish synchronization with replica. If we set client-output-buffer-limit big, master may be OOM when there are many replicas that separately keep much memory. Because replication buffers of different replica client are the same, one simple idea is that all replicas only use one replication buffer, that will effectively save memory. Since replication backlog content is the same as replicas' output buffer, now we can discard replication backlog memory and use global shared replication buffer to implement replication backlog mechanism. ## Implementation I create one global "replication buffer" which contains content of replication stream. The structure of "replication buffer" is similar to the reply list that exists in every client. But the node of list is `replBufBlock`, which has `id, repl_offset, refcount` fields. ```c /* Replication buffer blocks is the list of replBufBlock. * * +--------------+ +--------------+ +--------------+ * | refcount = 1 | ... | refcount = 0 | ... | refcount = 2 | * +--------------+ +--------------+ +--------------+ * | / \ * | / \ * | / \ * Repl Backlog Replia_A Replia_B * * Each replica or replication backlog increments only the refcount of the * 'ref_repl_buf_node' which it points to. So when replica walks to the next * node, it should first increase the next node's refcount, and when we trim * the replication buffer nodes, we remove node always from the head node which * refcount is 0. If the refcount of the head node is not 0, we must stop * trimming and never iterate the next node. */ /* Similar with 'clientReplyBlock', it is used for shared buffers between * all replica clients and replication backlog. */ typedef struct replBufBlock { int refcount; /* Number of replicas or repl backlog using. */ long long id; /* The unique incremental number. */ long long repl_offset; /* Start replication offset of the block. */ size_t size, used; char buf[]; } replBufBlock; ``` So now when we feed replication stream into replication backlog and all replicas, we only need to feed stream into replication buffer `feedReplicationBuffer`. In this function, we set some fields of replication backlog and replicas to references of the global replication buffer blocks. And we also need to check replicas' output buffer limit to free if exceeding `client-output-buffer-limit`, and trim replication backlog if exceeding `repl-backlog-size`. When sending reply to replicas, we also need to iterate replication buffer blocks and send its content, when totally sending one block for replica, we decrease current node count and increase the next current node count, and then free the block which reference is 0 from the head of replication buffer blocks. Since now we use linked list to manage replication backlog, it may cost much time for iterating all linked list nodes to find corresponding replication buffer node. So we create a rax tree to store some nodes for index, but to avoid rax tree occupying too much memory, i record one per 64 nodes for index. Currently, to make partial resynchronization as possible as much, we always let replication backlog as the last reference of replication buffer blocks, backlog size may exceeds our setting if slow replicas that reference vast replication buffer blocks, and this method doesn't increase memory usage since they share replication buffer. To avoid freezing server for freeing unreferenced replication buffer blocks when we need to trim backlog for exceeding backlog size setting, we trim backlog incrementally (free 64 blocks per call now), and make it faster in `beforeSleep` (free 640 blocks). ### Other changes - `mem_total_replication_buffers`: we add this field in INFO command, it means the total memory of replication buffers used. - `mem_clients_slaves`: now even replica is slow to replicate, and its output buffer memory is not 0, but it still may be 0, since replication backlog and replicas share one global replication buffer, only if replication buffer memory is more than the repl backlog setting size, we consider the excess as replicas' memory. Otherwise, we think replication buffer memory is the consumption of repl backlog. - Key eviction Since all replicas and replication backlog share global replication buffer, we think only the part of exceeding backlog size the extra separate consumption of replicas. Because we trim backlog incrementally in the background, backlog size may exceeds our setting if slow replicas that reference vast replication buffer blocks disconnect. To avoid massive eviction loop, we don't count the delayed freed replication backlog into used memory even if there are no replicas, i.e. we also regard this memory as replicas's memory. - `client-output-buffer-limit` check for replica clients It doesn't make sense to set the replica clients output buffer limit lower than the repl-backlog-size config (partial sync will succeed and then replica will get disconnected). Such a configuration is ignored (the size of repl-backlog-size will be used). This doesn't have memory consumption implications since the replica client will share the backlog buffers memory. - Drop replication backlog after loading data if needed We always create replication backlog if server is a master, we need it because we put DELs in it when loading expired keys in RDB, but if RDB doesn't have replication info or there is no rdb, it is not possible to support partial resynchronization, to avoid extra memory of replication backlog, we drop it. - Multi IO threads Since all replicas and replication backlog use global replication buffer, if I/O threads are enabled, to guarantee data accessing thread safe, we must let main thread handle sending the output buffer to all replicas. But before, other IO threads could handle sending output buffer of all replicas. ## Other optimizations This solution resolve some other problem: - When replicas disconnect with master since of out of output buffer limit, releasing the output buffer of replicas may freeze server if we set big `client-output-buffer-limit` for replicas, but now, it doesn't cause freezing. - This implementation may mitigate reply list copy cost time(also freezes server) when one replication has huge reply buffer and another replica can copy buffer for full synchronization. now, we just copy reference info, it is very light. - If we set replication backlog size big, it also may cost much time to copy replication backlog into replica's output buffer. But this commit eliminates this problem. - Resizing replication backlog size doesn't empty current replication backlog content.
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# Make sure replication backlog is full and will be trimmed.
for {set j 0} {$j < 2048} {incr j} {
$master select [expr $j%16]
$master set $j somevalue px 10
}
after 20
wait_for_condition 500 100 {
[status $master master_repl_offset] == [status $replica master_repl_offset] &&
[status $master master_repl_offset] == [status $sub_replica master_repl_offset]
} else {
fail "Replicas and master offsets were unable to match *exactly*."
}
$replica config resetstat
catch {
Wait for replicas when shutting down (#9872) To avoid data loss, this commit adds a grace period for lagging replicas to catch up the replication offset. Done: * Wait for replicas when shutdown is triggered by SIGTERM and SIGINT. * Wait for replicas when shutdown is triggered by the SHUTDOWN command. A new blocked client type BLOCKED_SHUTDOWN is introduced, allowing multiple clients to call SHUTDOWN in parallel. Note that they don't expect a response unless an error happens and shutdown is aborted. * Log warning for each replica lagging behind when finishing shutdown. * CLIENT_PAUSE_WRITE while waiting for replicas. * Configurable grace period 'shutdown-timeout' in seconds (default 10). * New flags for the SHUTDOWN command: - NOW disables the grace period for lagging replicas. - FORCE ignores errors writing the RDB or AOF files which would normally prevent a shutdown. - ABORT cancels ongoing shutdown. Can't be combined with other flags. * New field in the output of the INFO command: 'shutdown_in_milliseconds'. The value is the remaining maximum time to wait for lagging replicas before finishing the shutdown. This field is present in the Server section **only** during shutdown. Not directly related: * When shutting down, if there is an AOF saving child, it is killed **even** if AOF is disabled. This can happen if BGREWRITEAOF is used when AOF is off. * Client pause now has end time and type (WRITE or ALL) per purpose. The different pause purposes are *CLIENT PAUSE command*, *failover* and *shutdown*. If clients are unpaused for one purpose, it doesn't affect client pause for other purposes. For example, the CLIENT UNPAUSE command doesn't affect client pause initiated by the failover or shutdown procedures. A completed failover or a failed shutdown doesn't unpause clients paused by the CLIENT PAUSE command. Notes: * DEBUG RESTART doesn't wait for replicas. * We already have a warning logged when a replica disconnects. This means that if any replica connection is lost during the shutdown, it is either logged as disconnected or as lagging at the time of exit. Co-authored-by: Oran Agra <oran@redislabs.com>
2022-01-02 02:50:15 -05:00
# Unlike the test above, here we use SIGTERM. This is just to
# increase coverage and let each test use a different shutdown
# approach.
restart_server 0 true false
set master [srv 0 client]
}
wait_for_condition 50 1000 {
[status $replica master_link_status] eq {up} &&
[status $sub_replica master_link_status] eq {up}
} else {
fail "Replicas didn't sync after master restart"
}
# Replication backlog is full
assert {[status $master repl_backlog_first_byte_offset] > [status $master second_repl_offset]}
assert {[status $master sync_partial_ok] == 0}
assert {[status $master sync_full] == 1}
Replication backlog and replicas use one global shared replication buffer (#9166) ## Background For redis master, one replica uses one copy of replication buffer, that is a big waste of memory, more replicas more waste, and allocate/free memory for every reply list also cost much. If we set client-output-buffer-limit small and write traffic is heavy, master may disconnect with replicas and can't finish synchronization with replica. If we set client-output-buffer-limit big, master may be OOM when there are many replicas that separately keep much memory. Because replication buffers of different replica client are the same, one simple idea is that all replicas only use one replication buffer, that will effectively save memory. Since replication backlog content is the same as replicas' output buffer, now we can discard replication backlog memory and use global shared replication buffer to implement replication backlog mechanism. ## Implementation I create one global "replication buffer" which contains content of replication stream. The structure of "replication buffer" is similar to the reply list that exists in every client. But the node of list is `replBufBlock`, which has `id, repl_offset, refcount` fields. ```c /* Replication buffer blocks is the list of replBufBlock. * * +--------------+ +--------------+ +--------------+ * | refcount = 1 | ... | refcount = 0 | ... | refcount = 2 | * +--------------+ +--------------+ +--------------+ * | / \ * | / \ * | / \ * Repl Backlog Replia_A Replia_B * * Each replica or replication backlog increments only the refcount of the * 'ref_repl_buf_node' which it points to. So when replica walks to the next * node, it should first increase the next node's refcount, and when we trim * the replication buffer nodes, we remove node always from the head node which * refcount is 0. If the refcount of the head node is not 0, we must stop * trimming and never iterate the next node. */ /* Similar with 'clientReplyBlock', it is used for shared buffers between * all replica clients and replication backlog. */ typedef struct replBufBlock { int refcount; /* Number of replicas or repl backlog using. */ long long id; /* The unique incremental number. */ long long repl_offset; /* Start replication offset of the block. */ size_t size, used; char buf[]; } replBufBlock; ``` So now when we feed replication stream into replication backlog and all replicas, we only need to feed stream into replication buffer `feedReplicationBuffer`. In this function, we set some fields of replication backlog and replicas to references of the global replication buffer blocks. And we also need to check replicas' output buffer limit to free if exceeding `client-output-buffer-limit`, and trim replication backlog if exceeding `repl-backlog-size`. When sending reply to replicas, we also need to iterate replication buffer blocks and send its content, when totally sending one block for replica, we decrease current node count and increase the next current node count, and then free the block which reference is 0 from the head of replication buffer blocks. Since now we use linked list to manage replication backlog, it may cost much time for iterating all linked list nodes to find corresponding replication buffer node. So we create a rax tree to store some nodes for index, but to avoid rax tree occupying too much memory, i record one per 64 nodes for index. Currently, to make partial resynchronization as possible as much, we always let replication backlog as the last reference of replication buffer blocks, backlog size may exceeds our setting if slow replicas that reference vast replication buffer blocks, and this method doesn't increase memory usage since they share replication buffer. To avoid freezing server for freeing unreferenced replication buffer blocks when we need to trim backlog for exceeding backlog size setting, we trim backlog incrementally (free 64 blocks per call now), and make it faster in `beforeSleep` (free 640 blocks). ### Other changes - `mem_total_replication_buffers`: we add this field in INFO command, it means the total memory of replication buffers used. - `mem_clients_slaves`: now even replica is slow to replicate, and its output buffer memory is not 0, but it still may be 0, since replication backlog and replicas share one global replication buffer, only if replication buffer memory is more than the repl backlog setting size, we consider the excess as replicas' memory. Otherwise, we think replication buffer memory is the consumption of repl backlog. - Key eviction Since all replicas and replication backlog share global replication buffer, we think only the part of exceeding backlog size the extra separate consumption of replicas. Because we trim backlog incrementally in the background, backlog size may exceeds our setting if slow replicas that reference vast replication buffer blocks disconnect. To avoid massive eviction loop, we don't count the delayed freed replication backlog into used memory even if there are no replicas, i.e. we also regard this memory as replicas's memory. - `client-output-buffer-limit` check for replica clients It doesn't make sense to set the replica clients output buffer limit lower than the repl-backlog-size config (partial sync will succeed and then replica will get disconnected). Such a configuration is ignored (the size of repl-backlog-size will be used). This doesn't have memory consumption implications since the replica client will share the backlog buffers memory. - Drop replication backlog after loading data if needed We always create replication backlog if server is a master, we need it because we put DELs in it when loading expired keys in RDB, but if RDB doesn't have replication info or there is no rdb, it is not possible to support partial resynchronization, to avoid extra memory of replication backlog, we drop it. - Multi IO threads Since all replicas and replication backlog use global replication buffer, if I/O threads are enabled, to guarantee data accessing thread safe, we must let main thread handle sending the output buffer to all replicas. But before, other IO threads could handle sending output buffer of all replicas. ## Other optimizations This solution resolve some other problem: - When replicas disconnect with master since of out of output buffer limit, releasing the output buffer of replicas may freeze server if we set big `client-output-buffer-limit` for replicas, but now, it doesn't cause freezing. - This implementation may mitigate reply list copy cost time(also freezes server) when one replication has huge reply buffer and another replica can copy buffer for full synchronization. now, we just copy reference info, it is very light. - If we set replication backlog size big, it also may cost much time to copy replication backlog into replica's output buffer. But this commit eliminates this problem. - Resizing replication backlog size doesn't empty current replication backlog content.
2021-10-25 02:24:31 -04:00
assert {[status $master rdb_last_load_keys_expired] == 2048}
assert {[status $replica sync_full] == 1}
set digest [$master debug digest]
assert {$digest eq [$replica debug digest]}
assert {$digest eq [$sub_replica debug digest]}
}
}}}