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Variables
Backend connection
backend.conn.is_tls
backend.conn.tls_protocol
backend.socket.congestion_algorithm
backend.socket.cwnd
backend.socket.tcpi_advmss
backend.socket.tcpi_bytes_acked
backend.socket.tcpi_bytes_received
backend.socket.tcpi_data_segs_in
backend.socket.tcpi_data_segs_out
backend.socket.tcpi_delivery_rate
backend.socket.tcpi_delta_retrans
backend.socket.tcpi_last_data_sent
backend.socket.tcpi_max_pacing_rate
backend.socket.tcpi_min_rtt
backend.socket.tcpi_notsent_bytes
backend.socket.tcpi_pacing_rate
backend.socket.tcpi_pmtu
backend.socket.tcpi_rcv_mss
backend.socket.tcpi_rcv_rtt
backend.socket.tcpi_rcv_space
backend.socket.tcpi_rcv_ssthresh
backend.socket.tcpi_reordering
backend.socket.tcpi_rtt
backend.socket.tcpi_rttvar
backend.socket.tcpi_segs_in
backend.socket.tcpi_segs_out
backend.socket.tcpi_snd_cwnd
backend.socket.tcpi_snd_mss
backend.socket.tcpi_snd_ssthresh
backend.socket.tcpi_total_retrans
backend.{NAME}.connections_open
backend.{NAME}.connections_used
backend.{NAME}.healthy
bereq.between_bytes_timeout
bereq.connect_timeout
bereq.first_byte_timeout
beresp.backend.alternate_ips
beresp.backend.ip
beresp.backend.port
beresp.backend.requests
beresp.backend.src_ip
beresp.handshake_time_to_origin_ms
beresp.used_alternate_path_to_origin
ratecounter.{NAME}.bucket.10s
ratecounter.{NAME}.bucket.20s
ratecounter.{NAME}.bucket.30s
ratecounter.{NAME}.bucket.40s
ratecounter.{NAME}.bucket.50s
ratecounter.{NAME}.bucket.60s
ratecounter.{NAME}.rate.10s
ratecounter.{NAME}.rate.1s
ratecounter.{NAME}.rate.60s
req.backend
req.backend.healthy
req.backend.is_origin
req.backend.is_shield
Backend request
Backend response
Cache object
Client connection
Client request
Client response
Date and time
ESI
Geolocation
Math constants limits
Miscellaneous
Segmented caching
Server
fastly.toml
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Reference documentation
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Variables
Backend connection
backend.socket.tcpi_total_retrans
INTEGER
, read-only.
Available in
fetch
Number of TCP retransmissions for the backend connection.