Connection timeouts connecting to Azure Database for MySql Flexi

Connection timeouts connecting to Azure Database for MySql Flexible Server (with apparently no resource exhaustion)

We have an ASP .Net 8 Web API hosted on Azure App Service (Windows). It connects to an Azure Database for MySql Flexible Server v5.7, using Pomelo.EntityFrameworkCore.MySql 8.0.2. We are not using Private Access/VNet. It is a multi-tenant application, and all databases are InnoDB databases.

When we were on the older Azure Database for MySql SINGLE server, we never had any connection issues. It had 4 vCores and 32 GB RAM. Since we moved to the newer Azure Database for MySql FLEXIBLE server, also with 4 vCores and 32 GB RAM, we occasionally (and by this, I mean perhaps a dozen times a day) get connection timeout errors like these:

MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
  ---> MySqlConnector.MySqlException (0x80004005): Connect Timeout expired.
    at MySqlConnector.Core.ServerSession.OpenTcpSocketAsync(ConnectionSettings cs, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 1046
    at MySqlConnector.Core.ServerSession.ConnectAsync(ConnectionSettings cs, MySqlConnection connection, Int64 startingTimestamp, ILoadBalancer loadBalancer, Activity activity, IOBehavior ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/Core/ServerSession.cs:line 425
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 932
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 938
    at MySqlConnector.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Int64 startingTimestamp, Activity activity, Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 951
    at MySqlConnector.MySqlConnection.OpenAsync(Nullable`1 ioBehavior, CancellationToken cancellationToken) in /_/src/MySqlConnector/MySqlConnection.cs:line 419
    at Microsoft.EntityFrameworkCore.ServerVersion.AutoDetect(String connectionString)
    at PropWorx.API.Extensions.ConfigureExtensions.<>c__DisplayClass5_0.<DbContextConfiguration>b__0(DbContextOptionsBuilder options) in C:\Users\fabsr\source\repos\PropWorx.API\PropWorx.API\Extensions\ConfigureExtensions.cs:line 150
    at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CreateDbContextOptions[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at ResolveService(ILEmitResolverBuilderRuntimeContext, ServiceProviderEngineScope)
    at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
    at lambda_method134(Closure, Object, HttpContext, IServiceProvider)
    at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
    at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
    at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
    at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
    at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

When this happens, it happens for around a minute, and it affects all users trying to connect at that point. Moreover, although I do see an increase in queries being executed at that point in time (perhaps double the usual) - which most likely is related to the connection timeout - both CPU and RAM usage are low (around 15%) and the connection count is way below the limit of around 4096 (it's at around 500).

The connection string I'm using in the Web API is pretty basic:

$"Server={serverAddress};UserID={username};Password={password};Database={databaseName};SslMode=Required;TreatTinyAsBoolean=true;ConvertZeroDateTime=true;"

I am using EnableRetryOnFailure:

DbContextOptions<TenantContext> options = new DbContextOptionsBuilder<TenantContext>()
    .UseMySql(connectionString,
        new MySqlServerVersion(ServerVersion.AutoDetect(connectionString)),
        builder => builder.EnableRetryOnFailure())
    .Options;

These are the server parameters we currently have:

aad_auth_only   OFF
aad_auth_validate_oids_in_tenant    ON
audit_log_enabled   OFF
audit_log_events    CONNECTION
audit_log_exclude_users azure_superuser
audit_log_include_users 
audit_slow_log_enabled  ON
auto_generate_certs OFF
auto_increment_increment    1
auto_increment_offset   1
autocommit  ON
automatic_sp_privileges ON
avoid_temporal_upgrade  OFF
azure_innodb_hpk_auto_add   OFF
azure_innodb_hpk_show   OFF
back_log    2831
basedir /mysql/
big_tables  OFF
bind_address    *
binlog_cache_size   131072
binlog_checksum CRC32
binlog_direct_non_transactional_updates OFF
binlog_error_action ABORT_SERVER
binlog_expire_logs_seconds  0
binlog_format   ROW
binlog_group_commit_sync_delay  0
binlog_group_commit_sync_no_delay_count 0
binlog_gtid_simple_recovery ON
binlog_max_flush_queue_time 0
binlog_order_commits    ON
binlog_row_image    MINIMAL
binlog_rows_query_log_events    OFF
binlog_stmt_cache_size  32768
binlog_transaction_dependency_history_size  32000
binlog_transaction_dependency_tracking  WRITESET
block_encryption_mode   aes-128-ecb
bulk_insert_buffer_size 8388608
character_set_client    utf8mb4
character_set_connection    utf8mb4
character_set_database  utf8mb4
character_set_filesystem    binary
character_set_results   utf8mb4
character_set_server    latin1
character_set_system    utf8
character_sets_dir  /mysql/share/charsets/
check_proxy_users   OFF
collation_connection    utf8mb4_general_ci
collation_database  utf8mb4_general_ci
collation_server    latin1_swedish_ci
completion_type NO_CHAIN
concurrent_insert   AUTO
connect_timeout 10
core_file   ON
datadir /app/work/data/
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_authentication_plugin   mysql_native_password
default_password_lifetime   0
default_storage_engine  InnoDB
default_tmp_storage_engine  InnoDB
default_week_format 0
delay_key_write OFF
delayed_insert_limit    100
delayed_insert_timeout  300
delayed_queue_size  1000
disabled_storage_engines    MyISAM,MRG_MyISAM,BLACKHOLE,FEDEATED,ARCHIVE
disconnect_on_expired_password  ON
div_precision_increment 4
end_markers_in_json OFF
enforce_gtid_consistency    ON
eq_range_index_dive_limit   200
error_count 0
error_log_enabled   OFF
error_server_log_file   OFF
event_scheduler OFF
expire_logs_days    0
explicit_defaults_for_timestamp ON
expr_analyzer_cache_type    ON
external_user   
flush   OFF
flush_time  0
foreign_key_checks  ON
ft_boolean_syntax   + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit    20
ft_stopword_file    (built-in)
general_log OFF
general_log_file    /app/work/serverlogs/mysql-general-propworx-san-mysql-flexible-server-57-uszr-2024021909.log
group_concat_max_len    1024
gtid_executed_compression_period    1000
gtid_mode   ON
gtid_next   AUTOMATIC
gtid_owned  
gtid_purged 28ac0c76-cf0b-11ee-a869-6045bd41deab:1-425431,
 8790a5c8-c67b-11ee-b686-6045bd41dbe2:1-1822618
have_compress   YES
have_crypt  YES
have_dynamic_loading    YES
have_geometry   YES
have_openssl    YES
have_profiling  YES
have_query_cache    YES
have_rtree_keys YES
have_ssl    YES
have_statement_timeout  YES
have_symlink    YES
host_cache_size 279
hostname    ba3d1002be29
identity    0
ignore_builtin_innodb   OFF
ignore_db_dirs  
init_connect    
init_file   
init_file_string    
init_slave  
innodb_adaptive_flushing    ON
innodb_adaptive_flushing_lwm    10
innodb_adaptive_hash_index  OFF
innodb_adaptive_hash_index_parts    8
innodb_adaptive_max_sleep_delay 150000
innodb_api_bk_commit_interval   5
innodb_api_disable_rowlock  OFF
innodb_api_enable_binlog    OFF
innodb_api_enable_mdl   OFF
innodb_api_trx_level    0
innodb_autoextend_increment 64
innodb_autoinc_lock_mode    1
innodb_buffer_pool_chunk_size   134217728
innodb_buffer_pool_dump_at_shutdown ON
innodb_buffer_pool_dump_now OFF
innodb_buffer_pool_dump_pct 100
innodb_buffer_pool_filename ib_buffer_pool
innodb_buffer_pool_instances    8
innodb_buffer_pool_load_abort   OFF
innodb_buffer_pool_load_at_startup  OFF
innodb_buffer_pool_load_now OFF
innodb_buffer_pool_size 25769803776
innodb_change_buffer_max_size   25
innodb_change_buffering all
innodb_checksum_algorithm   crc32
innodb_checksums    ON
innodb_cmp_per_index_enabled    OFF
innodb_commit_concurrency   0
innodb_compression_failure_threshold_pct    5
innodb_compression_level    6
innodb_compression_pad_pct_max  50
innodb_concurrency_tickets  5000
innodb_data_file_path   ibdata1:12M:autoextend
innodb_data_home_dir    
innodb_deadlock_detect  ON
innodb_default_row_format   dynamic
innodb_disable_sort_file_cache  OFF
innodb_doublewrite  OFF
innodb_fast_shutdown    1
innodb_fatal_semaphore_wait_threshold   600
innodb_file_format  Barracuda
innodb_file_format_check    ON
innodb_file_format_max  Barracuda
innodb_file_per_table   ON
innodb_fill_factor  100
innodb_flush_log_at_timeout 1
innodb_flush_log_at_trx_commit  1
innodb_flush_method fsync
innodb_flush_neighbors  0
innodb_flush_sync   ON
innodb_flushing_avg_loops   30
innodb_force_load_corrupted OFF
innodb_force_recovery   0
innodb_ft_aux_table 
innodb_ft_cache_size    8000000
innodb_ft_enable_diag_print OFF
innodb_ft_enable_stopword   ON
innodb_ft_max_token_size    84
innodb_ft_min_token_size    3
innodb_ft_num_word_optimize 2000
innodb_ft_result_cache_limit    2000000000
innodb_ft_server_stopword_table 
innodb_ft_sort_pll_degree   2
innodb_ft_total_cache_size  640000000
innodb_ft_user_stopword_table   
innodb_io_capacity  200
innodb_io_capacity_max  2000
innodb_large_prefix ON
innodb_lock_wait_timeout    50
innodb_locks_unsafe_for_binlog  OFF
innodb_log_buffer_size  16777216
innodb_log_checksums    ON
innodb_log_compressed_pages ON
innodb_log_file_size    268435456
innodb_log_files_in_group   2
innodb_log_group_home_dir   ./
innodb_log_write_ahead_size 8192
innodb_lru_scan_depth   1024
innodb_max_dirty_pages_pct  75.000000
innodb_max_dirty_pages_pct_lwm  0.000000
innodb_max_purge_lag    0
innodb_max_purge_lag_delay  0
innodb_max_undo_log_size    1073741824
innodb_monitor_disable  
innodb_monitor_enable   
innodb_monitor_reset    
innodb_monitor_reset_all    
innodb_old_blocks_pct   37
innodb_old_blocks_time  1000
innodb_online_alter_log_max_size    134217728
innodb_open_files   10000
innodb_optimize_fulltext_only   OFF
innodb_page_cleaners    4
innodb_page_size    16384
innodb_print_all_deadlocks  OFF
innodb_purge_batch_size 300
innodb_purge_rseg_truncate_frequency    128
innodb_purge_threads    1
innodb_random_read_ahead    OFF
innodb_read_ahead_threshold 56
innodb_read_io_threads  4
innodb_read_only    OFF
innodb_replication_delay    0
innodb_rollback_on_timeout  OFF
innodb_rollback_segments    128
innodb_sort_buffer_size 1048576
innodb_spin_wait_delay  6
innodb_stats_auto_recalc    ON
innodb_stats_include_delete_marked  OFF
innodb_stats_method nulls_equal
innodb_stats_on_metadata    OFF
innodb_stats_persistent ON
innodb_stats_persistent_sample_pages    20
innodb_stats_sample_pages   8
innodb_stats_transient_sample_pages 8
innodb_status_output    OFF
innodb_status_output_locks  OFF
innodb_strict_mode  ON
innodb_support_xa   ON
innodb_sync_array_size  1
innodb_sync_spin_loops  30
innodb_table_locks  ON
innodb_temp_data_file_path  ibtmp1:12M:autoextend
innodb_thread_concurrency   0
innodb_thread_sleep_delay   10000
innodb_tmpdir   /mnt/temp
innodb_undo_directory   ./
innodb_undo_log_truncate    OFF
innodb_undo_logs    128
innodb_undo_tablespaces 0
innodb_use_native_aio   ON
innodb_version  5.7.44
innodb_write_io_threads 4
insert_id   0
interactive_timeout 28800
internal_tmp_disk_storage_engine    InnoDB
join_buffer_size    262144
keep_files_on_create    OFF
key_buffer_size 8388608
key_cache_age_threshold 300
key_cache_block_size    1024
key_cache_division_limit    100
keyring_operations  ON
large_files_support ON
large_page_size 0
large_pages OFF
last_insert_id  0
lc_messages en_US
lc_messages_dir /mysql/share/
lc_time_names   en_US
license GPL
local_infile    ON
lock_wait_timeout   31536000
locked_in_memory    OFF
log_bin ON
log_bin_basename    /app/work/binlogs/mysql-bin
log_bin_index   /app/work/data/mysql-bin.index
log_bin_trust_function_creators ON
log_bin_use_v1_row_events   OFF
log_builtin_as_identified_by_password   OFF
log_error   stderr
log_error_verbosity 3
log_output  NONE
log_queries_not_using_indexes   OFF
log_slave_updates   ON
log_slow_admin_statements   OFF
log_slow_slave_statements   OFF
log_statements_unsafe_for_binlog    ON
log_syslog  ON
log_syslog_facility daemon
log_syslog_include_pid  ON
log_syslog_tag  
log_throttle_queries_not_using_indexes  0
log_timestamps  UTC
log_warnings    2
logical_server_name propworx-san-mysql-flexible-server-57-uszr
long_query_time 10.000000
low_priority_updates    OFF
lower_case_file_system  ON
lower_case_table_names  1
master_info_repository  TABLE
master_verify_checksum  OFF
max_allowed_packet  536870912
max_binlog_cache_size   18446744073709547520
max_binlog_size 104857600
max_binlog_stmt_cache_size  18446744073709547520
max_connect_errors  100
max_connections 2731
max_delayed_threads 20
max_digest_length   1024
max_error_count 64
max_execution_time  0
max_heap_table_size 16777216
max_insert_delayed_threads  20
max_join_size   18446744073709551615
max_length_for_sort_data    1024
max_points_in_geometry  65536
max_prepared_stmt_count 16382
max_relay_log_size  104857600
max_seeks_for_key   4294967295
max_sort_length 1024
max_sp_recursion_depth  0
max_tmp_tables  32
max_user_connections    0
max_write_lock_count    18446744073709551615
metadata_locks_cache_size   1024
metadata_locks_hash_instances   8
min_examined_row_limit  0
multi_range_count   256
myisam_data_pointer_size    6
myisam_max_sort_file_size   9223372036853727232
myisam_mmap_size    18446744073709551615
myisam_recover_options  OFF
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
myisam_use_mmap OFF
mysql_native_password_proxy_users   OFF
net_buffer_length   16384
net_read_timeout    120
net_retry_count 10
net_write_timeout   240
new OFF
ngram_token_size    2
offline_mode    OFF
old OFF
old_alter_table OFF
old_passwords   0
open_files_limit    22741
optimizer_prune_level   1
optimizer_search_depth  62
optimizer_switch    index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosesc...
optimizer_trace enabled=off,one_line=off
optimizer_trace_features    greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
optimizer_trace_limit   1
optimizer_trace_max_mem_size    16384
optimizer_trace_offset  -1
parser_max_mem_size 18446744073709551615
performance_schema  ON
performance_schema_accounts_size    -1
performance_schema_digests_size 10000
performance_schema_events_stages_history_long_size  10000
performance_schema_events_stages_history_size   10
performance_schema_events_statements_history_long_size  10000
performance_schema_events_statements_history_size   10
performance_schema_events_transactions_history_long_size    10000
performance_schema_events_transactions_history_size 10
performance_schema_events_waits_history_long_size   10000
performance_schema_events_waits_history_size    10
performance_schema_hosts_size   -1
performance_schema_max_cond_classes 80
performance_schema_max_cond_instances   -1
performance_schema_max_digest_length    1024
performance_schema_max_file_classes 80
performance_schema_max_file_handles 32768
performance_schema_max_file_instances   -1
performance_schema_max_index_stat   -1
performance_schema_max_memory_classes   320
performance_schema_max_metadata_locks   -1
performance_schema_max_mutex_classes    200
performance_schema_max_mutex_instances  -1
performance_schema_max_prepared_statements_instances    -1
performance_schema_max_program_instances    -1
performance_schema_max_rwlock_classes   40
performance_schema_max_rwlock_instances -1
performance_schema_max_socket_classes   10
performance_schema_max_socket_instances -1
performance_schema_max_sql_text_length  1024
performance_schema_max_stage_classes    150
performance_schema_max_statement_classes    196
performance_schema_max_statement_stack  10
performance_schema_max_table_handles    -1
performance_schema_max_table_instances  -1
performance_schema_max_table_lock_stat  -1
performance_schema_max_thread_classes   50
performance_schema_max_thread_instances -1
performance_schema_session_connect_attrs_size   512
performance_schema_setup_actors_size    -1
performance_schema_setup_objects_size   -1
performance_schema_show_processlist OFF
performance_schema_users_size   -1
pid_file    /app/work/data/ba3d1002be29.pid
plugin_dir  /mysql/lib/plugin/
port    3306
preload_buffer_size 32768
profiling   OFF
profiling_history_size  15
protocol_version    10
proxy_user  
pseudo_slave_mode   OFF
pseudo_thread_id    1503866
query_alloc_block_size  8192
query_cache_limit   1048576
query_cache_min_res_unit    4096
query_cache_size    0
query_cache_type    OFF
query_cache_wlock_invalidate    OFF
query_prealloc_size 8192
rand_seed1  0
rand_seed2  0
range_alloc_block_size  4096
range_optimizer_max_mem_size    8388608
rbr_exec_mode   STRICT
read_buffer_size    131072
read_only   OFF
read_rnd_buffer_size    262144
relay_log   /mnt/relaylogs/relay_bin
relay_log_basename  /mnt/relaylogs/relay_bin
relay_log_index /mnt/relaylogs/relay_bin.index
relay_log_info_file relay-log.info
relay_log_info_repository   TABLE
relay_log_purge ON
relay_log_recovery  ON
relay_log_space_limit   8589934592
replication_optimize_for_static_plugin_config   OFF
replication_sender_observe_commit_only  OFF
report_host 
report_password 
report_port 3306
report_user 
require_secure_transport    OFF
rpl_stop_slave_timeout  31536000
secure_auth ON
secure_file_priv    
server_id   2070254791
server_id_bits  32
server_uuid 28ac0c76-cf0b-11ee-a869-6045bd41deab
session_track_gtids OFF
session_track_schema    ON
session_track_state_change  OFF
session_track_system_variables  time_zone, autocommit, character_set_client, character_set_results, character_set_connection
session_track_transaction_info  OFF
sha256_password_auto_generate_rsa_keys  OFF
sha256_password_private_key_path    private_key.pem
sha256_password_proxy_users OFF
sha256_password_public_key_path public_key.pem
show_compatibility_56   OFF
show_create_table_verbosity OFF
show_old_temporals  OFF
skip_external_locking   ON
skip_name_resolve   ON
skip_networking OFF
skip_show_database  OFF
slave_allow_batching    OFF
slave_checkpoint_group  512
slave_checkpoint_period 300
slave_compressed_protocol   OFF
slave_exec_mode STRICT
slave_load_tmpdir   /mnt/temp
slave_max_allowed_packet    1073741824
slave_net_timeout   60
slave_parallel_type LOGICAL_CLOCK
slave_parallel_workers  32
slave_pending_jobs_size_max 268435456
slave_preserve_commit_order ON
slave_rows_search_algorithms    TABLE_SCAN,INDEX_SCAN
slave_skip_errors   OFF
slave_sql_verify_checksum   ON
slave_transaction_retries   10
slave_type_conversions  
slow_launch_time    2
slow_query_log  OFF
slow_query_log_file /app/serverlogs/slowlogs/mysql-slow-propworx-san-mysql-flexible-server-57-uszr-2024032809.log
socket  /tmp/mysql/mysql.sock
sort_buffer_size    524288
sql_auto_is_null    OFF
sql_big_selects ON
sql_buffer_result   OFF
sql_log_bin ON
sql_log_off OFF
sql_mode    STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER
sql_notes   ON
sql_quote_show_create   ON
sql_require_primary_key OFF
sql_safe_updates    OFF
sql_select_limit    18446744073709551615
sql_slave_skip_counter  0
sql_warnings    OFF
ssl_ca  /app/work/ca.pem
ssl_capath  
ssl_cert    /app/work/cert.pem
ssl_cipher  ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-CCM:DHE-RSA-AES256-CCM:DHE-RSA-AES128-C...
ssl_crl 
ssl_crlpath 
ssl_key /app/work/key.pem
stored_program_cache    256
super_read_only OFF
sync_binlog 1
sync_frm    ON
sync_master_info    0
sync_relay_log  0
sync_relay_log_info 1
system_time_zone    UTC
table_definition_cache  10000
table_open_cache    10000
table_open_cache_instances  16
thread_cache_size   35
thread_handling one-thread-per-connection
thread_pool_new_conn_high_prio  OFF
thread_stack    262144
time_format %H:%i:%s
time_zone   +00:00
timestamp   1711635902.056424
tls_version TLSv1.2
tmp_table_size  16777216
tmpdir  /mnt/temp
transaction_alloc_block_size    8192
transaction_allow_batching  OFF
transaction_isolation   REPEATABLE-READ
transaction_prealloc_size   4096
transaction_read_only   OFF
transaction_write_set_extraction    XXHASH64
tx_isolation    REPEATABLE-READ
tx_read_only    OFF
unique_checks   ON
updatable_views_with_limit  YES
version 5.7.44-log
version_comment MySQL Community Server (GPL)
version_compile_machine x86_64
version_compile_os  Linux
wait_timeout    28800
warning_count   0

Sorry, I didn't know how to paste an HTML table in this post. My question is, what else could be the culprit? What else should I look at?

Nothing has changed in our API code. The only thing that's changed is the type of MySql Server.

Answers

Since you've already ruled out high CPU, RAM, and connection counts as potential causes, there are several other factors you can investigate to determine the cause of the connection timeout issues:

Network Latency: Although you mentioned that you're not using Private Access/VNet, network latency can still affect connectivity between your Azure App Service and the Azure Database for MySQL Flexible Server. You can monitor network latency between your web API and the database server using tools like ping or traceroute.
Firewall Rules: Check if there are any firewall rules in place that might be causing intermittent connection issues. Ensure that the necessary ports (e.g., 3306 for MySQL) are open and that there are no IP restrictions blocking the connectivity.
Connection Pool Configuration: Verify that your connection pool configuration is appropriate for your workload. You may need to adjust settings such as MinPoolSize, MaxPoolSize, ConnectionLifetime, and ConnectionTimeout based on the number of concurrent users and the frequency of database connections.
Azure Resource Health: Check the health status of your Azure resources, including the App Service and the MySQL Flexible Server. Azure provides resource health monitoring that can help identify any ongoing issues with the underlying infrastructure.
Query Performance: Review the queries being executed by your web API to ensure they are optimized and not causing excessive load on the database server. Long-running or poorly optimized queries can lead to connection timeouts, especially during periods of high traffic.
Database Logs: Examine the MySQL error log and slow query log for any errors or warnings that might indicate underlying issues with the database server. Look for patterns or recurring errors around the times when connection timeouts occur.
Retry Logic: While you're already using EnableRetryOnFailure in Entity Framework Core, ensure that the retry logic is configured appropriately to handle transient errors like connection timeouts. You may need to adjust the retry interval and maximum retry count based on your specific scenario.
Azure Service Outages: Check the Azure Service Health dashboard for any ongoing outages or service disruptions that might be impacting the availability of Azure services, including Azure App Service and Azure Database for MySQL.

By investigating these areas, you should be able to identify the root cause of the connection timeout issues and take appropriate action to resolve them. If the problem persists, you may also consider reaching out to Azure support for further assistance.

Connection timeouts connecting to Azure Database for MySql Flexi

Answers

Hot

Latest