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environment_variables.md

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gRPC environment variables

gRPC C core based implementations (those contained in this repository) expose some configuration as environment variables that can be set.

  • http_proxy The URI of the proxy to use for HTTP CONNECT support.

  • GRPC_ABORT_ON_LEAKS A debugging aid to cause a call to abort() when gRPC objects are leaked past grpc_shutdown(). Set to 1 to cause the abort, if unset or 0 it does not abort the process.

  • GOOGLE_APPLICATION_CREDENTIALS The path to find the credentials to use when Google credentials are created

  • GRPC_SSL_CIPHER_SUITES A colon separated list of cipher suites to use with OpenSSL Defaults to: ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-GCM-SHA384

  • GRPC_DEFAULT_SSL_ROOTS_FILE_PATH PEM file to load SSL roots from

  • GRPC_POLL_STRATEGY [posix-style environments only] Declares which polling engines to try when starting gRPC. This is a comma-separated list of engines, which are tried in priority order first -> last. Available polling engines include:

    • epoll (linux-only) - a polling engine based around the epoll family of system calls
    • poll - a portable polling engine based around poll(), intended to be a fallback engine when nothing better exists
    • legacy - the (deprecated) original polling engine for gRPC

  • GRPC_TRACE A comma separated list of tracers that provide additional insight into how gRPC C core is processing requests via debug logs. Available tracers include:

    • api - traces api calls to the C core
    • bdp_estimator - traces behavior of bdp estimation logic
    • call_combiner - traces call combiner state
    • call_error - traces the possible errors contributing to final call status
    • channel - traces operations on the C core channel stack
    • client_channel - traces client channel activity, including resolver and load balancing policy interaction
    • combiner - traces combiner lock state
    • compression - traces compression operations
    • connectivity_state - traces connectivity state changes to channels
    • channel_stack_builder - traces information about channel stacks being built
    • executor - traces grpc's internal thread pool ('the executor')
    • http - traces state in the http2 transport engine
    • http1 - traces HTTP/1.x operations performed by gRPC
    • inproc - traces the in-process transport
    • flowctl - traces http2 flow control
    • op_failure - traces error information when failure is pushed onto a completion queue
    • round_robin - traces the round_robin load balancing policy
    • pick_first - traces the pick first load balancing policy
    • resource_quota - trace resource quota objects internals
    • glb - traces the grpclb load balancer
    • queue_pluck
    • queue_timeout
    • server_channel - lightweight trace of significant server channel events
    • secure_endpoint - traces bytes flowing through encrypted channels
    • timer - timers (alarms) in the grpc internals
    • timer_check - more detailed trace of timer logic in grpc internals
    • transport_security - traces metadata about secure channel establishment
    • tcp - traces bytes in and out of a channel
    • tsi - traces tsi transport security

    The following tracers will only run in binaries built in DEBUG mode. This is accomplished by invoking CONFIG=dbg make <target>

    • alarm_refcount - refcounting traces for grpc_alarm structure
    • metadata - tracks creation and mutation of metadata
    • closure - tracks closure creation, scheduling, and completion
    • pending_tags - traces still-in-progress tags on completion queues
    • polling - traces the selected polling engine
    • queue_refcount
    • error_refcount
    • stream_refcount
    • workqueue_refcount
    • fd_refcount
    • cq_refcount
    • auth_context_refcount
    • security_connector_refcount
    • resolver_refcount
    • lb_policy_refcount
    • chttp2_refcount

    'all' can additionally be used to turn all traces on. Individual traces can be disabled by prefixing them with '-'.

    'refcount' will turn on all of the tracers for refcount debugging.

    if 'list_tracers' is present, then all of the available tracers will be printed when the program starts up.

    Example: export GRPC_TRACE=all,-pending_tags

  • GRPC_VERBOSITY Default gRPC logging verbosity - one of:

    • DEBUG - log all gRPC messages
    • INFO - log INFO and ERROR message
    • ERROR - log only errors

  • GRPC_TRACE_FUZZER if set, the fuzzers will output trace (it is usually supressed).

  • GRPC_DNS_RESOLVER Declares which DNS resolver to use. The default is ares if gRPC is built with c-ares support. Otherwise, the value of this environment variable is ignored. Available DNS resolver include:

    • native (default)- a DNS resolver based around getaddrinfo(), creates a new thread to perform name resolution
    • ares - a DNS resolver based around the c-ares library

  • GRPC_DISABLE_CHANNEL_CONNECTIVITY_WATCHER The channel connectivity watcher uses one extra thread to check the channel state every 500 ms on the client side. It can help reconnect disconnected client channels (mostly due to idleness), so that the next RPC on this channel won't fail. Set to 1 to turn off this watcher and save a thread. Please note this is a temporary work-around, it will be removed in the future once we have support for automatically reestablishing failed connections.