redict/tests/integration/psync2-pingoff.tcl
Binbin cea7809cea
Fix race condition in psync2-pingoff test (#9712)
Test failed on freebsd:
```
*** [err]: Make the old master a replica of the new one and check conditions in tests/integration/psync2-pingoff.tcl
Expected '162' to be equal to '176' (context: type eval line 18 cmd {assert_equal [status $R(0) master_repl_offset] [status $R(1) master_repl_offset]} proc ::test)
```

There are two possible race conditions in the test.

1. The code waits for sync_full to increment, and assumes that means the
master did the fork. But in fact there are cases the master will increment
that sync_full counter (after replica asks for sync), but will see that
there's already a fork running and will delay the fork creation.

In this case the INCR will be executed before the fork happens, so it'll
not be in the command stream. Solve that by waiting for `master_link_status: up`
on the replica before the INCR.

2. The repl-ping-replica-period is still high (1 second), so there's a chance the
master will send an additional PING between the two calls to INFO (the line that
fails is the one that samples INFO from both servers). So there's a chance one of
them will have an incremented offset due to PING and the other won't have it yet.

In theory we can wait for the repl_offset to match, but then we risk facing a
situation where that race will hide an offset mis-match. so instead, i think we
should just change repl-ping-replica-period to prevent further pings from being pushed.

Co-authored-by: Oran Agra <oran@redislabs.com>
2021-11-01 16:07:08 +02:00

251 lines
9.5 KiB
Tcl

# These tests were added together with the meaningful offset implementation
# in redis 6.0.0, which was later abandoned in 6.0.4, they used to test that
# servers are able to PSYNC with replicas even if the replication stream has
# PINGs at the end which present in one sever and missing on another.
# We keep these tests just because they reproduce edge cases in the replication
# logic in hope they'll be able to spot some problem in the future.
start_server {tags {"psync2 external:skip"}} {
start_server {} {
# Config
set debug_msg 0 ; # Enable additional debug messages
for {set j 0} {$j < 2} {incr j} {
set R($j) [srv [expr 0-$j] client]
set R_host($j) [srv [expr 0-$j] host]
set R_port($j) [srv [expr 0-$j] port]
$R($j) CONFIG SET repl-ping-replica-period 1
if {$debug_msg} {puts "Log file: [srv [expr 0-$j] stdout]"}
}
# Setup replication
test "PSYNC2 pingoff: setup" {
$R(1) replicaof $R_host(0) $R_port(0)
$R(0) set foo bar
wait_for_condition 50 1000 {
[status $R(1) master_link_status] == "up" &&
[$R(0) dbsize] == 1 && [$R(1) dbsize] == 1
} else {
fail "Replicas not replicating from master"
}
}
test "PSYNC2 pingoff: write and wait replication" {
$R(0) INCR counter
$R(0) INCR counter
$R(0) INCR counter
wait_for_condition 50 1000 {
[$R(0) GET counter] eq [$R(1) GET counter]
} else {
fail "Master and replica don't agree about counter"
}
}
# In this test we'll make sure the replica will get stuck, but with
# an active connection: this way the master will continue to send PINGs
# every second (we modified the PING period earlier)
test "PSYNC2 pingoff: pause replica and promote it" {
$R(1) MULTI
$R(1) DEBUG SLEEP 5
$R(1) SLAVEOF NO ONE
$R(1) EXEC
$R(1) ping ; # Wait for it to return back available
}
test "Make the old master a replica of the new one and check conditions" {
# We set the new master's ping period to a high value, so that there's
# no chance for a race condition of sending a PING in between the two
# INFO calls in the assert for master_repl_offset match below.
$R(1) CONFIG SET repl-ping-replica-period 1000
assert_equal [status $R(1) sync_full] 0
$R(0) REPLICAOF $R_host(1) $R_port(1)
wait_for_condition 50 1000 {
[status $R(0) master_link_status] == "up"
} else {
fail "The new master was not able to sync"
}
# make sure replication is still alive and kicking
$R(1) incr x
wait_for_condition 50 1000 {
[status $R(0) loading] == 0 &&
[$R(0) get x] == 1
} else {
fail "replica didn't get incr"
}
assert_equal [status $R(0) master_repl_offset] [status $R(1) master_repl_offset]
}
}}
start_server {tags {"psync2 external:skip"}} {
start_server {} {
start_server {} {
start_server {} {
start_server {} {
test {test various edge cases of repl topology changes with missing pings at the end} {
set master [srv -4 client]
set master_host [srv -4 host]
set master_port [srv -4 port]
set replica1 [srv -3 client]
set replica2 [srv -2 client]
set replica3 [srv -1 client]
set replica4 [srv -0 client]
$replica1 replicaof $master_host $master_port
$replica2 replicaof $master_host $master_port
$replica3 replicaof $master_host $master_port
$replica4 replicaof $master_host $master_port
wait_for_condition 50 1000 {
[status $master connected_slaves] == 4
} else {
fail "replicas didn't connect"
}
$master incr x
wait_for_condition 50 1000 {
[$replica1 get x] == 1 && [$replica2 get x] == 1 &&
[$replica3 get x] == 1 && [$replica4 get x] == 1
} else {
fail "replicas didn't get incr"
}
# disconnect replica1 and replica2
# and wait for the master to send a ping to replica3 and replica4
$replica1 replicaof no one
$replica2 replicaof 127.0.0.1 1 ;# we can't promote it to master since that will cycle the replication id
$master config set repl-ping-replica-period 1
set replofs [status $master master_repl_offset]
wait_for_condition 50 100 {
[status $replica3 master_repl_offset] > $replofs &&
[status $replica4 master_repl_offset] > $replofs
} else {
fail "replica didn't sync in time"
}
# make everyone sync from the replica1 that didn't get the last ping from the old master
# replica4 will keep syncing from the old master which now syncs from replica1
# and replica2 will re-connect to the old master (which went back in time)
set new_master_host [srv -3 host]
set new_master_port [srv -3 port]
$replica3 replicaof $new_master_host $new_master_port
$master replicaof $new_master_host $new_master_port
$replica2 replicaof $master_host $master_port
wait_for_condition 50 1000 {
[status $replica2 master_link_status] == "up" &&
[status $replica3 master_link_status] == "up" &&
[status $replica4 master_link_status] == "up" &&
[status $master master_link_status] == "up"
} else {
fail "replicas didn't connect"
}
# make sure replication is still alive and kicking
$replica1 incr x
wait_for_condition 50 1000 {
[$replica2 get x] == 2 &&
[$replica3 get x] == 2 &&
[$replica4 get x] == 2 &&
[$master get x] == 2
} else {
fail "replicas didn't get incr"
}
# make sure we have the right amount of full syncs
assert_equal [status $master sync_full] 6
assert_equal [status $replica1 sync_full] 2
assert_equal [status $replica2 sync_full] 0
assert_equal [status $replica3 sync_full] 0
assert_equal [status $replica4 sync_full] 0
# force psync
$master client kill type master
$replica2 client kill type master
$replica3 client kill type master
$replica4 client kill type master
# make sure replication is still alive and kicking
$replica1 incr x
wait_for_condition 50 1000 {
[$replica2 get x] == 3 &&
[$replica3 get x] == 3 &&
[$replica4 get x] == 3 &&
[$master get x] == 3
} else {
fail "replicas didn't get incr"
}
# make sure we have the right amount of full syncs
assert_equal [status $master sync_full] 6
assert_equal [status $replica1 sync_full] 2
assert_equal [status $replica2 sync_full] 0
assert_equal [status $replica3 sync_full] 0
assert_equal [status $replica4 sync_full] 0
}
}}}}}
start_server {tags {"psync2 external:skip"}} {
start_server {} {
start_server {} {
for {set j 0} {$j < 3} {incr j} {
set R($j) [srv [expr 0-$j] client]
set R_host($j) [srv [expr 0-$j] host]
set R_port($j) [srv [expr 0-$j] port]
$R($j) CONFIG SET repl-ping-replica-period 1
}
test "Chained replicas disconnect when replica re-connect with the same master" {
# Add a second replica as a chained replica of the current replica
$R(1) replicaof $R_host(0) $R_port(0)
$R(2) replicaof $R_host(1) $R_port(1)
wait_for_condition 50 1000 {
[status $R(2) master_link_status] == "up"
} else {
fail "Chained replica not replicating from its master"
}
# Do a write on the master, and wait for the master to
# send some PINGs to its replica
$R(0) INCR counter2
set replofs [status $R(0) master_repl_offset]
wait_for_condition 50 100 {
[status $R(1) master_repl_offset] > $replofs &&
[status $R(2) master_repl_offset] > $replofs
} else {
fail "replica didn't sync in time"
}
set sync_partial_master [status $R(0) sync_partial_ok]
set sync_partial_replica [status $R(1) sync_partial_ok]
$R(0) CONFIG SET repl-ping-replica-period 100
# Disconnect the master's direct replica
$R(0) client kill type replica
wait_for_condition 50 1000 {
[status $R(1) master_link_status] == "up" &&
[status $R(2) master_link_status] == "up" &&
[status $R(0) sync_partial_ok] == $sync_partial_master + 1 &&
[status $R(1) sync_partial_ok] == $sync_partial_replica
} else {
fail "Disconnected replica failed to PSYNC with master"
}
# Verify that the replica and its replica's meaningful and real
# offsets match with the master
assert_equal [status $R(0) master_repl_offset] [status $R(1) master_repl_offset]
assert_equal [status $R(0) master_repl_offset] [status $R(2) master_repl_offset]
# make sure replication is still alive and kicking
$R(0) incr counter2
wait_for_condition 50 1000 {
[$R(1) get counter2] == 2 && [$R(2) get counter2] == 2
} else {
fail "replicas didn't get incr"
}
assert_equal [status $R(0) master_repl_offset] [status $R(1) master_repl_offset]
assert_equal [status $R(0) master_repl_offset] [status $R(2) master_repl_offset]
}
}}}